xpress_decompress.c: make 'lens' and 'decode_table' share memory
authorEric Biggers <ebiggers3@gmail.com>
Mon, 20 Jul 2015 04:35:31 +0000 (23:35 -0500)
committerEric Biggers <ebiggers3@gmail.com>
Wed, 22 Jul 2015 04:55:44 +0000 (23:55 -0500)
src/xpress_decompress.c

index 2951be1..8a9f491 100644 (file)
@@ -132,10 +132,12 @@ xpress_decompress(const void *compressed_data, size_t compressed_size,
                  void *uncompressed_data, size_t uncompressed_size, void *_ctx)
 {
        const u8 *cdata = compressed_data;
-       u8 lens[XPRESS_NUM_SYMBOLS];
        u8 *lens_p;
-       u16 decode_table[(1 << XPRESS_TABLEBITS) + 2 * XPRESS_NUM_SYMBOLS]
-                       _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+       union {
+               u16 decode_table[(1 << XPRESS_TABLEBITS) + 2 * XPRESS_NUM_SYMBOLS]
+                               _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+               u8 lens[XPRESS_NUM_SYMBOLS];
+       } u;
        struct input_bitstream istream;
 
        /* XPRESS uses only one Huffman code.  It contains 512 symbols, and the
@@ -144,21 +146,21 @@ xpress_decompress(const void *compressed_data, size_t compressed_size,
        if (compressed_size < XPRESS_NUM_SYMBOLS / 2)
                return -1;
 
-       lens_p = lens;
+       lens_p = u.lens;
        for (unsigned i = 0; i < XPRESS_NUM_SYMBOLS / 2; i++) {
                *lens_p++ = cdata[i] & 0xf;
                *lens_p++ = cdata[i] >> 4;
        }
 
-       if (make_huffman_decode_table(decode_table, XPRESS_NUM_SYMBOLS,
-                                     XPRESS_TABLEBITS, lens,
+       if (make_huffman_decode_table(u.decode_table, XPRESS_NUM_SYMBOLS,
+                                     XPRESS_TABLEBITS, u.lens,
                                      XPRESS_MAX_CODEWORD_LEN))
                return -1;
 
        init_input_bitstream(&istream, cdata + XPRESS_NUM_SYMBOLS / 2,
                             compressed_size - XPRESS_NUM_SYMBOLS / 2);
 
-       return xpress_decode_window(&istream, decode_table,
+       return xpress_decode_window(&istream, u.decode_table,
                                    uncompressed_data, uncompressed_size);
 }