fix wrongly disallowed rx of max possible size

* done with changes but now segfaulting

* fixed the bug

* fix some bad indents

* some cleanings

* updated readme

README.md

@@ -19,6 +19,10 @@ The library lets you register listeners (callback functions) to wait for (1) any
 a particular frame Type, or (3) a specific message ID. This  high-level API lets you 
 easily implement various async communication patterns.
 
+TinyFrame is re-entrant and supports creating multiple instances with the limitation
+that their structure (field sizes and checksum type) must be the same. There is a support
+for adding multi-threaded access to a shared instance using a mutex (via a callback stub).
+
 ## Frame structure
 
 All fields in the message frame have a configurable size (see the top of the header file).
@@ -49,7 +53,9 @@ DATA_CKSUM .. checksum, implemented as XOR of all preceding bytes in the message
 
 - All TinyFrame functions, typedefs and macros start with the `TF_` prefix.
 - Both peers must include the library with the same parameters (configured at the top of the header file)
-- Start by calling `TF_Init()` with `TF_MASTER` or `TF_SLAVE` as the argument
+- Start by calling `TF_Init()` with `TF_MASTER` or `TF_SLAVE` as the argument. This creates a handle.
+  Use `TF_InitStatic()` to avoid the use of malloc(). If multiple instances are used, you can tag them 
+  using the `tf.userdata` / `tf.usertag` field.
 - Implement `TF_WriteImpl()` - declared at the bottom of the header file as `extern`.
   This function is used by `TF_Send()` and others to write bytes to your UART (or other physical layer).
   A frame can be sent in it's entirety, or in multiple parts, depending on its size.

TF_Integration.example.c

@@ -10,19 +10,19 @@
  * listener timeout feature.
  */
 
-void TF_WriteImpl(const uint8_t *buff, size_t len)
+void TF_WriteImpl(TinyFrame *tf, const uint8_t *buff, size_t len)
 {
     // send to UART
 }
 
 /** Claim the TX interface before composing and sending a frame */
-void TF_ClaimTx(void)
+void TF_ClaimTx(TinyFrame *tf)
 {
     // take mutex
 }
 
 /** Free the TX interface after composing and sending a frame */
-void TF_ReleaseTx(void)
+void TF_ReleaseTx(TinyFrame *tf)
 {
     // release mutex
 }

TinyFrame.c

@@ -1,6 +1,6 @@
 //---------------------------------------------------------------------------
 #include "TinyFrame.h"
-#include <string.h>
+#include <malloc.h>
 //---------------------------------------------------------------------------
 
 // Compatibility with ESP8266 SDK
@@ -14,71 +14,9 @@
 #define TF_MAX(a, b) ((a)>(b)?(a):(b))
 #define TF_MIN(a, b) ((a)<(b)?(a):(b))
 
-enum TFState {
-	TFState_SOF = 0,      //!< Wait for SOF
-	TFState_LEN,          //!< Wait for Number Of Bytes
-	TFState_HEAD_CKSUM,   //!< Wait for header Checksum
-	TFState_ID,           //!< Wait for ID
-	TFState_TYPE,         //!< Wait for message type
-	TFState_DATA,         //!< Receive payload
-	TFState_DATA_CKSUM    //!< Wait for Checksum
-};
-
-typedef struct _IdListener_struct_ {
-	TF_ID id;
-	TF_Listener fn;
-	TF_TICKS timeout;     // nr of ticks remaining to disable this listener
-	TF_TICKS timeout_max; // the original timeout is stored here
-	void *userdata;
-	void *userdata2;
-} IdListener;
-
-typedef struct _TypeListener_struct_ {
-	TF_TYPE type;
-	TF_Listener fn;
-} TypeListener;
-
-typedef struct _GenericListener_struct_ {
-	TF_Listener fn;
-} GenericListener;
-
-/**
- * Frame parser internal state
- */
-static struct TinyFrameStruct {
-	/* Own state */
-	TF_Peer peer_bit;       //!< Own peer bit (unqiue to avoid msg ID clash)
-	TF_ID next_id;          //!< Next frame / frame chain ID
-
-	/* Parser state */
-	enum TFState state;
-	TF_TICKS parser_timeout_ticks;
-	TF_ID id;               //!< Incoming packet ID
-	TF_LEN len;             //!< Payload length
-	uint8_t data[TF_MAX_PAYLOAD_RX]; //!< Data byte buffer
-	TF_LEN rxi;             //!< Field size byte counter
-	TF_CKSUM cksum;         //!< Checksum calculated of the data stream
-	TF_CKSUM ref_cksum;     //!< Reference checksum read from the message
-	TF_TYPE type;           //!< Collected message type number
-	bool discard_data;      //!< Set if (len > TF_MAX_PAYLOAD) to read the frame, but ignore the data.
-
-	/* --- Callbacks --- */
-
-	/* Transaction callbacks */
-	IdListener id_listeners[TF_MAX_ID_LST];
-	TypeListener type_listeners[TF_MAX_TYPE_LST];
-	GenericListener generic_listeners[TF_MAX_GEN_LST];
-
-	// Those counters are used to optimize look-up times.
-	// They point to the highest used slot number,
-	// or close to it, depending on the removal order.
-	TF_COUNT count_id_lst;
-	TF_COUNT count_type_lst;
-	TF_COUNT count_generic_lst;
-
-	// Buffer for building frames
-	uint8_t sendbuf[TF_SENDBUF_LEN];
-} tf;
+// TODO It would be nice to have per-instance configurable checksum types, but that would
+// mandate configurable field sizes unless we use u32 everywhere (and possibly shorten
+// it when encoding to the buffer). I don't really like this idea so much. -MP
 
 //region Checksums
 
@@ -98,6 +36,7 @@ static struct TinyFrameStruct {
 
 #elif TF_CKSUM_TYPE == TF_CKSUM_CRC16
 
+// TODO try to replace with an algorithm
 /** CRC table for the CRC-16. The poly is 0x8005 (x^16 + x^15 + x^2 + 1) */
 static const uint16_t crc16_table[256] = {
     0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
@@ -145,6 +84,7 @@ static inline uint16_t crc16_byte(uint16_t cksum, const uint8_t byte)
 
 #elif TF_CKSUM_TYPE == TF_CKSUM_CRC32
 
+// TODO try to replace with an algorithm
 static const uint32_t crc32_table[] = { /* CRC polynomial 0xedb88320 */
     0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
     0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
@@ -204,28 +144,48 @@ static inline uint32_t crc32_byte(uint32_t cksum, const uint8_t byte)
 
 //endregion
 
-
-void _TF_FN TF_Init(TF_Peer peer_bit)
+/** Init with a user-allocated buffer */
+void _TF_FN TF_InitStatic(TinyFrame *tf, TF_Peer peer_bit)
 {
-	// Zero it out
-	memset(&tf, 0, sizeof(struct TinyFrameStruct));
+    if (tf == NULL) return;
 
-	tf.peer_bit = peer_bit;
+    // Zero it out, keeping user config
+    uint32_t usertag = tf->usertag;
+    void * userdata = tf->userdata;
+
+    memset(tf, 0, sizeof(struct TinyFrame_));
+
+    tf->usertag = usertag;
+    tf->userdata = userdata;
+
+    tf->peer_bit = peer_bit;
+}
+
+/** Init with malloc */
+TinyFrame * _TF_FN TF_Init(TF_Peer peer_bit)
+{
+    TinyFrame *tf = malloc(sizeof(TinyFrame));
+    TF_InitStatic(tf, peer_bit);
+    return tf;
+}
+
+/** Release the struct */
+void TF_DeInit(TinyFrame *tf)
+{
+    if (tf == NULL) return;
+    free(tf);
 }
 
 //region Listeners
 
-static void _TF_FN renew_id_listener(IdListener *lst)
+/** Reset ID listener's timeout to the original value */
+static inline void _TF_FN renew_id_listener(struct TF_IdListener_ *lst)
 {
     lst->timeout = lst->timeout_max;
 }
 
-/**
- * Notify callback about ID listener demise & clean it
- *
- * @param lst - listener to clean
- */
-static void _TF_FN cleanup_id_listener(TF_COUNT i, IdListener *lst)
+/** Notify callback about ID listener's demise & let it free any resources in userdata */
+static void _TF_FN cleanup_id_listener(TinyFrame *tf, TF_COUNT i, struct TF_IdListener_ *lst)
 {
     TF_Msg msg;
     if (lst->fn == NULL) return;
@@ -235,48 +195,41 @@ static void _TF_FN cleanup_id_listener(TF_COUNT i, IdListener *lst)
         msg.userdata = lst->userdata;
         msg.userdata2 = lst->userdata2;
         msg.data = NULL; // this is a signal that the listener should clean up
-		lst->fn(&msg); // return value is ignored here - use TF_STAY or TF_CLOSE
+        lst->fn(tf, &msg); // return value is ignored here - use TF_STAY or TF_CLOSE
     }
 
     lst->fn = NULL; // Discard listener
 
-	if (i == tf.count_id_lst - 1) {
-		tf.count_id_lst--;
+    if (i == tf->count_id_lst - 1) {
+        tf->count_id_lst--;
     }
 }
 
-/**
- * Clean up Type listener
- *
- * @param lst - listener to clean
- */
-static inline void _TF_FN cleanup_type_listener(TF_COUNT i, TypeListener *lst)
+/** Clean up Type listener */
+static inline void _TF_FN cleanup_type_listener(TinyFrame *tf, TF_COUNT i, struct TF_TypeListener_ *lst)
 {
     lst->fn = NULL; // Discard listener
-	if (i == tf.count_type_lst - 1) {
-		tf.count_type_lst--;
+    if (i == tf->count_type_lst - 1) {
+        tf->count_type_lst--;
     }
 }
 
-/**
- * Clean up Generic listener
- *
- * @param lst - listener to clean
- */
-static inline void _TF_FN cleanup_generic_listener(TF_COUNT i, GenericListener *lst)
+/** Clean up Generic listener */
+static inline void _TF_FN cleanup_generic_listener(TinyFrame *tf, TF_COUNT i, struct TF_GenericListener_ *lst)
 {
     lst->fn = NULL; // Discard listener
-	if (i == tf.count_generic_lst - 1) {
-		tf.count_generic_lst--;
+    if (i == tf->count_generic_lst - 1) {
+        tf->count_generic_lst--;
     }
 }
 
