Branch data     Line data    Source code

       1                 :            : /* inffast.c -- fast decoding
       2                 :            :  * Copyright (C) 1995-2004 Mark Adler
       3                 :            :  * For conditions of distribution and use, see copyright notice in zlib.h
       4                 :            :  */
       5                 :            : 
       6                 :            : #include <linux/zutil.h>
       7                 :            : #include "inftrees.h"
       8                 :            : #include "inflate.h"
       9                 :            : #include "inffast.h"
      10                 :            : 
      11                 :            : #ifndef ASMINF
      12                 :            : 
      13                 :            : union uu {
      14                 :            :         unsigned short us;
      15                 :            :         unsigned char b[2];
      16                 :            : };
      17                 :            : 
      18                 :            : /* Endian independed version */
      19                 :            : static inline unsigned short
      20                 :            : get_unaligned16(const unsigned short *p)
      21                 :            : {
      22                 :            :         union uu  mm;
      23                 :            :         unsigned char *b = (unsigned char *)p;
      24                 :            : 
      25                 :            :         mm.b[0] = b[0];
      26                 :            :         mm.b[1] = b[1];
      27                 :            :         return mm.us;
      28                 :            : }
      29                 :            : 
      30                 :            : /*
      31                 :            :    Decode literal, length, and distance codes and write out the resulting
      32                 :            :    literal and match bytes until either not enough input or output is
      33                 :            :    available, an end-of-block is encountered, or a data error is encountered.
      34                 :            :    When large enough input and output buffers are supplied to inflate(), for
      35                 :            :    example, a 16K input buffer and a 64K output buffer, more than 95% of the
      36                 :            :    inflate execution time is spent in this routine.
      37                 :            : 
      38                 :            :    Entry assumptions:
      39                 :            : 
      40                 :            :         state->mode == LEN
      41                 :            :         strm->avail_in >= 6
      42                 :            :         strm->avail_out >= 258
      43                 :            :         start >= strm->avail_out
      44                 :            :         state->bits < 8
      45                 :            : 
      46                 :            :    On return, state->mode is one of:
      47                 :            : 
      48                 :            :         LEN -- ran out of enough output space or enough available input
      49                 :            :         TYPE -- reached end of block code, inflate() to interpret next block
      50                 :            :         BAD -- error in block data
      51                 :            : 
      52                 :            :    Notes:
      53                 :            : 
      54                 :            :     - The maximum input bits used by a length/distance pair is 15 bits for the
      55                 :            :       length code, 5 bits for the length extra, 15 bits for the distance code,
      56                 :            :       and 13 bits for the distance extra.  This totals 48 bits, or six bytes.
      57                 :            :       Therefore if strm->avail_in >= 6, then there is enough input to avoid
      58                 :            :       checking for available input while decoding.
      59                 :            : 
      60                 :            :     - The maximum bytes that a single length/distance pair can output is 258
      61                 :            :       bytes, which is the maximum length that can be coded.  inflate_fast()
      62                 :            :       requires strm->avail_out >= 258 for each loop to avoid checking for
      63                 :            :       output space.
      64                 :            : 
      65                 :            :     - @start:   inflate()'s starting value for strm->avail_out
      66                 :            :  */
      67                 :          0 : void inflate_fast(z_streamp strm, unsigned start)
      68                 :            : {
      69                 :            :     struct inflate_state *state;
      70                 :            :     const unsigned char *in;    /* local strm->next_in */
      71                 :            :     const unsigned char *last;  /* while in < last, enough input available */
      72                 :            :     unsigned char *out;         /* local strm->next_out */
      73                 :            :     unsigned char *beg;         /* inflate()'s initial strm->next_out */
      74                 :            :     unsigned char *end;         /* while out < end, enough space available */
      75                 :            : #ifdef INFLATE_STRICT
      76                 :            :     unsigned dmax;              /* maximum distance from zlib header */
      77                 :            : #endif
      78                 :            :     unsigned wsize;             /* window size or zero if not using window */
      79                 :            :     unsigned whave;             /* valid bytes in the window */
      80                 :            :     unsigned write;             /* window write index */
      81                 :            :     unsigned char *window;      /* allocated sliding window, if wsize != 0 */
      82                 :            :     unsigned long hold;         /* local strm->hold */
      83                 :            :     unsigned bits;              /* local strm->bits */
      84                 :            :     code const *lcode;          /* local strm->lencode */
      85                 :            :     code const *dcode;          /* local strm->distcode */
      86                 :            :     unsigned lmask;             /* mask for first level of length codes */
