ta_file_read_all.c

// Read file as binary, but append \0 to the end of the buffer
// filename: name of file to read
// buf     : if file read successfully, this will be set to a pointer to the file contents on the heap
// len     : if file read successfully, this will be set to the file length
// Returns 0 on success, negative error code on failure (see stderr for more info)
// WARN: you must free(buf) when you're done with it!!
int ta_file_read_all(const char *filename, char **buf, size_t *len)
{
    assert(filename);
    assert(buf);
    assert(len);

    // Open file
    FILE *fs = fopen(filename, "rb");
    if (!fs) {
        fprintf(stderr, "Unable to open %s for reading\n", filename);
        return -1;
    }

    // Calculate length
    fseek(fs, 0, SEEK_END);
    long tell = ftell(fs);
    if (tell < 0) {
        fprintf(stderr, "Unable to determine length of %s\n", filename);
        return -2;
    }
    rewind(fs);

    // Error on empty file
    assert(tell > 0);

    size_t buflen = (size_t)tell + 1;
    char *buffer = (char *)calloc(1, buflen);  // extra byte for nil
    if (!buffer) {
        fprintf(stderr, "Failed to allocate buffer\n");
        return -3;
    }
    size_t read = fread(buffer, 1, tell, fs);
    if (read != buflen - 1) {
        fprintf(stderr, "Failed to read entire file\n");
        return -4;
    }

    // Close file
    fclose(fs);

    *buf = buffer;
    *len = buflen;
    return 0;
}