support for deleting files, and setting file size.

fat16.c

@@ -16,7 +16,7 @@ void read_bs(const BLOCKDEV* dev, Fat16BootSector* info, const uint32_t addr);
 uint32_t find_bs(const BLOCKDEV* dev);
 
 /** Get cluster's starting address */
-uint32_t clu_start(const FAT16* fat, const uint16_t cluster);
+uint32_t clu_addr(const FAT16* fat, const uint16_t cluster);
 
 /** Find following cluster using FAT for jumps */
 uint16_t next_clu(const FAT16* fat, uint16_t cluster);
@@ -36,8 +36,8 @@ uint16_t alloc_cluster(const FAT16* fat);
 /** Zero out entire cluster. */
 void wipe_cluster(const FAT16* fat, const uint16_t clu);
 
-/** Write new file size (also to the disk). Does not allocate clusters. */
+/** Free cluster chain, starting at given number */
-void set_file_size(FAT16_FILE* file, uint32_t size);
+void free_cluster_chain(const FAT16* fat, uint16_t clu);
 
 /**
  * Check if there is already a file of given RAW name
@@ -45,6 +45,12 @@ void set_file_size(FAT16_FILE* file, uint32_t size);
  */
 bool dir_contains_file_raw(FAT16_FILE* dir, char* fname);
 
+/** Write a value into FAT */
+void write_fat(const FAT16* fat, const uint16_t cluster, const uint16_t value);
+
+/** Read a value from FAT */
+uint16_t read_fat(const FAT16* fat, const uint16_t cluster);
+
 
 // =========== INTERNAL FUNCTION IMPLEMENTATIONS =========
 
@@ -126,8 +132,22 @@ void read_bs(const BLOCKDEV* dev, Fat16BootSector* info, const uint32_t addr)
 }
 
 
+void write_fat(const FAT16* fat, const uint16_t cluster, const uint16_t value)
+{
+	fat->dev->seek(fat->fat_addr + (cluster * 2));
+	fat->dev->write16(value);
+}
+
+
+uint16_t read_fat(const FAT16* fat, const uint16_t cluster)
+{
+	fat->dev->seek(fat->fat_addr + (cluster * 2));
+	return fat->dev->read16();
+}
+
+
 /** Get cluster starting address */
-uint32_t clu_start(const FAT16* fat, const uint16_t cluster)
+uint32_t clu_addr(const FAT16* fat, const uint16_t cluster)
 {
 	if (cluster < 2) return fat->rd_addr;
 	return fat->data_addr + (cluster - 2) * fat->bs.bytes_per_cluster;
@@ -136,8 +156,7 @@ uint32_t clu_start(const FAT16* fat, const uint16_t cluster)
 
 uint16_t next_clu(const FAT16* fat, uint16_t cluster)
 {
-	fat->dev->seek(fat->fat_addr + (cluster * 2));
+	return read_fat(fat, cluster);
-	return fat->dev->read16();
 }
 
 
@@ -151,7 +170,7 @@ uint32_t clu_add(const FAT16* fat, uint16_t cluster, uint32_t addr)
 		addr -= fat->bs.bytes_per_cluster;
 	}
 
-	return clu_start(fat, cluster) + addr;
+	return clu_addr(fat, cluster) + addr;
 }
 
 
@@ -163,7 +182,7 @@ uint32_t clu_add(const FAT16* fat, uint16_t cluster, uint32_t addr)
  */
 void wipe_cluster(const FAT16* fat, const uint16_t clu)
 {
-	uint32_t addr = clu_start(fat, clu);
+	uint32_t addr = clu_addr(fat, clu);
 
 	const BLOCKDEV* dev = fat->dev;
 
@@ -185,14 +204,11 @@ uint16_t alloc_cluster(const FAT16* fat)
 	for (i = 2; i < fat->bs.fat_size_sectors * 256; i++)
 	{
 		// read value from FAT
-		fat->dev->seek(fat->fat_addr + (i * 2));
+		b = read_fat(fat, i);
-		b = fat->dev->read16();
+		if (b == 0) // unused cluster
-		if (b == 0)
 		{
 			// Write FFFF to "i", to mark end of file
-			b = 0xFFFF;
+			write_fat(fat, i, 0xFFFF);
-			fat->dev->seek(fat->fat_addr + (i * 2));
-			fat->dev->write16(b);
 
 			// Wipe the cluster
 			wipe_cluster(fat, i);
@@ -212,13 +228,30 @@ bool append_cluster(const FAT16* fat, const uint16_t clu)
 	if (clu2 == 0xFFFF) return false;
 
