deflate.c

/* deflate.c -- compress data using the deflation algorithm
 * Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

/*
 *  ALGORITHM
 *
 *      The "deflation" process depends on being able to identify portions
 *      of the input text which are identical to earlier input (within a
 *      sliding window trailing behind the input currently being processed).
 *
 *      The most straightforward technique turns out to be the fastest for
 *      most input files: try all possible matches and select the longest.
 *      The key feature of this algorithm is that insertions into the string
 *      dictionary are very simple and thus fast, and deletions are avoided
 *      completely. Insertions are performed at each input character, whereas
 *      string matches are performed only when the previous match ends. So it
 *      is preferable to spend more time in matches to allow very fast string
 *      insertions and avoid deletions. The matching algorithm for small
 *      strings is inspired from that of Rabin & Karp. A brute force approach
 *      is used to find longer strings when a small match has been found.
 *      A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
 *      (by Leonid Broukhis).
 *         A previous version of this file used a more sophisticated algorithm
 *      (by Fiala and Greene) which is guaranteed to run in linear amortized
 *      time, but has a larger average cost, uses more memory and is patented.
 *      However the F&G algorithm may be faster for some highly redundant
 *      files if the parameter max_chain_length (described below) is too large.
 *
 *  ACKNOWLEDGEMENTS
 *
 *      The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
 *      I found it in 'freeze' written by Leonid Broukhis.
 *      Thanks to many people for bug reports and testing.
 *
 *  REFERENCES
 *
 *      Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
 *      Available in http://tools.ietf.org/html/rfc1951
 *
 *      A description of the Rabin and Karp algorithm is given in the book
 *         "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
 *
 *      Fiala,E.R., and Greene,D.H.
 *         Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
 *
 */

/* @(#) $Id$ */

#include "deflate.h"
#include "match.h"

#if defined(X86_CPUID)
# include "arch/x86/x86.h"
#endif

const char deflate_copyright[] = " deflate 1.2.8.f Copyright 1995-2013 Jean-loup Gailly and Mark Adler ";
/*
  If you use the zlib library in a product, an acknowledgment is welcome
  in the documentation of your product. If for some reason you cannot
  include such an acknowledgment, I would appreciate that you keep this
  copyright string in the executable of your product.
 */

/* ===========================================================================
 *  Function prototypes.
 */

typedef block_state (*compress_func) (deflate_state *s, int flush);
/* Compression function. Returns the block state after the call. */

local void fill_window           (deflate_state *s);
local block_state deflate_stored (deflate_state *s, int flush);
local block_state deflate_fast   (deflate_state *s, int flush);
block_state deflate_quick        (deflate_state *s, int flush);
#ifdef MEDIUM_STRATEGY
local block_state deflate_medium (deflate_state *s, int flush);
#endif
local block_state deflate_slow   (deflate_state *s, int flush);
local block_state deflate_rle    (deflate_state *s, int flush);
local block_state deflate_huff   (deflate_state *s, int flush);
local void lm_init               (deflate_state *s);
local void putShortMSB           (deflate_state *s, uInt b);
ZLIB_INTERNAL void flush_pending(z_stream *strm);
ZLIB_INTERNAL int read_buf(z_stream *strm, unsigned char *buf, unsigned size);

#ifdef DEBUG
local  void check_match(deflate_state *s, IPos start, IPos match, int length);
#endif

extern void crc_reset(deflate_state *const s);
extern void crc_finalize(deflate_state *const s);
extern void copy_with_crc(z_stream *strm, unsigned char *dst, long size);

/* ===========================================================================
 * Local data
 */

#define NIL 0
/* Tail of hash chains */

#ifndef TOO_FAR
#  define TOO_FAR 4096
#endif
/* Matches of length 3 are discarded if their distance exceeds TOO_FAR */

/* Values for max_lazy_match, good_match and max_chain_length, depending on
 * the desired pack level (0..9). The values given below have been tuned to
 * exclude worst case performance for pathological files. Better values may be
 * found for specific files.
 */
typedef struct config_s {
    uint16_t good_length; /* reduce lazy search above this match length */
    uint16_t max_lazy;    /* do not perform lazy search above this match length */
    uint16_t nice_length; /* quit search above this match length */
    uint16_t max_chain;
    compress_func func;
} config;

local const config configuration_table[10] = {
/*      good lazy nice chain */
/* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */

#ifdef X86_QUICK_STRATEGY
/* 1 */ {4,    4,  8,    4, deflate_quick},
/* 2 */ {4,    4,  8,    4, deflate_fast}, /* max speed, no lazy matches */
#else
/* 1 */ {4,    4,  8,    4, deflate_fast}, /* max speed, no lazy matches */
/* 2 */ {4,    5, 16,    8, deflate_fast},
#endif

/* 3 */ {4,    6, 32,   32, deflate_fast},

#ifdef MEDIUM_STRATEGY
/* 4 */ {4,    4, 16,   16, deflate_medium},  /* lazy matches */
/* 5 */ {8,   16, 32,   32, deflate_medium},
/* 6 */ {8,   16, 128, 128, deflate_medium},
#else
/* 4 */ {4,    4, 16,   16, deflate_slow},  /* lazy matches */
/* 5 */ {8,   16, 32,   32, deflate_slow},
/* 6 */ {8,   16, 128, 128, deflate_slow},
#endif

/* 7 */ {8,   32, 128, 256, deflate_slow},
/* 8 */ {32, 128, 258, 1024, deflate_slow},
/* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */

/* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
 * meaning.
 */

#define EQUAL 0
/* result of memcmp for equal strings */

/* rank Z_BLOCK between Z_NO_FLUSH and Z_PARTIAL_FLUSH */
#define RANK(f) (((f) << 1) - ((f) > 4 ? 9 : 0))


/* ===========================================================================
 * Insert string str in the dictionary and set match_head to the previous head
 * of the hash chain (the most recent string with same hash key). Return
 * the previous length of the hash chain.
 * IN  assertion: all calls to to INSERT_STRING are made with consecutive
 *    input characters and the first MIN_MATCH bytes of str are valid
 *    (except for the last MIN_MATCH-1 bytes of the input file).
 */
#ifdef X86_SSE4_2_CRC_HASH
local inline Pos insert_string_sse(deflate_state *const s, const Pos str) {
    Pos ret;
    unsigned *ip, val, h = 0;

    ip = (unsigned *)&s->window[str];
    val = *ip;

    if (s->level >= 6)
        val &= 0xFFFFFF;