-bool _TF_FN TF_AddIdListener(TF_Msg *msg, TF_Listener cb, TF_TICKS timeout)
+/** Add a new ID listener. Returns 1 on success. */
+bool _TF_FN TF_AddIdListener(TinyFrame *tf, TF_Msg *msg, TF_Listener cb, TF_TICKS timeout)
 {
     TF_COUNT i;
-	IdListener *lst;
+    struct TF_IdListener_ *lst;
     for (i = 0; i < TF_MAX_ID_LST; i++) {
-		lst = &tf.id_listeners[i];
+        lst = &tf->id_listeners[i];
         // test for empty slot
         if (lst->fn == NULL) {
             lst->fn = cb;
@@ -284,8 +237,8 @@ bool _TF_FN TF_AddIdListener(TF_Msg *msg, TF_Listener cb, TF_TICKS timeout)
             lst->userdata = msg->userdata;
             lst->userdata2 = msg->userdata2;
             lst->timeout_max = lst->timeout = timeout;
-			if (i >= tf.count_id_lst) {
-				tf.count_id_lst = (TF_COUNT) (i + 1);
+            if (i >= tf->count_id_lst) {
+                tf->count_id_lst = (TF_COUNT) (i + 1);
             }
             return true;
         }
@@ -293,18 +246,19 @@ bool _TF_FN TF_AddIdListener(TF_Msg *msg, TF_Listener cb, TF_TICKS timeout)
     return false;
 }
 
-bool _TF_FN TF_AddTypeListener(TF_TYPE frame_type, TF_Listener cb)
+/** Add a new Type listener. Returns 1 on success. */
+bool _TF_FN TF_AddTypeListener(TinyFrame *tf, TF_TYPE frame_type, TF_Listener cb)
 {
     TF_COUNT i;
-	TypeListener *lst;
+    struct TF_TypeListener_ *lst;
     for (i = 0; i < TF_MAX_TYPE_LST; i++) {
-		lst = &tf.type_listeners[i];
+        lst = &tf->type_listeners[i];
         // test for empty slot
         if (lst->fn == NULL) {
             lst->fn = cb;
             lst->type = frame_type;
-			if (i >= tf.count_type_lst) {
-				tf.count_type_lst = (TF_COUNT) (i + 1);
+            if (i >= tf->count_type_lst) {
+                tf->count_type_lst = (TF_COUNT) (i + 1);
             }
             return true;
         }
@@ -312,17 +266,18 @@ bool _TF_FN TF_AddTypeListener(TF_TYPE frame_type, TF_Listener cb)
     return false;
 }
 
-bool _TF_FN TF_AddGenericListener(TF_Listener cb)
+/** Add a new Generic listener. Returns 1 on success. */
+bool _TF_FN TF_AddGenericListener(TinyFrame *tf, TF_Listener cb)
 {
     TF_COUNT i;
-	GenericListener *lst;
+    struct TF_GenericListener_ *lst;
     for (i = 0; i < TF_MAX_GEN_LST; i++) {
-		lst = &tf.generic_listeners[i];
+        lst = &tf->generic_listeners[i];
         // test for empty slot
         if (lst->fn == NULL) {
             lst->fn = cb;
-			if (i >= tf.count_generic_lst) {
-				tf.count_generic_lst = (TF_COUNT) (i + 1);
+            if (i >= tf->count_generic_lst) {
+                tf->count_generic_lst = (TF_COUNT) (i + 1);
             }
             return true;
         }
@@ -330,45 +285,48 @@ bool _TF_FN TF_AddGenericListener(TF_Listener cb)
     return false;
 }
 
-bool _TF_FN TF_RemoveIdListener(TF_ID frame_id)
+/** Remove a ID listener by its frame ID. Returns 1 on success. */
+bool _TF_FN TF_RemoveIdListener(TinyFrame *tf, TF_ID frame_id)
 {
     TF_COUNT i;
-	IdListener *lst;
-	for (i = 0; i < tf.count_id_lst; i++) {
-		lst = &tf.id_listeners[i];
+    struct TF_IdListener_ *lst;
+    for (i = 0; i < tf->count_id_lst; i++) {
+        lst = &tf->id_listeners[i];
         // test if live & matching
         if (lst->fn != NULL && lst->id == frame_id) {
-			cleanup_id_listener(i, lst);
+            cleanup_id_listener(tf, i, lst);
             return true;
         }
     }
     return false;
 }
 
-bool _TF_FN TF_RemoveTypeListener(TF_TYPE type)
+/** Remove a type listener by its type. Returns 1 on success. */
+bool _TF_FN TF_RemoveTypeListener(TinyFrame *tf, TF_TYPE type)
 {
     TF_COUNT i;
-	TypeListener *lst;
-	for (i = 0; i < tf.count_type_lst; i++) {
-		lst = &tf.type_listeners[i];
+    struct TF_TypeListener_ *lst;
+    for (i = 0; i < tf->count_type_lst; i++) {
+        lst = &tf->type_listeners[i];
         // test if live & matching
         if (lst->fn != NULL    && lst->type == type) {
-			cleanup_type_listener(i, lst);
+            cleanup_type_listener(tf, i, lst);
             return true;
         }
     }
     return false;
 }
 
-bool _TF_FN TF_RemoveGenericListener(TF_Listener cb)
+/** Remove a generic listener by its function pointer. Returns 1 on success. */
+bool _TF_FN TF_RemoveGenericListener(TinyFrame *tf, TF_Listener cb)
 {
     TF_COUNT i;
-	GenericListener *lst;
-	for (i = 0; i < tf.count_generic_lst; i++) {
-		lst = &tf.generic_listeners[i];
+    struct TF_GenericListener_ *lst;
+    for (i = 0; i < tf->count_generic_lst; i++) {
+        lst = &tf->generic_listeners[i];
         // test if live & matching
         if (lst->fn == cb) {
-			cleanup_generic_listener(i, lst);
+            cleanup_generic_listener(tf, i, lst);
             return true;
         }
     }
@@ -376,64 +334,72 @@ bool _TF_FN TF_RemoveGenericListener(TF_Listener cb)
 }
 
 /** Handle a message that was just collected & verified by the parser */
-static void _TF_FN TF_HandleReceivedMessage(void)
+static void _TF_FN TF_HandleReceivedMessage(TinyFrame *tf)
 {
     TF_COUNT i;
-	IdListener *ilst;
-	TypeListener *tlst;
-	GenericListener *glst;
+    struct TF_IdListener_ *ilst;
+    struct TF_TypeListener_ *tlst;
+    struct TF_GenericListener_ *glst;
     TF_Result res;
 
     // Prepare message object
     TF_Msg msg;
-	msg.frame_id = tf.id;
+    TF_ClearMsg(&msg);
+    msg.frame_id = tf->id;
     msg.is_response = false;
-	msg.type = tf.type;
-	msg.data = tf.data;
-	msg.len = tf.len;
+    msg.type = tf->type;
+    msg.data = tf->data;
+    msg.len = tf->len;
 
-	//dumpFrameInfo(&msg);
-
-	// Any listener can consume the message (return true),
-	// or let someone else handle it.
+    // Any listener can consume the message, or let someone else handle it.
 
     // The loop upper bounds are the highest currently used slot index
-	// (or close to it, depending on the order of listener removals)
+    // (or close to it, depending on the order of listener removals).
 
     // ID listeners first
-	for (i = 0; i < tf.count_id_lst; i++) {
-		ilst = &tf.id_listeners[i];
+    for (i = 0; i < tf->count_id_lst; i++) {
+        ilst = &tf->id_listeners[i];
+
         if (ilst->fn && ilst->id == msg.frame_id) {
             msg.userdata = ilst->userdata; // pass userdata pointer to the callback
             msg.userdata2 = ilst->userdata2;
-			res = ilst->fn(&msg);
+            res = ilst->fn(tf, &msg);
             ilst->userdata = msg.userdata; // put it back (may have changed the pointer or set to NULL)
             ilst->userdata2 = msg.userdata2; // put it back (may have changed the pointer or set to NULL)
 
             if (res != TF_NEXT) {
-				if (res == TF_CLOSE) {
-					cleanup_id_listener(i, ilst);
-				}
-				else if (res == TF_RENEW) {
+                // if it's TF_CLOSE, we assume user already cleaned up userdata
+                if (res == TF_RENEW) {
                     renew_id_listener(ilst);
                 }
+                else if (res == TF_CLOSE) {
+                    // Set userdata to NULL to avoid calling user for cleanup
+                    ilst->userdata = NULL;
+                    ilst->userdata2 = NULL;
+                    cleanup_id_listener(tf, i, ilst);
+                }
                 return;
             }
         }
     }
+    // clean up for the following listeners that don't use userdata (this avoids data from
+    // an ID listener that returned TF_NEXT from leaking into Type and Generic listeners)
     msg.userdata = NULL;
     msg.userdata2 = NULL;
-	// clean up for the following listeners that don't use userdata
 
     // Type listeners
-	for (i = 0; i < tf.count_type_lst; i++) {
-		tlst = &tf.type_listeners[i];
+    for (i = 0; i < tf->count_type_lst; i++) {
+        tlst = &tf->type_listeners[i];
+
         if (tlst->fn && tlst->type == msg.type) {
-			res = tlst->fn(&msg);
+            res = tlst->fn(tf, &msg);
 
             if (res != TF_NEXT) {
+                // type listeners don't have userdata.
+                // TF_RENEW doesn't make sense here because type listeners don't expire = same as TF_STAY
+
                 if (res == TF_CLOSE) {
-					cleanup_type_listener(i, tlst);
+                    cleanup_type_listener(tf, i, tlst);
                 }
                 return;
             }
@@ -441,14 +407,22 @@ static void _TF_FN TF_HandleReceivedMessage(void)
     }
 
     // Generic listeners
-	for (i = 0; i < tf.count_generic_lst; i++) {
-		glst = &tf.generic_listeners[i];
+    for (i = 0; i < tf->count_generic_lst; i++) {
+        glst = &tf->generic_listeners[i];
+
         if (glst->fn) {
-			res = glst->fn(&msg);
+            res = glst->fn(tf, &msg);
 
             if (res != TF_NEXT) {
+                // generic listeners don't have userdata.
+                // TF_RENEW doesn't make sense here because generic listeners don't expire = same as TF_STAY
+
+                // note: It's not expected that user will have multiple generic listeners, or
+                // ever actually remove them. They're most useful as default callbacks if no other listener
+                // handled the message.
+
                 if (res == TF_CLOSE) {
-					cleanup_generic_listener(i, glst);
+                    cleanup_generic_listener(tf, i, glst);
                 }
                 return;
             }
@@ -458,173 +432,209 @@ static void _TF_FN TF_HandleReceivedMessage(void)
 
