win32_common.c: Remove code for windows version detection

[wimlib] / src / lzms-decompress.c

diff --git a/src/lzms-decompress.c b/src/lzms-decompress.c
index 2bc1c754cd69e49b86c17cce9e934ed888392cd4..f8bfcdb17344b3055d343e7be7615897484d7bfc 100644 (file)
--- a/src/lzms-decompress.c
+++ b/src/lzms-decompress.c
@@ -160,18 +160,28 @@
  * have equal frequency.  Following that, each code must be rebuilt whenever a
  * certain number of symbols has been decoded with it.
  *
- * In general, multiple valid Huffman codes can be constructed from a set of
- * symbol frequencies.  Like other compression formats such as XPRESS, LZX, and
- * DEFLATE, the LZMS format solves this ambiguity by requiring that all Huffman
- * codes be constructed in canonical form.  This form requires that same-length
- * codewords be lexicographically ordered the same way as the corresponding
- * symbols and that all shorter codewords lexicographically precede longer
- * codewords.
+ * Like other compression formats such as XPRESS, LZX, and DEFLATE, the LZMS
+ * format requires that all Huffman codes be constructed in canonical form.
+ * This form requires that same-length codewords be lexicographically ordered
+ * the same way as the corresponding symbols and that all shorter codewords
+ * lexicographically precede longer codewords.  Such a code can be constructed
+ * directly from codeword lengths, although in LZMS this is not actually
+ * necessary because the codes are built using adaptive symbol frequencies.
  *
- * Codewords in all the LZMS Huffman codes are limited to 15 bits.  If the
- * canonical code for a given set of symbol frequencies has any codewords longer
- * than 15 bits, then all frequencies must be divided by 2, rounding up, and the
- * code construction must be attempted again.
+ * Even with the canonical code restriction, the same frequencies can be used to
+ * construct multiple valid Huffman codes.  Therefore, the decompressor needs to
+ * construct the right one.  Specifically, the LZMS format requires that the
+ * Huffman code be constructed as if the well-known priority queue algorithm is
+ * used and frequency ties are always broken in favor of leaf nodes.  See
+ * make_canonical_huffman_code() in compress_common.c for more information.
+ *
+ * Codewords in LZMS are guaranteed to not exceed 15 bits.  The format otherwise
+ * places no restrictions on codeword length.  Therefore, the Huffman code
+ * construction algorithm that a correct LZMS decompressor uses need not
+ * implement length-limited code construction.  But if it does (e.g. by virtue
+ * of being shared among multiple compression algorithms), the details of how it
+ * does so are unimportant, provided that the maximum codeword length parameter
+ * is set to at least 15 bits.
  *
  * An LZMS-compressed block seemingly cannot have a compressed size greater than
  * or equal to the uncompressed size.  In such cases the block must be stored
@@ -190,10 +200,10 @@
 #  include "config.h"
 #endif
 
-#include "wimlib.h"
 #include "wimlib/compress_common.h"
 #include "wimlib/decompressor_ops.h"
 #include "wimlib/decompress_common.h"
+#include "wimlib/error.h"
 #include "wimlib/lzms.h"
 #include "wimlib/util.h"
 
@@ -664,7 +674,6 @@ static int
 lzms_copy_lz_match(struct lzms_decompressor *ctx, u32 length, u32 offset)
 {
        u8 *out_next;
-       u8 *matchptr;
 
        if (length > ctx->out_end - ctx->out_next) {
                LZMS_DEBUG("Match overrun!");
@@ -676,11 +685,10 @@ lzms_copy_lz_match(struct lzms_decompressor *ctx, u32 length, u32 offset)
        }
 
        out_next = ctx->out_next;
-       matchptr = out_next - offset;
-       while (length--)
-               *out_next++ = *matchptr++;
 
-       ctx->out_next = out_next;
+       lz_copy(out_next, length, offset, ctx->out_end);
+       ctx->out_next = out_next + length;
+
        return 0;
 }
 
@@ -1032,17 +1040,16 @@ lzms_free_decompressor(void *_ctx)
 {
        struct lzms_decompressor *ctx = _ctx;
 
-       FREE(ctx);
+       ALIGNED_FREE(ctx);
 }
 
 static int
-lzms_create_decompressor(size_t max_block_size,
-                        const struct wimlib_decompressor_params_header *params,
-                        void **ctx_ret)
+lzms_create_decompressor(size_t max_block_size, void **ctx_ret)
 {
        struct lzms_decompressor *ctx;
 
-       ctx = MALLOC(sizeof(struct lzms_decompressor));
+       ctx = ALIGNED_MALLOC(sizeof(struct lzms_decompressor),
+                            DECODE_TABLE_ALIGNMENT);
        if (ctx == NULL)
                return WIMLIB_ERR_NOMEM;