    __asm__ __volatile__ (
        "crc32 %1,%0\n\t"
        : "+r" (h)
        : "r" (val)
    );

    ret = s->head[h & s->hash_mask];
    s->head[h & s->hash_mask] = str;
    s->prev[str & s->w_mask] = ret;
    return ret;
}
#endif

local inline Pos insert_string_c(deflate_state *const s, const Pos str) {
    Pos ret;

    UPDATE_HASH(s, s->ins_h, str);
    ret = s->prev[str & s->w_mask] = s->head[s->ins_h];
    s->head[s->ins_h] = str;

    return ret;
}

local inline Pos insert_string(deflate_state *const s, const Pos str) {
#ifdef X86_SSE4_2_CRC_HASH
    if (x86_cpu_has_sse42)
        return insert_string_sse(s, str);
#endif
    return insert_string_c(s, str);
}


#ifndef NOT_TWEAK_COMPILER
local inline void
bulk_insert_str(deflate_state *const s, Pos startpos, uInt count) {
    uInt idx;
    for (idx = 0; idx < count; idx++) {
        insert_string(s, startpos + idx);
    }
}
#endif

/* ===========================================================================
 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
 * prev[] will be initialized on the fly.
 */
#define CLEAR_HASH(s) \
    s->head[s->hash_size-1] = NIL; \
    memset((unsigned char *)s->head, 0, (unsigned)(s->hash_size-1)*sizeof(*s->head));

/* ========================================================================= */
int ZEXPORT deflateInit_(z_stream *strm, int level, const char *version, int stream_size) {
    return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL, Z_DEFAULT_STRATEGY, version, stream_size);
    /* Todo: ignore strm->next_in if we use it as window */
}

/* ========================================================================= */
int ZEXPORT deflateInit2_(z_stream *strm, int level, int method, int windowBits,
                           int memLevel, int strategy, const char *version, int stream_size) {
    unsigned window_padding = 0;
    deflate_state *s;
    int wrap = 1;
    static const char my_version[] = ZLIB_VERSION;

    uint16_t *overlay;
    /* We overlay pending_buf and d_buf+l_buf. This works since the average
     * output size for (length,distance) codes is <= 24 bits.
     */

#if defined(X86_SSE2_FILL_WINDOW) || defined(X86_SSE4_2_CRC_HASH)
    x86_check_features();
#endif

    if (version == Z_NULL || version[0] != my_version[0] || stream_size != sizeof(z_stream)) {
        return Z_VERSION_ERROR;
    }
    if (strm == Z_NULL)
        return Z_STREAM_ERROR;

    strm->msg = Z_NULL;
    if (strm->zalloc == (alloc_func)0) {
        strm->zalloc = zcalloc;
        strm->opaque = NULL;
    }
    if (strm->zfree == (free_func)0)
        strm->zfree = zcfree;

    if (level == Z_DEFAULT_COMPRESSION)
        level = 6;

    if (windowBits < 0) { /* suppress zlib wrapper */
        wrap = 0;
        windowBits = -windowBits;
#ifdef GZIP
    } else if (windowBits > 15) {
        wrap = 2;       /* write gzip wrapper instead */
        windowBits -= 16;
#endif
    }
    if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED || windowBits < 8 ||
        windowBits > 15 || level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
        return Z_STREAM_ERROR;
    }
    if (windowBits == 8)
        windowBits = 9;  /* until 256-byte window bug fixed */

#ifdef X86_QUICK_STRATEGY
    if (level == 1)
        windowBits = 13;
#endif

    s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
    if (s == Z_NULL)
        return Z_MEM_ERROR;
    strm->state = (struct internal_state *)s;
    s->strm = strm;

    s->wrap = wrap;
    s->gzhead = Z_NULL;
    s->w_bits = windowBits;
    s->w_size = 1 << s->w_bits;
    s->w_mask = s->w_size - 1;

#ifdef X86_SSE4_2_CRC_HASH
    if (x86_cpu_has_sse42)
        s->hash_bits = 15;
    else
#endif
        s->hash_bits = memLevel + 7;

    s->hash_size = 1 << s->hash_bits;
    s->hash_mask = s->hash_size - 1;
    s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);

#ifdef X86_PCLMULQDQ_CRC
    window_padding = 8;
#endif

    s->window = (unsigned char *) ZALLOC(strm, s->w_size + window_padding, 2*sizeof(unsigned char));
    s->prev   = (Pos *)  ZALLOC(strm, s->w_size, sizeof(Pos));
    s->head   = (Pos *)  ZALLOC(strm, s->hash_size, sizeof(Pos));

    s->high_water = 0;      /* nothing written to s->window yet */

    s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */

    overlay = (uint16_t *) ZALLOC(strm, s->lit_bufsize, sizeof(uint16_t)+2);
    s->pending_buf = (unsigned char *) overlay;
    s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(uint16_t)+2L);

    if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
        s->pending_buf == Z_NULL) {
        s->status = FINISH_STATE;
        strm->msg = ERR_MSG(Z_MEM_ERROR);
        deflateEnd(strm);
        return Z_MEM_ERROR;
    }
    s->d_buf = overlay + s->lit_bufsize/sizeof(uint16_t);
    s->l_buf = s->pending_buf + (1+sizeof(uint16_t))*s->lit_bufsize;

    s->level = level;
    s->strategy = strategy;
    s->method = (unsigned char)method;

    return deflateReset(strm);
}

/* ========================================================================= */
int ZEXPORT deflateSetDictionary(z_stream *strm, const unsigned char *dictionary, uInt  dictLength) {
    deflate_state *s;
    uInt str, n;
    int wrap;
    unsigned avail;
    const unsigned char *next;

    if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL)
        return Z_STREAM_ERROR;
    s = strm->state;
    wrap = s->wrap;
    if (wrap == 2 || (wrap == 1 && s->status != INIT_STATE) || s->lookahead)
        return Z_STREAM_ERROR;

    /* when using zlib wrappers, compute Adler-32 for provided dictionary */
    if (wrap == 1)
        strm->adler = adler32(strm->adler, dictionary, dictLength);
    s->wrap = 0;                    /* avoid computing Adler-32 in read_buf */

    /* if dictionary would fill window, just replace the history */
    if (dictLength >= s->w_size) {
        if (wrap == 0) {            /* already empty otherwise */
            CLEAR_HASH(s);
            s->strstart = 0;
            s->block_start = 0L;
            s->insert = 0;
        }
        dictionary += dictLength - s->w_size;  /* use the tail */
        dictLength = s->w_size;
    }