 //endregion Listeners
 
-void _TF_FN TF_Accept(const uint8_t *buffer, size_t count)
+/** Handle a received byte buffer */
+void _TF_FN TF_Accept(TinyFrame *tf, const uint8_t *buffer, size_t count)
 {
     size_t i;
     for (i = 0; i < count; i++) {
-		TF_AcceptChar(buffer[i]);
+        TF_AcceptChar(tf, buffer[i]);
     }
 }
 
-void _TF_FN TF_ResetParser(void)
+/** Reset the parser's internal state. */
+void _TF_FN TF_ResetParser(TinyFrame *tf)
 {
-	tf.state = TFState_SOF;
+    tf->state = TFState_SOF;
+    // more init will be done by the parser when the first byte is received
 }
 
-/** SOF was received */
-static void _TF_FN TF_ParsBeginFrame(void) {
+/** SOF was received - prepare for the frame */
+static void _TF_FN pars_begin_frame(TinyFrame *tf) {
     // Reset state vars
-	CKSUM_RESET(tf.cksum);
+    CKSUM_RESET(tf->cksum);
 #if TF_USE_SOF_BYTE
-	CKSUM_ADD(tf.cksum, TF_SOF_BYTE);
+    CKSUM_ADD(tf->cksum, TF_SOF_BYTE);
 #endif
 
-	tf.discard_data = false;
+    tf->discard_data = false;
 
     // Enter ID state
-	tf.state = TFState_ID;
-	tf.rxi = 0;
+    tf->state = TFState_ID;
+    tf->rxi = 0;
 }
 
-void _TF_FN TF_AcceptChar(unsigned char c)
+/** Handle a received char - here's the main state machine */
+void _TF_FN TF_AcceptChar(TinyFrame *tf, unsigned char c)
 {
     // Parser timeout - clear
-	if (tf.parser_timeout_ticks >= TF_PARSER_TIMEOUT_TICKS) {
-		TF_ResetParser();
+    if (tf->parser_timeout_ticks >= TF_PARSER_TIMEOUT_TICKS) {
+        TF_ResetParser(tf);
     }
-	tf.parser_timeout_ticks = 0;
+    tf->parser_timeout_ticks = 0;
 
-// DRY snippet - collect multi-byte number from the input stream
+// DRY snippet - collect multi-byte number from the input stream, byte by byte
+// This is a little dirty, but makes the code easier to read. It's used like e.g. if(),
+// the body is run only after the entire number (of data type 'type') was received
+// and stored to 'dest'
 #define COLLECT_NUMBER(dest, type) dest = (type)(((dest) << 8) | c); \
-								   if (++tf.rxi == sizeof(type))
+                                   if (++tf->rxi == sizeof(type))
 
 #if !TF_USE_SOF_BYTE
-	if (tf.state == TFState_SOF) {
+    if (tf->state == TFState_SOF) {
         TF_ParsBeginFrame();
     }
 #endif
 
-	switch (tf.state) {
+    //@formatter:off
+    switch (tf->state) {
         case TFState_SOF:
             if (c == TF_SOF_BYTE) {
-				TF_ParsBeginFrame();
+                pars_begin_frame(tf);
             }
             break;
 
         case TFState_ID:
-			CKSUM_ADD(tf.cksum, c);
-			COLLECT_NUMBER(tf.id, TF_ID) {
+            CKSUM_ADD(tf->cksum, c);
+            COLLECT_NUMBER(tf->id, TF_ID) {
                 // Enter LEN state
-				tf.state = TFState_LEN;
-				tf.rxi = 0;
+                tf->state = TFState_LEN;
+                tf->rxi = 0;
             }
             break;
 
         case TFState_LEN:
-			CKSUM_ADD(tf.cksum, c);
-			COLLECT_NUMBER(tf.len, TF_LEN) {
+            CKSUM_ADD(tf->cksum, c);
+            COLLECT_NUMBER(tf->len, TF_LEN) {
                 // Enter TYPE state
-				tf.state = TFState_TYPE;
-				tf.rxi = 0;
+                tf->state = TFState_TYPE;
+                tf->rxi = 0;
             }
             break;
 
         case TFState_TYPE:
-			CKSUM_ADD(tf.cksum, c);
-			COLLECT_NUMBER(tf.type, TF_TYPE) {
+            CKSUM_ADD(tf->cksum, c);
+            COLLECT_NUMBER(tf->type, TF_TYPE) {
                 #if TF_CKSUM_TYPE == TF_CKSUM_NONE
-				tf.state = TFState_DATA;
-				tf.rxi = 0;
+                    tf->state = TFState_DATA;
+                    tf->rxi = 0;
                 #else
                     // enter HEAD_CKSUM state
-				tf.state = TFState_HEAD_CKSUM;
-				tf.rxi = 0;
-				tf.ref_cksum = 0;
+                    tf->state = TFState_HEAD_CKSUM;
+                    tf->rxi = 0;
+                    tf->ref_cksum = 0;
                 #endif
             }
             break;
 
         case TFState_HEAD_CKSUM:
-			COLLECT_NUMBER(tf.ref_cksum, TF_CKSUM) {
+            COLLECT_NUMBER(tf->ref_cksum, TF_CKSUM) {
                 // Check the header checksum against the computed value
-				CKSUM_FINALIZE(tf.cksum);
+                CKSUM_FINALIZE(tf->cksum);
 
-				if (tf.cksum != tf.ref_cksum) {
-					TF_ResetParser();
+                if (tf->cksum != tf->ref_cksum) {
+                    TF_ResetParser(tf);
                     break;
                 }
 
-				if (tf.len == 0) {
-					TF_HandleReceivedMessage();
-					TF_ResetParser();
+                if (tf->len == 0) {
+                    // if the message has no body, we're done.
+                    TF_HandleReceivedMessage(tf);
+                    TF_ResetParser(tf);
                     break;
                 }
 
                 // Enter DATA state
-				tf.state = TFState_DATA;
-				tf.rxi = 0;
+                tf->state = TFState_DATA;
+                tf->rxi = 0;
 
-				CKSUM_RESET(tf.cksum); // Start collecting the payload
+                CKSUM_RESET(tf->cksum); // Start collecting the payload
 
-				if (tf.len >= TF_MAX_PAYLOAD_RX) {
+                if (tf->len > TF_MAX_PAYLOAD_RX) {
                     // ERROR - frame too long. Consume, but do not store.
-					tf.discard_data = true;
+                    tf->discard_data = true;
                 }
             }
             break;
 
         case TFState_DATA:
-			if (tf.discard_data) {
-				tf.rxi++;
+            if (tf->discard_data) {
+                tf->rxi++;
             } else {
-				CKSUM_ADD(tf.cksum, c);
-				tf.data[tf.rxi++] = c;
+                CKSUM_ADD(tf->cksum, c);
+                tf->data[tf->rxi++] = c;
             }
 
-			if (tf.rxi == tf.len) {
+            if (tf->rxi == tf->len) {
                 #if TF_CKSUM_TYPE == TF_CKSUM_NONE
                     // All done
                     TF_HandleReceivedMessage();
                     TF_ResetParser();
                 #else
                     // Enter DATA_CKSUM state
-				tf.state = TFState_DATA_CKSUM;
-				tf.rxi = 0;
-				tf.ref_cksum = 0;
+                    tf->state = TFState_DATA_CKSUM;
+                    tf->rxi = 0;
+                    tf->ref_cksum = 0;
                 #endif
             }
             break;
 
         case TFState_DATA_CKSUM:
-			COLLECT_NUMBER(tf.ref_cksum, TF_CKSUM) {
+            COLLECT_NUMBER(tf->ref_cksum, TF_CKSUM) {
                 // Check the header checksum against the computed value
-				CKSUM_FINALIZE(tf.cksum);
-				if (!tf.discard_data && tf.cksum == tf.ref_cksum) {
-					TF_HandleReceivedMessage();
+                CKSUM_FINALIZE(tf->cksum);
+                if (!tf->discard_data && tf->cksum == tf->ref_cksum) {
+                    TF_HandleReceivedMessage(tf);
                 }
 
-				TF_ResetParser();
+                TF_ResetParser(tf);
             }
             break;
     }
+    //@formatter:on
 
     // we get here after finishing HEAD, if no data are to be received - handle and clear
-	if (tf.len == 0 && tf.state == TFState_DATA) {
-		TF_HandleReceivedMessage();
-		TF_ResetParser();
+    if (tf->len == 0 && tf->state == TFState_DATA) {
+        TF_HandleReceivedMessage(tf);
+        TF_ResetParser(tf);
     }
 }
 
 // Helper macros for the Compose functions
-// use variables: si - signed int, b - byte, outbuf - target buffer, pos - count of bytes in buffer
+// use variables: si - signed int, b - byte, outbuff - target buffer, pos - count of bytes in buffer
+
+/**
+ * Write a number to the output buffer.
+ *
+ * @param type - data type
+ * @param num - number to write
+ * @param xtra - extra callback run after each byte, 'b' now contains the byte.
+ */
 #define WRITENUM_BASE(type, num, xtra) \
     for (si = sizeof(type)-1; si>=0; si--) { \
         b = (uint8_t)((num) >> (si*8) & 0xFF); \
         outbuff[pos++] = b; \
         xtra; \
     }
+
+/**
+ * Do nothing
+ */
 #define _NOOP()
+
+/**
+ * Write a number without adding its bytes to the checksum
+ *
+ * @param type - data type
+ * @param num - number to write
+ */
 #define WRITENUM(type, num)       WRITENUM_BASE(type, num, _NOOP())
+
+/**
+ * Write a number AND add its bytes to the checksum
+ *
+ * @param type - data type
+ * @param num - number to write
+ */
 #define WRITENUM_CKSUM(type, num) WRITENUM_BASE(type, num, CKSUM_ADD(cksum, b))
 
 /**
@@ -632,16 +642,10 @@ void _TF_FN TF_AcceptChar(unsigned char c)
  * The frame can be sent using TF_WriteImpl(), or received by TF_Accept()
  *
  * @param outbuff - buffer to store the result in
- * @param msgid - message ID is stored here, if not NULL
- * @param type - message type
- * @param len - payload size in bytes
- * @param explicit_id - ID to use in the frame (8-bit)
- * @param use_expl_id - whether to use the previous param
+ * @param msg - message written to the buffer
  * @return nr of bytes in outbuff used by the frame, 0 on failure
  */
-static inline size_t _TF_FN TF_ComposeHead(uint8_t *outbuff, TF_ID *id_ptr,
-									   TF_TYPE type, TF_LEN data_len,
-									   TF_ID explicit_id, bool use_expl_id)
+static inline size_t _TF_FN TF_ComposeHead(TinyFrame *tf, uint8_t *outbuff, TF_Msg *msg)
 {
     int8_t si = 0; // signed small int
     uint8_t b = 0;
@@ -654,17 +658,17 @@ static inline size_t _TF_FN TF_ComposeHead(uint8_t *outbuff, TF_ID *id_ptr,
     CKSUM_RESET(cksum);
 
