xpress_decode_match(): Allow lengths encoded in unnecessary bytes

[wimlib] / src / xpress-decompress.c

diff --git a/src/xpress-decompress.c b/src/xpress-decompress.c
index 87205543022ed76c041b6a5f9f5714ddeeaf4ee0..9c5d48662883baa0cb8edb4805f0ec27e0d3b90a 100644 (file)
--- a/src/xpress-decompress.c
+++ b/src/xpress-decompress.c
@@ -88,8 +88,10 @@
  *
  * Note: taking the low 8 bits of the symbol is the same as subtracting 256, the
  * number of symbols reserved for literals.
+ *
+ * Returns the match length, or -1 on error.
  */
-static int xpress_decode_match(int huffsym, unsigned window_pos,
+static int xpress_decode_match(unsigned huffsym, unsigned window_pos,
                               unsigned window_len, u8 window[],
                               struct input_bitstream *istream)
 {
@@ -105,27 +107,25 @@ static int xpress_decode_match(int huffsym, unsigned window_pos,
 
        ret = bitstream_read_bits(istream, offset_bsr, &match_offset);
        if (ret != 0)
-               return -1;
+               return ret;
        match_offset |= (1 << offset_bsr);
 
        if (len_hdr == 0xf) {
                ret = bitstream_read_byte(istream);
-               if (ret == -1)
-                       return -1;
+               if (ret < 0)
+                       return ret;
                match_len = ret;
                if (match_len == 0xff) {
                        ret = bitstream_read_byte(istream);
-                       if (ret == -1)
-                               return -1;
+                       if (ret < 0)
+                               return ret;
                        match_len = ret;
 
                        ret = bitstream_read_byte(istream);
-                       if (ret == -1)
-                               return -1;
+                       if (ret < 0)
+                               return ret;
 
                        match_len |= (ret << 8);
-                       if (match_len < 0xf)
-                               return -1;
                } else {
                        match_len += 0xf;
                }
@@ -162,23 +162,24 @@ static int xpress_decode_match(int huffsym, unsigned window_pos,
 
 /* Decodes the Huffman-encoded matches and literal bytes in a block of
  * XPRESS-encoded data. */
-static int xpress_decompress_literals(struct input_bitstream *istream,
-                                     u8 uncompressed_data[],
-                                     unsigned uncompressed_len,
-                                     const u8 lens[],
-                                     const u16 decode_table[])
+static int xpress_decompress_block(struct input_bitstream *istream,
+                                  u8 uncompressed_data[],
+                                  unsigned uncompressed_len,
+                                  const u8 lens[],
+                                  const u16 decode_table[])
 {
-       unsigned curpos = 0;
+       unsigned curpos;
        unsigned huffsym;
+       int ret;
        int match_len;
-       int ret = 0;
 
+       curpos = 0;
        while (curpos < uncompressed_len) {
                ret = read_huffsym(istream, decode_table, lens,
                                   XPRESS_NUM_SYMBOLS, XPRESS_TABLEBITS,
                                   &huffsym, XPRESS_MAX_CODEWORD_LEN);
                if (ret != 0)
-                       break;
+                       return ret;
 
                if (huffsym < XPRESS_NUM_CHARS) {
                        uncompressed_data[curpos++] = huffsym;
@@ -188,14 +189,12 @@ static int xpress_decompress_literals(struct input_bitstream *istream,
                                                        uncompressed_len,
                                                        uncompressed_data,
                                                        istream);
-                       if (match_len == -1) {
-                               ret = 1;
-                               break;
-                       }
+                       if (match_len < 0)
+                               return match_len;
                        curpos += match_len;
                }
        }
-       return ret;
+       return 0;
 }
 
 
@@ -221,7 +220,7 @@ int xpress_decompress(const void *__compressed_data, unsigned compressed_len,
         * in the first 256 bytes of the compressed data.
         */
        if (compressed_len < XPRESS_NUM_SYMBOLS / 2)
-               return WIMLIB_ERR_DECOMPRESSION;
+               return -1;
 
        for (i = 0; i < XPRESS_NUM_SYMBOLS / 2; i++) {
                *lens_p++ = compressed_data[i] & 0xf;
@@ -237,7 +236,7 @@ int xpress_decompress(const void *__compressed_data, unsigned compressed_len,
        init_input_bitstream(&istream, compressed_data + XPRESS_NUM_SYMBOLS / 2,
                             compressed_len - XPRESS_NUM_SYMBOLS / 2);
 
-       return xpress_decompress_literals(&istream, uncompressed_data,
-                                         uncompressed_len, lens,
-                                         decode_table);
+       return xpress_decompress_block(&istream, uncompressed_data,
+                                      uncompressed_len, lens,
+                                      decode_table);
 }