269 lines
6.8 KiB
C
269 lines
6.8 KiB
C
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#include <stdio.h>
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#include <stdlib.h>
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#include "lz.h"
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enum { MinMatchLength = 4 };
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int
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uxn_lz_compress(void *output, int output_size, const void *input, int input_size)
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{
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int dict_len, match_len, i, string_len, match_ctl;
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unsigned char *out = output, *combine = 0;
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const unsigned char *dict, *dict_best = 0, *in = input, *start = in,
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*end = in + input_size;
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while(in != end) {
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dict_len = (int)(in - start); /* Get available dictionary size (history of
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original output) */
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if(dict_len > 256)
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dict_len = 256; /* Limit history lookback to 256 bytes */
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dict = in - dict_len; /* Start of dictionary */
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string_len = (int)(end - in); /* Size of the string to search for */
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if(string_len > 0x3FFF + MinMatchLength)
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string_len = 0x3FFF + MinMatchLength;
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/* ^ Limit string length to what we can fit in 14 bits, plus the minimum
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* match length */
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match_len = 0; /* This will hold the length of our best match */
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for(; dict_len;
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dict += 1, dict_len -= 1) /* Iterate through the dictionary */
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{
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for(i = 0;; i++) /* Find common prefix length with the string */
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{
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if(i == string_len) {
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match_len = i;
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dict_best = dict;
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goto done_search;
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}
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/* ^ If we reach the end of the string, this is the best possible match.
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* End. */
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if(in[i] != dict[i % dict_len])
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break; /* Dictionary repeats if we hit the end */
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}
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if(i > match_len) {
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match_len = i;
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dict_best = dict;
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}
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}
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done_search:
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if(match_len >= MinMatchLength) /* Long enough? Use dictionary match */
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{
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if((output_size -= 2) < 0)
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goto overflow;
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match_ctl =
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match_len -
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MinMatchLength; /* More numeric range: treat 0 as 4, 1 as 5, etc. */
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if(match_ctl >
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0x3F) /* Match is long enough to use 2 bytes for the size */
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{
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if((output_size -= 1) < 0)
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goto overflow;
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*out++ = match_ctl >> 8 | 0x40 |
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0x80; /* High byte of the size, with both flags set */
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*out++ = match_ctl; /* Low byte of the size */
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} else /* Use 1 byte for the size */
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{
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*out++ = match_ctl | 0x80; /* Set the "dictionary" flag */
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}
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*out++ = in - dict_best -
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1; /* Write offset into history. (0 is -1, 1 is -2, ...) */
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in += match_len; /* Advance input by size of the match */
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combine = 0; /* Disable combining previous literal, if any */
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continue;
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}
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if(combine) /* Combine with previous literal */
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{
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if((output_size -= 1) < 0)
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goto overflow;
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if(++*combine == 127)
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combine = 0; /* If the literal hits its size limit, terminate it. */
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} else /* Start a new literal */
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{
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if((output_size -= 2) < 0)
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goto overflow;
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combine = out++; /* Store this address, and later use it to increment the
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literal size. */
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*combine = 0; /* The 0 here means literal of length 1. */
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}
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*out++ = *in++; /* Write 1 literal byte from the input to the output. */
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}
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return (int)(out - (unsigned char *)output);
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overflow:
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return -1;
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}
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int
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uxn_lz_expand(void *output, int output_size, const void *input, int input_size)
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{
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int num, offset, written = 0;
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unsigned char *out = output;
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const unsigned char *from, *in = input;
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while(input_size) {
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num = *in++;
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if(num > 127) /* Dictionary */
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{
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if((input_size -= 1) < 0)
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goto malformed;
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num &= 0x7F;
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if(num & 0x40) {
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if((input_size -= 1) < 0)
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goto malformed;
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num = *in++ | num << 8 & 0x3FFF;
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}
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num += MinMatchLength;
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offset = *in++ + 1;
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if(offset > written)
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goto malformed;
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from = out + written - offset;
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} else /* Literal */
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{
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input_size -= ++num;
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if(input_size < 0)
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goto malformed;
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from = in, in += num;
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}
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if(written + num > output_size)
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goto overflow;
