9

我正在尝试从文件系统中读取二进制文件，然后用 JavaScript 对其进行 base64 编码。我正在使用FileReader API来读取数据和在此处找到的 base64 编码器。

我的代码似乎接近工作，问题是生成的base64数据是错误的。这是我到目前为止所得到的：

function saveResource() {
    var file = $(".resourceFile")[0].files[0];

    var reader = new FileReader();
    reader.onload = function(evt) {
        var fileData = evt.target.result;
        var bytes = new Uint8Array(fileData);
        var binaryText = '';

        for (var index = 0; index < bytes.byteLength; index++) {
            binaryText += String.fromCharCode( bytes[index] );
        }

        console.log(Base64.encode(binaryText));

    };
    reader.readAsArrayBuffer(file);
};

这是我正在测试的文件（它是一个 100x100 的蓝色方块）：

在此处输入图像描述

根据在线 base64 解码器/编码器，此文件应编码为：

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

...但相反，我从 JavaScript 中得到的是：

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woooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooA8O/w5k=woooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooAMKiwoooA8O/w5k=

如果我不得不冒险猜测，我会说这个问题与二进制数据中的不可打印字符有关（如果我对纯文本文档进行编码，那可以正常工作）。但是解决这个问题的最佳方法是什么？

编辑

看起来这可能是 base64 库本身的问题（或者如果不是，那么如何将Uint8Array其解包为库调用的字符串）。如果我改用浏览器的btoa()功能，并直接传递它，那就行了。太糟糕了，该功能并非在所有浏览器中都存在。Uint8Array binaryText

4

2 回答 2

8

和谷歌来救援。我找到了以下代码，它将输入数据作为“字节”的普通数组（0到255之间的数字，包括在内；如果Uint8Array直接传递给它也可以正常工作），并将其添加到我正在使用的库中：

//note:  it is assumed that the Base64 object has already been defined
//License:  Apache 2.0
Base64.byteToCharMap_ = null;
Base64.charToByteMap_ = null;
Base64.byteToCharMapWebSafe_ = null;
Base64.charToByteMapWebSafe_ = null;
Base64.ENCODED_VALS_BASE =
    'ABCDEFGHIJKLMNOPQRSTUVWXYZ' +
    'abcdefghijklmnopqrstuvwxyz' +
    '0123456789';

/**
 * Our default alphabet. Value 64 (=) is special; it means "nothing."
 * @type {string}
 */
Base64.ENCODED_VALS = Base64.ENCODED_VALS_BASE + '+/=';
Base64.ENCODED_VALS_WEBSAFE = Base64.ENCODED_VALS_BASE + '-_.';

/**
 * Base64-encode an array of bytes.
 *
 * @param {Array.<number>|Uint8Array} input An array of bytes (numbers with
 *     value in [0, 255]) to encode.
 * @param {boolean=} opt_webSafe Boolean indicating we should use the
 *     alternative alphabet.
 * @return {string} The base64 encoded string.
 */
Base64.encodeByteArray = function(input, opt_webSafe) {
  Base64.init_();

  var byteToCharMap = opt_webSafe ?
                      Base64.byteToCharMapWebSafe_ :
                      Base64.byteToCharMap_;

  var output = [];

  for (var i = 0; i < input.length; i += 3) {
    var byte1 = input[i];
    var haveByte2 = i + 1 < input.length;
    var byte2 = haveByte2 ? input[i + 1] : 0;
    var haveByte3 = i + 2 < input.length;
    var byte3 = haveByte3 ? input[i + 2] : 0;

    var outByte1 = byte1 >> 2;
    var outByte2 = ((byte1 & 0x03) << 4) | (byte2 >> 4);
    var outByte3 = ((byte2 & 0x0F) << 2) | (byte3 >> 6);
    var outByte4 = byte3 & 0x3F;

    if (!haveByte3) {
      outByte4 = 64;

      if (!haveByte2) {
        outByte3 = 64;
      }
    }

    output.push(byteToCharMap[outByte1],
                byteToCharMap[outByte2],
                byteToCharMap[outByte3],
                byteToCharMap[outByte4]);
  }

  return output.join('');
};

/**
 * Lazy static initialization function. Called before
 * accessing any of the static map variables.
 * @private
 */
Base64.init_ = function() {
  if (!Base64.byteToCharMap_) {
    Base64.byteToCharMap_ = {};
    Base64.charToByteMap_ = {};
    Base64.byteToCharMapWebSafe_ = {};
    Base64.charToByteMapWebSafe_ = {};

    // We want quick mappings back and forth, so we precompute two maps.
    for (var i = 0; i < Base64.ENCODED_VALS.length; i++) {
      Base64.byteToCharMap_[i] =
          Base64.ENCODED_VALS.charAt(i);
      Base64.charToByteMap_[Base64.byteToCharMap_[i]] = i;
      Base64.byteToCharMapWebSafe_[i] =
          Base64.ENCODED_VALS_WEBSAFE.charAt(i);
      Base64.charToByteMapWebSafe_[
          Base64.byteToCharMapWebSafe_[i]] = i;
    }
  }
};

包含上述函数的库的完整代码可在此处获得，但未经修改的形式似乎依赖于许多其他库。上面稍微修改过的版本应该适用于只需要快速修复此问题的任何人。

于 2013-03-01T04:17:10.050 回答
1

将二进制文件视为数组缓冲区，这与任何字符编码无关。您的蓝色方块 (.jpg) 有 361 个本机字节，表示 0..255（十进制）的八位字节，它们不是字符！

这意味着：使用 ArrayBuffer 使用众所周知的 base64 算法将其编码为 Base64。

随着 Perl 回到原点，如上图所示：

my $fh = IO::File->new;
$fh->open("d:/tmp/x.jpg", O_BINARY|O_CREAT|O_RDWR|O_TRUNC) or die $!;

$fh->print(decode_base64("/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRofHh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/2wBD
AQkJCQwLDBgNDRgyIRwhMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjL/wAARCABkAGQDASIAAhEBAxEB/8QAFQABAQAA
AAAAAAAAAAAAAAAAAAf/xAAUEAEAAAAAAAAAAAAAAAAAAAAA/8QAFgEBAQEAAAAAAAAAAAAAAAAAAAUH/8QAFBEBAAAAAAAAAAAAAAAAAAAAAP/aAAwDAQACEQMR
AD8AjgDcUwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAB//2Q==
"));


$fh->close;
于 2014-03-03T21:54:26.690 回答