    /* insert dictionary into window and hash */
    avail = strm->avail_in;
    next = strm->next_in;
    strm->avail_in = dictLength;
    strm->next_in = (const unsigned char *)dictionary;
    fill_window(s);
    while (s->lookahead >= MIN_MATCH) {
        str = s->strstart;
        n = s->lookahead - (MIN_MATCH-1);
        bulk_insert_str(s, str, n);
        s->strstart = str + n;
        s->lookahead = MIN_MATCH-1;
        fill_window(s);
    }
    s->strstart += s->lookahead;
    s->block_start = (long)s->strstart;
    s->insert = s->lookahead;
    s->lookahead = 0;
    s->match_length = s->prev_length = MIN_MATCH-1;
    s->match_available = 0;
    strm->next_in = next;
    strm->avail_in = avail;
    s->wrap = wrap;
    return Z_OK;
}

/* ========================================================================= */
int ZEXPORT deflateResetKeep(z_stream *strm) {
    deflate_state *s;

    if (strm == Z_NULL || strm->state == Z_NULL || strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
        return Z_STREAM_ERROR;
    }

    strm->total_in = strm->total_out = 0;
    strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
    strm->data_type = Z_UNKNOWN;

    s = (deflate_state *)strm->state;
    s->pending = 0;
    s->pending_out = s->pending_buf;

    if (s->wrap < 0) {
        s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
    }
    s->status = s->wrap ? INIT_STATE : BUSY_STATE;
#ifdef GZIP
    strm->adler = s->wrap == 2 ? crc32(0L, Z_NULL, 0) : adler32(0L, Z_NULL, 0);
#else
    strm->adler = adler32(0L, Z_NULL, 0);
#endif
    s->last_flush = Z_NO_FLUSH;

    _tr_init(s);

    return Z_OK;
}

/* ========================================================================= */
int ZEXPORT deflateReset(z_stream *strm) {
    int ret;

    ret = deflateResetKeep(strm);
    if (ret == Z_OK)
        lm_init(strm->state);
    return ret;
}

/* ========================================================================= */
int ZEXPORT deflateSetHeader(z_stream *strm, gz_headerp head) {
    if (strm == Z_NULL || strm->state == Z_NULL)
        return Z_STREAM_ERROR;
    if (strm->state->wrap != 2)
        return Z_STREAM_ERROR;
    strm->state->gzhead = head;
    return Z_OK;
}

/* ========================================================================= */
int ZEXPORT deflatePending(z_stream *strm, unsigned *pending, int *bits) {
    if (strm == Z_NULL || strm->state == Z_NULL)
        return Z_STREAM_ERROR;
    if (pending != Z_NULL)
        *pending = strm->state->pending;
    if (bits != Z_NULL)
        *bits = strm->state->bi_valid;
    return Z_OK;
}

/* ========================================================================= */
int ZEXPORT deflatePrime(z_stream *strm, int bits, int value) {
    deflate_state *s;
    int put;

    if (strm == Z_NULL || strm->state == Z_NULL)
        return Z_STREAM_ERROR;
    s = strm->state;
    if ((unsigned char *)(s->d_buf) < s->pending_out + ((Buf_size + 7) >> 3))
        return Z_BUF_ERROR;
    do {
        put = Buf_size - s->bi_valid;
        if (put > bits)
            put = bits;
        s->bi_buf |= (uint16_t)((value & ((1 << put) - 1)) << s->bi_valid);
        s->bi_valid += put;
        _tr_flush_bits(s);
        value >>= put;
        bits -= put;
    } while (bits);
    return Z_OK;
}

/* ========================================================================= */
int ZEXPORT deflateParams(z_stream *strm, int level, int strategy) {
    deflate_state *s;
    compress_func func;
    int err = Z_OK;

    if (strm == Z_NULL || strm->state == Z_NULL)
        return Z_STREAM_ERROR;
    s = strm->state;

    if (level == Z_DEFAULT_COMPRESSION)
        level = 6;
    if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
        return Z_STREAM_ERROR;
    }
    func = configuration_table[s->level].func;

    if ((strategy != s->strategy || func != configuration_table[level].func) && strm->total_in != 0) {
        /* Flush the last buffer: */
        err = deflate(strm, Z_BLOCK);
        if (err == Z_BUF_ERROR && s->pending == 0)
            err = Z_OK;
    }
    if (s->level != level) {
        s->level = level;
        s->max_lazy_match   = configuration_table[level].max_lazy;
        s->good_match       = configuration_table[level].good_length;
        s->nice_match       = configuration_table[level].nice_length;
        s->max_chain_length = configuration_table[level].max_chain;
    }
    s->strategy = strategy;
    return err;
}

/* ========================================================================= */
int ZEXPORT deflateTune(z_stream *strm, int good_length, int max_lazy, int nice_length, int max_chain) {
    deflate_state *s;

    if (strm == Z_NULL || strm->state == Z_NULL)
        return Z_STREAM_ERROR;
    s = strm->state;
    s->good_match = good_length;
    s->max_lazy_match = max_lazy;
    s->nice_match = nice_length;
    s->max_chain_length = max_chain;
    return Z_OK;
}

/* =========================================================================
 * For the default windowBits of 15 and memLevel of 8, this function returns
 * a close to exact, as well as small, upper bound on the compressed size.
 * They are coded as constants here for a reason--if the #define's are
 * changed, then this function needs to be changed as well.  The return
 * value for 15 and 8 only works for those exact settings.
 *
 * For any setting other than those defaults for windowBits and memLevel,
 * the value returned is a conservative worst case for the maximum expansion
 * resulting from using fixed blocks instead of stored blocks, which deflate
 * can emit on compressed data for some combinations of the parameters.
 *
 * This function could be more sophisticated to provide closer upper bounds for
 * every combination of windowBits and memLevel.  But even the conservative
 * upper bound of about 14% expansion does not seem onerous for output buffer
 * allocation.
 */
uLong ZEXPORT deflateBound(z_stream *strm, uLong sourceLen) {
    deflate_state *s;
    uLong complen, wraplen;
    unsigned char *str;

    /* conservative upper bound for compressed data */
    complen = sourceLen + ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5;

    /* if can't get parameters, return conservative bound plus zlib wrapper */
    if (strm == Z_NULL || strm->state == Z_NULL)
        return complen + 6;

    /* compute wrapper length */
    s = strm->state;
    switch (s->wrap) {
    case 0:                                 /* raw deflate */
        wraplen = 0;
        break;
    case 1:                                 /* zlib wrapper */
        wraplen = 6 + (s->strstart ? 4 : 0);
        break;
    case 2:                                 /* gzip wrapper */
        wraplen = 18;
        if (s->gzhead != Z_NULL) {          /* user-supplied gzip header */
            if (s->gzhead->extra != Z_NULL) {
                wraplen += 2 + s->gzhead->extra_len;
            }
            str = s->gzhead->name;
            if (str != Z_NULL) {
                do {
                    wraplen++;
                } while (*str++);
            }
            str = s->gzhead->comment;
            if (str != Z_NULL) {
                do {
                    wraplen++;
                } while (*str++);
            }
            if (s->gzhead->hcrc)
                wraplen += 2;
        }
        break;
    default:                                /* for compiler happiness */
        wraplen = 6;
    }

