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157 lines (144 loc) · 4.49 KB
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package com.qiniu.util;
import com.qiniu.common.Constants;
import java.io.*;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/**
* 计算文件内容或者二进制数据的etag, etag算法是七牛用来标志数据唯一性的算法。
* 文档：<a href="https://github.com/qiniu/qetag">etag算法</a>
*/
public final class Etag {
private Etag() {
}
/**
* 计算二进制数据的etag
*
* @param data 二进制数据
* @param offset 起始字节索引
* @param length 需要计算的字节长度
* @return 二进制数据的etag
*/
public static String data(byte[] data, int offset, int length) {
try {
return stream(new ByteArrayInputStream(data, offset, length), length);
} catch (IOException e) {
throw new AssertionError(e);
}
}
/**
* 计算二进制数据的etag
*
* @param data 二进制数据
* @return 二进制数据的etag
*/
public static String data(byte[] data) {
return data(data, 0, data.length);
}
/**
* 计算文件内容的etag
*
* @param file 文件对象
* @return 文件内容的etag
* @throws IOException 文件读取异常
*/
public static String file(File file) throws IOException {
FileInputStream fi = null;
try {
fi = new FileInputStream(file);
return stream(fi, file.length());
} finally {
if (fi != null) {
try {
fi.close();
} catch (Throwable t) {
}
}
}
}
/**
* 计算文件内容的etag
*
* @param filePath 文件路径
* @return 文件内容的etag
* @throws IOException 文件读取异常
*/
public static String file(String filePath) throws IOException {
File f = new File(filePath);
return file(f);
}
/**
* 计算输入流的etag，如果计算完毕不需要这个InputStream对象，请自行关闭流
*
* @param in 数据输入流
* @param len 数据流长度
* @return 数据流的etag值
* @throws IOException 文件读取异常
*/
public static String stream(InputStream in, long len) throws IOException {
if (len == 0) {
return "Fto5o-5ea0sNMlW_75VgGJCv2AcJ";
}
byte[] buffer = new byte[64 * 1024];
byte[][] blocks = new byte[(int) ((len + Constants.BLOCK_SIZE - 1) / Constants.BLOCK_SIZE)][];
for (int i = 0; i < blocks.length; i++) {
long left = len - (long) Constants.BLOCK_SIZE * i;
long read = left > Constants.BLOCK_SIZE ? Constants.BLOCK_SIZE : left;
blocks[i] = oneBlock(buffer, in, (int) read);
}
return resultEncode(blocks);
}
/**
* 单块计算hash
*
* @param buffer 数据缓冲区
* @param in 输入数据
* @param len 输入数据长度
* @return 计算结果
* @throws IOException 读取出错
*/
private static byte[] oneBlock(byte[] buffer, InputStream in, int len) throws IOException {
MessageDigest sha1;
try {
sha1 = MessageDigest.getInstance("sha-1");
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
int buffSize = buffer.length;
while (len != 0) {
int next = buffSize > len ? len : buffSize;
//noinspection ResultOfMethodCallIgnored
in.read(buffer, 0, next);
sha1.update(buffer, 0, next);
len -= next;
}
return sha1.digest();
}
/**
* 合并结果
*
* @param sha1s 每块计算结果的列表
* @return 最终的结果
*/
private static String resultEncode(byte[][] sha1s) {
byte head = 0x16;
byte[] finalHash = sha1s[0];
int len = finalHash.length;
byte[] ret = new byte[len + 1];
if (sha1s.length != 1) {
head = (byte) 0x96;
MessageDigest sha1;
try {
sha1 = MessageDigest.getInstance("sha-1");
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
for (byte[] s : sha1s) {
sha1.update(s);
}
finalHash = sha1.digest();
}
ret[0] = head;
System.arraycopy(finalHash, 0, ret, 1, len);
return UrlSafeBase64.encodeToString(ret);
}
}