/*
*
- * Copyright (C) 2012, 2013 Eric Biggers
+ * Copyright (C) 2012, 2013, 2015 Eric Biggers
*
* This file is free software; you can redistribute it and/or modify it under
* the terms of the GNU Lesser General Public License as published by the Free
/* This value is chosen for fast decompression. */
#define XPRESS_TABLEBITS 12
-/* Decode the matches and literal bytes in a region of XPRESS-encoded data. */
static int
-xpress_decode_window(struct input_bitstream *istream, const u16 *decode_table,
- u8 *window, unsigned window_size)
+xpress_decompress(const void *restrict compressed_data, size_t compressed_size,
+ void *restrict uncompressed_data, size_t uncompressed_size,
+ void *restrict _ctx)
{
- u8 *window_ptr = window;
- u8 *window_end = &window[window_size];
- unsigned sym;
- unsigned match_len;
- unsigned offset_high_bit;
- unsigned match_offset;
+ const u8 * const in_begin = compressed_data;
+ u8 * const out_begin = uncompressed_data;
+ u8 *out_next = out_begin;
+ u8 * const out_end = out_begin + uncompressed_size;
+ 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 is;
+
+ /* Read the Huffman codeword lengths. */
+ if (compressed_size < XPRESS_NUM_SYMBOLS / 2)
+ return -1;
+ for (int i = 0; i < XPRESS_NUM_SYMBOLS / 2; i++) {
+ u.lens[2 * i + 0] = in_begin[i] & 0xf;
+ u.lens[2 * i + 1] = in_begin[i] >> 4;
+ }
+
+ /* Build a decoding table for the Huffman code. */
+ if (make_huffman_decode_table(u.decode_table, XPRESS_NUM_SYMBOLS,
+ XPRESS_TABLEBITS, u.lens,
+ XPRESS_MAX_CODEWORD_LEN))
+ return -1;
+
+ /* Decode the matches and literals. */
- while (window_ptr != window_end) {
+ init_input_bitstream(&is, in_begin + XPRESS_NUM_SYMBOLS / 2,
+ compressed_size - XPRESS_NUM_SYMBOLS / 2);
+
+ while (out_next != out_end) {
+ unsigned sym;
+ unsigned log2_offset;
+ u32 length;
+ u32 offset;
- sym = read_huffsym(istream, decode_table,
+ sym = read_huffsym(&is, u.decode_table,
XPRESS_TABLEBITS, XPRESS_MAX_CODEWORD_LEN);
if (sym < XPRESS_NUM_CHARS) {
/* Literal */
- *window_ptr++ = sym;
- continue;
- }
+ *out_next++ = sym;
+ } else {
+ /* Match */
+ length = sym & 0xf;
+ log2_offset = (sym >> 4) & 0xf;
- /* Match */
- match_len = sym & 0xf;
- offset_high_bit = (sym >> 4) & 0xf;
+ bitstream_ensure_bits(&is, 16);
- bitstream_ensure_bits(istream, 16);
+ offset = ((u32)1 << log2_offset) |
+ bitstream_pop_bits(&is, log2_offset);
- match_offset = (1 << offset_high_bit) |
- bitstream_pop_bits(istream, offset_high_bit);
+ if (length == 0xf) {
+ length += bitstream_read_byte(&is);
+ if (length == 0xf + 0xff)
+ length = bitstream_read_u16(&is);
+ }
+ length += XPRESS_MIN_MATCH_LEN;
- if (match_len == 0xf) {
- match_len += bitstream_read_byte(istream);
- if (match_len == 0xf + 0xff)
- match_len = bitstream_read_u16(istream);
- }
- match_len += XPRESS_MIN_MATCH_LEN;
+ if (unlikely(offset > out_next - out_begin))
+ return -1;
- if (unlikely(match_offset > window_ptr - window))
- return -1;
+ if (unlikely(length > out_end - out_next))
+ return -1;
- if (unlikely(match_len > window_end - window_ptr))
- return -1;
+ lz_copy(out_next, length, offset, out_end,
+ XPRESS_MIN_MATCH_LEN);
- lz_copy(window_ptr, match_len, match_offset, window_end,
- XPRESS_MIN_MATCH_LEN);
-
- window_ptr += match_len;
+ out_next += length;
+ }
}
return 0;
}
-static int
-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);
- struct input_bitstream istream;
-
- /* XPRESS uses only one Huffman code. It contains 512 symbols, and the
- * code lengths of these symbols are given literally as 4-bit integers
- * in the first 256 bytes of the compressed data. */
- if (compressed_size < XPRESS_NUM_SYMBOLS / 2)
- return -1;
-
- lens_p = 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,
- 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,
- uncompressed_data, uncompressed_size);
-}
-
static int
xpress_create_decompressor(size_t max_block_size, void **dec_ret)
{
git://wimlib.net / wimlib / blobdiff