我正在使用Okamura的lzss：https://oku.edu.mie-u.ac.jp/~okumura/compression/lzss.c
的实现int enc_i = 0;
int getbit(int n, unsigned char *enco_buf) /* get n bits */
{
int i, x;
static int buf, mask = 0;
x = 0;
for (i = 0; i < n; i++) {
if (mask == 0) {
//if ((buf = fgetc(infile)) == EOF) return EOF;
//if ((buf = fgetc(infile)) == EOF) return EOF;
if((buf = enco_buf[enc_i]) == '\0') break;
//buf = enco_buf[enc_i];
enc_i++;
//printf("\nValue of enc : %d\n", enc_i);
mask = 128;
}
x <<= 1;
if (buf & mask) x++;
mask >>= 1;
}
return x;
}
void decode(unsigned char *enco_buf)
{
int i, j, k, r, c;
outfile = fopen ("test_lib.txt", "wb");
for (i = 0; i < N - F; i++) buffer[i] = ' ';
r = N - F;
while ((c = getbit(1, enco_buf)) != '\0') {
if (c) {
if ((c = getbit(8, enco_buf)) == '\0') break;
fputc(c, outfile);
buffer[r++] = c; r &= (N - 1);
} else {
if ((i = getbit(EI, enco_buf)) == '\0') break;
if ((j = getbit(EJ, enco_buf)) == '\0') break;
for (k = 0; k <= j + 1; k++) {
c = buffer[(i + k) & (N - 1)];
fputc(c, outfile);
buffer[r++] = c; r &= (N - 1);
}
}
}
fclose(outfile);
}
我没有从文件中获取输入，而是采用一个编码缓冲区，我将其传递给函数decode（），后者依次传递给getbit（）。但它正在解码到一定数量的比特，即。 43.我猜的是我把'\ 0'而不是EOF（因为它在文件结束标记中）来检测字符串结束。这可能是执行break语句执行'\ 0'的问题。这可能不是真的，但情况可能如此。编码部分没有问题，因为我用原始代码验证了它。任何人都可以建议问题出在哪里？
编辑：源代码：
/* LZSS encoder-decoder (Haruhiko Okumura; public domain) */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "lzss_lib.h"
#define EI 11 /* typically 10..13 */
#define EJ 4 /* typically 4..5 */
#define P 1 /* If match length <= P then output one character */
#define N (1 << EI) /* buffer size */
#define F ((1 << EJ) + 1) /* lookahead buffer size */
int bit_buffer = 0, bit_mask = 128;
unsigned long codecount = 0, textcount = 0;
unsigned char buffer[N * 2];
int payload_i = 0;
int enc_i = 0;
FILE *infile, *outfile;
void error(void)
{
printf("Output error\n"); exit(1);
}
void putbit1(unsigned char *put_buf0)
{
bit_buffer |= bit_mask;
if ((bit_mask >>= 1) == 0) {
put_buf0[payload_i] = bit_buffer;
payload_i++;
bit_buffer = 0; bit_mask = 128; codecount++;
}
}
void putbit0(unsigned char *put_buf1)
{
if ((bit_mask >>= 1) == 0) {
put_buf1[payload_i] = bit_buffer;
payload_i++;
bit_buffer = 0; bit_mask = 128; codecount++;
}
}
void flush_bit_buffer(unsigned char *flush_bit)
{
if (bit_mask != 128) {
flush_bit[payload_i] = bit_buffer;
codecount++;
}
}
void output1(int c, unsigned char *buf_output1)
{
int mask;
putbit1(buf_output1);
mask = 256;
while (mask >>= 1) {
if (c & mask) putbit1(buf_output1);
else putbit0(buf_output1);
}
}
void output2(int x, int y, unsigned char *buf_output2)
{
int mask;
putbit0(buf_output2);
mask = N;
while (mask >>= 1) {
if (x & mask) putbit1(buf_output2);
else putbit0(buf_output2);
}
mask = (1 << EJ);
while (mask >>= 1) {
if (y & mask) putbit1(buf_output2);
else putbit0(buf_output2);
}
}
void encode(unsigned char *string_buf, unsigned char *out_buf, unsigned long *out_buf_len)
{
int i, j, f1, x, y, r, s, bufferend, c, tt;
tt = 0;
for (i = 0; i < N - F; i++) buffer[i] = ' ';
for (i = N - F; i < N * 2; i++) {
if((c = string_buf[tt]) == '\0') break;