     // Gen ID
-	if (use_expl_id) {
-		id = explicit_id;
+    if (msg->is_response) {
+        id = msg->frame_id;
     }
     else {
-		id = (TF_ID) (tf.next_id++ & TF_ID_MASK);
-		if (tf.peer_bit) {
+        id = (TF_ID) (tf->next_id++ & TF_ID_MASK);
+        if (tf->peer_bit) {
             id |= TF_ID_PEERBIT;
         }
     }
 
-	if (id_ptr != NULL) *id_ptr = id;
+    msg->frame_id = id; // put the resolved ID into the message object for later use
 
     // --- Start ---
     CKSUM_RESET(cksum);
@@ -675,8 +679,8 @@ static inline size_t _TF_FN TF_ComposeHead(uint8_t *outbuff, TF_ID *id_ptr,
 #endif
 
     WRITENUM_CKSUM(TF_ID, id);
-	WRITENUM_CKSUM(TF_LEN, data_len);
-	WRITENUM_CKSUM(TF_TYPE, type);
+    WRITENUM_CKSUM(TF_LEN, msg->len);
+    WRITENUM_CKSUM(TF_TYPE, msg->type);
 
 #if TF_CKSUM_TYPE != TF_CKSUM_NONE
     CKSUM_FINALIZE(cksum);
@@ -696,7 +700,9 @@ static inline size_t _TF_FN TF_ComposeHead(uint8_t *outbuff, TF_ID *id_ptr,
  * @param cksum - checksum variable, used for all calls to TF_ComposeBody. Must be reset before first use! (CKSUM_RESET(cksum);)
  * @return nr of bytes in outbuff used
  */
-static size_t _TF_FN TF_ComposeBody(uint8_t *outbuff, const uint8_t *data, TF_LEN data_len, TF_CKSUM *cksum)
+static size_t _TF_FN TF_ComposeBody(uint8_t *outbuff,
+                                    const uint8_t *data, TF_LEN data_len,
+                                    TF_CKSUM *cksum)
 {
     TF_LEN i = 0;
     uint8_t b = 0;
@@ -731,104 +737,109 @@ static size_t _TF_FN TF_ComposeTail(uint8_t *outbuff, TF_CKSUM *cksum)
     return pos;
 }
 
-// send with listener
-static bool _TF_FN TF_SendFrame(TF_Msg *msg, TF_Listener listener, TF_TICKS timeout)
+/**
+ * Send a message
+ *
+ * @param tf - instance
+ * @param msg - message object
+ * @param listener - ID listener, or NULL
+ * @param timeout - listener timeout, 0 is none
+ * @return true if sent
+ */
+static bool _TF_FN TF_SendFrame(TinyFrame *tf, TF_Msg *msg, TF_Listener listener, TF_TICKS timeout)
 {
     size_t len = 0;
     size_t remain = 0;
     size_t sent = 0;
     TF_CKSUM cksum = 0;
 
-	TF_ClaimTx();
+    TF_ClaimTx(tf);
 
-	len = TF_ComposeHead(tf.sendbuf,
-					 &msg->frame_id,
-					 msg->type,
-					 msg->len,
-					 msg->frame_id,
-					 msg->is_response);
-
-	if (listener) TF_AddIdListener(msg, listener, timeout);
+    len = TF_ComposeHead(tf, tf->sendbuf, msg);
+    if (listener) TF_AddIdListener(tf, msg, listener, timeout);
 
     CKSUM_RESET(cksum);
 
     remain = msg->len;
     while (remain > 0) {
         size_t chunk = TF_MIN(TF_SENDBUF_LEN - len, remain);
-		len += TF_ComposeBody(tf.sendbuf+len, msg->data+sent, (TF_LEN) chunk, &cksum);
+        len += TF_ComposeBody(tf->sendbuf+len, msg->data+sent, (TF_LEN) chunk, &cksum);
         remain -= chunk;
         sent += chunk;
 
         // Flush if the buffer is full and we have more to send
         if (remain > 0 && len == TF_SENDBUF_LEN) {
-			TF_WriteImpl((const uint8_t *) tf.sendbuf, len);
+            TF_WriteImpl(tf, (const uint8_t *) tf->sendbuf, len);
             len = 0;
         }
     }
 
+    // Checksum only if message had a body
+    if (msg->len > 0) {
         // Flush if checksum wouldn't fit in the buffer
         if (TF_SENDBUF_LEN - len < sizeof(TF_CKSUM)) {
-		TF_WriteImpl((const uint8_t *) tf.sendbuf, len);
+            TF_WriteImpl(tf, (const uint8_t *) tf->sendbuf, len);
             len = 0;
         }
 
         // Add checksum, flush what remains to be sent
-	len += TF_ComposeTail(tf.sendbuf+len, &cksum);
-	TF_WriteImpl((const uint8_t *) tf.sendbuf, len);
+        len += TF_ComposeTail(tf->sendbuf + len, &cksum);
+    }
 
-	TF_ReleaseTx();
+    TF_WriteImpl(tf, (const uint8_t *) tf->sendbuf, len);
+    TF_ReleaseTx(tf);
 
     return true;
 }
 
-// send without listener
-bool _TF_FN TF_Send(TF_Msg *msg)
+/** send without listener */
+bool _TF_FN TF_Send(TinyFrame *tf, TF_Msg *msg)
 {
-	return TF_SendFrame(msg, NULL, 0);
+    return TF_SendFrame(tf, msg, NULL, 0);
 }
 
-// send without listener and struct
-bool _TF_FN TF_SendSimple(TF_TYPE type, const uint8_t *data, TF_LEN len)
+/** send without listener and struct */
+bool _TF_FN TF_SendSimple(TinyFrame *tf, TF_TYPE type, const uint8_t *data, TF_LEN len)
 {
     TF_Msg msg;
     TF_ClearMsg(&msg);
     msg.type = type;
     msg.data = data;
     msg.len = len;
-	return TF_Send(&msg);
+    return TF_Send(tf, &msg);
 }
 
-// send without listener and struct
-bool _TF_FN TF_QuerySimple(TF_TYPE type, const uint8_t *data, TF_LEN len, TF_Listener listener, TF_TICKS timeout, void *userdata)
+/** send with a listener waiting for a reply, without the struct */
+bool _TF_FN TF_QuerySimple(TinyFrame *tf, TF_TYPE type, const uint8_t *data, TF_LEN len, TF_Listener listener, TF_TICKS timeout)
 {
     TF_Msg msg;
     TF_ClearMsg(&msg);
     msg.type = type;
     msg.data = data;
     msg.len = len;
-	msg.userdata = userdata;
-	return TF_SendFrame(&msg, listener, timeout);
+    return TF_SendFrame(tf, &msg, listener, timeout);
 }
 
-// send with listener
-bool _TF_FN TF_Query(TF_Msg *msg, TF_Listener listener, TF_TICKS timeout)
+/** send with a listener waiting for a reply */
+bool _TF_FN TF_Query(TinyFrame *tf, TF_Msg *msg, TF_Listener listener, TF_TICKS timeout)
 {
-	return TF_SendFrame(msg, listener, timeout);
+    return TF_SendFrame(tf, msg, listener, timeout);
 }
 
-// Like TF_Send, but with explicit frame ID
-bool _TF_FN TF_Respond(TF_Msg *msg)
+/** Like TF_Send, but with explicit frame ID (set inside the msg object), use for responses */
+bool _TF_FN TF_Respond(TinyFrame *tf, TF_Msg *msg)
 {
     msg->is_response = true;
-	return TF_Send(msg);
+    return TF_Send(tf, msg);
 }
 
-bool _TF_FN TF_RenewIdListener(TF_ID id)
+/** Externally renew an ID listener */
+bool _TF_FN TF_RenewIdListener(TinyFrame *tf, TF_ID id)
 {
     TF_COUNT i;
-	IdListener *lst;
-	for (i = 0; i < tf.count_id_lst; i++) {
-		lst = &tf.id_listeners[i];
+    struct TF_IdListener_ *lst;
+    for (i = 0; i < tf->count_id_lst; i++) {
+        lst = &tf->id_listeners[i];
         // test if live & matching
         if (lst->fn != NULL && lst->id == id) {
             renew_id_listener(lst);
@@ -839,34 +850,40 @@ bool _TF_FN TF_RenewIdListener(TF_ID id)
 }
 
 /** Timebase hook - for timeouts */
-void _TF_FN TF_Tick(void)
+void _TF_FN TF_Tick(TinyFrame *tf)
 {
     TF_COUNT i = 0;
-	IdListener *lst;
+    struct TF_IdListener_ *lst;
 
     // increment parser timeout (timeout is handled when receiving next byte)
-	if (tf.parser_timeout_ticks < TF_PARSER_TIMEOUT_TICKS) {
-		tf.parser_timeout_ticks++;
+    if (tf->parser_timeout_ticks < TF_PARSER_TIMEOUT_TICKS) {
+        tf->parser_timeout_ticks++;
     }
 
     // decrement and expire ID listeners
-	for (i = 0; i < tf.count_id_lst; i++) {
-		lst = &tf.id_listeners[i];
+    for (i = 0; i < tf->count_id_lst; i++) {
+        lst = &tf->id_listeners[i];
         if (!lst->fn || lst->timeout == 0) continue;
         // count down...
         if (--lst->timeout == 0) {
             // Listener has expired
-			cleanup_id_listener(i, lst);
+            cleanup_id_listener(tf, i, lst);
         }
     }
 }
 
-void __attribute__((weak)) TF_ClaimTx(void)
+/** Default impl for claiming write mutex; can be specific to the instance */
+void __attribute__((weak)) TF_ClaimTx(TinyFrame *tf)
 {
+    (void) tf;
+
     // do nothing
 }
 
-void __attribute__((weak)) TF_ReleaseTx(void)
+/** Default impl for releasing write mutex; can be specific to the instance */
+void __attribute__((weak)) TF_ReleaseTx(TinyFrame *tf)
 {
+    (void) tf;
+
     // do nothing
 }

TinyFrame.h

@@ -10,12 +10,13 @@
  * Upstream URL: https://github.com/MightyPork/TinyFrame
  */
 
-#define TF_VERSION "1.2.0"
+#define TF_VERSION "2.0.4"
 
 //---------------------------------------------------------------------------
 #include <stdint.h>  // for uint8_t etc
 #include <stdbool.h> // for bool
-#include <stdlib.h>  // for NULL
+#include <stddef.h>  // for NULL
+#include <string.h>  // for memset()
 //---------------------------------------------------------------------------
 
