Variable chunk size support (currently XPRESS only)

[wimlib] / src / xpress-compress.c

diff --git a/src/xpress-compress.c b/src/xpress-compress.c
index 5a314b69356a949c620f4c47e05e01d5f3d64b76..518a0e3ba70b23fdd24a85df93a95c5da33f4f52 100644 (file)
--- a/src/xpress-compress.c
+++ b/src/xpress-compress.c
@@ -36,6 +36,10 @@
 #include "wimlib/util.h"
 #include "wimlib/xpress.h"
 
+#ifdef HAVE_ALLOCA_H
+#  include <alloca.h>
+#endif
+
 #include <string.h>
 
 /* Intermediate XPRESS match/literal representation.  */
@@ -132,6 +136,7 @@ xpress_record_match(unsigned len, unsigned offset, void *_ctx)
 static const struct lz_params xpress_lz_params = {
        .min_match      = XPRESS_MIN_MATCH_LEN,
        .max_match      = XPRESS_MAX_MATCH_LEN,
+       .max_offset     = XPRESS_MAX_OFFSET,
        .good_match     = 16,
        .nice_match     = 32,
        .max_chain_len  = 16,
@@ -149,13 +154,17 @@ wimlib_xpress_compress(const void * restrict uncompressed_data,
        struct output_bitstream ostream;
 
        struct xpress_record_ctx record_ctx;
-       struct xpress_match matches[uncompressed_len];
-       u8 udata[uncompressed_len + 8];
+
+       struct xpress_match *matches;
+       input_idx_t *prev_tab;
+       u8 *udata;
+
        u16 codewords[XPRESS_NUM_SYMBOLS];
        u8 lens[XPRESS_NUM_SYMBOLS];
        input_idx_t num_matches;
        input_idx_t compressed_len;
        input_idx_t i;
+       const size_t stack_max = 65536;
 
        /* XPRESS requires 256 bytes of overhead for the Huffman code, so it's
         * impossible to compress 256 bytes or less of data to less than the
@@ -169,6 +178,21 @@ wimlib_xpress_compress(const void * restrict uncompressed_data,
        if (uncompressed_len < XPRESS_NUM_SYMBOLS / 2 + 1 + 4)
                return 0;
 
+       if (uncompressed_len <= stack_max) {
+               matches = alloca(uncompressed_len * sizeof(matches[0]));
+               udata = alloca(uncompressed_len + 8);
+               prev_tab = alloca(uncompressed_len * sizeof(prev_tab[0]));
+       } else {
+               matches = MALLOC(uncompressed_len * sizeof(matches[0]));
+               udata = MALLOC(uncompressed_len + 8);
+               prev_tab = MALLOC(uncompressed_len * sizeof(prev_tab[0]));
+               if (matches == NULL || udata == NULL || prev_tab == NULL) {
+                       WARNING("Failed to allocate memory for compression...");
+                       compressed_len = 0;
+                       goto out_free;
+               }
+       }
+
        /* Copy the data to a temporary buffer, but only to avoid
         * inconsequential accesses of uninitialized memory in
         * lz_analyze_block().  */
@@ -183,7 +207,8 @@ wimlib_xpress_compress(const void * restrict uncompressed_data,
                         xpress_record_match,
                         xpress_record_literal,
                         &record_ctx,
-                        &xpress_lz_params);
+                        &xpress_lz_params,
+                        prev_tab);
 
        num_matches = (record_ctx.matches - matches);
 
@@ -206,8 +231,10 @@ wimlib_xpress_compress(const void * restrict uncompressed_data,
 
        /* Flush any pending data and get the length of the compressed data.  */
        compressed_len = flush_output_bitstream(&ostream);
-       if (compressed_len == ~(input_idx_t)0)
-               return 0;
+       if (compressed_len == ~(input_idx_t)0) {
+               compressed_len = 0;
+               goto out_free;
+       }
        compressed_len += XPRESS_NUM_SYMBOLS / 2;
 
 #if defined(ENABLE_XPRESS_DEBUG) || defined(ENABLE_VERIFY_COMPRESSION) || 1
@@ -218,15 +245,24 @@ wimlib_xpress_compress(const void * restrict uncompressed_data,
                ERROR("Failed to decompress data we "
                      "compressed using XPRESS algorithm");
                wimlib_assert(0);
-               return 0;
+               compressed_len = 0;
+               goto out_free;
        }
 
        if (memcmp(uncompressed_data, udata, uncompressed_len)) {
                ERROR("Data we compressed using XPRESS algorithm "
                      "didn't decompress to original");
                wimlib_assert(0);
-               return 0;
+               compressed_len = 0;
+               goto out_free;
        }
 #endif
+
+out_free:
+       if (uncompressed_len > stack_max) {
+               FREE(matches);
+               FREE(udata);
+               FREE(prev_tab);
+       }
        return compressed_len;
 }