tinyobj_parse_obj fails to read .mtl file

[hk-dunky]

I attempted to load an OBJ file with tinyobj_parse_obj from gordon/gordon.obj. It contains an MTL file, gordon/gordon.mtl. The reading failed and I got the following output:

open: No such file or directory
TINYOBJ: Failed to parse material file 'gordon.mtl^M': -2

Not sure what the first line is. Maybe an error on my side.
I believe the ^M is a carriage return as it displays in Vim. I don't know why that's there as it's in the file name. I believe it also misses that gordon.mtl is in gordon/. I know there is a branch that fixes this.

[syoyo]

Probably your .obj contains mixture of line endings(CRLF and LF)

Please post a minimal reproducible .obj file and code.

[hk-dunky]

main.c:

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include "tinyobj_loader_c.h"

static char* mmap_file(size_t* len, const char* filename) {
#ifdef _WIN64
	HANDLE file =
		CreateFileA(filename, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING,
				FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL);
	assert(file != INVALID_HANDLE_VALUE);

	HANDLE fileMapping = CreateFileMapping(file, NULL, PAGE_READONLY, 0, 0, NULL);
	assert(fileMapping != INVALID_HANDLE_VALUE);

	LPVOID fileMapView = MapViewOfFile(fileMapping, FILE_MAP_READ, 0, 0, 0);
	auto fileMapViewChar = (const char*)fileMapView;
	assert(fileMapView != NULL);
#else

	FILE* f;
	long file_size;
	struct stat sb;
	char* p;
	int fd;

	(*len) = 0;

	f = fopen(filename, "r");
	if (!f)
	{
		perror("open");
		return NULL;
	}
	fseek(f, 0, SEEK_END);
	file_size = ftell(f);
	fclose(f);

	fd = open(filename, O_RDONLY);
	if (fd == -1) {
		perror("open");
		return NULL;
	}

	if (fstat(fd, &sb) == -1) {
		perror("fstat");
		return NULL;
	}

	if (!S_ISREG(sb.st_mode)) {
		fprintf(stderr, "%s is not a file\n", "lineitem.tbl");
		return NULL;
	}

	p = (char*)mmap(0, (size_t)file_size, PROT_READ, MAP_SHARED, fd, 0);

	if (p == MAP_FAILED) {
		perror("mmap");
		return NULL;
	}

	if (close(fd) == -1) {
		perror("close");
		return NULL;
	}

	(*len) = (size_t)file_size;

	return p;

#endif
}

static void get_file_data(const char* filename, char** data, size_t* len) {
	const char* ext = strrchr(filename, '.');

	size_t data_len = 0;

	if (strcmp(ext, ".gz") == 0) {
		assert(0); /* todo */

	} else {
		*data = mmap_file(&data_len, filename);
	}

	(*len) = data_len;
}

int main(void)
{
	tinyobj_attrib_t attrib;
	tinyobj_shape_t *shapes;
	tinyobj_material_t *mats;
	size_t num_shapes, num_mats;

	tinyobj_parse_obj(&attrib, &shapes, &num_shapes, &mats, &num_mats, "gordon/gordon.obj", get_file_data, TINYOBJ_FLAG_TRIANGULATE);

	tinyobj_attrib_free(&attrib);
	tinyobj_shapes_free(shapes, num_shapes);
	tinyobj_materials_free(mats, num_mats);

	return 0;
}

gordon/gordon.obj:

mtllib gordon.mtl

For gordon/gordon.mtl an empty file reproduces the issue.

[syoyo]

The issue is that simply sting gordon.mtl(from mtllib line) is passed to get_file_data callback.

You'll need to implement a file reader callback something like:

const char *obj_dir = ...;

static void get_file_data(const char* filename, char** data, size_t* len) {
  const char* ext = strrchr(filename, '.');

  size_t data_len = 0;

  if (strcmp(ext, ".gz") == 0) {
    assert(0); /* todo */
  } else if (strcmp(ext, ".mtl") == 0) {
    const char *filepath = concat_str(obj_dir, filename);
    *data = mmap_file(&data_len, filepath);
  } else {
    *data = mmap_file(&data_len, filename);
  }

  (*len) = data_len;
}

We are better to polish file callback function API(e.g. add userdata pointer to callback arguments, use dedicated callback API for .mtl file, etc).

[hk-dunky]

Ah, thanks. I'll see if that fixes it.