其实ByteString没什么好看的。看之前以为有重要内容，看完后发现没有，不过既然已经看了，就记录下来吧。
ByteString封装了以下几点
1、就是把一些输入类型(字符串/字节数组/ByteBuffer/byte)转成字节数组，并封装成新的ByteString返回。
比如ByteString.of(...)
2、封装了对ByteString的比较、加密操作，方便使用
比如ByteString.encode(...)、base64(...)、md5(...)、sha1()、....
ByteString.startWith(...）、endWith(...)
差不多就这些东西。
public class ByteString implements Serializable, Comparable<ByteString> {
static final char[] HEX_DIGITS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
/** A singleton empty {@code ByteString}. */
public static final ByteString EMPTY = ByteString.of();
final byte[] data;
transient int hashCode; // Lazily computed; 0 if unknown.
transient String utf8; // Lazily computed.
ByteString(byte[] data) {
this.data = data; // Trusted internal constructor doesn't clone data.
}
/**
* Returns a new byte string containing a clone of the bytes of {@code data}.
*/
public static ByteString of(byte... data) {
if (data == null) {
throw new IllegalArgumentException("data == null");
}
return new ByteString(data.clone());
}
//复制data的缓存中byteCount个字节的内容到新的byte[]，返回一个新的ByteString
public static ByteString of(byte[] data, int offset, int byteCount) {
if (data == null) {
throw new IllegalArgumentException("data == null");
}
checkOffsetAndCount(data.length, offset, byteCount);//校验参数
byte[] copy = new byte[byteCount];
System.arraycopy(data, offset, copy, 0, byteCount);
return new ByteString(copy);
}
//复制data的缓存中0-data.remaining()的内容到copy数组，返回新的ByteString
public static ByteString of(ByteBuffer data) {
if (data == null) {
throw new IllegalArgumentException("data == null");
}
byte[] copy = new byte[data.remaining()];//
data.get(copy);
return new ByteString(copy);
}
//把string转byte[]存入新建的ByteString返回，byteString.utf8保存了string的原字符串
public static ByteString encodeUtf8(String s) {
if (s == null) {
throw new IllegalArgumentException("s == null");
}
ByteString byteString = new ByteString(s.getBytes(Util.UTF_8));
byteString.utf8 = s;
return byteString;
}
/** Returns a new byte string containing the {@code charset}-encoded bytes of {@code s}. */
public static ByteString encodeString(String s, Charset charset) {
if (s == null) {
throw new IllegalArgumentException("s == null");
}
if (charset == null) {
throw new IllegalArgumentException("charset == null");
}
return new ByteString(s.getBytes(charset));
}
//获取data[]对应的UTF8字符串
public String utf8() {
String result = utf8;
// We don't care if we double-allocate in racy code.
return result != null ? result : (utf8 = new String(data, Util.UTF_8));
}
//把data[]转成charset的字符串
public String string(Charset charset) {
if (charset == null) {
throw new IllegalArgumentException("charset == null");
}
return new String(data, charset);
}
//把data[]用Base64编码后返回
public String base64() {
return Base64.encode(data);
}
//把data[]用md5加密后返回
public ByteString md5() {
return digest("MD5");
}
//把data[]用sha1加密后返回
public ByteString sha1() {
return digest("SHA-1");
}
//把data用sha256加密后返回
public ByteString sha256() {
return digest("SHA-256");
}
//把data用sha512加密后返回
public ByteString sha512() {
return digest("SHA-512");
}
//加密的api
private ByteString digest(String algorithm) {
try {
return ByteString.of(MessageDigest.getInstance(algorithm).digest(data));
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
/** Returns the 160-bit SHA-1 HMAC of this byte string. */
public ByteString hmacSha1(ByteString key) {
return hmac("HmacSHA1", key);
}
/** Returns the 256-bit SHA-256 HMAC of this byte string. */
public ByteString hmacSha256(ByteString key) {
return hmac("HmacSHA256", key);
}
/** Returns the 512-bit SHA-512 HMAC of this byte string. */
public ByteString hmacSha512(ByteString key) {
return hmac("HmacSHA512", key);
}
private ByteString hmac(String algorithm, ByteString key) {
try {
Mac mac = Mac.getInstance(algorithm);
mac.init(new SecretKeySpec(key.toByteArray(), algorithm));
return ByteString.of(mac.doFinal(data));
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
} catch (InvalidKeyException e) {
throw new IllegalArgumentException(e);
}
}
//如果data是url的字节数组，用Base64对该url的字节数组编码，返回编码后的字符串
public String base64Url() {
return Base64.encodeUrl(data);
}
/**
* Decodes the Base64-encoded bytes and returns their value as a byte string.
