Hello Ketil, Friday, February 1, 2008, 10:52:02 AM, you wrote:
f <- openFile "name" >>= withLocking >>= withEncoding utf8
Attaching modifiers to handles appears to solve the problem of retaining 100% backwards compatibility, while opening for dealing with modern character sets.
may be it's too draconian restriction but i proposed just to use new library in the new code. we can provide easy way to switch from Handles by providing emulation module System.Stream.IO which exports things with the old names - Handle, hGetContents... - but new implementation
Somebody raised the question of reading a Content-type field, etc: would it be possible to "rewind" a handle after setting encoding? For Content-type fields, I suspect the header is usually limited to ASCII anyway, so adding decoding for subsequent text is probably sufficient. But how about a 'withDefaultEncoding' modifier that inspects the first two (or four?) bytes for a Unicode BOM, and either sets decoding accordingly and continues, or sets encoding according to locale *and* lets the user read the first bytes when reading from the handle.
core of my library is *interfaces*, not implementations. openFile provides a getByte/putByte interfaces and also trivial getChar/putChar which just reads/writes one byte. withEncoding modifier provides another getChar/putChar implementations what process several bytes at once. you can dress file to one or another modifier at any moment, its internal read/write pointer isn't affected: f <- openFile "name" content <- readLine f -- read first line using Latin-1 f' <- withEncoding (lookup content) f str <- readLine f' -- read second line using encoding given on first line -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com