I am attempting to extract file from a zip archive that is there in a memstream.

I’ve initialized the memstream like below:

f = open_memstream(&response_str, &size);

This is used by libcurl to write data into, set in the curl options.

curl_easy_setopt(curl, CURLOPT_WRITEDATA, f);

I then do an fflush and fseek to 0.

fflush(f);
fseek(f, 0L, SEEK_SET);

When i print out the data in the file pointer, it seems to be printing the correct value.

I can even write its contents into a file like below:

    dest_file = fopen("derivates.zip", "wb");
    for (int i =0; i<size; i++) {
        file_read_buffer = fgetc(f);
        
        fprintf(dest_file, "%c", file_read_buffer);
    }

This creates a zip archive that i can then open using my operating system’s installed unzip tools.

However, i want to be able to read the file contents using libzip without having to first write the contents into the file.

I was trying out something like this:

file_descriptor_f = fileno(f);
archive = zip_fdopen(file_descriptor_f, 0, &err);

However, i noticed that this doesn’t work, because the file_descriptor_f value that I get becomes -1. I suspect that since memstream is only an interface to read and write to a file in memory, there is no actual file out there and hence no valid file descriptor.

I was wondering if there was a way to read zip files using libzip using just a file pointer (FILE *f).