int ZEXPORT deflate (strm, flush)
    z_streamp strm;
    int flush;
{
    int old_flush; /* value of flush param for previous deflate call */
    deflate_state *s;

    if (deflateStateCheck(strm) || flush > Z_BLOCK || flush < 0) {
        return Z_STREAM_ERROR;
    }
    s = strm->state;

    if (strm->next_out == Z_NULL ||
        (strm->avail_in != 0 && strm->next_in == Z_NULL) ||
        (s->status == FINISH_STATE && flush != Z_FINISH)) {
        ERR_RETURN(strm, Z_STREAM_ERROR);
    }
    if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);

    old_flush = s->last_flush;
    s->last_flush = flush;

    /* Flush as much pending output as possible */
    if (s->pending != 0) {
        flush_pending(strm);
        if (strm->avail_out == 0) {
            /* Since avail_out is 0, deflate will be called again with
             * more output space, but possibly with both pending and
             * avail_in equal to zero. There won't be anything to do,
             * but this is not an error situation so make sure we
             * return OK instead of BUF_ERROR at next call of deflate:
             */
            s->last_flush = -1;
            return Z_OK;
        }

    /* Make sure there is something to do and avoid duplicate consecutive
     * flushes. For repeated and useless calls with Z_FINISH, we keep
     * returning Z_STREAM_END instead of Z_BUF_ERROR.
     */
    } else if (strm->avail_in == 0 && RANK(flush) <= RANK(old_flush) &&
               flush != Z_FINISH) {
        ERR_RETURN(strm, Z_BUF_ERROR);
    }

    /* User must not provide more input after the first FINISH: */
    if (s->status == FINISH_STATE && strm->avail_in != 0) {
        ERR_RETURN(strm, Z_BUF_ERROR);
    }

    /* Write the header */
    if (s->status == INIT_STATE && s->wrap == 0)
        s->status = BUSY_STATE;
    if (s->status == INIT_STATE) {
        /* zlib header */
        uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
        uInt level_flags;

        if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
            level_flags = 0;
        else if (s->level < 6)
            level_flags = 1;
        else if (s->level == 6)
            level_flags = 2;
        else
            level_flags = 3;
        header |= (level_flags << 6);
        if (s->strstart != 0) header |= PRESET_DICT;
        header += 31 - (header % 31);

        putShortMSB(s, header);

        /* Save the adler32 of the preset dictionary: */
        if (s->strstart != 0) {
            putShortMSB(s, (uInt)(strm->adler >> 16));
            putShortMSB(s, (uInt)(strm->adler & 0xffff));
        }
        strm->adler = adler32(0L, Z_NULL, 0);
        s->status = BUSY_STATE;

        /* Compression must start with an empty pending buffer */
        flush_pending(strm);
        if (s->pending != 0) {
            s->last_flush = -1;
            return Z_OK;
        }
    }
#ifdef GZIP
    if (s->status == GZIP_STATE) {
        /* gzip header */
        strm->adler = crc32(0L, Z_NULL, 0);
        put_byte(s, 31);
        put_byte(s, 139);
        put_byte(s, 8);
        if (s->gzhead == Z_NULL) {
            put_byte(s, 0);
            put_byte(s, 0);
            put_byte(s, 0);
            put_byte(s, 0);
            put_byte(s, 0);
            put_byte(s, s->level == 9 ? 2 :
                     (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
                      4 : 0));
            put_byte(s, OS_CODE);
            s->status = BUSY_STATE;