 // Select checksum type (0 = none, 8 = ~XOR, 16 = CRC16 0x8005, 32 = CRC32)
@@ -24,7 +25,7 @@
 #define TF_CKSUM_CRC16 16
 #define TF_CKSUM_CRC32 32
 
-#include <TF_Config.h>
+#include "TF_Config.h"
 
 //region Resolve data types
 
@@ -74,17 +75,6 @@
 #error Bad value for TF_CKSUM_TYPE, must be 8, 16 or 32
 #endif
 
-
-// Bytes added to TF_MAX_PAYLOAD for the send buffer size.
-#define TF_OVERHEAD_BYTES \
-	(1*TF_USE_SOF_BYTE + \
-		sizeof(TF_ID) + \
-		sizeof(TF_LEN) + \
-		sizeof(TF_CKSUM) + \
-		sizeof(TF_TYPE) + \
-		sizeof(TF_CKSUM) \
-	)
-
 //endregion
 
 //---------------------------------------------------------------------------
@@ -98,9 +88,10 @@
 /** Peer bit enum (used for init) */
 typedef enum {
     TF_SLAVE = 0,
-	TF_MASTER,
+    TF_MASTER = 1,
 } TF_Peer;
 
+/** Response from listeners */
 typedef enum {
     TF_NEXT = 0,   //!< Not handled, let other listeners handle it
     TF_STAY = 1,   //!< Handled, stay
@@ -124,15 +115,11 @@ typedef struct _TF_MSG_STRUCT_ {
  */
 static inline void TF_ClearMsg(TF_Msg *msg)
 {
-	msg->frame_id = 0;
-	msg->is_response = false;
-	msg->type = 0;
-	msg->data = NULL;
-	msg->len = 0;
-	msg->userdata = NULL;
-	msg->userdata2 = NULL;
+    memset(msg, 0, sizeof(TF_Msg));
 }
 
+typedef struct TinyFrame_ TinyFrame;
+
 /**
  * TinyFrame Type Listener callback
  *
@@ -142,21 +129,124 @@ static inline void TF_ClearMsg(TF_Msg *msg)
  * @param len - number of bytes in the buffer
  * @return listener result
  */
-typedef TF_Result (*TF_Listener)(TF_Msg *msg);
+typedef TF_Result (*TF_Listener)(TinyFrame *tf, TF_Msg *msg);
+
+// -------------------------------------------------------------------
+
+// region Internal
+
+enum TFState_ {
+    TFState_SOF = 0,      //!< Wait for SOF
+    TFState_LEN,          //!< Wait for Number Of Bytes
+    TFState_HEAD_CKSUM,   //!< Wait for header Checksum
+    TFState_ID,           //!< Wait for ID
+    TFState_TYPE,         //!< Wait for message type
+    TFState_DATA,         //!< Receive payload
+    TFState_DATA_CKSUM    //!< Wait for Checksum
+};
+
+struct TF_IdListener_ {
+    TF_ID id;
+    TF_Listener fn;
+    TF_TICKS timeout;     // nr of ticks remaining to disable this listener
+    TF_TICKS timeout_max; // the original timeout is stored here
+    void *userdata;
+    void *userdata2;
+};
+
+struct TF_TypeListener_ {
+    TF_TYPE type;
+    TF_Listener fn;
+};
+
+struct TF_GenericListener_ {
+    TF_Listener fn;
+};
+
+/**
+ * Frame parser internal state.
+ */
+struct TinyFrame_ {
+    /* Public user data */
+    void *userdata;
+    uint32_t usertag;
+
+    // --- the rest of the struct is internal, do not access directly ---
+
+    /* Own state */
+    TF_Peer peer_bit;       //!< Own peer bit (unqiue to avoid msg ID clash)
+    TF_ID next_id;          //!< Next frame / frame chain ID
+
+    /* Parser state */
+    enum TFState_ state;
+    TF_TICKS parser_timeout_ticks;
+    TF_ID id;               //!< Incoming packet ID
+    TF_LEN len;             //!< Payload length
+    uint8_t data[TF_MAX_PAYLOAD_RX]; //!< Data byte buffer
+    TF_LEN rxi;             //!< Field size byte counter
+    TF_CKSUM cksum;         //!< Checksum calculated of the data stream
+    TF_CKSUM ref_cksum;     //!< Reference checksum read from the message
+    TF_TYPE type;           //!< Collected message type number
+    bool discard_data;      //!< Set if (len > TF_MAX_PAYLOAD) to read the frame, but ignore the data.
+
+    /* --- Callbacks --- */
+
+    /* Transaction callbacks */
+    struct TF_IdListener_ id_listeners[TF_MAX_ID_LST];
+    struct TF_TypeListener_ type_listeners[TF_MAX_TYPE_LST];
+    struct TF_GenericListener_ generic_listeners[TF_MAX_GEN_LST];
+
+    // Those counters are used to optimize look-up times.
+    // They point to the highest used slot number,
+    // or close to it, depending on the removal order.
+    TF_COUNT count_id_lst;
+    TF_COUNT count_type_lst;
+    TF_COUNT count_generic_lst;
+
+    // Buffer for building frames
+    uint8_t sendbuf[TF_SENDBUF_LEN];
+};
+
+// endregion
+
+// -------------------------------------------------------------------
 
 /**
  * Initialize the TinyFrame engine.
- * This can also be used to completely reset it (removing all listeners etc)
+ * This can also be used to completely reset it (removing all listeners etc).
+ *
+ * The field .userdata (or .usertag) can be used to identify different instances
+ * in the TF_WriteImpl() function etc. Set this field after the init.
+ *
+ * This function is a wrapper around TF_InitStatic that calls malloc() to obtain
+ * the instance.
  *
  * @param peer_bit - peer bit to use for self
  */
-void TF_Init(TF_Peer peer_bit);
+TinyFrame *TF_Init(TF_Peer peer_bit);
+
+
+/**
+ * Initialize the TinyFrame engine using a statically allocated instance struct.
+ *
+ * The .userdata / .usertag field is preserved when TF_InitStatic is called.
+ *
+ * @param peer_bit - peer bit to use for self
+ */
+void TF_InitStatic(TinyFrame *tf, TF_Peer peer_bit);
+
+/**
+ * De-init the dynamically allocated TF instance
+ *
+ * @param tf
+ */
+void TF_DeInit(TinyFrame *tf);
 
 /**
  * Reset the frame parser state machine.
  * This does not affect registered listeners.
  */
-void TF_ResetParser(void);
+void TF_ResetParser(TinyFrame *tf);
 
 /**
  * Register a frame type listener.
@@ -166,14 +256,14 @@ void TF_ResetParser(void);
  * @param timeout - timeout in ticks to auto-remove the listener (0 = keep forever)
  * @return slot index (for removing), or TF_ERROR (-1)
  */
-bool TF_AddIdListener(TF_Msg *msg, TF_Listener cb, TF_TICKS timeout);
+bool TF_AddIdListener(TinyFrame *tf, TF_Msg *msg, TF_Listener cb, TF_TICKS timeout);
 
 /**
  * Remove a listener by the message ID it's registered for
  *
  * @param frame_id - the frame we're listening for
  */
-bool TF_RemoveIdListener(TF_ID frame_id);
+bool TF_RemoveIdListener(TinyFrame *tf, TF_ID frame_id);
 
 /**
  * Register a frame type listener.
@@ -182,14 +272,14 @@ bool TF_RemoveIdListener(TF_ID frame_id);
  * @param cb - callback
  * @return slot index (for removing), or TF_ERROR (-1)
  */
-bool TF_AddTypeListener(TF_TYPE frame_type, TF_Listener cb);
+bool TF_AddTypeListener(TinyFrame *tf, TF_TYPE frame_type, TF_Listener cb);
 
 /**
  * Remove a listener by type.
  *
  * @param type - the type it's registered for
  */
-bool TF_RemoveTypeListener(TF_TYPE type);
+bool TF_RemoveTypeListener(TinyFrame *tf, TF_TYPE type);
 
 /**
  * Register a generic listener.
@@ -197,14 +287,14 @@ bool TF_RemoveTypeListener(TF_TYPE type);
  * @param cb - callback
  * @return slot index (for removing), or TF_ERROR (-1)
  */
-bool TF_AddGenericListener(TF_Listener cb);
+bool TF_AddGenericListener(TinyFrame *tf, TF_Listener cb);
 
 /**
  * Remove a generic listener by function pointer
  *
  * @param cb - callback function to remove
  */
-bool TF_RemoveGenericListener(TF_Listener cb);
+bool TF_RemoveGenericListener(TinyFrame *tf, TF_Listener cb);
 
 /**
  * Send a frame, no listener
@@ -212,17 +302,12 @@ bool TF_RemoveGenericListener(TF_Listener cb);
  * @param msg - message struct. ID is stored in the frame_id field
  * @return success
  */
-bool TF_Send(TF_Msg *msg);
+bool TF_Send(TinyFrame *tf, TF_Msg *msg);
 
 /**
  * Like TF_Send, but without the struct
  */
-bool TF_SendSimple(TF_TYPE type, const uint8_t *data, TF_LEN len);
-
-/**
- * Like TF_Query, but without the struct
- */
-bool TF_QuerySimple(TF_TYPE type, const uint8_t *data, TF_LEN len, TF_Listener listener, TF_TICKS timeout, void *userdata);
+bool TF_SendSimple(TinyFrame *tf, TF_TYPE type, const uint8_t *data, TF_LEN len);
 
 /**
  * Send a frame, and optionally attach an ID listener.
@@ -232,7 +317,13 @@ bool TF_QuerySimple(TF_TYPE type, const uint8_t *data, TF_LEN len, TF_Listener l
  * @param timeout - listener expiry time in ticks
  * @return success
  */
-bool TF_Query(TF_Msg *msg, TF_Listener listener, TF_TICKS timeout);
+bool TF_Query(TinyFrame *tf, TF_Msg *msg, TF_Listener listener, TF_TICKS timeout);
+
+/**
+ * Like TF_Query, but without the struct
+ */
+bool TF_QuerySimple(TinyFrame *tf, TF_TYPE type, const uint8_t *data, TF_LEN len,
+                    TF_Listener listener, TF_TICKS timeout);
 
 /**
  * Send a response to a received message.
@@ -240,15 +331,15 @@ bool TF_Query(TF_Msg *msg, TF_Listener listener, TF_TICKS timeout);
  * @param msg - message struct. ID is read from frame_id. set ->renew to reset listener timeout
  * @return success
  */
-bool TF_Respond(TF_Msg *msg);
+bool TF_Respond(TinyFrame *tf, TF_Msg *msg);
 