    /* if not default parameters, return conservative bound */
    if (s->w_bits != 15 || s->hash_bits != 8 + 7)
        return complen + wraplen;

    /* default settings: return tight bound for that case */
    return sourceLen + (sourceLen >> 12) + (sourceLen >> 14) + (sourceLen >> 25) + 13 - 6 + wraplen;
}

/* =========================================================================
 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
 * IN assertion: the stream state is correct and there is enough room in
 * pending_buf.
 */
local void putShortMSB(deflate_state *s, uInt b) {
    put_byte(s, (unsigned char)(b >> 8));
    put_byte(s, (unsigned char)(b & 0xff));
}

/* =========================================================================
 * Flush as much pending output as possible. All deflate() output goes
 * through this function so some applications may wish to modify it
 * to avoid allocating a large strm->next_out buffer and copying into it.
 * (See also read_buf()).
 */
ZLIB_INTERNAL void flush_pending(z_stream *strm) {
    unsigned len;
    deflate_state *s = strm->state;

    _tr_flush_bits(s);
    len = s->pending;
    if (len > strm->avail_out)
        len = strm->avail_out;
    if (len == 0)
        return;

    memcpy(strm->next_out, s->pending_out, len);
    strm->next_out  += len;
    s->pending_out  += len;
    strm->total_out += len;
    strm->avail_out  -= len;
    s->pending -= len;
    if (s->pending == 0) {
        s->pending_out = s->pending_buf;
    }
}

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

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

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

    s->strm = strm; /* just in case */
    old_flush = s->last_flush;
    s->last_flush = flush;

    /* Write the header */
    if (s->status == INIT_STATE) {
#ifdef GZIP
        if (s->wrap == 2) {
            crc_reset(s);
            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;
            } 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, (unsigned char)(s->gzhead->time & 0xff));
                put_byte(s, (unsigned char)((s->gzhead->time >> 8) & 0xff));
                put_byte(s, (unsigned char)((s->gzhead->time >> 16) & 0xff));
                put_byte(s, (unsigned char)((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;
            }
        } else
#endif
        {
            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);

            s->status = BUSY_STATE;
            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);
        }
    }
#ifdef GZIP
    if (s->status == EXTRA_STATE) {
        if (s->gzhead->extra != Z_NULL) {
            uInt beg = s->pending;  /* start of bytes to update crc */

            while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
                if (s->pending == s->pending_buf_size) {
                    if (s->gzhead->hcrc && s->pending > beg)
                        strm->adler = crc32(strm->adler, s->pending_buf + beg, s->pending - beg);
                    flush_pending(strm);
                    beg = s->pending;
                    if (s->pending == s->pending_buf_size)
                        break;
                }
                put_byte(s, s->gzhead->extra[s->gzindex]);
                s->gzindex++;
            }
            if (s->gzhead->hcrc && s->pending > beg)
                strm->adler = crc32(strm->adler, s->pending_buf + beg, s->pending - beg);
            if (s->gzindex == s->gzhead->extra_len) {
                s->gzindex = 0;
                s->status = NAME_STATE;
            }
        } else {
            s->status = NAME_STATE;
        }
    }
    if (s->status == NAME_STATE) {
        if (s->gzhead->name != Z_NULL) {
            uInt beg = s->pending;  /* start of bytes to update crc */
            int val;

            do {
                if (s->pending == s->pending_buf_size) {
                    if (s->gzhead->hcrc && s->pending > beg)
                        strm->adler = crc32(strm->adler, s->pending_buf + beg, s->pending - beg);
                    flush_pending(strm);
                    beg = s->pending;
                    if (s->pending == s->pending_buf_size) {
                        val = 1;
                        break;
                    }
                }
                val = s->gzhead->name[s->gzindex++];
                put_byte(s, val);
            } while (val != 0);
            if (s->gzhead->hcrc && s->pending > beg)
                strm->adler = crc32(strm->adler, s->pending_buf + beg, s->pending - beg);
            if (val == 0) {
                s->gzindex = 0;
                s->status = COMMENT_STATE;
            }
        } else {
            s->status = COMMENT_STATE;
        }
    }
    if (s->status == COMMENT_STATE) {
        if (s->gzhead->comment != Z_NULL) {
            uInt beg = s->pending;  /* start of bytes to update crc */
            int val;

            do {
                if (s->pending == s->pending_buf_size) {
                    if (s->gzhead->hcrc && s->pending > beg)
                        strm->adler = crc32(strm->adler, s->pending_buf + beg, s->pending - beg);
                    flush_pending(strm);
                    beg = s->pending;
                    if (s->pending == s->pending_buf_size) {
                        val = 1;
                        break;
                    }
                }
                val = s->gzhead->comment[s->gzindex++];
                put_byte(s, val);
            } while (val != 0);
            if (s->gzhead->hcrc && s->pending > beg)
                strm->adler = crc32(strm->adler, s->pending_buf + beg, s->pending - beg);
            if (val == 0)
                s->status = HCRC_STATE;
        } else {
            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 + 2 <= s->pending_buf_size) {
                put_byte(s, (unsigned char)(strm->adler & 0xff));
                put_byte(s, (unsigned char)((strm->adler >> 8) & 0xff));
                strm->adler = crc32(0L, Z_NULL, 0);
                s->status = BUSY_STATE;
            }
        } else {
            s->status = BUSY_STATE;
        }
    }
#endif

    /* 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);
    }

    /* 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;

#ifdef X86_QUICK_STRATEGY
        if (s->level == 1 && !x86_cpu_has_sse42)
            bstate = s->strategy == Z_HUFFMAN_ONLY ? deflate_huff(s, flush) :
                    (s->strategy == Z_RLE ? deflate_rle(s, flush) : deflate_fast(s, flush));
        else
#endif
            bstate = 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;
            }
        }
    }
    Assert(strm->avail_out > 0, "bug2");

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

    /* Write the trailer */
#ifdef GZIP
    if (s->wrap == 2) {
        crc_finalize(s);
        put_byte(s, (unsigned char)(strm->adler & 0xff));
        put_byte(s, (unsigned char)((strm->adler >> 8) & 0xff));
        put_byte(s, (unsigned char)((strm->adler >> 16) & 0xff));
        put_byte(s, (unsigned char)((strm->adler >> 24) & 0xff));
        put_byte(s, (unsigned char)(strm->total_in & 0xff));
        put_byte(s, (unsigned char)((strm->total_in >> 8) & 0xff));
        put_byte(s, (unsigned char)((strm->total_in >> 16) & 0xff));
        put_byte(s, (unsigned char)((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;
}