buffer[i] = c; textcount++; tt++;
}
bufferend = i; r = N - F; s = 0;
while (r < bufferend) {
f1 = (F <= bufferend - r) ? F : bufferend - r;
x = 0; y = 1; c = buffer[r];
for (i = r - 1; i >= s; i--)
if (buffer[i] == c) {
for (j = 1; j < f1; j++)
if (buffer[i + j] != buffer[r + j]) break;
if (j > y) {
x = i; y = j;
}
}
if (y <= P) { y = 1; output1(c, out_buf); }
else output2(x & (N - 1), y - 2, out_buf);
r += y; s += y;
if (r >= N * 2 - F) {
for (i = 0; i < N; i++) buffer[i] = buffer[i + N];
bufferend -= N; r -= N; s -= N;
while (bufferend < N * 2) {
if((c = string_buf[tt]) == '\0') break;
buffer[bufferend++] = c; textcount++; tt++;
}
}
}
flush_bit_buffer(out_buf);
*out_buf_len = codecount;
printf("text: %ld bytes\n", textcount);
printf("code: %ld bytes (%ld%%)\n", codecount, (codecount * 100) / textcount);
}
int getbit(int n, unsigned char *enco_buf) /* get n bits */
{
int i, x;
static int buf, mask = 0;
x = 0;
for (i = 0; i < n; i++) {
if (mask == 0) {
//if ((buf = fgetc(infile)) == EOF) return EOF;
//if ((buf = fgetc(infile)) == EOF) return EOF;
if((buf = enco_buf[enc_i]) == '\0') break;
//buf = enco_buf[enc_i];
enc_i++;
printf("\nValue of enc : %d\n", enc_i);
mask = 128;
}
x <<= 1;
if (buf & mask) x++;
mask >>= 1;
}
return x;
}
void decode(unsigned char *enco_buf)
{
int i, j, k, r, c;
outfile = fopen ("test_lib.txt", "wb");
for (i = 0; i < N - F; i++) buffer[i] = ' ';
r = N - F;
while ((c = getbit(1, enco_buf)) != '\0') {
if (c) {
if ((c = getbit(8, enco_buf)) == '\0') break;
fputc(c, outfile);
buffer[r++] = c; r &= (N - 1);
} else {
if ((i = getbit(EI, enco_buf)) == '\0') break;
if ((j = getbit(EJ, enco_buf)) == '\0') break;
for (k = 0; k <= j + 1; k++) {
c = buffer[(i + k) & (N - 1)];
fputc(c, outfile);
buffer[r++] = c; r &= (N - 1);
}
}
}
fclose(outfile);
}
和测试示例：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "lzss_lib.h"
unsigned char compr_data[4096];
unsigned long pw = 0;
unsigned long payload_len = 0;
volatile int errno;
unsigned char *unc_data = "d(2306):AuthorisationScheme:RADIUSserveratfd04:bd3:80e8:1::1usingPAPD/6LoWPANd(2306):WritingModule:SecurityConfigD/6LoWPANd(2306):WritingModule:RunCoordinatorD/6LoWPANd(2306):RequestingmoduleaddressD/6LoWPANd(2306):WritingModule:GetAddressD/smartcard-jni(2781):SmartCard_state_update_callback:status=6D/SmartCardNative(2781):status=6D/smartcard(2781):PN532Smartcard_loop_threadexitD/smartcard-jni(2781):SmartCard_loop_thread:SMARTCARD_STATUS_ABORTD/smartcard(2781):Smartcard_loop_uninitD/smartcard(2781):2D/serialcomm_pn532(2781):PN532:Readingfrom/dev/ttyUSB0-->D/smartcard(2781):Received(0x3)fromPN532:(dataBuf[0]:0x1)(0x1f5988)D/smartcard(2781):ReceivedStatusfromPN532:OK(cmd:0x2)D/smartcard-jni(2781):SmartCard_listener_update_callbackD/smartcard(2781):Received(0x1c2)fromPN532:(dataBuf[0]:0x32)(0x1f5988)D/smartcard(2781):vd(2306):AuthorisationScheme:RADIUSserveratfd04:bd3:80e8:1::1usingPAPD/6LoWPANd(2306):";
FILE *outfile;
int main(void) {
memset (compr_data, '\0', sizeof(compr_data));
encode(unc_data, compr_data, &payload_len);
decode(compr_data);
return 0;
}