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

#include "zlib.h"

int main(int argc, char *argv[]) {
  const int len = 3 << 20; /* 3 MiB */
  unsigned char buffer[len];
  if (getrandom(buffer, len, GRND_RANDOM) != len) {
    perror("getrandom()");
    exit(1);
  }

  z_stream c_stream; /* compression stream */
  int err;
  int estimateLen = 0;
  unsigned char *outBuf = NULL;

  c_stream.zalloc = Z_NULL;
  c_stream.zfree = Z_NULL;
  c_stream.opaque = (voidpf)0;
  c_stream.avail_in = len;
  c_stream.next_in = (z_const unsigned char *)buffer;
  c_stream.avail_out = 0;
  c_stream.next_out = outBuf;

  err = deflateInit2(&c_stream, Z_DEFAULT_COMPRESSION, Z_DEFLATED, -MAX_WBITS,
                     Z_BEST_COMPRESSION, Z_DEFAULT_STRATEGY);
  if (err != Z_OK) {
    fprintf(stderr, "deflateInit2() error: %d\n", err);
    exit(1);
  }

  /* calculate actual output length and update structure */
  estimateLen = deflateBound(&c_stream, len);
  fprintf(stderr, "estimateLen = %d\n", estimateLen);
  outBuf = malloc(estimateLen);

  if (outBuf != NULL) {
    /* update zlib configuration */
    c_stream.avail_out = estimateLen;
    c_stream.next_out = outBuf;

    /* do the compression */
    err = deflate(&c_stream, Z_FINISH);

    if (err == Z_STREAM_END) {
      fprintf(stderr, "deflate(): OK\n");
    } else {
      fprintf(stderr, "deflate() error: got %d; expected Z_STREAM_END (%d)\n",
              err, Z_STREAM_END);
      exit(1);
    }
  }

  err = deflateEnd(&c_stream);
  if (err != Z_OK) {
    fprintf(stderr, "deflateEnd() error: %d\n", err);
    exit(1);
  }

  free(outBuf);
}

estimateLen = 3588101
deflate(): OK

estimateLen = 3146695
deflate() error: got 0; expected Z_STREAM_END (1)