 /**
- * Renew ID listener timeout
+ * Renew an ID listener timeout externally (as opposed to by returning TF_RENEW from the ID listener)
  *
  * @param id - listener ID to renew
  * @return true if listener was found and renewed
  */
-bool TF_RenewIdListener(TF_ID id);
+bool TF_RenewIdListener(TinyFrame *tf, TF_ID id);
 
 /**
  * Accept incoming bytes & parse frames
@@ -256,21 +347,14 @@ bool TF_RenewIdListener(TF_ID id);
  * @param buffer - byte buffer to process
  * @param count - nr of bytes in the buffer
  */
-void TF_Accept(const uint8_t *buffer, size_t count);
+void TF_Accept(TinyFrame *tf, const uint8_t *buffer, size_t count);
 
 /**
  * Accept a single incoming byte
  *
  * @param c - a received char
  */
-void TF_AcceptChar(uint8_t c);
-
-/**
- * 'Write bytes' function that sends data to UART
- *
- * ! Implement this in your application code !
- */
-extern void TF_WriteImpl(const uint8_t *buff, size_t len);
+void TF_AcceptChar(TinyFrame *tf, uint8_t c);
 
 /**
  * This function should be called periodically.
@@ -280,12 +364,21 @@ extern void TF_WriteImpl(const uint8_t *buff, size_t len);
  *
  * (suggestion - call this in a SysTick handler)
  */
-void TF_Tick(void);
+void TF_Tick(TinyFrame *tf);
+
+// --- TO BE IMPLEMENTED BY USER ---
+
+/**
+ * 'Write bytes' function that sends data to UART
+ *
+ * ! Implement this in your application code !
+ */
+extern void TF_WriteImpl(TinyFrame *tf, const uint8_t *buff, size_t len);
 
 /** Claim the TX interface before composing and sending a frame */
-extern void TF_ClaimTx(void);
+extern void TF_ClaimTx(TinyFrame *tf);
 
 /** Free the TX interface after composing and sending a frame */
-extern void TF_ReleaseTx(void);
+extern void TF_ReleaseTx(TinyFrame *tf);
 
 #endif

demo/demo.c

@@ -7,6 +7,7 @@
 // those magic defines are needed so we can use clone()
 #define _GNU_SOURCE
 #define __USE_GNU
+
 #include <sched.h>
 
 #include <unistd.h>
@@ -15,10 +16,14 @@
 #include <string.h>
 #include <arpa/inet.h>
 #include <signal.h>
+#include <malloc.h>
+#include <stdlib.h>
 
 volatile int sockfd = -1;
 volatile bool conn_disband = false;
 
+TinyFrame *demo_tf;
+
 /**
  * Close socket
  */
@@ -34,7 +39,7 @@ void demo_disconn(void)
  * @param buff
  * @param len
  */
-void TF_WriteImpl(const uint8_t *buff, size_t len)
+void TF_WriteImpl(TinyFrame *tf, const uint8_t *buff, size_t len)
 {
     printf("\033[32mTF_WriteImpl - sending frame:\033[0m\n");
     dumpFrame(buff, len);
@@ -42,7 +47,8 @@ void TF_WriteImpl(const uint8_t *buff, size_t len)
 
     if (sockfd != -1) {
         write(sockfd, buff, len);
-	} else {
+    }
+    else {
         printf("\nNo peer!\n");
     }
 }
@@ -91,7 +97,7 @@ static int demo_client(void* unused)
     while ((n = read(sockfd, recvBuff, sizeof(recvBuff) - 1)) > 0) {
         printf("\033[36m--- RX %ld bytes ---\033[0m\n", n);
         dumpFrame(recvBuff, (size_t) n);
-		TF_Accept(recvBuff, (size_t) n);
+        TF_Accept(demo_tf, recvBuff, (size_t) n);
     }
     return 0;
 }
@@ -143,7 +149,7 @@ static int demo_server(void* unused)
         while ((n = read(sockfd, recvBuff, sizeof(recvBuff) - 1)) > 0 && !conn_disband) {
             printf("\033[36m--- RX %ld bytes ---\033[0m\n", n);
             dumpFrame(recvBuff, n);
-			TF_Accept(recvBuff, (size_t) n);
+            TF_Accept(demo_tf, recvBuff, (size_t) n);
         }
 
         if (n < 0) {
@@ -205,7 +211,8 @@ void demo_init(TF_Peer peer)
     // CLONE_FILES --- share stdout and stderr
     if (peer == TF_MASTER) {
         retc = clone(&demo_client, (char *) stack + 8192, CLONE_VM | CLONE_FILES, 0);
-	} else {
+    }
+    else {
         retc = clone(&demo_server, (char *) stack + 8192, CLONE_VM | CLONE_FILES, 0);
     }
 

demo/demo.h

@@ -11,6 +11,8 @@
 
 #define PORT 9798
 
+extern TinyFrame *demo_tf;
+
 /** Sleep and wait for ^C */
 void demo_sleep(void);
 

demo/multipart_tx/Makefile

@@ -1,11 +1,12 @@
 CFILES=../utils.c ../../TinyFrame.c
 INCLDIRS=-I. -I.. -I../..
-CFLAGS=-O0 -ggdb --std=gnu99 -Wno-main -Wall -Wextra $(CFILES) $(INCLDIRS)
+CFLAGS=-O0 -ggdb --std=gnu99 -Wno-main -Wall -Wno-unused -Wextra $(CFILES) $(INCLDIRS)
+
+
+build: test.bin
 
 run: test.bin
 	./test.bin
 
-build: test.bin
-
 test.bin: test.c $(CFILES)
 	gcc test.c $(CFLAGS) -o test.bin

demo/multipart_tx/test.c

@@ -3,29 +3,32 @@
 #include "../../TinyFrame.h"
 #include "../utils.h"
 
+TinyFrame *demo_tf;
+
 extern const char *romeo;
 
 /**
  * This function should be defined in the application code.
  * It implements the lowest layer - sending bytes to UART (or other)
  */
-void TF_WriteImpl(const uint8_t *buff, size_t len)
+void TF_WriteImpl(TinyFrame *tf, const uint8_t *buff, size_t len)
 {
     printf("--------------------\n");
     printf("\033[32mTF_WriteImpl - sending frame:\033[0m\n");
     dumpFrame(buff, len);
 
     // Send it back as if we received it
-	TF_Accept(buff, len);
+    TF_Accept(tf, buff, len);
 }
 
 /** An example listener function */
-TF_Result myListener(TF_Msg *msg)
+TF_Result myListener(TinyFrame *tf, TF_Msg *msg)
 {
     dumpFrameInfo(msg);
-  if (strcmp(msg->data, romeo) == 0) {
+    if (strcmp((const char *) msg->data, romeo) == 0) {
         printf("FILE TRANSFERRED OK!\r\n");
-  } else {
+    }
+    else {
         printf("FAIL!!!!\r\n");
     }
     return TF_STAY;
@@ -36,16 +39,16 @@ void main(void)
     TF_Msg msg;
 
     // Set up the TinyFrame library
-	TF_Init(TF_MASTER); // 1 = master, 0 = slave
-	TF_AddGenericListener(myListener);
+    demo_tf = TF_Init(TF_MASTER); // 1 = master, 0 = slave
+    TF_AddGenericListener(demo_tf, myListener);
 
     printf("------ Simulate sending a LOOONG message --------\n");
 
     TF_ClearMsg(&msg);
     msg.type = 0x22;
     msg.data = (pu8) romeo;
-	msg.len = strlen(romeo);
-	TF_Send(&msg);
+    msg.len = (TF_LEN) strlen(romeo);
+    TF_Send(demo_tf, &msg);
 }
 
 const char *romeo = "THE TRAGEDY OF ROMEO AND JULIET\n"

demo/simple/Makefile

@@ -1,6 +1,6 @@
 CFILES=../utils.c ../../TinyFrame.c
 INCLDIRS=-I. -I.. -I../..
-CFLAGS=-O0 -ggdb --std=gnu99 -Wno-main -Wall -Wextra $(CFILES) $(INCLDIRS)
+CFLAGS=-O0 -ggdb --std=gnu99 -Wno-main -Wno-unused -Wall -Wextra $(CFILES) $(INCLDIRS)
 
 run: test.bin
 	./test.bin

demo/simple/test.c

@@ -3,29 +3,30 @@
 #include "../../TinyFrame.h"
 #include "../utils.h"
 
+TinyFrame *demo_tf;
 
 /**
  * This function should be defined in the application code.
  * It implements the lowest layer - sending bytes to UART (or other)
  */
-void TF_WriteImpl(const uint8_t *buff, size_t len)
+void TF_WriteImpl(TinyFrame *tf, const uint8_t *buff, size_t len)
 {
     printf("--------------------\n");
     printf("\033[32mTF_WriteImpl - sending frame:\033[0m\n");
     dumpFrame(buff, len);
 
     // Send it back as if we received it
-	TF_Accept(buff, len);
+    TF_Accept(tf, buff, len);
 }
 
 /** An example listener function */
-TF_Result myListener(TF_Msg *msg)
+TF_Result myListener(TinyFrame *tf, TF_Msg *msg)
 {
     dumpFrameInfo(msg);
     return TF_STAY;
 }
 
-TF_Result testIdListener(TF_Msg *msg)
+TF_Result testIdListener(TinyFrame *tf, TF_Msg *msg)
 {
     printf("OK - ID Listener triggered for msg!\n");
     dumpFrameInfo(msg);
@@ -38,8 +39,8 @@ void main(void)
     const char *longstr = "Lorem ipsum dolor sit amet.";
 
     // Set up the TinyFrame library
-	TF_Init(TF_MASTER); // 1 = master, 0 = slave
-	TF_AddGenericListener(myListener);
+    demo_tf = TF_Init(TF_MASTER); // 1 = master, 0 = slave
+    TF_AddGenericListener(demo_tf, myListener);
 
     printf("------ Simulate sending a message --------\n");
 