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while(num--)
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out[written++] = *from++;
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}
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return written;
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overflow:
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malformed:
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return -1;
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}
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int
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uxn_lz_expand_stream(struct uxn_lz_expand_t *a)
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{
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/* Copy struct to stack variables for compiler optimizations */
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unsigned char *next_in = a->next_in, *next_out = a->next_out;
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int avail_in = a->avail_in, avail_out = a->avail_out;
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int dict_len = a->dict_len, copy_num = a->copy_num;
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unsigned char dict_read_pos = a->dict_read_pos,
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dict_write_pos = a->dict_write_pos, *dict = a->dict;
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int result = 0;
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switch(a->state) {
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case 0:
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for(; avail_in;) {
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copy_num = *next_in++;
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avail_in--;
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if(copy_num > 127) /* Dictionary */
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{
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copy_num &= 0x7F;
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if(copy_num & 0x40) {
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case 1:
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if(!avail_in) {
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a->state = 1;
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goto need_more;
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}
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avail_in--;
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copy_num = *next_in++ | copy_num << 8 & 0x3FFF;
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}
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copy_num += MinMatchLength;
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case 2:
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if(!avail_in) {
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a->state = 2;
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goto need_more;
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}
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avail_in--;
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dict_read_pos = *next_in++ + 1;
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if(dict_read_pos > dict_len) {
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a->state = 5;
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result = -1;
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goto flush;
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} /* Malformed */
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dict_read_pos = dict_write_pos - dict_read_pos;
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if((dict_len += copy_num) > 256)
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dict_len = 256;
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case 3:
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do {
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if(!avail_out) {
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a->state = 3;
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goto need_more;
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}
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*next_out++ = dict[dict_write_pos++] = dict[dict_read_pos++];
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avail_out--;
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} while(--copy_num);
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} else /* Literal */
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{
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copy_num++;
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if((dict_len += copy_num) > 256)
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dict_len = 256;
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case 4:
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do {
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if(!avail_in || !avail_out) {
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a->state = 4;
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goto need_more;
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}
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*next_out++ = dict[dict_write_pos++] = *next_in++;
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avail_in--, avail_out--;
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} while(--copy_num);
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}
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}
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a->state = 0;
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case 5:;
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}
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need_more:
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flush:
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/* Flush stack variables back to struct */
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a->next_in = next_in, a->next_out = next_out;
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a->avail_in = avail_in, a->avail_out = avail_out;
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a->dict_len = dict_len, a->copy_num = copy_num;
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a->dict_read_pos = dict_read_pos, a->dict_write_pos = dict_write_pos;
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return result;
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}
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unsigned int
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uxn_checksum(unsigned int seed, void *bytes, unsigned int bytes_size)
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{
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unsigned int x = seed >> 16, y = seed, c;
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unsigned char *in = bytes, *end = in + bytes_size;
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for(; in != end; in++) {
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c = *in << 8 | *in;
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x = x * 0x2443 + c;
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y = y * 0x118d + c;
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}
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return x << 16 | (y & 0xFFFF);
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}
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/* cc lz_main.c -o main && ./main */
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int
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main(int argc, char *argv[])
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{
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char *s;
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char *my_byte_buffer = malloc(1000000);
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FILE *fp = fopen("example.txt", "rb");
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char buffer[1000000];
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size_t i;
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for(i = 0; i < 1000000; ++i) {
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int c = getc(fp);
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if(c == EOF) {
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buffer[i] = 0x00;
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break;
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}
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buffer[i] = c;
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}
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int res = uxn_lz_compress(my_byte_buffer, 1000000, &buffer, i);
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if(res < 0)
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printf("ERROR\n");
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printf("!!!%d -> %d\n", (int)i, (int)res);
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FILE *out_file;
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out_file = fopen("compressed.bin", "wb");
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fwrite(my_byte_buffer, 1, res, out_file);
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fclose(out_file);
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/* Other way */
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char *output2 = malloc(1000000);
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int res2 = uxn_lz_expand(output2, 1000000, &buffer, i);
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printf("!!!%d -> %d\n", (int)res, (int)res2);
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return 0;
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}
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