在 node.js 中读取二进制数据

问题描述

我在读取 node.js 中的二进制数据时遇到问题.我就是这样做的:

I'm having problems reading binary data in node.js. This is what I do:

$ cat test.js 
var fs = require('fs'),
    binary = fs.readFileSync('./binary', 'binary').toString('binary');
process.stdout.write(binary.substring(0, 48));
$ xxd binary
00000000: 7f45 4c46 0201 0100 0000 0000 0000 0000  .ELF............
00000010: 0300 3e00 0100 0000 0008 0000 0000 0000  ..>.............
00000020: 4000 0000 0000 0000 10a0 0000 0000 0000  @...............
$ node test.js | xxd
00000000: 7f45 4c46 0201 0100 0000 0000 0000 0000  .ELF............
00000010: 0300 3e00 0100 0000 0008 0000 0000 0000  ..>.............
00000020: 4000 0000 0000 0000 10c2 a000 0000 0000  @...............
00000030: 00                                       .
$

注意在使用节点读取时如何在索引 0x29 处插入 0xc2 字节.这是为什么?我已经对 readFileSync 和 toString 说明了二进制编码.我也尝试过 ascii，但得到了不同且同样错误的结果.

Notice how a 0xc2 byte is inserted at index 0x29 when reading with node. Why is that? I've stated binary encoding both to readFileSync and toString. I've also tried ascii but then I get a different and equally wrong result.

推荐答案

'binary' 编码是 'latin1' 的别名，你显然没有读取非字符数据时需要.

The 'binary' encoding is an alias for 'latin1', which you clearly don't want when reading non-character data.

如果您想要原始数据，根本不要指定编码 (或提供 null)*.你会得到一个 Buffer 而不是一个字符串，它然后你想直接使用而不是使用 toString 就可以了.

If you want the raw data, don't specify an encoding at all (or supply null)*. You'll get a Buffer instead of a string, which you'd then want to use directly rather than using toString on it.

*(一些 API [如 fs.watch] 也接受 'buffer'，但它不在 编码列表 和 readFileSync 没有说是.[谢谢 Patrick 提供列表链接.])

* (Some APIs [like fs.watch] also accept 'buffer', but it's not on the list of encodings and readFileSync doesn't say it does. [Thanks Patrick for providing the list link.])

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