File.dirname: add a spec for Shift JIS handling #1330
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While trying to speedup various `File.*` methods, I realized they were way slower and complicated than they should for no apparent reason. However after asking Nobu he explained that Shift JIS encoded text can contain `0x5C` (ASCII backslash) as the second byte of a two byte character sequence. Since on Windows `0x5C` is `File::ALT_SEPARATOR`, this can easily break naive path related algorithms searching for directory separators.
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While trying to speedup various
File.*methods, I realized they were way slower and complicated than they should for no apparent reason. However after asking Nobu he explained that Shift JIS encoded text can contain0x5C(ASCII backslash) as the second byte of a two byte character sequence.Since on Windows
0x5CisFile::ALT_SEPARATOR, this can easily break naive path related algorithms searching for directory separators.cc @eregon what do you think of that spec? I think it would have helped me figure things out way sooner, so would have been valuable. If you agree I can generalize it to more "path handling" methods.