Buffer to string

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Buffer to string

Introduction

  • 在 node 中網路傳輸、讀存取檔案經常是使用 buffer，但是在查看時都要經過轉換，文件上也沒有寫很清楚，所以才特別紀錄
  • 基本上 buffer 是處理 binary 相對方便
  • 他是類似 array 的狀態，每一個值代表一個 byte，所以在十進位中其值為 0~255
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    var buff = Buffer.from([1, 2, 3]);
    var buff = Buffer.from('hello world', 'utf8');
    • new Buffer(array) is deprecated
    • use Buffer.from(array) instead

    toString

  • 基本上跟 c 語言很像， character 和數字是相關的，可以互相轉換
  • 可以利用 .toString([encoding[, start[, end]]])
    • 預設 encoding 是 utf8
      Encoding Description
      ‘ascii’ for 7 bit ASCII data only. This encoding method is way fast, but is limited to the ascii character set. To convert a null character into 0x00, you should use ‘utf8’.
      ‘utf8’ Multibyte encoded Unicode characters. It has become the dominant character encoding for the world wide web.
      ‘utf16le’ 2 or 4 bytes, little-endian encoded Unicode characters, surrogate pairs (U+10000 to U+10FFFF) are supported.
      ‘ucs2’ Alias of ‘utf16le’.
      ‘base64’ Base64 string encoding.
      ‘binary’ Method of encoding raw binary data into strings by using only the first 8 bits of each character. This encoding method is deprecated.
      ‘hex’ This method is used to encode each byte as two hexadecimal characters.
    • start 是起始位置
    • end 是終止位置
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      const buf1 = Buffer.allocUnsafe(26);

      for (let i = 0; i < 26; i++) {
        // 97 is the decimal ASCII value for 'a'.
        buf1[i] = i + 97;
      }
      console.log(buf1.toString('utf8'));
      // Prints: abcdefghijklmnopqrstuvwxyz
      console.log(buf1.toString('utf8', 0, 5));
      // Prints: abcde

      Reference

  • Using Buffers in Node.js
  • Buffer - Node.js v14.13.1 Documentation
  • List of encodings that Node.js supports