      87                 :            :     unsigned dmask;             /* mask for first level of distance codes */
      88                 :            :     code this;                  /* retrieved table entry */
      89                 :            :     unsigned op;                /* code bits, operation, extra bits, or */
      90                 :            :                                 /*  window position, window bytes to copy */
      91                 :            :     unsigned len;               /* match length, unused bytes */
      92                 :            :     unsigned dist;              /* match distance */
      93                 :            :     unsigned char *from;        /* where to copy match from */
      94                 :            : 
      95                 :            :     /* copy state to local variables */
      96                 :          0 :     state = (struct inflate_state *)strm->state;
      97                 :          0 :     in = strm->next_in;
      98                 :          0 :     last = in + (strm->avail_in - 5);
      99                 :          0 :     out = strm->next_out;
     100                 :          0 :     beg = out - (start - strm->avail_out);
     101                 :          0 :     end = out + (strm->avail_out - 257);
     102                 :            : #ifdef INFLATE_STRICT
     103                 :            :     dmax = state->dmax;
     104                 :            : #endif
     105                 :          0 :     wsize = state->wsize;
     106                 :          0 :     whave = state->whave;
     107                 :          0 :     write = state->write;
     108                 :          0 :     window = state->window;
     109                 :          0 :     hold = state->hold;
     110                 :          0 :     bits = state->bits;
     111                 :          0 :     lcode = state->lencode;
     112                 :          0 :     dcode = state->distcode;
     113                 :          0 :     lmask = (1U << state->lenbits) - 1;
     114                 :          0 :     dmask = (1U << state->distbits) - 1;
     115                 :            : 
     116                 :            :     /* decode literals and length/distances until end-of-block or not enough
     117                 :            :        input data or output space */
     118                 :            :     do {
     119         [ #  # ]:          0 :         if (bits < 15) {
     120                 :          0 :             hold += (unsigned long)(*in++) << bits;
     121                 :          0 :             bits += 8;
     122                 :          0 :             hold += (unsigned long)(*in++) << bits;
     123                 :          0 :             bits += 8;
     124                 :            :         }
     125                 :          0 :         this = lcode[hold & lmask];
     126                 :            :       dolen:
     127                 :          0 :         op = (unsigned)(this.bits);
     128                 :          0 :         hold >>= op;
     129                 :          0 :         bits -= op;
     130                 :          0 :         op = (unsigned)(this.op);
     131         [ #  # ]:          0 :         if (op == 0) {                          /* literal */
     132                 :          0 :             *out++ = (unsigned char)(this.val);
     133                 :            :         }
     134         [ #  # ]:          0 :         else if (op & 16) {                     /* length base */
     135                 :          0 :             len = (unsigned)(this.val);
     136                 :          0 :             op &= 15;                           /* number of extra bits */
     137         [ #  # ]:          0 :             if (op) {
     138         [ #  # ]:          0 :                 if (bits < op) {
     139                 :          0 :                     hold += (unsigned long)(*in++) << bits;
     140                 :          0 :                     bits += 8;
     141                 :            :                 }
     142                 :          0 :                 len += (unsigned)hold & ((1U << op) - 1);
     143                 :          0 :                 hold >>= op;
     144                 :          0 :                 bits -= op;
     145                 :            :             }
     146         [ #  # ]:          0 :             if (bits < 15) {
     147                 :          0 :                 hold += (unsigned long)(*in++) << bits;
     148                 :          0 :                 bits += 8;
     149                 :          0 :                 hold += (unsigned long)(*in++) << bits;
     150                 :          0 :                 bits += 8;
     151                 :            :             }
     152                 :          0 :             this = dcode[hold & dmask];
     153                 :            :           dodist:
     154                 :          0 :             op = (unsigned)(this.bits);
     155                 :          0 :             hold >>= op;
     156                 :          0 :             bits -= op;
     157                 :            :             op = (unsigned)(this.op);
     158         [ #  # ]:          0 :             if (op & 16) {                      /* distance base */
     159                 :          0 :                 dist = (unsigned)(this.val);
     160                 :          0 :                 op &= 15;                       /* number of extra bits */
     161         [ #  # ]:          0 :                 if (bits < op) {
     162                 :          0 :                     hold += (unsigned long)(*in++) << bits;
     163                 :          0 :                     bits += 8;
     164         [ #  # ]:          0 :                     if (bits < op) {
     165                 :          0 :                         hold += (unsigned long)(*in++) << bits;
     166                 :          0 :                         bits += 8;
     167                 :            :                     }
     168                 :            :                 }
     169                 :          0 :                 dist += (unsigned)hold & ((1U << op) - 1);
     170                 :            : #ifdef INFLATE_STRICT
     171                 :            :                 if (dist > dmax) {
     172                 :            :                     strm->msg = (char *)"invalid distance too far back";
     173                 :            :                     state->mode = BAD;