            /* Compression must start with an empty pending buffer */
            flush_pending(strm);
            if (s->pending != 0) {
                s->last_flush = -1;
                return Z_OK;
            }
        }
        else {
            put_byte(s, (s->gzhead->text ? 1 : 0) +
                     (s->gzhead->hcrc ? 2 : 0) +
                     (s->gzhead->extra == Z_NULL ? 0 : 4) +
                     (s->gzhead->name == Z_NULL ? 0 : 8) +
                     (s->gzhead->comment == Z_NULL ? 0 : 16)
                     );
            put_byte(s, (Byte)(s->gzhead->time & 0xff));
            put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
            put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
            put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
            put_byte(s, s->level == 9 ? 2 :
                     (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
                      4 : 0));
            put_byte(s, s->gzhead->os & 0xff);
            if (s->gzhead->extra != Z_NULL) {
                put_byte(s, s->gzhead->extra_len & 0xff);
                put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
            }
            if (s->gzhead->hcrc)
                strm->adler = crc32(strm->adler, s->pending_buf,
                                    s->pending);
            s->gzindex = 0;
            s->status = EXTRA_STATE;
        }
    }
    if (s->status == EXTRA_STATE) {
        if (s->gzhead->extra != Z_NULL) {
            ulg beg = s->pending;   /* start of bytes to update crc */
            uInt left = (s->gzhead->extra_len & 0xffff) - s->gzindex;
            while (s->pending + left > s->pending_buf_size) {
                uInt copy = s->pending_buf_size - s->pending;
                zmemcpy(s->pending_buf + s->pending,
                        s->gzhead->extra + s->gzindex, copy);
                s->pending = s->pending_buf_size;
                HCRC_UPDATE(beg);
                s->gzindex += copy;
                flush_pending(strm);
                if (s->pending != 0) {
                    s->last_flush = -1;
                    return Z_OK;
                }
                beg = 0;
                left -= copy;
            }
            zmemcpy(s->pending_buf + s->pending,
                    s->gzhead->extra + s->gzindex, left);
            s->pending += left;
            HCRC_UPDATE(beg);
            s->gzindex = 0;
        }
        s->status = NAME_STATE;
    }
    if (s->status == NAME_STATE) {
        if (s->gzhead->name != Z_NULL) {
            ulg beg = s->pending;   /* start of bytes to update crc */
            int val;
            do {
                if (s->pending == s->pending_buf_size) {
                    HCRC_UPDATE(beg);
                    flush_pending(strm);
                    if (s->pending != 0) {
                        s->last_flush = -1;
                        return Z_OK;
                    }
                    beg = 0;
                }
                val = s->gzhead->name[s->gzindex++];
                put_byte(s, val);
            } while (val != 0);
            HCRC_UPDATE(beg);
            s->gzindex = 0;
        }
        s->status = COMMENT_STATE;
    }
    if (s->status == COMMENT_STATE) {
        if (s->gzhead->comment != Z_NULL) {
            ulg beg = s->pending;   /* start of bytes to update crc */
            int val;
            do {
                if (s->pending == s->pending_buf_size) {
                    HCRC_UPDATE(beg);
                    flush_pending(strm);
                    if (s->pending != 0) {
                        s->last_flush = -1;
                        return Z_OK;
                    }
                    beg = 0;
                }
                val = s->gzhead->comment[s->gzindex++];
                put_byte(s, val);
            } while (val != 0);
            HCRC_UPDATE(beg);
        }
        s->status = HCRC_STATE;
    }
    if (s->status == HCRC_STATE) {
        if (s->gzhead->hcrc) {
            if (s->pending + 2 > s->pending_buf_size) {
                flush_pending(strm);
                if (s->pending != 0) {
                    s->last_flush = -1;
                    return Z_OK;
                }
            }
            put_byte(s, (Byte)(strm->adler & 0xff));
            put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
            strm->adler = crc32(0L, Z_NULL, 0);
        }
        s->status = BUSY_STATE;

        /* Compression must start with an empty pending buffer */
        flush_pending(strm);
        if (s->pending != 0) {
            s->last_flush = -1;
            return Z_OK;
        }
    }
#endif

    /* Start a new block or continue the current one.
     */
    if (strm->avail_in != 0 || s->lookahead != 0 ||
        (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
        block_state bstate;

        bstate = s->level == 0 ? deflate_stored(s, flush) :
                 s->strategy == Z_HUFFMAN_ONLY ? deflate_huff(s, flush) :
                 s->strategy == Z_RLE ? deflate_rle(s, flush) :
                 (*(configuration_table[s->level].func))(s, flush);

        if (bstate == finish_started || bstate == finish_done) {
            s->status = FINISH_STATE;
        }
        if (bstate == need_more || bstate == finish_started) {
            if (strm->avail_out == 0) {
                s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
            }
            return Z_OK;
            /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
             * of deflate should use the same flush parameter to make sure
             * that the flush is complete. So we don't have to output an
             * empty block here, this will be done at next call. This also
             * ensures that for a very small output buffer, we emit at most
             * one empty block.
             */
        }
        if (bstate == block_done) {
            if (flush == Z_PARTIAL_FLUSH) {
                _tr_align(s);
            } else if (flush != Z_BLOCK) { /* FULL_FLUSH or SYNC_FLUSH */
                _tr_stored_block(s, (char*)0, 0L, 0);
                /* For a full flush, this empty block will be recognized
                 * as a special marker by inflate_sync().
                 */
                if (flush == Z_FULL_FLUSH) {
                    CLEAR_HASH(s);             /* forget history */
                    if (s->lookahead == 0) {
                        s->strstart = 0;
                        s->block_start = 0L;
                        s->insert = 0;
                    }
                }
            }
            flush_pending(strm);
            if (strm->avail_out == 0) {
              s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
              return Z_OK;
            }
        }
    }

    if (flush != Z_FINISH) return Z_OK;
    if (s->wrap <= 0) return Z_STREAM_END;

    /* Write the trailer */
#ifdef GZIP
    if (s->wrap == 2) {
        put_byte(s, (Byte)(strm->adler & 0xff));
        put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
        put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
        put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
        put_byte(s, (Byte)(strm->total_in & 0xff));
        put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
        put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
        put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
    }
    else
#endif
    {
        putShortMSB(s, (uInt)(strm->adler >> 16));
        putShortMSB(s, (uInt)(strm->adler & 0xffff));
    }
    flush_pending(strm);
    /* If avail_out is zero, the application will call deflate again
     * to flush the rest.
     */
    if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
    return s->pending != 0 ? Z_OK : Z_STREAM_END;
}