/* version 2023-10-04 */

/* gcc -Wall -o zunlib zunlib.c -lz */

/* typical usage: ./zunlib file.z > file */

#include <zlib.h>

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>

int main(int n, char **v)
{
  char *filename;
  FILE *f;
  struct stat statbuf;
  unsigned char *buf;
  int ret;

  if (n != 2) { fprintf(stderr, "gimme file.z to unzip\n"); return 1; }

  filename = v[1];

  f = fopen(v[1], "r");
  if (f == NULL) { perror(filename); return 1; }
  if (fstat(fileno(f), &statbuf)) { perror(filename); return 1; }
  buf = malloc(statbuf.st_size); if (buf == NULL) abort();
  fread(buf, statbuf.st_size, 1, f);
  fclose(f);

  z_stream s;
  s.next_in = buf;
  s.avail_in = statbuf.st_size;
  s.zalloc = NULL;
  s.zfree = NULL;
  s.opaque = NULL;

  ret = inflateInit(&s);
  if (ret != Z_OK) { fprintf(stderr, "zlib error\n"); return 1; }

  unsigned char output[4096];

  while (1) {
    s.next_out = output;
    s.avail_out = 4096;
    ret = inflate(&s, Z_NO_FLUSH);
    if (ret == Z_OK || ret == Z_STREAM_END) {
      int n = 4096-s.avail_out;
      if (n > 0) if (fwrite(output, n, 1, stdout) != 1) { fprintf(stderr, "output error\n"); return 1; }
    }
    if (ret == Z_STREAM_END) break;
    if (ret != Z_OK) { fprintf(stderr, "error in input\n"); return 1; }
  }
  ret = inflateEnd(&s);
  if (ret != Z_OK) { fprintf(stderr, "error with zlib closing\n"); return 1; }

  if (fflush(stdout)) { fprintf(stderr, "fflush failed, output is bad\n"); return 1; }

  return 0;
}