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。