/* ========================================================================= */
int ZEXPORT deflateEnd(z_stream *strm) {
    int status;

    if (strm == Z_NULL || strm->state == Z_NULL)
        return Z_STREAM_ERROR;

    status = strm->state->status;
    if (status != INIT_STATE &&
        status != EXTRA_STATE &&
        status != NAME_STATE &&
        status != COMMENT_STATE &&
        status != HCRC_STATE &&
        status != BUSY_STATE &&
        status != FINISH_STATE) {
      return Z_STREAM_ERROR;
    }

    /* Deallocate in reverse order of allocations: */
    TRY_FREE(strm, strm->state->pending_buf);
    TRY_FREE(strm, strm->state->head);
    TRY_FREE(strm, strm->state->prev);
    TRY_FREE(strm, strm->state->window);

    ZFREE(strm, strm->state);
    strm->state = Z_NULL;

    return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
}

/* =========================================================================
 * Copy the source state to the destination state.
 */
int ZEXPORT deflateCopy(z_stream *dest, z_stream *source) {
    deflate_state *ds;
    deflate_state *ss;
    uint16_t *overlay;

    if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
        return Z_STREAM_ERROR;
    }

    ss = source->state;

    memcpy((void *)dest, (void *)source, sizeof(z_stream));

    ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
    if (ds == Z_NULL)
        return Z_MEM_ERROR;
    dest->state = (struct internal_state *) ds;
    memcpy((void *)ds, (void *)ss, sizeof(deflate_state));
    ds->strm = dest;

    ds->window = (unsigned char *) ZALLOC(dest, ds->w_size, 2*sizeof(unsigned char));
    ds->prev   = (Pos *)  ZALLOC(dest, ds->w_size, sizeof(Pos));
    ds->head   = (Pos *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));
    overlay = (uint16_t *) ZALLOC(dest, ds->lit_bufsize, sizeof(uint16_t)+2);
    ds->pending_buf = (unsigned char *) overlay;

    if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL || ds->pending_buf == Z_NULL) {
        deflateEnd(dest);
        return Z_MEM_ERROR;
    }

    memcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(unsigned char));
    memcpy((void *)ds->prev, (void *)ss->prev, ds->w_size * sizeof(Pos));
    memcpy((void *)ds->head, (void *)ss->head, ds->hash_size * sizeof(Pos));
    memcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);

    ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
    ds->d_buf = overlay + ds->lit_bufsize/sizeof(uint16_t);
    ds->l_buf = ds->pending_buf + (1+sizeof(uint16_t))*ds->lit_bufsize;

    ds->l_desc.dyn_tree = ds->dyn_ltree;
    ds->d_desc.dyn_tree = ds->dyn_dtree;
    ds->bl_desc.dyn_tree = ds->bl_tree;

    return Z_OK;
}

/* ===========================================================================
 * Read a new buffer from the current input stream, update the adler32
 * and total number of bytes read.  All deflate() input goes through
 * this function so some applications may wish to modify it to avoid
 * allocating a large strm->next_in buffer and copying from it.
 * (See also flush_pending()).
 */
ZLIB_INTERNAL int read_buf(z_stream *strm, unsigned char *buf, unsigned size) {
    unsigned len = strm->avail_in;

    if (len > size)
        len = size;
    if (len == 0)
        return 0;

    strm->avail_in  -= len;

#ifdef GZIP
    if (strm->state->wrap == 2)
        copy_with_crc(strm, buf, len);
    else
#endif
    {
        memcpy(buf, strm->next_in, len);
        if (strm->state->wrap == 1)
            strm->adler = adler32(strm->adler, buf, len);
    }
    strm->next_in  += len;
    strm->total_in += len;

    return (int)len;
}

/* ===========================================================================
 * Initialize the "longest match" routines for a new zlib stream
 */
local void lm_init(deflate_state *s) {
    s->window_size = (ulg)2L*s->w_size;

    CLEAR_HASH(s);

    /* Set the default configuration parameters:
     */
    s->max_lazy_match   = configuration_table[s->level].max_lazy;
    s->good_match       = configuration_table[s->level].good_length;
    s->nice_match       = configuration_table[s->level].nice_length;
    s->max_chain_length = configuration_table[s->level].max_chain;

    s->strstart = 0;
    s->block_start = 0L;
    s->lookahead = 0;
    s->insert = 0;
    s->match_length = s->prev_length = MIN_MATCH-1;
    s->match_available = 0;
    s->ins_h = 0;
}

#ifdef DEBUG
/* ===========================================================================
 * Check that the match at match_start is indeed a match.
 */
local void check_match(deflate_state *s, IPos start, IPos match, int length) {
    /* check that the match is indeed a match */
    if (memcmp(s->window + match, s->window + start, length) != EQUAL) {
        fprintf(stderr, " start %u, match %u, length %d\n", start, match, length);
        do {
            fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
        } while (--length != 0);
        z_error("invalid match");
    }
    if (z_verbose > 1) {
        fprintf(stderr, "\\[%d,%d]", start-match, length);
        do {
            putc(s->window[start++], stderr);
        } while (--length != 0);
    }
}
#else
#  define check_match(s, start, match, length)
#endif /* DEBUG */

/* ===========================================================================
 * Fill the window when the lookahead becomes insufficient.
 * Updates strstart and lookahead.
 *
 * IN assertion: lookahead < MIN_LOOKAHEAD
 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
 *    At least one byte has been read, or avail_in == 0; reads are
 *    performed for at least two bytes (required for the zip translate_eol
 *    option -- not supported here).
 */
#ifdef X86_SSE2_FILL_WINDOW
extern void fill_window_sse(deflate_state *s);
#endif
local void fill_window_c(deflate_state *s);

local void fill_window(deflate_state *s) {
#ifdef X86_SSE2_FILL_WINDOW
# ifndef X86_NOCHECK_SSE2
    if (x86_cpu_has_sse2) {
# endif
        fill_window_sse(s);
# ifndef X86_NOCHECK_SSE2
    } else {
        fill_window_c(s);
    }
# endif

#else
    fill_window_c(s);
#endif
}

local void fill_window_c(deflate_state *s) {
    register unsigned n;
    register Pos *p;
    unsigned more;    /* Amount of free space at the end of the window. */
    uInt wsize = s->w_size;

    Assert(s->lookahead < MIN_LOOKAHEAD, "already enough lookahead");

    do {
        more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);

