sanchayanmaity/gem5
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

A few memory system performance enhancements.

Browse source 
base/compression/lzss_compression.cc:
base/compression/lzss_compression.hh:
    Rework for better performance

--HG--
extra : convert_revision : b13d706e0e23cbe7122b611258354c66cf5f3c70
This commit is contained in:
Erik Hallnor 2004-03-24 04:41:19 -05:00
parent b18a36a6f2
commit 81882c0d10
2 changed files with 29 additions and 23 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

43
base/compression/lzss_compression.cc
View file

@ -36,21 +36,32 @@
#include "base/misc.hh" //for fatal
int
LZSSCompression::findSubString(uint8_t *src, int front, int back, int size)
void
LZSSCompression::findSubString(uint8_t *src, int back, int size, uint16_t &L,
uint16_t &P)
{
int subSize = 0;
int max_length = 2048;
if (size - back < max_length) {
max_length = size - back;
}
for (int i = 0; i < max_length; ++i) {
if (src[front+i] != src[back+i]) {
return subSize;
int front = 0;
int max_length = size - back;
L = 0;
P = back - 1;
while (front < back) {
while (src[front] != src[back] && front < back) ++front;
if (front >= back) {
return;
}
int i = 1;
while (src[front+i] == src[back+i] && i < max_length) ++i;
if (i >= L) {
L = i;
P = front;
}
if (src[front+i] != src[back+i-1]) {
// can't find a longer substring until past this point.
front += i;
} else {
++front;
}
++subSize;
}
return subSize;
}
int
@ -106,13 +117,7 @@ LZSSCompression::compress(uint8_t *dest, uint8_t *src, int size)
++i;
continue;
}
for (int j = 0; j < i; ++j) {
int sub_size = findSubString(src, j, i, size);
if (sub_size >= L) {
L = sub_size;
P = j;
}
}
findSubString(src, i, size, L, P);
if (L > 1) {
// Output the string reference
emitString(&dest[dest_index], P, L);

9
base/compression/lzss_compression.hh
View file

@ -41,14 +41,15 @@
class LZSSCompression
{
/**
* Finds the longest substrings that start at the given offsets.
* Finds the longest substring for the given offset.
* @param src The source block that we search for substrings.
* @param front The smaller offset.
* @param back The larger offset.
* @param size The size of the source block.
* @return The size of the longest substring.
* @param L The length of the largest substring.
* @param P The starting offset of the largest substring.
*/
int findSubString(uint8_t *src, int front, int back, int size);
void findSubString(uint8_t *src, int back, int size, uint16_t &L,
uint16_t &P);
/**
* Emit an encoded byte to the compressed data array. If the 2 high