     174                 :            :                     break;
     175                 :            :                 }
     176                 :            : #endif
     177                 :          0 :                 hold >>= op;
     178                 :          0 :                 bits -= op;
     179                 :          0 :                 op = (unsigned)(out - beg);     /* max distance in output */
     180         [ #  # ]:          0 :                 if (dist > op) {                /* see if copy from window */
     181                 :          0 :                     op = dist - op;             /* distance back in window */
     182         [ #  # ]:          0 :                     if (op > whave) {
     183                 :          0 :                         strm->msg = (char *)"invalid distance too far back";
     184                 :          0 :                         state->mode = BAD;
     185                 :          0 :                         break;
     186                 :            :                     }
     187                 :            :                     from = window;
     188         [ #  # ]:          0 :                     if (write == 0) {           /* very common case */
     189                 :          0 :                         from += wsize - op;
     190         [ #  # ]:          0 :                         if (op < len) {         /* some from window */
     191                 :          0 :                             len -= op;
     192                 :            :                             do {
     193                 :          0 :                                 *out++ = *from++;
     194         [ #  # ]:          0 :                             } while (--op);
     195                 :          0 :                             from = out - dist;  /* rest from output */
     196                 :            :                         }
     197                 :            :                     }
     198         [ #  # ]:          0 :                     else if (write < op) {      /* wrap around window */
     199                 :          0 :                         from += wsize + write - op;
     200                 :          0 :                         op -= write;
     201         [ #  # ]:          0 :                         if (op < len) {         /* some from end of window */
     202                 :          0 :                             len -= op;
     203                 :            :                             do {
     204                 :          0 :                                 *out++ = *from++;
     205         [ #  # ]:          0 :                             } while (--op);
     206                 :            :                             from = window;
     207         [ #  # ]:          0 :                             if (write < len) {  /* some from start of window */
     208                 :            :                                 op = write;
     209                 :          0 :                                 len -= op;
     210                 :            :                                 do {
     211                 :          0 :                                     *out++ = *from++;
     212         [ #  # ]:          0 :                                 } while (--op);
     213                 :          0 :                                 from = out - dist;      /* rest from output */
     214                 :            :                             }
     215                 :            :                         }
     216                 :            :                     }
     217                 :            :                     else {                      /* contiguous in window */
     218                 :          0 :                         from += write - op;
     219         [ #  # ]:          0 :                         if (op < len) {         /* some from window */
     220                 :          0 :                             len -= op;
     221                 :            :                             do {
     222                 :          0 :                                 *out++ = *from++;
     223         [ #  # ]:          0 :                             } while (--op);
     224                 :          0 :                             from = out - dist;  /* rest from output */
     225                 :            :                         }
     226                 :            :                     }
     227         [ #  # ]:          0 :                     while (len > 2) {
     228                 :          0 :                         *out++ = *from++;
     229                 :          0 :                         *out++ = *from++;
     230                 :          0 :                         *out++ = *from++;
     231                 :          0 :                         len -= 3;
     232                 :            :                     }
     233         [ #  # ]:          0 :                     if (len) {
     234                 :          0 :                         *out++ = *from++;
     235         [ #  # ]:          0 :                         if (len > 1)
     236                 :          0 :                             *out++ = *from++;
     237                 :            :                     }
     238                 :            :                 }
     239                 :            :                 else {
     240                 :            :                     unsigned short *sout;
     241                 :            :                     unsigned long loops;
     242                 :            : 
     243                 :          0 :                     from = out - dist;          /* copy direct from output */
     244                 :            :                     /* minimum length is three */
     245                 :            :                     /* Align out addr */
     246         [ #  # ]:          0 :                     if (!((long)(out - 1) & 1)) {
     247                 :          0 :                         *out++ = *from++;
     248                 :          0 :                         len--;
     249                 :            :                     }
     250                 :            :                     sout = (unsigned short *)(out);
     251         [ #  # ]:          0 :                     if (dist > 2) {
     252                 :            :                         unsigned short *sfrom;
     253                 :            : 
     254                 :            :                         sfrom = (unsigned short *)(from);
