So as an example, when I read the π character (\u03C0) from a File using the FileReader API, I get the pi character back to me when I read it using FileReader.readAsText(blob) which is expected. But when I use FileReader.readAsBinaryString(blob), I get the result \xcf\x80 instead, which doesn't seem to have any visible correlation with the pi character. What's going on? (This probably has something to do with the way UTF-8/16 is encoded...)
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gengkev
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2`CF80` is the UTF-8 encoding for π. – deceze Feb 19 '12 at 02:15
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...oh, you're right...thanks! – gengkev Feb 19 '12 at 04:34
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...that was probably too obvious, but you can post that as an answer if you like. – gengkev Feb 19 '12 at 04:37
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FileReader.readAsText takes the encoding of the file into account. In particular, since you have the file encoded in UTF-8, there may be multiple bytes per character. Reading it as text, the UTF-8 is read as it is, and you get your string.
FileReader.readAsBinaryString, on the other hand, does exactly what it says. It reads the file byte by byte. It doesn't recognise multi-byte characters, which in particular is good news for binary files (basically anything except a text file). Since π is a two-byte character, you get the two individual bytes that make it up in your string.
This difference can be seen in many places. In particular when encoding is lost and you see characters like é displayed as é.
Niet the Dark Absol
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thanks...so when I try to append \xA2 to a BlobBuilder it turns out as \xC2\xA2 because that's what it is UTF-8 encoded, but how can I get back \xA2? (it's a single-byte character) – gengkev Feb 20 '12 at 17:33
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Oh well, if that's all you needed... :)
CF80 is the UTF-8 encoding for π.
deceze
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