 	// Write "i" to "clu"
-	fat->dev->seek(fat->fat_addr + (clu * 2));
+	write_fat(fat, clu, clu2);
-	fat->dev->write16(clu2);
 
 	return true;
 }
 
 
+void free_cluster_chain(const FAT16* fat, uint16_t clu)
+{
+	do {
+		// get address of the next cluster
+		const uint16_t clu2 = read_fat(fat, clu);
+
+		// mark cluster as unused
+		write_fat(fat, clu, 0x0000);
+
+		printf("Cluster free at %d\n", clu);
+
+		// advance
+		clu = clu2;
+
+	} while (clu != 0xFFFF);
+}
+
+
 /**
  * Check if there is already a file of given RAW name
  * Raw name - name as found on disk, not "display name".
@@ -244,18 +277,6 @@ bool dir_contains_file_raw(FAT16_FILE* dir, char* fname)
 }
 
 
-/** Write new file size (also to the disk). Does not allocate clusters. */
-void set_file_size(FAT16_FILE* file, uint32_t size)
-{
-	// Find address for storing the size
-	const uint32_t addr = clu_add(file->fat, file->clu, file->num * 32 + 28);
-	file->size = size;
-
-	const BLOCKDEV* dev = file->fat->dev;
-	dev->seek(addr);
-	dev->store(&size, 4);
-}
-
 
 // =============== PUBLIC FUNCTION IMPLEMENTATIONS =================
 
@@ -309,7 +330,7 @@ bool fat16_fseek(FAT16_FILE* file, uint32_t addr)
 		addr -= file->fat->bs.bytes_per_cluster;
 	}
 
-	file->cur_abs = clu_start(file->fat, file->cur_clu) + addr;
+	file->cur_abs = clu_addr(file->fat, file->cur_clu) + addr;
 	file->cur_ofs = addr;
 
 	// Physically seek to that location
@@ -331,7 +352,7 @@ void fat16_fopen(const FAT16* fat, FAT16_FILE* file, const uint16_t dir_cluster,
 	uint32_t addr;
 	if (dir_cluster == 0)
 	{
-		addr = clu_start(fat, dir_cluster) + num * 32; // root directory, max 512 entries.
+		addr = clu_addr(fat, dir_cluster) + num * 32; // root directory, max 512 entries.
 	} else
 	{
 		addr = clu_add(fat, dir_cluster, num * 32); // cluster + N (wrapping to next cluster if needed)
@@ -461,7 +482,7 @@ bool fat16_fread(FAT16_FILE* file, void* target, uint32_t len)
 		if (file->cur_ofs >= fat->bs.bytes_per_cluster)
 		{
 			file->cur_clu = next_clu(fat, file->cur_clu);
-			file->cur_abs = clu_start(fat, file->cur_clu);
+			file->cur_abs = clu_addr(fat, file->cur_clu);
 			file->cur_ofs = 0;
 		}
 
@@ -519,13 +540,13 @@ bool fat16_fwrite(FAT16_FILE* file, void* src, uint32_t len)
 
 				// advance cursors to the next cluster
 				file->cur_clu = next_clu(fat, file->cur_clu);
-				file->cur_abs = clu_start(fat, file->cur_clu);
+				file->cur_abs = clu_addr(fat, file->cur_clu);
 				file->cur_ofs = 0;
 			}
 		}
 
 		// Save new size
-		set_file_size(file, pos_start + len);
+		fat16_set_file_size(file, pos_start + len);
 
 		// Seek back to where it was before
 		fat16_fseek(file, pos_start);
@@ -553,7 +574,7 @@ bool fat16_fwrite(FAT16_FILE* file, void* src, uint32_t len)
 		if (file->cur_ofs >= fat->bs.bytes_per_cluster)
 		{
 			file->cur_clu = next_clu(fat, file->cur_clu);
-			file->cur_abs = clu_start(fat, file->cur_clu);
+			file->cur_abs = clu_addr(fat, file->cur_clu);
 			file->cur_ofs = 0;
 		}
 
@@ -880,7 +901,47 @@ char* fat16_undisplay_name(const char* name, char* fixed)
 }
 
 
+/** Write new file size (also to the disk). Does not allocate clusters. */
+void fat16_set_file_size(FAT16_FILE* file, uint32_t size)
+{
+	const FAT16* fat = file->fat;
+	const BLOCKDEV* dev = file->fat->dev;
 
