zlib de/compress(es) file content rather than string

zlib-(de)compress(es)-file-content

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

/*
 * A good example for using zlib is correlated de/compress file instead of string
 */

void decompress_one_file(char *infilename, char *outfilename);
void compress_one_file(char *infilename, char *outfilename);

int main(int argc, char **argv)
{
    compress_one_file(argv[1],argv[2]);
    decompress_one_file(argv[2],argv[3]);
}

unsigned long file_size(char *filename)
{
    FILE *pFile = fopen(filename, "rb");
    fseek (pFile, 0, SEEK_END);
    unsigned long size = ftell(pFile);
    fclose (pFile);
    return size;
}

void decompress_one_file(char *infilename, char *outfilename)
{
    gzFile infile = gzopen(infilename, "rb");
    FILE *outfile = fopen(outfilename, "wb");
    if (!infile || !outfile) return;
    
    char buffer[128];
    int num_read = 0;
    while ((num_read = gzread(infile, buffer, sizeof(buffer))) > 0) {
        fwrite(buffer, 1, num_read, outfile);
    }
    
    gzclose(infile);
    fclose(outfile);
}

void compress_one_file(char *infilename, char *outfilename)
{
    FILE *infile = fopen(infilename, "rb");
    gzFile outfile = gzopen(outfilename, "wb");
    if (!infile || !outfile) return;
    
    char inbuffer[128];
    int num_read = 0;
    unsigned long total_read = 0, total_wrote = 0;
    while ((num_read = fread(inbuffer, 1, sizeof(inbuffer), infile)) > 0) {
        total_read += num_read;
        gzwrite(outfile, inbuffer, num_read);
    }
    fclose(infile);
    gzclose(outfile);
    
    printf("Read %ld bytes, Wrote %ld bytes, Compression factor %4.2f%%\n",
           total_read, file_size(outfilename),
           (1.0-file_size(outfilename)*1.0/total_read)*100.0);
}