+/*
+ * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+/**
+ * @file
+ *
+ * Xpress Compression Algorithm (MS-XCA) decompression
+ *
+ */
+
+#include "wimboot.h"
+#include "huffman.h"
+#include "xpress.h"
+
+#pragma GCC diagnostic ignored "-Wcast-align"
+
+/**
+ * Decompress XCA-compressed data
+ *
+ * @v data Compressed data
+ * @v len Length of compressed data
+ * @v buf Decompression buffer, or NULL
+ * @ret out_len Length of decompressed data, or negative error
+ */
+ssize_t xca_decompress ( const void *data, size_t len, void *buf ) {
+ const void *src = data;
+ const void *end = ( uint8_t * ) src + len;
+ uint8_t *out = buf;
+ size_t out_len = 0;
+ size_t out_len_threshold = 0;
+ const struct xca_huf_len *lengths;
+ struct xca xca;
+ uint32_t accum = 0;
+ int extra_bits = 0;
+ unsigned int huf;
+ struct huffman_symbols *sym;
+ unsigned int raw;
+ unsigned int match_len;
+ unsigned int match_offset_bits;
+ unsigned int match_offset;
+ const uint8_t *copy;
+ int rc;
+
+ /* Process data stream */
+ while ( src < end ) {
+
+ /* (Re)initialise decompressor if applicable */
+ if ( out_len >= out_len_threshold ) {
+
+ /* Construct symbol lengths */
+ lengths = src;
+ src = ( uint8_t * ) src + sizeof ( *lengths );
+ if ( src > end ) {
+ DBG ( "XCA too short to hold Huffman lengths table.\n");
+ return -1;
+ }
+ for ( raw = 0 ; raw < XCA_CODES ; raw++ )
+ xca.lengths[raw] = xca_huf_len ( lengths, raw );
+
+ /* Construct Huffman alphabet */
+ if ( ( rc = huffman_alphabet ( &xca.alphabet,
+ xca.lengths,
+ XCA_CODES ) ) != 0 )
+ return rc;
+
+ /* Initialise state */
+ accum = XCA_GET16 ( src );
+ accum <<= 16;
+ accum |= XCA_GET16 ( src );
+ extra_bits = 16;
+
+ /* Determine next threshold */
+ out_len_threshold = ( out_len + XCA_BLOCK_SIZE );
+ }
+
+ /* Determine symbol */
+ huf = ( accum >> ( 32 - HUFFMAN_BITS ) );
+ sym = huffman_sym ( &xca.alphabet, huf );
+ raw = huffman_raw ( sym, huf );
+ accum <<= huffman_len ( sym );
+ extra_bits -= huffman_len ( sym );
+ if ( extra_bits < 0 ) {
+ accum |= ( XCA_GET16 ( src ) << ( -extra_bits ) );
+ extra_bits += 16;
+ }
+
+ /* Process symbol */
+ if ( raw < XCA_END_MARKER ) {
+
+ /* Literal symbol - add to output stream */
+ if ( buf )
+ *(out++) = raw;
+ out_len++;
+
+ } else if ( ( raw == XCA_END_MARKER ) &&
+ ( (uint8_t *) src >= ( ( uint8_t * ) end - 1 ) ) ) {
+
+ /* End marker symbol */
+ return out_len;
+
+ } else {
+
+ /* LZ77 match symbol */
+ raw -= XCA_END_MARKER;
+ match_offset_bits = ( raw >> 4 );
+ match_len = ( raw & 0x0f );
+ if ( match_len == 0x0f ) {
+ match_len = XCA_GET8 ( src );
+ if ( match_len == 0xff ) {
+ match_len = XCA_GET16 ( src );
+ } else {
+ match_len += 0x0f;
+ }
+ }
+ match_len += 3;
+ if ( match_offset_bits ) {
+ match_offset =
+ ( ( accum >> ( 32 - match_offset_bits ))
+ + ( 1 << match_offset_bits ) );
+ } else {
+ match_offset = 1;
+ }
+ accum <<= match_offset_bits;
+ extra_bits -= match_offset_bits;
+ if ( extra_bits < 0 ) {
+ accum |= ( XCA_GET16 ( src ) << (-extra_bits) );
+ extra_bits += 16;
+ }
+
+ /* Copy data */
+ out_len += match_len;
+ if ( buf ) {
+ copy = ( out - match_offset );
+ while ( match_len-- )
+ *(out++) = *(copy++);
+ }
+ }
+ }
+
+ return out_len;
+}
projects / Ventoy.git / commitdiff