Decoding NSASCIIStringEncoding Is Not Strict
The documentation for
NSASCIIStringEncodingis clearly false: “Strict 7-bit ASCII encoding within 8-bit chars; ASCII values 0…127 only.” TheNSString.hheader file contains the same falsehood:NSASCIIStringEncoding = 1, /* 0..127 only */Curiously, though, the
CFString.hheader file has a more useful comment:kCFStringEncodingASCII = 0x0600, /* 0..127 (in creating CFString, values greater than 0x7F are treated as corresponding Unicode value) */
Another oddity with the documentation for NSString decoding: it only says that -initWithBytes:length:encoding: returns nil if the byte string is too long, but it says that -initWithData:encoding: returns nil if the data is not valid for the encoding. You would think these methods would be consistent.
However, I have found that NSASCIIStringEncoding does work as expected when encoding. That is, if the string is non-ASCII it will give you a nil data unless you request a lossy conversion.
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It appears from disassembling Foundation framework that initWithData:encoding: simply calls through to initWithBytes:length:encoding: using the data bytes and length. The return value documentation for initWithBytes:length:encoding: doesn't make a lot of sense to me. I suspect those docs are messed up.
