c代码如何实现LZSS算法

LZSS 算法是一种常用的无损压缩算法，下面是一个 C 语言实现 LZSS 算法的示例代码：

#include <stdio.h>
#include <string.h>
#define WINDOW_SIZE 4096
#define LOOK_AHEAD_SIZE 18
#define MIN_MATCH 3

unsigned char window[WINDOW_SIZE];
unsigned char lookAheadBuffer[LOOK_AHEAD_SIZE];
int lookAheadSize;

void slideWindow(int n)
{
    memcpy(window, window + n, WINDOW_SIZE - n);
    memset(window + WINDOW_SIZE - n, 0, n);
}

int searchMatch(int start, int *matchPos)
{
    int longestMatch = 0;
    for (int i = 0; i < WINDOW_SIZE - start; i++) {
        int len = 0;
        while (len < LOOK_AHEAD_SIZE && lookAheadBuffer[len] == window[start + i + len]) {
            len++;
        }
        if (len > longestMatch) {
            longestMatch = len;
            *matchPos = start + i;
        }
        if (longestMatch == LOOK_AHEAD_SIZE) {
            break;
        }
    }
    return longestMatch;
}

void outputLiteral(unsigned char ch)
{
    printf("%d ", ch);
}

void outputCode(int offset, int length)
{
    printf("(%d,%d) ", offset, length);
}

void compress(unsigned char *data, int size)
{
    int i = 0;
    while (i < size) {
        if (lookAheadSize < LOOK_AHEAD_SIZE && i < size) {
            lookAheadBuffer[lookAheadSize++] = data[i++];
        }
        if (lookAheadSize == LOOK_AHEAD_SIZE || i == size) {
            int matchPos;
            int len = searchMatch(0, &matchPos);
            if (len >= MIN_MATCH) {
                outputCode(matchPos, len);
                slideWindow(len);
                lookAheadSize -= len;
                memmove(lookAheadBuffer, lookAheadBuffer + len, lookAheadSize);
            } else {
                outputLiteral(lookAheadBuffer[0]);
                slideWindow(1);
                lookAheadSize--;
                memmove(lookAheadBuffer, lookAheadBuffer + 1, lookAheadSize);
            }
        }
    }
}

int main()
{
    unsigned char data[] = "hello worldhello worldhello worldhello worldhello world";
    compress(data, strlen(data));
    return 0;
}

代码中 `WINDOW_SIZE` 定义了滑动窗口的大小，`LOOK_AHEAD_SIZE` 定义了查找缓冲区的大小，`MIN_MATCH` 定义了最小匹配长度。

`slideWindow` 函数实现了滑动窗口的功能，将窗口向左移动 `n` 个字节。

`searchMatch` 函数实现了查找匹配的功能，从窗口的起始位置开始查找最长的匹配。

`outputLiteral` 函数输出字面量。

`outputCode` 函数输出匹配码。

`compress` 函数是 LZSS 算法的核心实现，它将输入数据压缩成字面量和匹配码的序列，并输出到标准输出流中。