java lz77 压缩
时间: 2023-12-01 17:43:45 浏览: 18
以下是使用Java实现LZ77压缩的示例代码:
```java
import java.io.*;
import java.util.*;
public class LZ77Compressor {
private static final int LOOK_AHEAD_BUFFER_SIZE = 4096;
private static final int SEARCH_BUFFER_SIZE = 4096;
private static final int MAX_MATCH_LENGTH = 18;
private static final int MIN_MATCH_LENGTH = 3;
public static void compress(String inputFilePath, String outputFilePath) throws IOException {
FileInputStream inputStream = new FileInputStream(inputFilePath);
FileOutputStream outputStream = new FileOutputStream(outputFilePath);
byte[] searchBuffer = new byte[SEARCH_BUFFER_SIZE];
byte[] lookAheadBuffer = new byte[LOOK_AHEAD_BUFFER_SIZE];
int searchBufferOffset = 0;
int lookAheadBufferOffset = 0;
int bytesRead = inputStream.read(lookAheadBuffer,0, LOOK_AHEAD_BUFFER_SIZE);
while (bytesRead != -1) {
int matchOffset = 0;
int matchLength = 0;
for (int i = Math.max(lookAheadBufferOffset - SEARCH_BUFFER_SIZE, 0); i < lookAheadBufferOffset; i++) {
int currentMatchLength = 0;
while (currentMatchLength < MAX_MATCH_LENGTH && i + currentMatchLength < lookAheadBufferOffset && lookAheadBuffer[i + currentMatchLength] == lookAheadBuffer[lookAheadBufferOffset + currentMatchLength]) {
currentMatchLength++;
}
if (currentMatchLength > matchLength) {
matchOffset = lookAheadBufferOffset - i;
matchLength = currentMatchLength;
}
}
if (matchLength >= MIN_MATCH_LENGTH) {
outputStream.write((byte) ((matchOffset >> 4) & 0xFF));
outputStream.write((byte) (((matchOffset & 0xF) << 4) | (matchLength - MIN_MATCH_LENGTH)));
lookAheadBufferOffset += matchLength;
} else {
outputStream.write((byte) 0);
outputStream.write(lookAheadBuffer[lookAheadBufferOffset]);
lookAheadBufferOffset++; }
if (lookAheadBufferOffset >= LOOK_AHEAD_BUFFER_SIZE) {
System.arraycopy(lookAheadBuffer, LOOK_AHEAD_BUFFER_SIZE - SEARCH_BUFFER_SIZE, searchBuffer, 0, SEARCH_BUFFER_SIZE);
lookAheadBufferOffset = SEARCH_BUFFER_SIZE;
bytesRead = inputStream.read(lookAheadBuffer, SEARCH_BUFFER_SIZE, LOOK_AHEAD_BUFFER_SIZE - SEARCH_BUFFER_SIZE);
} else {
bytesRead = inputStream.read(lookAheadBuffer, lookAheadBufferOffset, LOOK_AHEAD_BUFFER_SIZE - lookAheadBufferOffset);
}
}
inputStream.close();
outputStream.close();
}
}
```
使用上述代码,你可以将指定的文件进行LZ77压缩。具体使用方法如下:
```java
LZ77Compressor.compress("input.txt", "output.lz77");
```
其中,`input.txt`是要压缩的文件路径,`output.lz77`是压缩后的文件路径。