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fastjson 2.0.54版本发布，性能进一步提升

这又是一个性能优化Bug修复的版本更新版本，大家按需升级。

1. 性能优化

这个版本的性能优化包括：

1.1 使用SWAR(SIMD Within A Register)技巧来优化序列化字符串的性能

序列化时，写字符串检测是否存在特别字符是一个性能关键点，这个版本使用SWAR(SIMD Within A Register)的技巧来做快速检测。如下

package com.alibaba.fastjson2;
class JSONWriterUTF8 {
    protected final long byteVectorQuote;
JSONWriterUTF8(Context ctx) {
// " -> 0x22, ' -> 0x27
this.byteVectorQuote = this.useSingleQuote ? 0x2727_2727_2727_2727L : 0x2222_2222_2222_2222L;
}
public void writeStringLatin1(byte[] value) {
    final long vecQuote = this.byteVectorQuote;
    int i = 0;
    final int upperBound = (value.length - i) & ~7;
    // 这里一次检测8个byte是否存在特别字符
    for (; i < upperBound; i += 8) {
        if (containsEscaped(IOUtils.getLongLittleEndian(value, i), vecQuote)) {
            break;
        }
    }
    // ...
}
static boolean containsEscaped(long v, long quote) {
/*
for (int i = 0; i < 8; ++i) {
byte c = (byte) data;
if (c == quote || c == '\' || c < ' ') {
return true;
}
data >>>= 8;
}
return false;
*/
long x22 = v ^ quote; // " -> 0x22, ' -> 0x27
long x5c = v ^ 0x5c5c5c5c5c5c5c5cL;
x22 = (x22 - 0x0101010101010101L) & ~x22;
x5c = (x5c - 0x0101010101010101L) & ~x5c;

return ((x22 | x5c | (0x7F7F_7F7F_7F7F_7F7FL - v + 0x1010_1010_1010_1010L) | v) & 0x8080808080808080L) != 0;

}

}
</tr></table>

... (truncated)

• a0bb6c0 2.0.54 release
• 118333f fix compatible error
• b25d78d fix testcase
• 3d1cb1d support setUseGsonAnnotation, for issue #3258
• 949e867 fix readComment, for issue #3260
• 2c76718 CACHE_THRESHOLD 8M
• 15d1850 fix #3264
• fb9dc31 code style
• b4a816e fix comment
• a9e4453 vector write
• Additional commits viewable in compare view

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