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This commit is contained in:
neauoire 2023-11-16 20:58:52 -08:00
parent 2a10a1cf81
commit 40fd28b1d8
1 changed files with 30 additions and 24 deletions
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54
cli/lz/ulzenc.c
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@ -17,33 +17,37 @@ char *raw, *mem;
int
uxn_lz_compress(void *output, const void *input, int input_size)
{
int dict_len, match_len, i, string_len, match_ctl;
int i, dict_len, match_len, string_len, match_ctl;
unsigned char *out = output, *combine = 0;
const unsigned char *dict, *dict_best = 0, *in = input, *start = in, *end = in + input_size;
while(in != end) {
dict_len = (int)(in - start); /* Get available dictionary size (history of original output) */
/* Get available dictionary size (history of original output) */
dict_len = (int)(in - start);
/* Limit history lookback to 256 bytes */
if(dict_len > 256)
dict_len = 256; /* Limit history lookback to 256 bytes */
dict = in - dict_len; /* Start of dictionary */
string_len = (int)(end - in); /* Size of the string to search for */
dict_len = 256;
/* Start of dictionary */
dict = in - dict_len;
/* Size of the string to search for */
string_len = (int)(end - in);
if(string_len > 0x3FFF + MinMatchLength)
string_len = 0x3FFF + MinMatchLength;
/* ^ Limit string length to what we can fit in 14 bits, plus the minimum
* match length */
match_len = 0; /* This will hold the length of our best match */
for(; dict_len; dict += 1, dict_len -= 1) /* Iterate through the dictionary */
{
for(i = 0;; i++) /* Find common prefix length with the string */
{
/* ^ Limit string length to what we can fit in 14 bits, plus the minimum match length */
/* This will hold the length of our best match */
match_len = 0;
/* Iterate through the dictionary */
for(; dict_len; dict += 1, dict_len -= 1) {
/* Find common prefix length with the string */
for(i = 0;; i++) {
if(i == string_len) {
match_len = i;
dict_best = dict;
goto done_search;
}
/* ^ If we reach the end of the string, this is the best possible match.
* End. */
/* ^ If we reach the end of the string, this is the best possible match. End. */
/* Dictionary repeats if we hit the end */
if(in[i] != dict[i % dict_len])
break; /* Dictionary repeats if we hit the end */
break;
}
if(i > match_len) {
match_len = i;
@ -51,17 +55,18 @@ uxn_lz_compress(void *output, const void *input, int input_size)
}
}
done_search:
if(match_len >= MinMatchLength) /* Long enough? Use dictionary match */
{
match_ctl = match_len - MinMatchLength; /* More numeric range: treat 0 as 4, 1 as 5, etc. */
if(match_ctl > 0x3F) /* Match is long enough to use 2 bytes for the size */
{
/* Long enough? Use dictionary match */
if(match_len >= MinMatchLength) {
/* More numeric range: treat 0 as 4, 1 as 5, etc. */
match_ctl = match_len - MinMatchLength;
/* Match is long enough to use 2 bytes for the size */
if(match_ctl > 0x3F) {
*out++ = match_ctl >> 8 | 0x40 | 0x80; /* High byte of the size, with both flags set */
*out++ = match_ctl; /* Low byte of the size */
} else /* Use 1 byte for the size */
{
} else {
/* Set the "dictionary" flag */
*out++ = match_ctl | 0x80;
} /* Set the "dictionary" flag */
}
*out++ = in - dict_best - 1; /* Write offset into history. (0 is -1, 1 is -2, ...) */
in += match_len; /* Advance input by size of the match */
combine = 0; /* Disable combining previous literal, if any */
@ -79,7 +84,8 @@ uxn_lz_compress(void *output, const void *input, int input_size)
/* The 0 here means literal of length 1. */
*combine = 0;
}
*out++ = *in++; /* Write 1 literal byte from the input to the output. */
/* Write 1 literal byte from the input to the output. */
*out++ = *in++;
}
return (int)(out - (unsigned char *)output);
}