+	// Find address for storing the size
+	const uint32_t addr = clu_add(fat, file->clu, file->num * 32 + 28);
+	file->size = size;
 
+	dev->seek(addr);
+	dev->store(&size, 4);
 
+	// Seek to the end of the file, to make sure clusters are allocated
+	fat16_fseek(file, size - 1);
 
+	const uint16_t next = next_clu(fat, file->cur_clu);
+	if (next != 0xFFFF)
+	{
+		printf("Trimming file clusters\n");
+
+		free_cluster_chain(fat, next);
+
+		// Mark that there's no further clusters
+		write_fat(fat, file->cur_clu, 0xFFFF);
+	}
+}
+
+
+void fat16_delete_file(FAT16_FILE* file)
+{
+	const FAT16* fat = file->fat;
+
+	// seek to file record
+	fat->dev->seek(clu_add(fat, file->clu, file->num * 32));
+
+	// mark as deleted
+	fat->dev->write(0xE5); // "deleted" mark
+
+	// free allocated clusters
+	free_cluster_chain(fat, file->clu_start);
+
+	file->type = FT_DELETED;
+}

fat16.h

@@ -17,7 +17,7 @@ typedef struct {
 	// Absolute seek
 	void (*seek)(const uint32_t);
 	// Relative seek
-	void (*rseek)(const uint16_t);
+	void (*rseek)(const int16_t);
 } BLOCKDEV;
 
 
@@ -169,7 +169,14 @@ bool fat16_fwrite(FAT16_FILE* file, void* src, uint32_t len);
  */
 bool fat16_newfile(FAT16_FILE* directory, FAT16_FILE* file, const char* name);
 
+/**
+ * Write new file size (also to the disk).
+ * Allocates / frees needed clusters, does not erase them.
+ */
+void fat16_set_file_size(FAT16_FILE* file, uint32_t size);
 
+/** Delete a file entry and free clusters. Does NOT descend into subdirectories. */
+void fat16_delete_file(FAT16_FILE* file);
 
 // --------- NAVIGATION ------------
 

main.c

@@ -18,7 +18,7 @@ void test_seek(const uint32_t pos)
 	fseek(testf, pos, SEEK_SET);
 }
 
-void test_rseek(const uint16_t pos)
+void test_rseek(const int16_t pos)
 {
 	fseek(testf, pos, SEEK_CUR);
 }
@@ -112,22 +112,43 @@ int main(int argc, char const *argv[])
 	do {
 		if (!fat16_is_file_valid(&file)) continue;
 
-		printf("File name: %s, %c, %d B\n",
+		printf("File name: %s, %c, %d B, @ 0x%x\n",
 			fat16_display_name(&file, str),
-			file.type, file.size);
+			file.type, file.size, file.clu_start);
 
 	} while (fat16_next(&file));
 
 	fat16_open_root(&fat, &file);
 
-	printf("Exists? %d\n", fat16_find_file(&file, "nuclear.war"));
+//	bool found = fat16_find_file(&file, "NEW_FILE.DAT");
-	printf("Size: %d\n", file.size);
+//
+//	if (found)
+//	{
+//		fat16_delete_file(&file);
+//		fat16_set_file_size(&file, 16000);
+//	}
+
+	//printf("Exists? %d\n", fat16_find_file(&file, "nuclear.war"));
+	//printf("Size: %d\n", file.size);
+
+	//fat16_set_file_size(&file, 5);
 
 	//fat16_fseek(&file, 40000);
 	//fat16_fwrite(&file, "BANANA", 6);
 
 //	FAT16_FILE neu;
-	//fat16_newfile(&file, &neu, "NEWFILE.MP3");
+//	bool ok = fat16_newfile(&file, &neu, "NEWFILE3.DAT");
+//	if (!ok) {
+//		printf("FAIL.");
+//		return -1;
+//	}
+//
+//	char c = '_';
+//	for (uint16_t i = 0; i < 35000; i++) {
+//		fat16_fwrite(&neu, &i, 2);
+//		fat16_fwrite(&neu, &c, 1);
+//	}
+
 	//fat16_fwrite(&neu, "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 16);
 
 
@@ -147,6 +168,15 @@ int main(int argc, char const *argv[])
 //
 //	printf("%.5s\n", boo);
 
+
+//	char ham[20000];
+//
+//	fat16_find_file(&file, "HAMLET.TXT");
+//	fat16_fread(&file, ham, 20000);
+//	ham[19999] = 0;
+//	printf("%s\n", ham);
+
+
 	test_close();
 
 	return 0;