arch/powerpc/boot/gunzip_util.c

   1 /*
   2  * Copyright 2007 David Gibson, IBM Corporation.
   3  * Based on earlier work, Copyright (C) Paul Mackerras 1997.
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License
   7  * as published by the Free Software Foundation; either version
   8  * 2 of the License, or (at your option) any later version.
   9  */
  10
  11 #include <stddef.h>
  12 #include "string.h"
  13 #include "stdio.h"
  14 #include "ops.h"
  15 #include "gunzip_util.h"
  16
  17 #define HEAD_CRC        2
  18 #define EXTRA_FIELD     4
  19 #define ORIG_NAME       8
  20 #define COMMENT         0x10
  21 #define RESERVED        0xe0
  22
  23 /**
  24  * gunzip_start - prepare to decompress gzip data
  25  * @state:     decompressor state structure to be initialized
  26  * @src:       buffer containing gzip compressed or uncompressed data
  27  * @srclen:    size in bytes of the buffer at src
  28  *
  29  * If the buffer at @src contains a gzip header, this function
  30  * initializes zlib to decompress the data, storing the decompression
  31  * state in @state.  The other functions in this file can then be used
  32  * to decompress data from the gzipped stream.
  33  *
  34  * If the buffer at @src does not contain a gzip header, it is assumed
  35  * to contain uncompressed data.  The buffer information is recorded
  36  * in @state and the other functions in this file will simply copy
  37  * data from the uncompressed data stream at @src.
  38  *
  39  * Any errors, such as bad compressed data, cause an error to be
  40  * printed an the platform's exit() function to be called.
  41  */
  42 void gunzip_start(struct gunzip_state *state, void *src, int srclen)
  43 {
  44         char *hdr = src;
  45         int hdrlen = 0;
  46
  47         memset(state, 0, sizeof(*state));
  48
  49         /* Check for gzip magic number */
  50         if ((hdr[0] == 0x1f) && (hdr[1] == 0x8b)) {
  51                 /* gzip data, initialize zlib parameters */
  52                 int r, flags;
  53
  54                 state->s.workspace = state->scratch;
  55                 if (zlib_inflate_workspacesize() > sizeof(state->scratch))
  56                         fatal("insufficient scratch space for gunzip\n\r");
  57
  58                 /* skip header */
  59                 hdrlen = 10;
  60                 flags = hdr[3];
  61                 if (hdr[2] != Z_DEFLATED || (flags & RESERVED) != 0)
  62                         fatal("bad gzipped data\n\r");
  63                 if ((flags & EXTRA_FIELD) != 0)
  64                         hdrlen = 12 + hdr[10] + (hdr[11] << 8);
  65                 if ((flags & ORIG_NAME) != 0)
  66                         while (hdr[hdrlen++] != 0)
  67                                 ;
  68                 if ((flags & COMMENT) != 0)
  69                         while (hdr[hdrlen++] != 0)
  70                                 ;
  71                 if ((flags & HEAD_CRC) != 0)
  72                         hdrlen += 2;
  73                 if (hdrlen >= srclen)
  74                         fatal("gunzip_start: ran out of data in header\n\r");
  75
  76                 r = zlib_inflateInit2(&state->s, -MAX_WBITS);
  77                 if (r != Z_OK)
  78                         fatal("inflateInit2 returned %d\n\r", r);
  79         }
  80
  81         state->s.next_in = src + hdrlen;
  82         state->s.avail_in = srclen - hdrlen;
  83 }
  84
  85 /**
  86  * gunzip_partial - extract bytes from a gzip data stream
  87  * @state:     gzip state structure previously initialized by gunzip_start()
  88  * @dst:       buffer to store extracted data
  89  * @dstlen:    maximum number of bytes to extract
  90  *
  91  * This function extracts at most @dstlen bytes from the data stream
  92  * previously associated with @state by gunzip_start(), decompressing
  93  * if necessary.  Exactly @dstlen bytes are extracted unless the data
  94  * stream doesn't contain enough bytes, in which case the entire
  95  * remainder of the stream is decompressed.
  96  *
  97  * Returns the actual number of bytes extracted.  If any errors occur,
  98  * such as a corrupted compressed stream, an error is printed an the
  99  * platform's exit() function is called.
