Example for how to extract a file?

[probonopd]

Hello, thanks for this useful library.

I am trying to extract a file but I am getting This doesn't look like a squashfs image.

/*
Compile with:
gcc -o extract_diricon extract_diricon.c -lsquash -I../include -L. -lz

mkdir -p test
echo "Test" >> ./test/.DirIcon
mksquashfs ./test/ test.sfs -comp lzma

./extract_diricon -o 0 test.sfs 
This doesn't look like a squashfs image.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <getopt.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <squash.h>

void usage(char *progname) {
    fprintf(stderr, "Usage: %s [-o offset] squashfs_file\n", progname);
    exit(1);
}

int main(int argc, char **argv) {
    int opt;
    char *squashfs_file = NULL;
    off_t offset = 0;
    sqfs fs;
    struct stat buf;
    int vfd;
    char *buf2;
    size_t size;

    while ((opt = getopt(argc, argv, "o:")) != -1) {
        switch (opt) {
        case 'o':
            offset = strtoll(optarg, NULL, 0);
            break;
        default:
            usage(argv[0]);
        }
    }

    if (optind >= argc) {
        usage(argv[0]);
    }

    squashfs_file = argv[optind];

    memset(&fs, 0, sizeof(sqfs));
    if (sqfs_open_image(&fs, squashfs_file, offset) != 0) {
        fprintf(stderr, "Failed to open %s: %s\n", squashfs_file, strerror(errno));
        return 1;
    }

    if (squash_lstat(&fs, "/.DirIcon", &buf) < 0) {
        fprintf(stderr, "Failed to stat /.DirIcon: %s\n", strerror(errno));
        sqfs_destroy(&fs);
        return 1;
    }

    if (S_ISLNK(buf.st_mode)) {
        char link[1024];
        size_t link_len = squash_readlink(&fs, "/.DirIcon", link, sizeof(link) - 1);
        if (link_len < 0) {
            fprintf(stderr, "Failed to readlink /.DirIcon: %s\n", strerror(errno));
            sqfs_destroy(&fs);
            return 1;
        }
        link[link_len] = '\0';

        if (squash_lstat(&fs, link, &buf) < 0) {
            fprintf(stderr, "Failed to stat %s: %s\n", link, strerror(errno));
            sqfs_destroy(&fs);
            return 1;
        }
    }

    vfd = squash_open(&fs, "/.DirIcon");
    if (vfd < 0) {
        fprintf(stderr, "Failed to open /.DirIcon: %s\n", strerror(errno));
        sqfs_destroy(&fs);
        return 1;
    }

    size = squash_lseek(vfd, 0, SQUASH_SEEK_END);
    if (size <= 0) {
        fprintf(stderr, "Invalid file size for /.DirIcon\n");
        squash_close(vfd);
        sqfs_destroy(&fs);
        return 1;
    }

    if (squash_lseek(vfd, 0, SQUASH_SEEK_SET) < 0) {
        fprintf(stderr, "Failed to seek to the beginning of /.DirIcon: %s\n", strerror(errno));
        squash_close(vfd);
        sqfs_destroy(&fs);
        return 1;
    }

    buf2 = malloc(size);
    if (!buf2) {
        fprintf(stderr, "Failed to allocate memory for /.DirIcon\n");
        squash_close(vfd);
        sqfs_destroy(&fs);
        return 1;
    }

    ssize_t bytes_read = 0;
    size_t total_read = 0;
    while (total_read < size) {
        bytes_read = squash_read(vfd, buf2 + total_read, size - total_read);
        if (bytes_read < 0) {
            fprintf(stderr, "Failed to read /.DirIcon: %s\n", strerror(errno));
            free(buf2);
            squash_close(vfd);
            sqfs_destroy(&fs);
            return 1;
        }
        if (bytes_read == 0) {
            break;  // End of file
        }
        total_read += bytes_read;
    }

    if (total_read != size) {
        fprintf(stderr, "Warning: Read %zu bytes, expected %zu bytes\n", total_read, size);
    }

    fwrite(buf2, 1, total_read, stdout);
    free(buf2);
    squash_close(vfd);
    sqfs_destroy(&fs);
    return 0;
}

What am I doing wrong?

Is there an example for how to extract a file (following symlinks) somewhere?

Thank you very much.