lib/zlib_inflate/inflate_sync.c

   1 /* inflate.c -- zlib interface to inflate modules
   2  * Copyright (C) 1995-1998 Mark Adler
   3  * For conditions of distribution and use, see copyright notice in zlib.h
   4  */
   5
   6 #include <linux/zutil.h>
   7 #include "infblock.h"
   8 #include "infutil.h"
   9
  10 int zlib_inflateSync(
  11         z_streamp z
  12 )
  13 {
  14   uInt n;       /* number of bytes to look at */
  15   Byte *p;      /* pointer to bytes */
  16   uInt m;       /* number of marker bytes found in a row */
  17   uLong r, w;   /* temporaries to save total_in and total_out */
  18
  19   /* set up */
  20   if (z == NULL || z->state == NULL)
  21     return Z_STREAM_ERROR;
  22   if (z->state->mode != I_BAD)
  23   {
  24     z->state->mode = I_BAD;
  25     z->state->sub.marker = 0;
  26   }
  27   if ((n = z->avail_in) == 0)
  28     return Z_BUF_ERROR;
  29   p = z->next_in;
  30   m = z->state->sub.marker;
  31
  32   /* search */
  33   while (n && m < 4)
  34   {
  35     static const Byte mark[4] = {0, 0, 0xff, 0xff};
  36     if (*p == mark[m])
  37       m++;
  38     else if (*p)
  39       m = 0;
  40     else
  41       m = 4 - m;
  42     p++, n--;
  43   }
  44
  45   /* restore */
  46   z->total_in += p - z->next_in;
  47   z->next_in = p;
  48   z->avail_in = n;
  49   z->state->sub.marker = m;
  50
  51   /* return no joy or set up to restart on a new block */
  52   if (m != 4)
  53     return Z_DATA_ERROR;
  54   r = z->total_in;  w = z->total_out;
  55   zlib_inflateReset(z);
  56   z->total_in = r;  z->total_out = w;
  57   z->state->mode = BLOCKS;
  58   return Z_OK;
  59 }
  60
  61
  62 /* Returns true if inflate is currently at the end of a block generated
  63  * by Z_SYNC_FLUSH or Z_FULL_FLUSH. This function is used by one PPP
  64  * implementation to provide an additional safety check. PPP uses Z_SYNC_FLUSH
  65  * but removes the length bytes of the resulting empty stored block. When
  66  * decompressing, PPP checks that at the end of input packet, inflate is
  67  * waiting for these length bytes.
  68  */
  69 int zlib_inflateSyncPoint(
  70         z_streamp z
  71 )
  72 {
  73   if (z == NULL || z->state == NULL || z->state->blocks == NULL)
  74     return Z_STREAM_ERROR;
  75   return zlib_inflate_blocks_sync_point(z->state->blocks);
  76 }
  77
  78 /*
  79  * This subroutine adds the data at next_in/avail_in to the output history
  80  * without performing any output.  The output buffer must be "caught up";
  81  * i.e. no pending output (hence s->read equals s->write), and the state must
  82  * be BLOCKS (i.e. we should be willing to see the start of a series of
  83  * BLOCKS).  On exit, the output will also be caught up, and the checksum
  84  * will have been updated if need be.
  85  */
  86 static int zlib_inflate_addhistory(inflate_blocks_statef *s,
  87                                       z_stream              *z)
  88 {
  89     uLong b;              /* bit buffer */  /* NOT USED HERE */
  90     uInt k;               /* bits in bit buffer */ /* NOT USED HERE */
  91     uInt t;               /* temporary storage */
  92     Byte *p;              /* input data pointer */
  93     uInt n;               /* bytes available there */
  94     Byte *q;              /* output window write pointer */
  95     uInt m;               /* bytes to end of window or read pointer */
  96
  97     if (s->read != s->write)
  98         return Z_STREAM_ERROR;
  99     if (s->mode != TYPE)
 100         return Z_DATA_ERROR;
 101
 102     /* we're ready to rock */
 103     LOAD
 104     /* while there is input ready, copy to output buffer, moving
 105      * pointers as needed.
 106      */
 107     while (n) {
 108         t = n;  /* how many to do */
 109         /* is there room until end of buffer? */
 110         if (t > m) t = m;
 111         /* update check information */
 112         if (s->checkfn != NULL)
 113             s->check = (*s->checkfn)(s->check, q, t);
 114         memcpy(q, p, t);
 115         q += t;
 116         p += t;
 117         n -= t;
 118         z->total_out += t;
 119         s->read = q;    /* drag read pointer forward */
 120 /*      WWRAP  */       /* expand WWRAP macro by hand to handle s->read */
 121         if (q == s->end) {
 122             s->read = q = s->window;
 123             m = WAVAIL;
 124         }
 125     }
 126     UPDATE
 127     return Z_OK;
 128 }
 129
 130
 131 /*
 132  * This subroutine adds the data at next_in/avail_in to the output history
 133  * without performing any output.  The output buffer must be "caught up";
 134  * i.e. no pending output (hence s->read equals s->write), and the state must
 135  * be BLOCKS (i.e. we should be willing to see the start of a series of
 136  * BLOCKS).  On exit, the output will also be caught up, and the checksum
 137  * will have been updated if need be.
 138  */
 139
 140 int zlib_inflateIncomp(
 141         z_stream *z
 142
 143 )
 144 {
 145     if (z->state->mode != BLOCKS)
 146         return Z_DATA_ERROR;
 147     return zlib_inflate_addhistory(z->state->blocks, z);
 148 }