        /* If the window is almost full and there is insufficient lookahead,
         * move the upper half to the lower one to make room in the upper half.
         */
        if (s->strstart >= wsize+MAX_DIST(s)) {
            memcpy(s->window, s->window+wsize, (unsigned)wsize);
            s->match_start -= wsize;
            s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
            s->block_start -= (long) wsize;

            /* Slide the hash table (could be avoided with 32 bit values
               at the expense of memory usage). We slide even when level == 0
               to keep the hash table consistent if we switch back to level > 0
               later. (Using level 0 permanently is not an optimal usage of
               zlib, so we don't care about this pathological case.)
             */
            n = s->hash_size;
            p = &s->head[n];
#ifdef NOT_TWEAK_COMPILER
            do {
                unsigned m;
                m = *--p;
                *p = (Pos)(m >= wsize ? m-wsize : NIL);
            } while (--n);
#else
            /* As of I make this change, gcc (4.8.*) isn't able to vectorize
             * this hot loop using saturated-subtraction on x86-64 architecture.
             * To avoid this defect, we can change the loop such that
             *    o. the pointer advance forward, and
             *    o. demote the variable 'm' to be local to the loop, and
             *       choose type "Pos" (instead of 'unsigned int') for the
             *       variable to avoid unncessary zero-extension.
             */
            {
                unsigned int i;
                Pos *q = p - n;
                for (i = 0; i < n; i++) {
                    Pos m = *q;
                    Pos t = wsize;
                    *q++ = (Pos)(m >= t ? m-t: NIL);
                }
            }

#endif /* NOT_TWEAK_COMPILER */
            n = wsize;
            p = &s->prev[n];
#ifdef NOT_TWEAK_COMPILER
            do {
                unsigned m;
                m = *--p;
                *p = (Pos)(m >= wsize ? m-wsize : NIL);
                /* If n is not on any hash chain, prev[n] is garbage but
                 * its value will never be used.
                 */
            } while (--n);
#else
            {
                unsigned int i;
                Pos *q = p - n;
                for (i = 0; i < n; i++) {
                    Pos m = *q;
                    Pos t = wsize;
                    *q++ = (Pos)(m >= t ? m-t: NIL);
                }
            }
#endif /* NOT_TWEAK_COMPILER */
            more += wsize;
        }
        if (s->strm->avail_in == 0)
            break;

        /* If there was no sliding:
         *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
         *    more == window_size - lookahead - strstart
         * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
         * => more >= window_size - 2*WSIZE + 2
         * In the BIG_MEM or MMAP case (not yet supported),
         *   window_size == input_size + MIN_LOOKAHEAD  &&
         *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
         * Otherwise, window_size == 2*WSIZE so more >= 2.
         * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
         */
        Assert(more >= 2, "more < 2");

        n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
        s->lookahead += n;

        /* Initialize the hash value now that we have some input: */
        if (s->lookahead + s->insert >= MIN_MATCH) {
            uInt str = s->strstart - s->insert;
            s->ins_h = s->window[str];
            if (str >= 1)
                UPDATE_HASH(s, s->ins_h, str + 1 - (MIN_MATCH-1));
#if MIN_MATCH != 3
            Call UPDATE_HASH() MIN_MATCH-3 more times
#endif
            while (s->insert) {
                UPDATE_HASH(s, s->ins_h, str);
                s->prev[str & s->w_mask] = s->head[s->ins_h];
                s->head[s->ins_h] = (Pos)str;
                str++;
                s->insert--;
                if (s->lookahead + s->insert < MIN_MATCH)
                    break;
            }
        }
        /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
         * but this is not important since only literal bytes will be emitted.
         */
    } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);

    /* If the WIN_INIT bytes after the end of the current data have never been
     * written, then zero those bytes in order to avoid memory check reports of
     * the use of uninitialized (or uninitialised as Julian writes) bytes by
     * the longest match routines.  Update the high water mark for the next
     * time through here.  WIN_INIT is set to MAX_MATCH since the longest match
     * routines allow scanning to strstart + MAX_MATCH, ignoring lookahead.
     */
    if (s->high_water < s->window_size) {
        ulg curr = s->strstart + (ulg)(s->lookahead);
        ulg init;

        if (s->high_water < curr) {
            /* Previous high water mark below current data -- zero WIN_INIT
             * bytes or up to end of window, whichever is less.
             */
            init = s->window_size - curr;
            if (init > WIN_INIT)
                init = WIN_INIT;
            memset(s->window + curr, 0, (unsigned)init);
            s->high_water = curr + init;
        } else if (s->high_water < (ulg)curr + WIN_INIT) {
            /* High water mark at or above current data, but below current data
             * plus WIN_INIT -- zero out to current data plus WIN_INIT, or up
             * to end of window, whichever is less.
             */
            init = (ulg)curr + WIN_INIT - s->high_water;
            if (init > s->window_size - s->high_water)
                init = s->window_size - s->high_water;
            memset(s->window + s->high_water, 0, (unsigned)init);
            s->high_water += init;
        }
    }

    Assert((ulg)s->strstart <= s->window_size - MIN_LOOKAHEAD,
           "not enough room for search");
}

/* ===========================================================================
 * Flush the current block, with given end-of-file flag.
 * IN assertion: strstart is set to the end of the current match.
 */
#define FLUSH_BLOCK_ONLY(s, last) { \
    _tr_flush_block(s, (s->block_start >= 0L ? \
                   (char *)&s->window[(unsigned)s->block_start] : \
                   (char *)Z_NULL), \
                (ulg)((long)s->strstart - s->block_start), \
                (last)); \
    s->block_start = s->strstart; \
    flush_pending(s->strm); \
    Tracev((stderr, "[FLUSH]")); \
}

/* Same but force premature exit if necessary. */
#define FLUSH_BLOCK(s, last) { \
    FLUSH_BLOCK_ONLY(s, last); \
    if (s->strm->avail_out == 0) return (last) ? finish_started : need_more; \
}

/* ===========================================================================
 * Copy without compression as much as possible from the input stream, return
 * the current block state.
 * This function does not insert new strings in the dictionary since
 * uncompressible data is probably not useful. This function is used
 * only for the level=0 compression option.
 * NOTE: this function should be optimized to avoid extra copying from
 * window to pending_buf.
 */
local block_state deflate_stored(deflate_state *s, int flush) {
    /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
     * to pending_buf_size, and each stored block has a 5 byte header:
     */
    ulg max_block_size = 0xffff;
    ulg max_start;

    if (max_block_size > s->pending_buf_size - 5) {
        max_block_size = s->pending_buf_size - 5;
    }

