Node.js API详解之 string_decoder用法实例分析
本文实例讲述了Node.js API详解之 string_decoder用法。分享给大家供大家参考，具体如下：
string_decoder 模块提供了一个 API，用于把 Buffer 对象解码成字符串。
对于参数末尾不完整的多字节字符，string_decoder会将其保存在内部的buffer中，当再次解码时，补充到参数开头。
通过 const { StringDecoder } = require(‘string_decoder'); 的方式引用string_decoder模块。
目录：
- new StringDecoder([encoding])
- stringDecoder.write(buffer)
- stringDecoder.end([buffer])
new StringDecoder([encoding])
说明：
创建一个新的StringDecoder实例，可传递encoding参数作为字符编码格式，默认为'utf8′
stringDecoder.write(buffer)
说明：
返回一个解码后的字符串，并确保返回的字符串不包含残缺的多字节字符，残缺的多字节字符会被保存在一个内部的 buffer 中，
用于下次调用 stringDecoder.write() 或 stringDecoder.end()。
buffer：待解码的Buffer
demo：
const decoder = new StringDecoder('utf8');
//字符的16进制小于0x80属于单字节
let outString = decoder.write(Buffer.from([0x78, 0x69, 0x61, 0x6f, 0x71, 0x69, 0x61, 0x6e, 0x67]));
console.log(outString);
//xiaoqiang
//字符的16进制大于0x80属于双字节
outString = decoder.write(Buffer.from([0xC2, 0xA2]));
console.log(outString);
//￠
//单双字节混合，置于末尾
outString = decoder.write(Buffer.from([0x78, 0x69, 0x61, 0x6f, 0x71, 0x69, 0x61, 0x6e, 0x67, 0xC2]));
console.log(outString);
//xiaoqiang
outString = decoder.write(Buffer.from([0xA2]));
console.log(outString);
//￠
//单双字节混合，置于中间
outString = decoder.write(Buffer.from([0x78, 0x69, 0x61, 0x6f, 0x71, 0xC2, 0x69, 0x61, 0x6e, 0x67]));
console.log(outString);
//xiaoq?iang
outString = decoder.write(Buffer.from([0xA2]));
console.log(outString);
//?
//单双字节混合，置于开始
outString = decoder.write(Buffer.from([0xC2, 0x78, 0x69, 0x61, 0x6f, 0x71, 0x69, 0x61, 0x6e, 0x67]));
console.log(outString);
//?xiaoqiang
outString = decoder.write(Buffer.from([0xA2]));
console.log(outString);
//?
//单双字节混合，置于末尾
outString = decoder.write(Buffer.from([0x78, 0x69, 0x61, 0x6f, 0x71, 0x69, 0x61, 0x6e, 0x67, 0xC2]));
console.log(outString);
//xiaoqiang
outString = decoder.write(Buffer.from([0x78,0xA2]));
console.log(outString);
//?x?
stringDecoder.end([buffer])
说明：
以字符串的形式返回内部 buffer 中剩余的字节，残缺的字节会被替换成符合字符编码的字符
如果提供了 buffer 参数，则在返回剩余字节之前会再执行一次 stringDecoder.write()
demo：
const decoder = new StringDecoder('utf8');
//字符的16进制小于0x80属于单字节
let outString = decoder.write(Buffer.from([0x78, 0x69, 0x61, 0x6f, 0x71, 0x69, 0x61, 0x6e, 0x67]));
console.log(outString);
//xiaoqiang
outString = decoder.end();
console.log(outString);
//
//单双字节混合，置于末尾
outString = decoder.write(Buffer.from([0x78, 0x69, 0x61, 0x6f, 0x71, 0x69, 0x61, 0x6e, 0x67, 0xC2]));
console.log(outString);
//xiaoqiang
outString = decoder.end(Buffer.from([0xA2]));
console.log(outString);
//￠
//单双字节混合，置于末尾
outString = decoder.write(Buffer.from([0x78, 0x69, 0x61, 0x6f, 0x71, 0x69, 0x61, 0x6e, 0x67, 0xC2]));
console.log(outString);
//xiaoqiang
outString = decoder.end();
console.log(outString);
//?
希望本文所述对大家node.js程序设计有所帮助。
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