gopl.io/ch13/bzip/bzip2.c

// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/

// See page 362.

//!+
/* This file is gopl.io/ch13/bzip/bzip2.c,         */
/* a simple wrapper for libbzip2 suitable for cgo. */
#include <bzlib.h>

int bz2compress(bz_stream *s, int action,
                char *in, unsigned *inlen, char *out, unsigned *outlen) {
  s->next_in = in;
  s->avail_in = *inlen;
  s->next_out = out;
  s->avail_out = *outlen;
  int r = BZ2_bzCompress(s, action);
  *inlen -= s->avail_in;
  *outlen -= s->avail_out;

  /* "C code may store a Go pointer in C memory subject to rule 2: 
   * it must stop storing the pointer before it returns to Go." */
  s->next_in = NULL;
  s->next_out = NULL;
  
  return r;
}

//!-