denuvo-ref/precomp-cpp
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Skip uncompressed zlib blocks (BTYPE = 00) in brute mode

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- They can be useful in slow mode, but in brute mode, there are short false positive that can cause massive slowdown
This commit is contained in:
Christian Schneider 2017-08-13 11:09:44 +02:00
parent 9303a0b951
commit b63677c4d9
1 changed files with 8 additions and 5 deletions
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13
precomp.cpp
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@ -2743,12 +2743,13 @@ int inf(FILE *source, FILE *dest, int windowbits, int& compressed_stream_size) {
}
bool check_inf_result(int cb_pos, int windowbits, unsigned less_than_skip) {
bool check_inf_result(int cb_pos, int windowbits, bool use_brute_parameters = false) {
// first check BTYPE bits, skip 11 ("reserved (error)")
// don't skip BTYPE = 00 ("uncompressed"), because these can be useful for recursion
// and often occur in combination with static/dynamic BTYPE blocks
int btype = (in_buf[cb_pos] & 0x07) >> 1;
if (btype == 3) return false;
// skip BTYPE = 00 ("uncompressed") only in brute mode, because these can be useful for recursion
// and often occur in combination with static/dynamic BTYPE blocks
if ((use_brute_parameters) && (btype == 0)) return false;
int ret;
unsigned have = 0;
@ -2795,6 +2796,8 @@ bool check_inf_result(int cb_pos, int windowbits, unsigned less_than_skip) {
return true;
case Z_STREAM_END:
// Skip short streams - most likely false positives
unsigned less_than_skip = 32;
if (use_brute_parameters) less_than_skip = 1024;
return (have >= less_than_skip);
}
@ -4429,7 +4432,7 @@ bool compress_file(float min_percent, float max_percent) {
if (compression_method == 8) {
int windowbits = (in_buf[cb] >> 4) + 8;
if (check_inf_result(cb + 2, -windowbits, 32)) {
if (check_inf_result(cb + 2, -windowbits)) {
saved_input_file_pos = input_file_pos;
saved_cb = cb;
@ -4474,7 +4477,7 @@ bool compress_file(float min_percent, float max_percent) {
saved_input_file_pos = input_file_pos;
saved_cb = cb;
if (check_inf_result(cb, -15, 1024)) {
if (check_inf_result(cb, -15, true)) {
try_decompression_brute();
}