TONT 40093 有些文件在记事本里打开时怪怪的

联通电池。

原文链接：https://blogs.msdn.microsoft.com/oldnewthing/20040324-00/?p=40093

David Cumps discovered that certain text files come up strange in Notepad.

David Cumps发现某些特定的文本文件在记事本中打开时好像有些怪怪的。

The reason is that Notepad has to edit files in a variety of encodings, and when its back against the wall, sometimes it’s forced to guess.

原因是记事本需要应对不同编码的文件，而当被逼到没法的时候，（文件的编码）也就只能靠猜了。

Here’s the file “Hello” in various encodings:

以下是包含字符串『Hello』的文本文件，但编码不同：

48 65 6C 6C 6F

This is the traditional ANSI encoding.（这是传统的ANSI编码。）

48 00 65 00 6C 00 6C 00 6F 00

This is the Unicode (little-endian) encoding with no BOM.（这是不带BOM的小端序Unicode编码。）

FF FE 48 00 65 00 6C 00 6C 00 6F 00

This is the Unicode (little-endian) encoding with BOM. The BOM (FF FE) serves two purposes: First, it tags the file as a Unicode document, and second, the order in which the two bytes appear indicate that the file is little-endian.

这是带BOM的小端序Unicode编码。BOM（即开头的FF FE）用途有二：一来，标示该文件为Unicode编码；二来，这两个字节的顺序表明这个文件是小端序的。

00 48 00 65 00 6C 00 6C 00 6F

This is the Unicode (big-endian) encoding with no BOM. Notepad does not support this encoding.

这是不带BOM的大端序Unicode编码。记事本不支持这种编码。

FE FF 00 48 00 65 00 6C 00 6C 00 6F

This is the Unicode (big-endian) encoding with BOM. Notice that this BOM is in the opposite order from the little-endian BOM.

这是带BOM的大端序Unicode编码，注意BOM的字节顺序与小端序BOM相反。

EF BB BF 48 65 6C 6C 6F

This is UTF-8 encoding. The first three bytes are the UTF-8 encoding of the BOM.

这是UTF-8编码，开头的三个字节是UTF-8编码的BOM。

2B 2F 76 38 2D 48 65 6C 6C 6F

This is UTF-7 encoding. The first five bytes are the UTF-7 encoding of the BOM. Notepad doesn’t support this encoding.

这是UTF-7编码，开头的五个字节是UTF-7编码的BOM，记事本不支持这种编码。

Notice that the UTF7 BOM encoding is just the ASCII string “+/v8-“, which is difficult to distinguish from just a regular file that happens to begin with those five characters (as odd as they may be).

请注意，UTF-7的BOM头的编码正好是ASCII字符串『+/v8-』，如果文本文件正好以这五个字符开头，对猜测其编码会造成一定的困难（虽然以这五个字符开头本身就有点怪怪的了）。

The encodings that do not have special prefixes and which are still supported by Notepad are the traditional ANSI encoding (i.e., “plain ASCII”) and the Unicode (little-endian) encoding with no BOM. When faced with a file that lacks a special prefix, Notepad is forced to guess which of those two encodings the file actually uses. The function that does this work is IsTextUnicode, which studies a chunk of bytes and does some statistical analysis to come up with a guess.

不包含任何特殊的前缀、但仍被记事本支持的编码是传统的ANSI编码（亦即所谓的纯ASCII）和不带BOM的小端序Unicode编码。当面对没有特殊前缀的文本文件时，记事本将被迫猜测文件实际使用的编码。用以处理这项业务的函数叫IsTextUnicode，通过对一块字节进行研究、并进行某些统计性分析来对文件的编码进行猜测。

And as the documentation notes, “Absolute certainty is not guaranteed.” Short strings are most likely to be misdetected.

并且这个函数的文档亦有注明『无法保证对编码绝对准确的猜测』。短小的字符串被猜错的几率相对会比较大。