try.c

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include "zlib.h"

#if defined(MSDOS) || defined(OS2) || defined(WIN32) || defined(__CYGWIN__)
#  include <fcntl.h>
#  include <io.h>
#  define SET_BINARY_MODE(file) setmode(fileno(file), O_BINARY)
#else
#  define SET_BINARY_MODE(file)
#endif

// #define CHUNK 100
#define CHUNK 10

void zerr(int ret) ;

char * flush_flags[] = {
    "Z_NO_FLUSH",
    "Z_PARTIAL_FLUSH",
    "Z_SYNC_FLUSH",
    "Z_FULL_FLUSH",
    "Z_FINISH",
    "Z_BLOCK",
    "Z_TREES"
    } ;


static void

DispHex(void * ptr, int length)
{
    char * p = (char*)ptr;
    int i;
    for (i = 0; i < length; ++i) {
        fprintf(stderr, " %02x", 0xFF & *(p+i));
    }
    fprintf(stderr, "\n") ;
}

/* Compress from file source to file dest until EOF on source.
   def() returns Z_OK on success, Z_MEM_ERROR if memory could not be
   allocated for processing, Z_STREAM_ERROR if an invalid compression
   level is supplied, Z_VERSION_ERROR if the version of zlib.h and the
   version of the library linked do not match, or Z_ERRNO if there is
   an error reading or writing the files. */
int def(FILE* dest)
{
    int ret, flush;
    unsigned have;
    z_stream strm;
    unsigned char in[CHUNK];
    unsigned char out[CHUNK];
    int avail_in = 0;
    int index = -1 ;
    int strategy = Z_DEFAULT_STRATEGY;
    int level = Z_DEFAULT_COMPRESSION ;

    /* allocate deflate state */
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    strm.avail_in = 0;
    strm.next_in = Z_NULL;
    strm.avail_out = 0;
    strm.next_out = Z_NULL;
    level = 0;

    fprintf(stderr, "Chunk size is %d\n", CHUNK) ;
    ret = deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, -15, MAX_MEM_LEVEL, Z_DEFAULT_STRATEGY);
    
    if (ret != Z_OK)
        return ret;

    for (index = 0;  index < 2 ; ++ index) {
        strm.next_in = "Hello";
        strm.avail_in = 5;

        /* DEFLATE */
        do {
            strm.avail_out = CHUNK;
            strm.next_out = out;
            ret = deflate(&strm, Z_NO_FLUSH);    /* no bad return value */
            assert(ret != Z_STREAM_ERROR);  /* state not clobbered */
            have = CHUNK - strm.avail_out;
            fprintf(stderr, "\nDEFLATE out %d, return %d\n", have, ret);
            if (have) {
                DispHex(out, have);
            }
            if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
                (void)deflateEnd(&strm);
                return Z_ERRNO;
            }
        } while (strm.avail_out == 0);

        assert(strm.avail_in == 0);     /* all input will be used */


        /* FLUSH */
        char * FLUSH ;
        switch (index % 2)
        {
            case 0:
                // fprintf(stderr, "\n%d SETTING Z_SYNC_FLUSH\n", index);
                flush = Z_SYNC_FLUSH;
                FLUSH = "Z_SYNC_FLUSH" ;
                break;

            case 1:
                // fprintf(stderr, "\n%d SETTING Z_FULL_FLUSH\n", index);
                flush = Z_FULL_FLUSH;
                FLUSH = "Z_FULL_FLUSH" ;
                break; 
        }

        do {
            strm.avail_in = 0;
            strm.next_in = Z_NULL;
            strm.avail_out = CHUNK;
            strm.next_out = out;
            ret = deflate(&strm, flush);    /* no bad return value */
            assert(ret != Z_STREAM_ERROR);  /* state not clobbered */
            have = CHUNK - strm.avail_out;
            fprintf(stderr, "FLUSH [%s] out %d, return %d\n", FLUSH, have, ret);
            if (have) {
                DispHex(out, have);
            }            
            if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
                (void)deflateEnd(&strm);
                return Z_ERRNO;
            }
        } while (strm.avail_out == 0);

    } 

    fprintf(stderr, "\nRET %d\n", ret);
    // zerr(ret);
    // assert(ret == Z_STREAM_END);        /* stream will be complete */

    /* clean up and return */
    // (void)deflateEnd(&strm);
    return Z_OK;
}

/* report a zlib or i/o error */
void zerr(int ret)
{
    fputs("zpipe: ", stderr);
    switch (ret) {
    case Z_ERRNO:
        if (ferror(stdin))
            fputs("error reading stdin\n", stderr);
        if (ferror(stdout))
            fputs("error writing stdout\n", stderr);
        break;
    case Z_BUF_ERROR:
        fputs("buffer error\n", stderr);
        break;
    case Z_STREAM_ERROR:
        fputs("invalid compression level\n", stderr);
        break;
    case Z_DATA_ERROR:
        fputs("invalid or incomplete deflate data\n", stderr);
        break;
    case Z_MEM_ERROR:
        fputs("out of memory\n", stderr);
        break;
    case Z_VERSION_ERROR:
        fputs("zlib version mismatch!\n", stderr);
    }
}

/* compress or decompress from stdin to stdout */
int main(int argc, char **argv)
{
    int ret;
    fprintf(stderr, "This is [%s][%s]\n", ZLIB_VERSION, zlibVersion());

    /* avoid end-of-line conversions */
    SET_BINARY_MODE(stdin);
    SET_BINARY_MODE(stdout);

    def(stdout) ;

}