@@ -47,19 +48,19 @@ void main(void)
     msg.type = 0x22;
     msg.data = (pu8) "Hello TinyFrame";
     msg.len = 16;
-	TF_Send(&msg);
+    TF_Send(demo_tf, &msg);
 
     msg.type = 0x33;
     msg.data = (pu8) longstr;
     msg.len = (TF_LEN) (strlen(longstr) + 1); // add the null byte
-	TF_Send(&msg);
+    TF_Send(demo_tf, &msg);
 
     msg.type = 0x44;
     msg.data = (pu8) "Hello2";
     msg.len = 7;
-	TF_Send(&msg);
+    TF_Send(demo_tf, &msg);
 
     msg.len = 0;
     msg.type = 0x77;
-	TF_Query(&msg, testIdListener, 0);
+    TF_Query(demo_tf, &msg, testIdListener, 0);
 }

demo/socket_demo/Makefile

@@ -1,6 +1,6 @@
 CFILES=../demo.c ../utils.c ../../TinyFrame.c
 INCLDIRS=-I. -I.. -I../..
-CFLAGS=-O0 -ggdb --std=gnu99 -Wno-main -Wall -Wextra $(CFILES) $(INCLDIRS)
+CFLAGS=-O0 -ggdb --std=gnu99 -Wno-main -Wall -Wno-unused -Wextra $(CFILES) $(INCLDIRS)
 
 build: master.bin slave.bin
 

demo/socket_demo/master.c

@@ -5,14 +5,14 @@
 #include <stdio.h>
 #include "../demo.h"
 
-TF_Result testIdListener(TF_Msg *msg)
+TF_Result testIdListener(TinyFrame *tf, TF_Msg *msg)
 {
     printf("testIdListener()\n");
     dumpFrameInfo(msg);
     return TF_CLOSE;
 }
 
-TF_Result testGenericListener(TF_Msg *msg)
+TF_Result testGenericListener(TinyFrame *tf, TF_Msg *msg)
 {
     printf("testGenericListener()\n");
     dumpFrameInfo(msg);
@@ -21,15 +21,15 @@ TF_Result testGenericListener(TF_Msg *msg)
 
 int main(void)
 {
-	TF_Init(TF_MASTER);
-	TF_AddGenericListener(testGenericListener);
+    demo_tf = TF_Init(TF_MASTER);
+    TF_AddGenericListener(demo_tf, testGenericListener);
 
     demo_init(TF_MASTER);
 
-	TF_SendSimple(1, (pu8)"Ahoj", 5);
-	TF_SendSimple(1, (pu8)"Hello", 6);
+    TF_SendSimple(demo_tf, 1, (pu8) "Ahoj", 5);
+    TF_SendSimple(demo_tf, 1, (pu8) "Hello", 6);
 
-	TF_QuerySimple(2, (pu8)"Query!", 6, testIdListener, 0, NULL);
+    TF_QuerySimple(demo_tf, 2, (pu8) "Query!", 6, testIdListener, 0);
 
     demo_sleep();
 }

demo/socket_demo/slave.c

@@ -4,38 +4,37 @@
 
 #include <stdio.h>
 #include "../demo.h"
-#include <memory.h>
 
-TF_Result helloListener(TF_Msg *msg)
+TF_Result helloListener(TinyFrame *tf, TF_Msg *msg)
 {
     printf("helloListener()\n");
     dumpFrameInfo(msg);
     return TF_STAY;
 }
 
-TF_Result replyListener(TF_Msg *msg)
+TF_Result replyListener(TinyFrame *tf, TF_Msg *msg)
 {
     printf("replyListener()\n");
     dumpFrameInfo(msg);
     msg->data = (const uint8_t *) "response to query";
     msg->len = (TF_LEN) strlen((const char *) msg->data);
-	TF_Respond(msg);
+    TF_Respond(tf, msg);
 
     // unsolicited reply - will not be handled by the ID listener, which is already gone
     msg->data = (const uint8_t *) "SPAM";
     msg->len = 5;
-	TF_Respond(msg);
+    TF_Respond(tf, msg);
 
     // unrelated message
-	TF_SendSimple(77, (const uint8_t *) "NAZDAR", 7);
+    TF_SendSimple(tf, 77, (const uint8_t *) "NAZDAR", 7);
     return TF_STAY;
 }
 
 int main(void)
 {
-	TF_Init(TF_SLAVE);
-	TF_AddTypeListener(1, helloListener);
-	TF_AddTypeListener(2, replyListener);
+    demo_tf = TF_Init(TF_SLAVE);
+    TF_AddTypeListener(demo_tf, 1, helloListener);
+    TF_AddTypeListener(demo_tf, 2, replyListener);
 
     demo_init(TF_SLAVE);
     demo_sleep();

demo/utils.c

@@ -13,7 +13,8 @@ void dumpFrame(const uint8_t *buff, size_t len)
         printf("%3u \033[94m%02X\033[0m", buff[i], buff[i]);
         if (buff[i] >= 0x20 && buff[i] < 127) {
             printf(" %c", buff[i]);
-		} else {
+        }
+        else {
             printf(" \033[31m.\033[0m");
         }
         printf("\n");

utilities/payload_builder.c

@@ -0,0 +1,100 @@
+#include <string.h>
+#include "payload_builder.h"
+
+#define pb_check_capacity(pb, needed) \
+    if ((pb)->current + (needed) > (pb)->end) { \
+        if ((pb)->full_handler == NULL || !(pb)->full_handler(pb, needed)) (pb)->ok = 0; \
+    }
+
+/** Write from a buffer */
+bool pb_buf(PayloadBuilder *pb, const uint8_t *buf, uint32_t len)
+{
+    pb_check_capacity(pb, len);
+    if (!pb->ok) return false;
+
+    memcpy(pb->current, buf, len);
+    pb->current += len;
+    return true;
+}
+
+/** Write s zero terminated string */
+bool pb_string(PayloadBuilder *pb, const char *str)
+{
+    uint32_t len = (uint32_t) strlen(str);
+    pb_check_capacity(pb, len+1);
+    if (!pb->ok) return false;
+
+    memcpy(pb->current, str, len+1);
+    pb->current += len+1;
+    return true;
+}
+
+/** Write uint8_t to the buffer */
+bool pb_u8(PayloadBuilder *pb, uint8_t byte)
+{
+    pb_check_capacity(pb, 1);
+    if (!pb->ok) return false;
+
+    *pb->current++ = byte;
+    return true;
+}
+
+/** Write uint16_t to the buffer. */
+bool pb_u16(PayloadBuilder *pb, uint16_t word)
+{
+    pb_check_capacity(pb, 2);
+    if (!pb->ok) return false;
+
+    if (pb->bigendian) {
+        *pb->current++ = (uint8_t) ((word >> 8) & 0xFF);
+        *pb->current++ = (uint8_t) (word & 0xFF);
+    } else {
+        *pb->current++ = (uint8_t) (word & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 8) & 0xFF);
+    }
+    return true;
+}
+
+/** Write uint32_t to the buffer. */
+bool pb_u32(PayloadBuilder *pb, uint32_t word)
+{
+    pb_check_capacity(pb, 4);
+    if (!pb->ok) return false;
+
+    if (pb->bigendian) {
+        *pb->current++ = (uint8_t) ((word >> 24) & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 16) & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 8) & 0xFF);
+        *pb->current++ = (uint8_t) (word & 0xFF);
+    } else {
+        *pb->current++ = (uint8_t) (word & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 8) & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 16) & 0xFF);
+        *pb->current++ = (uint8_t) ((word >> 24) & 0xFF);
+    }
+    return true;
+}
+
+/** Write int8_t to the buffer. */
+bool pb_i8(PayloadBuilder *pb, int8_t byte)
+{
+    return pb_u8(pb, ((union conv8){.i8 = byte}).u8);
+}
+
+/** Write int16_t to the buffer. */
+bool pb_i16(PayloadBuilder *pb, int16_t word)
+{
+    return pb_u16(pb, ((union conv16){.i16 = word}).u16);
+}
+
+/** Write int32_t to the buffer. */
+bool pb_i32(PayloadBuilder *pb, int32_t word)
+{
+    return pb_u32(pb, ((union conv32){.i32 = word}).u32);
+}
+
+/** Write 4-byte float to the buffer. */
+bool pb_float(PayloadBuilder *pb, float f)
+{
+    return pb_u32(pb, ((union conv32){.f32 = f}).u32);
+}

utilities/payload_builder.h

@@ -0,0 +1,110 @@
+#ifndef PAYLOAD_BUILDER_H
+#define PAYLOAD_BUILDER_H
+
+/**
+ * PayloadBuilder, part of the TinyFrame utilities collection
+ * 
+ * (c) Ondřej Hruška, 2014-2017. MIT license.
+ * 
+ * The builder supports big and little endian which is selected when 
+ * initializing it or by accessing the bigendian struct field.
+ * 
+ * This module helps you with building payloads (not only for TinyFrame)
+ *
+ * The builder performs bounds checking and calls the provided handler when 
+ * the requested write wouldn't fit. Use the handler to realloc / flush the buffer
+ * or report an error.
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include "type_coerce.h"
+
+typedef struct PayloadBuilder_ PayloadBuilder;
+
+/**
+ * Full buffer handler. 
+ * 
+ * 'needed' more bytes should be written but the end of the buffer was reached.
+ * 
+ * Return true if the problem was solved (e.g. buffer was flushed and the 
+ * 'current' pointer moved to the beginning).
+ * 
+ * If false is returned, the 'ok' flag on the struct is set to false
+ * and all following writes are discarded.
+ */
+typedef bool (*pb_full_handler)(PayloadBuilder *pb, uint32_t needed);
+
+struct PayloadBuilder_ {
+    uint8_t *start;   //!< Pointer to the beginning of the buffer
+    uint8_t *current; //!< Pointer to the next byte to be read
+    uint8_t *end;     //!< Pointer to the end of the buffer (start + length)
+    pb_full_handler full_handler; //!< Callback for buffer overrun
+    bool bigendian;   //!< Flag to use big-endian parsing
+    bool ok;          //!< Indicates that all reads were successful
+};
+
+// --- initializer helper macros ---
+
+/** Start the builder. */
+#define pb_start_e(buf, capacity, bigendian, full_handler) ((PayloadBuilder){buf, buf, (buf)+(capacity), full_handler, bigendian, 1})
+
+/** Start the builder in big-endian mode */
+#define pb_start_be(buf, capacity, full_handler) pb_start_e(buf, capacity, 1, full_handler)
+
+/** Start the builder in little-endian mode */
+#define pb_start_le(buf, capacity, full_handler) pb_start_e(buf, capacity, 0, full_handler)
+
+/** Start the parser in little-endian mode (default) */
+#define pb_start(buf, capacity, full_handler) pb_start_le(buf, capacity, full_handler)
+
+// --- utilities ---
+
+/** Get already used bytes count */
+#define pb_length(pb) ((pb)->current - (pb)->start)
+
+/** Reset the current pointer to start */
+#define pb_rewind(pb) do { pb->current = pb->start; } while (0)
+
+
+/** Write from a buffer */
+bool pb_buf(PayloadBuilder *pb, const uint8_t *buf, uint32_t len);
+
+/** Write a zero terminated string */
+bool pb_string(PayloadBuilder *pb, const char *str);
+
+/** Write uint8_t to the buffer */
+bool pb_u8(PayloadBuilder *pb, uint8_t byte);
+
+/** Write boolean to the buffer. */
+static inline bool pb_bool(PayloadBuilder *pb, bool b)
+{
+    return pb_u8(pb, (uint8_t) b);
+}
+
+/** Write uint16_t to the buffer. */
+bool pb_u16(PayloadBuilder *pb, uint16_t word);
+
+/** Write uint32_t to the buffer. */
+bool pb_u32(PayloadBuilder *pb, uint32_t word);
+
+/** Write int8_t to the buffer. */
+bool pb_i8(PayloadBuilder *pb, int8_t byte);
+
+/** Write char (int8_t) to the buffer. */
+static inline bool pb_char(PayloadBuilder *pb, char c)
+{
+    return pb_i8(pb, c);
+}
+
+/** Write int16_t to the buffer. */
+bool pb_i16(PayloadBuilder *pb, int16_t word);
+
+/** Write int32_t to the buffer. */
+bool pb_i32(PayloadBuilder *pb, int32_t word);
+
+/** Write 4-byte float to the buffer. */
+bool pb_float(PayloadBuilder *pb, float f);
+
+#endif // PAYLOAD_BUILDER_H