 100  */
 101 int gunzip_partial(struct gunzip_state *state, void *dst, int dstlen)
 102 {
 103         int len;
 104
 105         if (state->s.workspace) {
 106                 /* gunzipping */
 107                 int r;
 108
 109                 state->s.next_out = dst;
 110                 state->s.avail_out = dstlen;
 111                 r = zlib_inflate(&state->s, Z_FULL_FLUSH);
 112                 if (r != Z_OK && r != Z_STREAM_END)
 113                         fatal("inflate returned %d msg: %s\n\r", r, state->s.msg);
 114                 len = state->s.next_out - (unsigned char *)dst;
 115         } else {
 116                 /* uncompressed image */
 117                 len = min(state->s.avail_in, (unsigned)dstlen);
 118                 memcpy(dst, state->s.next_in, len);
 119                 state->s.next_in += len;
 120                 state->s.avail_in -= len;
 121         }
 122         return len;
 123 }
 124
 125 /**
 126  * gunzip_exactly - extract a fixed number of bytes from a gzip data stream
 127  * @state:     gzip state structure previously initialized by gunzip_start()
 128  * @dst:       buffer to store extracted data
 129  * @dstlen:    number of bytes to extract
 130  *
 131  * This function extracts exactly @dstlen bytes from the data stream
 132  * previously associated with @state by gunzip_start(), decompressing
 133  * if necessary.
 134  *
 135  * If there are less @dstlen bytes available in the data stream, or if
 136  * any other errors occur, such as a corrupted compressed stream, an
 137  * error is printed an the platform's exit() function is called.
 138  */
 139 void gunzip_exactly(struct gunzip_state *state, void *dst, int dstlen)
 140 {
 141         int len;
 142
 143         len  = gunzip_partial(state, dst, dstlen);
 144         if (len < dstlen)
 145                 fatal("gunzip_block: ran out of data\n\r");
 146 }
 147
 148 /**
 149  * gunzip_discard - discard bytes from a gzip data stream
 150  * @state:     gzip state structure previously initialized by gunzip_start()
 151  * @len:       number of bytes to discard
 152  *
 153  * This function extracts, then discards exactly @len bytes from the
 154  * data stream previously associated with @state by gunzip_start().
 155  * Subsequent gunzip_partial(), gunzip_exactly() or gunzip_finish()
 156  * calls will extract the data following the discarded bytes in the
 157  * data stream.
 158  *
 159  * If there are less @len bytes available in the data stream, or if
 160  * any other errors occur, such as a corrupted compressed stream, an
 161  * error is printed an the platform's exit() function is called.
 162  */
 163 void gunzip_discard(struct gunzip_state *state, int len)
 164 {
 165         static char discard_buf[128];
 166
 167         while (len > sizeof(discard_buf)) {
 168                 gunzip_exactly(state, discard_buf, sizeof(discard_buf));
 169                 len -= sizeof(discard_buf);
 170         }
 171
 172         if (len > 0)
 173                 gunzip_exactly(state, discard_buf, len);
 174 }
 175
 176 /**
 177  * gunzip_finish - extract all remaining bytes from a gzip data stream
 178  * @state:     gzip state structure previously initialized by gunzip_start()
 179  * @dst:       buffer to store extracted data
 180  * @dstlen:    maximum number of bytes to extract
 181  *
 182  * This function extracts all remaining data, or at most @dstlen
 183  * bytes, from the stream previously associated with @state by
 184  * gunzip_start().  zlib is then shut down, so it is an error to use
 185  * any of the functions in this file on @state until it is
 186  * re-initialized with another call to gunzip_start().
 187  *
 188  * If any errors occur, such as a corrupted compressed stream, an
 189  * error is printed an the platform's exit() function is called.
 190  */
 191 int gunzip_finish(struct gunzip_state *state, void *dst, int dstlen)
 192 {
 193         int len;
 194
 195         if (state->s.workspace) {
 196                 len = gunzip_partial(state, dst, dstlen);
 197                 zlib_inflateEnd(&state->s);
 198         } else {
 199                 /* uncompressed image */
 200                 len = min(state->s.avail_in, (unsigned)dstlen);
 201                 memcpy(dst, state->s.next_in, len);
 202         }
 203
 204         return len;
 205 }