Reads and prints information about the contents of Blender (.blend) files

blendfile.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <error.h>

struct BlendFile
{
	int ptr_size;
	int endianness;
	int version_num;
	struct FileBlock *block_head;
};

struct FileBlock
{
	char  code[4];
	int   size;
	int   SDNA_index;
	int   count;
	char *data;
	struct FileBlock *next;
};

/*
struct SDNA
{
	int     name_c;
	char  **name_v;
	int     type_c;
	char  **type_v;
	short  *type_len_v;
	int     struct_c;
	short  *struct_type;
	int    *struct_field_c;
	short **struct_field_type;
	short **struct_field_name;
};
*/
 
struct BlendFile *read_blendfile(FILE *file);

static int  fread_w(void *buffer, size_t size, size_t count, FILE *stream);
static int  fseek_w(FILE *stream, long int offset, int origin);
static void file_err(FILE *file);

struct BlendFile *read_blendfile(FILE *file)
{
	char header_buf[12];
	
	if(fread_w(header_buf, 1, 12, file)) return NULL;

	int ptr_size, endianness, version_num;
	
	if(strncmp("BLENDER", header_buf, 7))
	{
		fprintf(stderr, "error: File header is malformed\n");
		return NULL;
	}

	ptr_size   = header_buf[7] == '_' ? 4 : 8;
	endianness = header_buf[8] == 'V';
	sscanf(header_buf+9, "%3d", &version_num);

	struct FileBlock *block_head = NULL;
	struct FileBlock *block_tail = NULL;

	for (;;)
	{
		struct FileBlock *block = malloc(sizeof(struct FileBlock));

		if (block == NULL)
		{
			perror("error");
			return NULL;
		}

		if (fread_w(block->code,  1, 4, file))  return NULL;
		if (fread_w(&block->size, 4, 1, file))  return NULL;
		if (fseek_w(file, ptr_size, SEEK_CUR))  return NULL;
		if (fread_w(&block->SDNA_index, 4, 1, file)) return NULL;
		if (fread_w(&block->count, 4, 1, file)) return NULL;

		char *data = malloc(block->size);

		if (data == NULL)
		{
			perror("error");
			return NULL;
		}

		if (fread_w(data, 1, block->size, file)) return NULL;
		
		block->data = data;

		if (block_head == NULL)
			block_head = block;
		else
			block_tail->next = block;
		
		block_tail = block;

		if (!strncmp("ENDB", block->code, 4)) break;
	}

	struct BlendFile *blendfile = malloc(sizeof(struct BlendFile));
	if (blendfile == NULL)
	{
		perror("error");
		return NULL;
	}

	blendfile->ptr_size    = ptr_size;
	blendfile->endianness  = endianness;
	blendfile->version_num = version_num;
	blendfile->block_head  = block_head;

	return blendfile;
}

static int fread_w(void *buffer, size_t size, size_t count, FILE *stream)
{
	if (fread(buffer, size, count, stream) != count)
	{
		file_err(stream);
		return 1;
	}
	return 0;
}

static int fseek_w(FILE *stream, long int offset, int origin)
{
	if (fseek(stream, offset, origin) == -1)
	{
		file_err(stream);
		return 1;
	}
	return 0;
}

static void file_err(FILE *file)
{
	if (feof(file)) fprintf(stderr, "error: Unexpected end of file\n");
	else perror("error");
}

int main(int argc, char **argv)
{
	if (argc < 2)
	{
		fprintf(stderr,
		        "error: Not enough arguments\n"
		        "usage: %s <file>\n",
		        argv[0]
		);
		return 2;
	}

	FILE *file = fopen(argv[1], "rb");
	
	if (file == NULL)
	{
		perror(argv[1]);
		return 1;
	}

	struct BlendFile *result = read_blendfile(file);

	if (fclose(file) == -1) perror("io error");

	if (result == NULL) return 1;

	printf("-- %s\n"
	       "   Pointer Size: %d (%d-bit)\n"
	       "   Endianness: %d (%s)\n"
	       "   Blender Version: %.2f\n"
	       "\n"
	       "-- File Blocks:\n"
	       , argv[1]
	       , result->ptr_size
	       , result->ptr_size << 3
	       , result->endianness
	       , result->endianness ? "big" : "little"
	       , result->version_num / 100.0f
	);

	struct FileBlock *node = result->block_head;

	while (node != NULL)
	{
		printf("  code: %.4s, size: %d, SDNA index: %d, count: %d\n"
		       , node->code
		       , node->size
		       , node->SDNA_index
		       , node->count
		);

		node = node->next;
	}

	return 0;
}