/src/main/java/com/alibaba/fastjson/serializer/SerialWriterStringEncoder.java

 1package com.alibaba.fastjson.serializer;
 2
 3import java.nio.ByteBuffer;
 4import java.nio.CharBuffer;
 5import java.nio.charset.CharacterCodingException;
 6import java.nio.charset.Charset;
 7import java.nio.charset.CharsetEncoder;
 8import java.nio.charset.CoderResult;
 9import java.nio.charset.CodingErrorAction;
10
11import com.alibaba.fastjson.JSONException;
12import com.alibaba.fastjson.util.ThreadLocalCache;
13
14public class SerialWriterStringEncoder {
15
16	private final CharsetEncoder encoder;
17
18	public SerialWriterStringEncoder(Charset cs) {
19		this(cs.newEncoder().onMalformedInput(CodingErrorAction.REPLACE).onUnmappableCharacter(CodingErrorAction.REPLACE));
20	}
21	
22	public SerialWriterStringEncoder(CharsetEncoder encoder) {
23	    this.encoder = encoder;
24	}
25
26	public byte[] encode(char[] chars, int off, int len) {
27		if (len == 0) {
28			return new byte[0];
29		}
30
31		encoder.reset();
32
33		int bytesLength = scale(len, encoder.maxBytesPerChar());
34
35		byte[] bytes = ThreadLocalCache.getBytes(bytesLength);
36
37		return encode(chars, off, len, bytes);
38	}
39
40	public CharsetEncoder getEncoder() {
41		return encoder;
42	}
43
44	public byte[] encode(char[] chars, int off, int len, byte[] bytes) {
45		ByteBuffer byteBuf = ByteBuffer.wrap(bytes);
46
47		CharBuffer charBuf = CharBuffer.wrap(chars, off, len);
48		try {
49			CoderResult cr = encoder.encode(charBuf, byteBuf, true);
50			if (!cr.isUnderflow()) {
51				cr.throwException();
52			}
53			cr = encoder.flush(byteBuf);
54			if (!cr.isUnderflow()) {
55				cr.throwException();
56			}
57		} catch (CharacterCodingException x) {
58			// Substitution is always enabled,
59			// so this shouldn't happen
60			throw new JSONException(x.getMessage(), x);
61		}
62
63		int bytesLength = byteBuf.position();
64		byte[] copy = new byte[bytesLength];
65		System.arraycopy(bytes, 0, copy, 0, bytesLength);
66		return copy;
67	}
68
69	private static int scale(int len, float expansionFactor) {
70		// We need to perform double, not float, arithmetic; otherwise
71		// we lose low order bits when len is larger than 2**24.
72		return (int) (len * (double) expansionFactor);
73	}
74
75}