Generate gzip file for testing Compress::Gzip ver1

test_gzip_generator.c

#include <stdio.h>
#include <string.h>
#include <zlib.h>
#include <time.h>

int main()
{
    char *filename = "test.gz";
    char *contents = "One\nTwo";
    int content_length = strlen(contents);
    unsigned char outbuffer[4096];
    FILE *file;
    z_stream strm;
    gz_header header;

    // Set a fixed UTC timestamp
    struct tm t;
    t.tm_year = 2012 - 1900;
    t.tm_mon = 8;
    t.tm_mday = 4;
    t.tm_hour = 22;
    t.tm_min = 6;
    t.tm_sec = 5;
    t.tm_isdst = -1; // Disable daylight saving time handling

    // Use timegm instead of mktime to convert to UTC
    time_t fixed_time = timegm(&t);

    // Initialize header information
    memset(&header, 0, sizeof(header));
    header.text = 1;
    header.time = fixed_time;
    header.os = 0x03;
    header.name = (Bytef *)"test.txt";
    header.comment = (Bytef *)"happy birthday";
    Bytef extra[] = {0x01, 0x02, 0x03, 0x04, 0x05};
    header.extra = extra;
    header.extra_len = sizeof(extra);
    header.hcrc = 1; // Enable CRC check

    // Initialize deflate stream
    memset(&strm, 0, sizeof(strm));
    deflateInit2(&strm, Z_BEST_COMPRESSION, Z_DEFLATED, MAX_WBITS + 16, 8, Z_DEFAULT_STRATEGY);

    // Set header
    deflateSetHeader(&strm, &header);

    // Set input data
    strm.next_in = (Bytef *)contents;
    strm.avail_in = content_length;

    // Open output file
    file = fopen(filename, "wb");

    // Compress and write output
    int ret;
    do
    {
        strm.avail_out = sizeof(outbuffer);
        strm.next_out = outbuffer;
        ret = deflate(&strm, Z_FINISH);
        fwrite(outbuffer, 1, sizeof(outbuffer) - strm.avail_out, file);
    } while (ret != Z_STREAM_END);

    // Finalize
    deflateEnd(&strm);
    fclose(file);

    return 0;
}