* Returns null if {@code base64} is not a Base64-encoded sequence of bytes.
*/
public static @Nullable
ByteString decodeBase64(String base64) {
if (base64 == null) {
throw new IllegalArgumentException("base64 == null");
}
byte[] decoded = Base64.decode(base64);
return decoded != null ? new ByteString(decoded) : null;
}
/** Returns this byte string encoded in hexadecimal. */
public String hex() {
char[] result = new char[data.length * 2];
int c = 0;
for (byte b : data) {
result[c++] = HEX_DIGITS[(b >> 4) & 0xf];
result[c++] = HEX_DIGITS[b & 0xf];
}
return new String(result);
}
/** Decodes the hex-encoded bytes and returns their value a byte string. */
public static ByteString decodeHex(String hex) {
if (hex == null) {
throw new IllegalArgumentException("hex == null");
}
if (hex.length() % 2 != 0) {
throw new IllegalArgumentException("Unexpected hex string: " + hex);
}
byte[] result = new byte[hex.length() / 2];
for (int i = 0; i < result.length; i++) {
int d1 = decodeHexDigit(hex.charAt(i * 2)) << 4;
int d2 = decodeHexDigit(hex.charAt(i * 2 + 1));
result[i] = (byte) (d1 + d2);
}
return of(result);
}
private static int decodeHexDigit(char c) {
if (c >= '0' && c <= '9') {
return c - '0';
}
if (c >= 'a' && c <= 'f') {
return c - 'a' + 10;
}
if (c >= 'A' && c <= 'F') {
return c - 'A' + 10;
}
throw new IllegalArgumentException("Unexpected hex digit: " + c);
}
//把输入流in的内容写入字节数组，封装成ByteString返回
public static ByteString read(InputStream in, int byteCount) throws IOException {
if (in == null) {
throw new IllegalArgumentException("in == null");
}
if (byteCount < 0) {
throw new IllegalArgumentException("byteCount < 0: " + byteCount);
}
byte[] result = new byte[byteCount];
for (int offset = 0, read; offset < byteCount; offset += read) {
read = in.read(result, offset, byteCount - offset);
if (read == -1) {
throw new EOFException();
}
}
return new ByteString(result);
}
//把data[]中A-Z之间的字符大写转小写，生成新的字节数组，封装成新的ByteString返回
public ByteString toAsciiLowercase() {
for (int i = 0; i < data.length; i++) {
byte c = data[i];
if (c < 'A' || c > 'Z') {
continue;
}
byte[] lowercase = data.clone();
lowercase[i++] = (byte) (c - ('A' - 'a'));
for (; i < lowercase.length; i++) {
c = lowercase[i];
if (c < 'A' || c > 'Z') {
continue;
}
lowercase[i] = (byte) (c - ('A' - 'a'));
}
return new ByteString(lowercase);
}
return this;
}
//把data[]中a-z之间的字符，小写转大写，生成新的字节数组，封装成新的ByteString后返回
public ByteString toAsciiUppercase() {
for (int i = 0; i < data.length; i++) {
byte c = data[i];
if (c < 'a' || c > 'z') {
continue;
}
byte[] lowercase = data.clone();
lowercase[i++] = (byte) (c - ('a' - 'A'));
for (; i < lowercase.length; i++) {
c = lowercase[i];
if (c < 'a' || c > 'z') {
continue;
}
lowercase[i] = (byte) (c - ('a' - 'A'));
}
return new ByteString(lowercase);
}
return this;
}
/**
* Returns a byte string that is a substring of this byte string, beginning at the specified
* index until the end of this string. Returns this byte string if {@code beginIndex} is 0.