     255                 :          0 :                         loops = len >> 1;
     256                 :            :                         do
     257                 :            : #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
     258                 :          0 :                             *sout++ = *sfrom++;
     259                 :            : #else
     260                 :            :                             *sout++ = get_unaligned16(sfrom++);
     261                 :            : #endif
     262         [ #  # ]:          0 :                         while (--loops);
     263                 :          0 :                         out = (unsigned char *)sout;
     264                 :          0 :                         from = (unsigned char *)sfrom;
     265                 :            :                     } else { /* dist == 1 or dist == 2 */
     266                 :            :                         unsigned short pat16;
     267                 :            : 
     268                 :          0 :                         pat16 = *(sout-1);
     269         [ #  # ]:          0 :                         if (dist == 1) {
     270                 :            :                                 union uu mm;
     271                 :            :                                 /* copy one char pattern to both bytes */
     272                 :          0 :                                 mm.us = pat16;
     273                 :          0 :                                 mm.b[0] = mm.b[1];
     274                 :          0 :                                 pat16 = mm.us;
     275                 :            :                         }
     276                 :          0 :                         loops = len >> 1;
     277                 :            :                         do
     278                 :          0 :                             *sout++ = pat16;
     279         [ #  # ]:          0 :                         while (--loops);
     280                 :          0 :                         out = (unsigned char *)sout;
     281                 :            :                     }
     282         [ #  # ]:          0 :                     if (len & 1)
     283                 :          0 :                         *out++ = *from++;
     284                 :            :                 }
     285                 :            :             }
     286         [ #  # ]:          0 :             else if ((op & 64) == 0) {          /* 2nd level distance code */
     287                 :          0 :                 this = dcode[this.val + (hold & ((1U << op) - 1))];
     288                 :          0 :                 goto dodist;
     289                 :            :             }
     290                 :            :             else {
     291                 :          0 :                 strm->msg = (char *)"invalid distance code";
     292                 :          0 :                 state->mode = BAD;
     293                 :          0 :                 break;
     294                 :            :             }
     295                 :            :         }
     296         [ #  # ]:          0 :         else if ((op & 64) == 0) {              /* 2nd level length code */
     297                 :          0 :             this = lcode[this.val + (hold & ((1U << op) - 1))];
     298                 :          0 :             goto dolen;
     299                 :            :         }
     300         [ #  # ]:          0 :         else if (op & 32) {                     /* end-of-block */
     301                 :          0 :             state->mode = TYPE;
     302                 :          0 :             break;
     303                 :            :         }
     304                 :            :         else {
     305                 :          0 :             strm->msg = (char *)"invalid literal/length code";
     306                 :          0 :             state->mode = BAD;
     307                 :          0 :             break;
     308                 :            :         }
     309         [ #  # ]:          0 :     } while (in < last && out < end);
     310                 :            : 
     311                 :            :     /* return unused bytes (on entry, bits < 8, so in won't go too far back) */
     312                 :          0 :     len = bits >> 3;
     313                 :          0 :     in -= len;
     314                 :          0 :     bits -= len << 3;
     315                 :          0 :     hold &= (1U << bits) - 1;
     316                 :            : 
     317                 :            :     /* update state and return */
     318                 :          0 :     strm->next_in = in;
     319                 :          0 :     strm->next_out = out;
     320         [ #  # ]:          0 :     strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
     321         [ #  # ]:          0 :     strm->avail_out = (unsigned)(out < end ?
     322                 :          0 :                                  257 + (end - out) : 257 - (out - end));
     323                 :          0 :     state->hold = hold;
     324                 :          0 :     state->bits = bits;
     325                 :          0 :     return;
     326                 :            : }
     327                 :            : 
     328                 :            : /*
     329                 :            :    inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
     330                 :            :    - Using bit fields for code structure
     331                 :            :    - Different op definition to avoid & for extra bits (do & for table bits)
     332                 :            :    - Three separate decoding do-loops for direct, window, and write == 0
     333                 :            :    - Special case for distance > 1 copies to do overlapped load and store copy
     334                 :            :    - Explicit branch predictions (based on measured branch probabilities)
     335                 :            :    - Deferring match copy and interspersed it with decoding subsequent codes
     336                 :            :    - Swapping literal/length else
     337                 :            :    - Swapping window/direct else
     338                 :            :    - Larger unrolled copy loops (three is about right)
     339                 :            :    - Moving len -= 3 statement into middle of loop
     340                 :            :  */
     341                 :            : 
     342                 :            : #endif /* !ASMINF */