utilities/payload_parser.c

@@ -0,0 +1,121 @@
+#include "payload_parser.h"
+
+#define pp_check_capacity(pp, needed) \
+    if ((pp)->current + (needed) > (pp)->end) { \
+        if ((pp)->empty_handler == NULL || !(pp)->empty_handler(pp, needed)) {(pp)->ok = 0;} ; \
+    }
+
+void pp_skip(PayloadParser *pp, uint32_t num)
+{
+    pp->current += num;
+}
+
+uint8_t pp_u8(PayloadParser *pp)
+{
+    pp_check_capacity(pp, 1);
+    if (!pp->ok) return 0;
+
+    return *pp->current++;
+}
+
+uint16_t pp_u16(PayloadParser *pp)
+{
+    pp_check_capacity(pp, 2);
+    if (!pp->ok) return 0;
+
+    uint16_t x = 0;
+
+    if (pp->bigendian) {
+        x |= *pp->current++ << 8;
+        x |= *pp->current++;
+    } else {
+        x |= *pp->current++;
+        x |= *pp->current++ << 8;
+    }
+    return x;
+}
+
+uint32_t pp_u32(PayloadParser *pp)
+{
+    pp_check_capacity(pp, 4);
+    if (!pp->ok) return 0;
+
+    uint32_t x = 0;
+
+    if (pp->bigendian) {
+        x |= (uint32_t) (*pp->current++ << 24);
+        x |= (uint32_t) (*pp->current++ << 16);
+        x |= (uint32_t) (*pp->current++ << 8);
+        x |= *pp->current++;
+    } else {
+        x |= *pp->current++;
+        x |= (uint32_t) (*pp->current++ << 8);
+        x |= (uint32_t) (*pp->current++ << 16);
+        x |= (uint32_t) (*pp->current++ << 24);
+    }
+    return x;
+}
+
+const uint8_t *pp_tail(PayloadParser *pp, uint32_t *length)
+{
+    int32_t len = (int) (pp->end - pp->current);
+    if (!pp->ok || len <= 0) {
+        if (length != NULL) *length = 0;
+        return NULL;
+    }
+
+    if (length != NULL) {
+        *length = (uint32_t) len;
+    }
+
+    return pp->current;
+}
+
+/** Read int8_t from the payload. */
+int8_t pp_i8(PayloadParser *pp)
+{
+    return ((union conv8) {.u8 = pp_u8(pp)}).i8;
+}
+
+/** Read int16_t from the payload. */
+int16_t pp_i16(PayloadParser *pp)
+{
+    return ((union conv16) {.u16 = pp_u16(pp)}).i16;
+}
+
+/** Read int32_t from the payload. */
+int32_t pp_i32(PayloadParser *pp)
+{
+    return ((union conv32) {.u32 = pp_u32(pp)}).i32;
+}
+
+/** Read 4-byte float from the payload. */
+float pp_float(PayloadParser *pp)
+{
+    return ((union conv32) {.u32 = pp_u32(pp)}).f32;
+}
+
+/** Read a zstring */
+uint32_t pp_string(PayloadParser *pp, char *buffer, uint32_t maxlen)
+{
+    pp_check_capacity(pp, 1);
+    uint32_t len = 0;
+    while (len < maxlen-1 && pp->current != pp->end) {
+        char c = *buffer++ = *pp->current++;
+        if (c == 0) break;
+        len++;
+    }
+    *buffer = 0;
+    return len;
+}
+
+/** Read a buffer */
+uint32_t pp_buf(PayloadParser *pp, uint8_t *buffer, uint32_t maxlen)
+{
+    uint32_t len = 0;
+    while (len < maxlen && pp->current != pp->end) {
+        *buffer++ = *pp->current++;
+        len++;
+    }
+    return len;
+}

utilities/payload_parser.h

@@ -0,0 +1,143 @@
+#ifndef PAYLOAD_PARSER_H
+#define PAYLOAD_PARSER_H
+
+/**
+ * PayloadParser, part of the TinyFrame utilities collection
+ * 
+ * (c) Ondřej Hruška, 2016-2017. MIT license.
+ * 
+ * This module helps you with parsing payloads (not only from TinyFrame).
+ * 
+ * The parser supports big and little-endian which is selected when 
+ * initializing it or by accessing the bigendian struct field.
+ *
+ * The parser performs bounds checking and calls the provided handler when 
+ * the requested read doesn't have enough data. Use the callback to take
+ * appropriate action, e.g. report an error.
+ * 
+ * If the handler function is not defined, the pb->ok flag is set to false
+ * (use this to check for success), and further reads won't have any effect 
+ * and always result in 0 or empty array.
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include "type_coerce.h"
+
+typedef struct PayloadParser_ PayloadParser;
+
+/**
+ * Empty buffer handler. 
+ * 
+ * 'needed' more bytes should be read but the end was reached.
+ * 
+ * Return true if the problem was solved (e.g. new data loaded into 
+ * the buffer and the 'current' pointer moved to the beginning).
+ *  
+ * If false is returned, the 'ok' flag on the struct is set to false
+ * and all following reads will fail / return 0.
+ */
+typedef bool (*pp_empty_handler)(PayloadParser *pp, uint32_t needed);
+
+struct PayloadParser_ {
+    uint8_t *start;   //!< Pointer to the beginning of the buffer
+    uint8_t *current; //!< Pointer to the next byte to be read
+    uint8_t *end;     //!< Pointer to the end of the buffer (start + length)
+    pp_empty_handler empty_handler; //!< Callback for buffer underrun
+    bool bigendian;   //!< Flag to use big-endian parsing
+    bool ok;          //!< Indicates that all reads were successful
+};
+
+// --- initializer helper macros ---
+
+/** Start the parser. */
+#define pp_start_e(buf, length, bigendian, empty_handler) ((PayloadParser){buf, buf, (buf)+(length), empty_handler, bigendian, 1})
+
+/** Start the parser in big-endian mode */
+#define pp_start_be(buf, length, empty_handler) pp_start_e(buf, length, 1, empty_handler)
+
+/** Start the parser in little-endian mode */
+#define pp_start_le(buf, length, empty_handler) pp_start_e(buf, length, 0, empty_handler)
+
+/** Start the parser in little-endian mode (default) */
+#define pp_start(buf, length, empty_handler) pp_start_le(buf, length, empty_handler)
+
+// --- utilities ---
+
+/** Get remaining length */
+#define pp_length(pp) ((pp)->end - (pp)->current)
+
+/** Reset the current pointer to start */
+#define pp_rewind(pp) do { pp->current = pp->start; } while (0)
+
+
+/**
+ * @brief Get the remainder of the buffer.
+ *
+ * Returns NULL and sets 'length' to 0 if there are no bytes left.
+ *
+ * @param pp
+ * @param length : here the buffer length will be stored. NULL to do not store.
+ * @return the remaining portion of the input buffer
+ */
+const uint8_t *pp_tail(PayloadParser *pp, uint32_t *length);
+
+/** Read uint8_t from the payload. */
+uint8_t pp_u8(PayloadParser *pp);
+
+/** Read bool from the payload. */
+static inline int8_t pp_bool(PayloadParser *pp)
+{
+    return pp_u8(pp) != 0;
+}
+
+/** Skip bytes */
+void pp_skip(PayloadParser *pp, uint32_t num);
+
+/** Read uint16_t from the payload. */
+uint16_t pp_u16(PayloadParser *pp);
+
+/** Read uint32_t from the payload. */
+uint32_t pp_u32(PayloadParser *pp);
+
+/** Read int8_t from the payload. */
+int8_t pp_i8(PayloadParser *pp);
+
+/** Read char (int8_t) from the payload. */
+static inline int8_t pp_char(PayloadParser *pp)
+{
+    return pp_i8(pp);
+}
+
+/** Read int16_t from the payload. */
+int16_t pp_i16(PayloadParser *pp);
+
+/** Read int32_t from the payload. */
+int32_t pp_i32(PayloadParser *pp);
+
+/** Read 4-byte float from the payload. */
+float pp_float(PayloadParser *pp);
+
+/**
+ * Parse a zero-terminated string
+ *
+ * @param pp - parser
+ * @param buffer - target buffer
+ * @param maxlen - buffer size
+ * @return actual number of bytes, excluding terminator
+ */
+uint32_t pp_string(PayloadParser *pp, char *buffer, uint32_t maxlen);
+
+/**
+ * Parse a buffer
+ *
+ * @param pp - parser
+ * @param buffer - target buffer
+ * @param maxlen - buffer size
+ * @return actual number of bytes, excluding terminator
+ */
+uint32_t pp_buf(PayloadParser *pp, uint8_t *buffer, uint32_t maxlen);
+
+
+#endif // PAYLOAD_PARSER_H

utilities/type_coerce.h

@@ -0,0 +1,32 @@
+#ifndef TYPE_COERCE_H
+#define TYPE_COERCE_H
+
+/**
+ * Structs for conversion between types,
+ * part of the TinyFrame utilities collection
+ * 
+ * (c) Ondřej Hruška, 2016-2017. MIT license.
+ * 
+ * This is a support header file for PayloadParser and PayloadBuilder.
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+
+union conv8 {
+    uint8_t u8;
+    int8_t i8;
+};
+
+union conv16 {
+    uint16_t u16;
+    int16_t i16;
+};
+
+union conv32 {
+    uint32_t u32;
+    int32_t i32;
+    float f32;
+};
+
+#endif // TYPE_COERCE_H