*/
public ByteString substring(int beginIndex) {
return substring(beginIndex, data.length);
}
//把data[]中beginIndex到endIndex之间的内容封装成新的字节数组，封装成ByteStirng返回
public ByteString substring(int beginIndex, int endIndex) {
if (beginIndex < 0) {
throw new IllegalArgumentException("beginIndex < 0");
}
if (endIndex > data.length) {
throw new IllegalArgumentException("endIndex > length(" + data.length + ")");
}
int subLen = endIndex - beginIndex;
if (subLen < 0) {
throw new IllegalArgumentException("endIndex < beginIndex");
}
if ((beginIndex == 0) && (endIndex == data.length)) {
return this;
}
byte[] copy = new byte[subLen];
System.arraycopy(data, beginIndex, copy, 0, subLen);
return new ByteString(copy);
}
//返回data[]第pos个字节
public byte getByte(int pos) {
return data[pos];
}
//返回ByteString中data[]的长度
public int size() {
return data.length;
}
//返回data[]的一个副本
public byte[] toByteArray() {
return data.clone();
}
//返回data[]本身
byte[] internalArray() {
return data;
}
//用data[]封装成一个只读的ByteBuffer视图返回
public ByteBuffer asByteBuffer() {
return ByteBuffer.wrap(data).asReadOnlyBuffer();
}
//把当前data[]中的内容写入out输出流中
public void write(OutputStream out) throws IOException {
if (out == null) {
throw new IllegalArgumentException("out == null");
}
out.write(data);
}
//把data[]中内容写入buffer中
void write(Buffer buffer) {
buffer.write(data, 0, data.length);
}
//比较当前ByteString.data[]的offset~offset+byteCount的内容与otherOffset.data[]的otherOffset~otherOffset+byteCount的内容
public boolean rangeEquals(int offset, ByteString other, int otherOffset, int byteCount) {
return other.rangeEquals(otherOffset, this.data, offset, byteCount);
}
/**
* Returns true if the bytes of this in {@code [offset..offset+byteCount)} equal the bytes of
* {@code other} in {@code [otherOffset..otherOffset+byteCount)}. Returns false if either range is
* out of bounds.
*/
public boolean rangeEquals(int offset, byte[] other, int otherOffset, int byteCount) {
return offset >= 0 && offset <= data.length - byteCount
&& otherOffset >= 0 && otherOffset <= other.length - byteCount
&& arrayRangeEquals(data, offset, other, otherOffset, byteCount);
}
//判断当前bytestring.data[]前缀
public final boolean startsWith(ByteString prefix) {
return rangeEquals(0, prefix, 0, prefix.size());
}
public final boolean startsWith(byte[] prefix) {
return rangeEquals(0, prefix, 0, prefix.length);
}
//判断当前bytestring.data[]后缀
public final boolean endsWith(ByteString suffix) {
return rangeEquals(size() - suffix.size(), suffix, 0, suffix.size());
}
public final boolean endsWith(byte[] suffix) {
return rangeEquals(size() - suffix.length, suffix, 0, suffix.length);
}
//判断other在当前ByteString所处的位置索引
public final int indexOf(ByteString other) {
return indexOf(other.internalArray(), 0);
}
...
@Override
public int compareTo(ByteString byteString) {
int sizeA = size();
int sizeB = byteString.size();
for (int i = 0, size = Math.min(sizeA, sizeB); i < size; i++) {
int byteA = getByte(i) & 0xff;//&0xff，防止java类型转换补码导致数据发生变化
int byteB = byteString.getByte(i) & 0xff;
if (byteA == byteB) {
continue;
}
return byteA < byteB ? -1 : 1;
}
if (sizeA == sizeB) {
return 0;
}
return sizeA < sizeB ? -1 : 1;
}
...
}