    /* Copy as much as possible from input to output: */
    for (;;) {
        /* Fill the window as much as possible: */
        if (s->lookahead <= 1) {
            Assert(s->strstart < s->w_size+MAX_DIST(s) || s->block_start >= (long)s->w_size, "slide too late");

            fill_window(s);
            if (s->lookahead == 0 && flush == Z_NO_FLUSH)
                return need_more;

            if (s->lookahead == 0)
                break; /* flush the current block */
        }
        Assert(s->block_start >= 0L, "block gone");

        s->strstart += s->lookahead;
        s->lookahead = 0;

        /* Emit a stored block if pending_buf will be full: */
        max_start = s->block_start + max_block_size;
        if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
            /* strstart == 0 is possible when wraparound on 16-bit machine */
            s->lookahead = (uInt)(s->strstart - max_start);
            s->strstart = (uInt)max_start;
            FLUSH_BLOCK(s, 0);
        }
        /* Flush if we may have to slide, otherwise block_start may become
         * negative and the data will be gone:
         */
        if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
            FLUSH_BLOCK(s, 0);
        }
    }
    s->insert = 0;
    if (flush == Z_FINISH) {
        FLUSH_BLOCK(s, 1);
        return finish_done;
    }
    if ((long)s->strstart > s->block_start)
        FLUSH_BLOCK(s, 0);
    return block_done;
}

/* ===========================================================================
 * Compress as much as possible from the input stream, return the current
 * block state.
 * This function does not perform lazy evaluation of matches and inserts
 * new strings in the dictionary only for unmatched strings or for short
 * matches. It is used only for the fast compression options.
 */
local block_state deflate_fast(deflate_state *s, int flush) {
    IPos hash_head;       /* head of the hash chain */
    int bflush;           /* set if current block must be flushed */

    for (;;) {
        /* Make sure that we always have enough lookahead, except
         * at the end of the input file. We need MAX_MATCH bytes
         * for the next match, plus MIN_MATCH bytes to insert the
         * string following the next match.
         */
        if (s->lookahead < MIN_LOOKAHEAD) {
            fill_window(s);
            if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
                return need_more;
            }
            if (s->lookahead == 0)
                break; /* flush the current block */
        }

        /* Insert the string window[strstart .. strstart+2] in the
         * dictionary, and set hash_head to the head of the hash chain:
         */
        hash_head = NIL;
        if (s->lookahead >= MIN_MATCH) {
            hash_head = insert_string(s, s->strstart);
        }

        /* Find the longest match, discarding those <= prev_length.
         * At this point we have always match_length < MIN_MATCH
         */
        if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
            /* To simplify the code, we prevent matches with the string
             * of window index 0 (in particular we have to avoid a match
             * of the string with itself at the start of the input file).
             */
            s->match_length = longest_match(s, hash_head);
            /* longest_match() sets match_start */
        }
        if (s->match_length >= MIN_MATCH) {
            check_match(s, s->strstart, s->match_start, s->match_length);

            _tr_tally_dist(s, s->strstart - s->match_start, s->match_length - MIN_MATCH, bflush);

            s->lookahead -= s->match_length;

            /* Insert new strings in the hash table only if the match length
             * is not too large. This saves time but degrades compression.
             */
            if (s->match_length <= s->max_insert_length &&
                s->lookahead >= MIN_MATCH) {
                s->match_length--; /* string at strstart already in table */
                do {
                    s->strstart++;
                    insert_string(s, s->strstart);
                    /* strstart never exceeds WSIZE-MAX_MATCH, so there are
                     * always MIN_MATCH bytes ahead.
                     */
                } while (--s->match_length != 0);
                s->strstart++;
            } else {
                s->strstart += s->match_length;
                s->match_length = 0;
                s->ins_h = s->window[s->strstart];
                UPDATE_HASH(s, s->ins_h, s->strstart+2 - (MIN_MATCH));
#if MIN_MATCH != 3
                Call UPDATE_HASH() MIN_MATCH-3 more times
#endif
                /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
                 * matter since it will be recomputed at next deflate call.
                 */
            }
        } else {
            /* No match, output a literal byte */
            Tracevv((stderr, "%c", s->window[s->strstart]));
            _tr_tally_lit(s, s->window[s->strstart], bflush);
            s->lookahead--;
            s->strstart++;
        }
        if (bflush)
            FLUSH_BLOCK(s, 0);
    }
    s->insert = s->strstart < MIN_MATCH-1 ? s->strstart : MIN_MATCH-1;
    if (flush == Z_FINISH) {
        FLUSH_BLOCK(s, 1);
        return finish_done;
    }
    if (s->last_lit)
        FLUSH_BLOCK(s, 0);
    return block_done;
}


#ifdef MEDIUM_STRATEGY
#include "deflate_medium.c"
#endif

/* ===========================================================================
 * Same as above, but achieves better compression. We use a lazy
 * evaluation for matches: a match is finally adopted only if there is
 * no better match at the next window position.
 */
local block_state deflate_slow(deflate_state *s, int flush) {
    IPos hash_head;          /* head of hash chain */
    int bflush;              /* set if current block must be flushed */

    /* Process the input block. */
    for (;;) {
        /* Make sure that we always have enough lookahead, except
         * at the end of the input file. We need MAX_MATCH bytes
         * for the next match, plus MIN_MATCH bytes to insert the
         * string following the next match.
         */
        if (s->lookahead < MIN_LOOKAHEAD) {
            fill_window(s);
            if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
                return need_more;
            }
            if (s->lookahead == 0)
                break; /* flush the current block */
        }

        /* Insert the string window[strstart .. strstart+2] in the
         * dictionary, and set hash_head to the head of the hash chain:
         */
        hash_head = NIL;
        if (s->lookahead >= MIN_MATCH) {
            hash_head = insert_string(s, s->strstart);
        }

        /* Find the longest match, discarding those <= prev_length.
         */
        s->prev_length = s->match_length, s->prev_match = s->match_start;
        s->match_length = MIN_MATCH-1;

        if (hash_head != NIL && s->prev_length < s->max_lazy_match && s->strstart - hash_head <= MAX_DIST(s)) {
            /* To simplify the code, we prevent matches with the string
             * of window index 0 (in particular we have to avoid a match
             * of the string with itself at the start of the input file).
             */
            s->match_length = longest_match(s, hash_head);
            /* longest_match() sets match_start */

            if (s->match_length <= 5 && (s->strategy == Z_FILTERED
#if TOO_FAR <= 32767
                || (s->match_length == MIN_MATCH && s->strstart - s->match_start > TOO_FAR)
#endif
                )) {

