Node.js API詳解之 string_decoder用法實(shí)例分析

更新時(shí)間：2020年04月29日 08:46:58 作者：李小強(qiáng)

這篇文章主要介紹了Node.js API詳解之 string_decoder用法,結(jié)合實(shí)例形式分析了Node.js API中string_decoder的功能、用法及操作注意事項(xiàng),需要的朋友可以參考下

本文實(shí)例講述了Node.js API詳解之 string_decoder用法。分享給大家供大家參考，具體如下：

string_decoder 模塊提供了一個(gè) API，用于把 Buffer 對象解碼成字符串。

對于參數(shù)末尾不完整的多字節(jié)字符，string_decoder會(huì)將其保存在內(nèi)部的buffer中，當(dāng)再次解碼時(shí)，補(bǔ)充到參數(shù)開頭。

通過 const { StringDecoder } = require(‘string_decoder'); 的方式引用string_decoder模塊。

new StringDecoder([encoding])
stringDecoder.write(buffer)
stringDecoder.end([buffer])

new StringDecoder([encoding])

說明：

創(chuàng)建一個(gè)新的StringDecoder實(shí)例，可傳遞encoding參數(shù)作為字符編碼格式，默認(rèn)為'utf8′

stringDecoder.write(buffer)

說明：

返回一個(gè)解碼后的字符串，并確保返回的字符串不包含殘缺的多字節(jié)字符，殘缺的多字節(jié)字符會(huì)被保存在一個(gè)內(nèi)部的 buffer 中，
用于下次調(diào)用 stringDecoder.write() 或 stringDecoder.end()。
buffer：待解碼的Buffer

demo：

const decoder = new StringDecoder('utf8');
 
//字符的16進(jìn)制小于0x80屬于單字節(jié)
let outString = decoder.write(Buffer.from([0x78, 0x69, 0x61, 0x6f, 0x71, 0x69, 0x61, 0x6e, 0x67]));
 
console.log(outString);
//xiaoqiang
 
//字符的16進(jìn)制大于0x80屬于雙字節(jié)
outString = decoder.write(Buffer.from([0xC2, 0xA2]));
 
console.log(outString);
//￠
 
//單雙字節(jié)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);
//￠
 
//單雙字節(jié)混合，置于中間
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);
//?
 
//單雙字節(jié)混合，置于開始
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);
//?
 
//單雙字節(jié)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])

說明：

以字符串的形式返回內(nèi)部 buffer 中剩余的字節(jié)，殘缺的字節(jié)會(huì)被替換成符合字符編碼的字符
如果提供了 buffer 參數(shù)，則在返回剩余字節(jié)之前會(huì)再執(zhí)行一次 stringDecoder.write()

demo：

const decoder = new StringDecoder('utf8');
 
//字符的16進(jìn)制小于0x80屬于單字節(jié)
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);
//
 
//單雙字節(jié)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);
//￠
 
//單雙字節(jié)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);
//?

希望本文所述對大家node.js程序設(shè)計(jì)有所幫助。

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