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gex-core/utils/payload_parser.h

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7 years ago
#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_ {
const uint8_t *start; //!< Pointer to the beginning of the buffer
const uint8_t *current; //!< Pointer to the next byte to be read
const uint8_t *end; //!< Pointer to the end of the buffer (start + length)
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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 */
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#define pp_length(pp) (uint32_t)((pp)->end - (pp)->current)
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/** 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