                /* If prev_match is also MIN_MATCH, match_start is garbage
                 * but we will ignore the current match anyway.
                 */
                s->match_length = MIN_MATCH-1;
            }
        }
        /* If there was a match at the previous step and the current
         * match is not better, output the previous match:
         */
        if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
            uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
            /* Do not insert strings in hash table beyond this. */

            check_match(s, s->strstart-1, s->prev_match, s->prev_length);

            _tr_tally_dist(s, s->strstart -1 - s->prev_match, s->prev_length - MIN_MATCH, bflush);

            /* Insert in hash table all strings up to the end of the match.
             * strstart-1 and strstart are already inserted. If there is not
             * enough lookahead, the last two strings are not inserted in
             * the hash table.
             */
            s->lookahead -= s->prev_length-1;

#ifdef NOT_TWEAK_COMPILER
            s->prev_length -= 2;
            do {
                if (++s->strstart <= max_insert) {
                    hash_head = insert_string(s, s->strstart);
                }
            } while (--s->prev_length != 0);
            s->match_available = 0;
            s->match_length = MIN_MATCH-1;
            s->strstart++;
#else
            {
                uInt mov_fwd = s->prev_length - 2;
                uInt insert_cnt = mov_fwd;
                if (unlikely(insert_cnt > max_insert - s->strstart))
                    insert_cnt = max_insert - s->strstart;

                bulk_insert_str(s, s->strstart + 1, insert_cnt);
                s->prev_length = 0;
                s->match_available = 0;
                s->match_length = MIN_MATCH-1;
                s->strstart += mov_fwd + 1;
            }
#endif /*NOT_TWEAK_COMPILER*/

            if (bflush) FLUSH_BLOCK(s, 0);

        } else if (s->match_available) {
            /* If there was no match at the previous position, output a
             * single literal. If there was a match but the current match
             * is longer, truncate the previous match to a single literal.
             */
            Tracevv((stderr, "%c", s->window[s->strstart-1]));
            _tr_tally_lit(s, s->window[s->strstart-1], bflush);
            if (bflush) {
                FLUSH_BLOCK_ONLY(s, 0);
            }
            s->strstart++;
            s->lookahead--;
            if (s->strm->avail_out == 0)
                return need_more;
        } else {
            /* There is no previous match to compare with, wait for
             * the next step to decide.
             */
            s->match_available = 1;
            s->strstart++;
            s->lookahead--;
        }
    }
    Assert(flush != Z_NO_FLUSH, "no flush?");
    if (s->match_available) {
        Tracevv((stderr, "%c", s->window[s->strstart-1]));
        _tr_tally_lit(s, s->window[s->strstart-1], bflush);
        s->match_available = 0;
    }
    s->insert = s->strstart < MIN_MATCH-1 ? s->strstart : MIN_MATCH-1;
    if (flush == Z_FINISH) {
        FLUSH_BLOCK(s, 1);
        return finish_done;
    }
    if (s->last_lit)
        FLUSH_BLOCK(s, 0);
    return block_done;
}

/* ===========================================================================
 * For Z_RLE, simply look for runs of bytes, generate matches only of distance
 * one.  Do not maintain a hash table.  (It will be regenerated if this run of
 * deflate switches away from Z_RLE.)
 */
local block_state deflate_rle(deflate_state *s, int flush) {
    int bflush;             /* set if current block must be flushed */
    uInt prev;              /* byte at distance one to match */
    unsigned char *scan, *strend;   /* scan goes up to strend for length of run */

    for (;;) {
        /* Make sure that we always have enough lookahead, except
         * at the end of the input file. We need MAX_MATCH bytes
         * for the longest run, plus one for the unrolled loop.
         */
        if (s->lookahead <= MAX_MATCH) {
            fill_window(s);
            if (s->lookahead <= MAX_MATCH && flush == Z_NO_FLUSH) {
                return need_more;
            }
            if (s->lookahead == 0)
                break; /* flush the current block */
        }

        /* See how many times the previous byte repeats */
        s->match_length = 0;
        if (s->lookahead >= MIN_MATCH && s->strstart > 0) {
            scan = s->window + s->strstart - 1;
            prev = *scan;
            if (prev == *++scan && prev == *++scan && prev == *++scan) {
                strend = s->window + s->strstart + MAX_MATCH;
                do {
                } while (prev == *++scan && prev == *++scan &&
                         prev == *++scan && prev == *++scan &&
                         prev == *++scan && prev == *++scan &&
                         prev == *++scan && prev == *++scan &&
                         scan < strend);
                s->match_length = MAX_MATCH - (int)(strend - scan);
                if (s->match_length > s->lookahead)
                    s->match_length = s->lookahead;
            }
            Assert(scan <= s->window+(uInt)(s->window_size-1), "wild scan");
        }

        /* Emit match if have run of MIN_MATCH or longer, else emit literal */
        if (s->match_length >= MIN_MATCH) {
            check_match(s, s->strstart, s->strstart - 1, s->match_length);

            _tr_tally_dist(s, 1, s->match_length - MIN_MATCH, bflush);

            s->lookahead -= s->match_length;
            s->strstart += s->match_length;
            s->match_length = 0;
        } else {
            /* No match, output a literal byte */
            Tracevv((stderr, "%c", s->window[s->strstart]));
            _tr_tally_lit(s, s->window[s->strstart], bflush);
            s->lookahead--;
            s->strstart++;
        }
        if (bflush)
            FLUSH_BLOCK(s, 0);
    }
    s->insert = 0;
    if (flush == Z_FINISH) {
        FLUSH_BLOCK(s, 1);
        return finish_done;
    }
    if (s->last_lit)
        FLUSH_BLOCK(s, 0);
    return block_done;
}

/* ===========================================================================
 * For Z_HUFFMAN_ONLY, do not look for matches.  Do not maintain a hash table.
 * (It will be regenerated if this run of deflate switches away from Huffman.)
 */
local block_state deflate_huff(deflate_state *s, int flush) {
    int bflush;             /* set if current block must be flushed */

    for (;;) {
        /* Make sure that we have a literal to write. */
        if (s->lookahead == 0) {
            fill_window(s);
            if (s->lookahead == 0) {
                if (flush == Z_NO_FLUSH)
                    return need_more;
                break;      /* flush the current block */
            }
        }

        /* Output a literal byte */
        s->match_length = 0;
        Tracevv((stderr, "%c", s->window[s->strstart]));
        _tr_tally_lit(s, s->window[s->strstart], bflush);
        s->lookahead--;
        s->strstart++;
        if (bflush)
            FLUSH_BLOCK(s, 0);
    }
    s->insert = 0;
    if (flush == Z_FINISH) {
        FLUSH_BLOCK(s, 1);
        return finish_done;
    }
    if (s->last_lit)
        FLUSH_BLOCK(s, 0);
    return block_done;
}