libghc-iconv-doc 0.4.1.3-5build1 / usr / share / doc / libghc-iconv-doc / html / iconv.txt

-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | String encoding conversion
--   
--   Provides an interface to the POSIX iconv library functions for string
--   encoding conversion.
@package iconv
@version 0.4.1.3


-- | String encoding conversion
module Codec.Text.IConv

-- | Convert text from one named string encoding to another.
--   
--   <ul>
--   <li>The conversion is done lazily.</li>
--   <li>An exception is thrown if conversion between the two encodings is
--   not supported.</li>
--   <li>An exception is thrown if there are any encoding conversion
--   errors.</li>
--   </ul>
convert :: EncodingName -> EncodingName -> ByteString -> ByteString

-- | A string encoding name, eg <tt>"UTF-8"</tt> or <tt>"LATIN1"</tt>.
--   
--   The range of string encodings available is determined by the
--   capabilities of the underlying iconv implementation.
--   
--   When using the GNU C or libiconv libraries, the permitted values are
--   listed by the <tt>iconv --list</tt> command, and all combinations of
--   the listed values are supported.
type EncodingName = String

-- | Convert text ignoring encoding conversion problems.
--   
--   If invalid byte sequences are found in the input they are ignored and
--   conversion continues if possible. This is not always possible
--   especially with stateful encodings. No placeholder character is
--   inserted into the output so there will be no indication that invalid
--   byte sequences were encountered.
--   
--   If there are characters in the input that have no direct corresponding
--   character in the output encoding then they are dealt in one of two
--   ways, depending on the <a>Fuzzy</a> argument. We can try and
--   <a>Transliterate</a> them into the nearest corresponding character(s)
--   or use a replacement character (typically <tt>'?'</tt> or the Unicode
--   replacement character). Alternatively they can simply be
--   <a>Discard</a>ed.
--   
--   In either case, no exceptions will occur. In the case of unrecoverable
--   errors, the output will simply be truncated. This includes the case of
--   unrecognised or unsupported encoding names; the output will be empty.
--   
--   <ul>
--   <li>This function only works with the GNU iconv implementation which
--   provides this feature beyond what is required by the iconv
--   specification.</li>
--   </ul>
convertFuzzy :: Fuzzy -> EncodingName -> EncodingName -> ByteString -> ByteString
data Fuzzy
Transliterate :: Fuzzy
Discard :: Fuzzy

-- | This variant does the conversion all in one go, so it is able to
--   report any conversion errors up front. It exposes all the possible
--   error conditions and never throws exceptions
--   
--   The disadvantage is that no output can be produced before the whole
--   input is consumed. This might be problematic for very large inputs.
convertStrictly :: EncodingName -> EncodingName -> ByteString -> Either ByteString ConversionError

-- | This version provides a more complete but less convenient conversion
--   interface. It exposes all the possible error conditions and never
--   throws exceptions.
--   
--   The conversion is still lazy. It returns a list of spans, where a span
--   may be an ordinary span of output text or a conversion error. This
--   somewhat complex interface allows both for lazy conversion and for
--   precise reporting of conversion problems. The other functions
--   <a>convert</a> and <a>convertStrictly</a> are actually simple wrappers
--   on this function.
convertLazily :: EncodingName -> EncodingName -> ByteString -> [Span]
data ConversionError

-- | The conversion from the input to output string encoding is not
--   supported by the underlying iconv implementation. This is usually
--   because a named encoding is not recognised or support for it was not
--   enabled on this system.
--   
--   The POSIX standard does not guarantee that all possible combinations
--   of recognised string encoding are supported, however most common
--   implementations do support all possible combinations.
UnsuportedConversion :: EncodingName -> EncodingName -> ConversionError

-- | This covers two possible conversion errors:
--   
--   <ul>
--   <li>There is a byte sequence in the input that is not valid in the
--   input encoding.</li>
--   <li>There is a valid character in the input that has no corresponding
--   character in the output encoding.</li>
--   </ul>
--   
--   Unfortunately iconv does not let us distinguish these two cases. In
--   either case, the Int parameter gives the byte offset in the input of
--   the unrecognised bytes or unconvertable character.
InvalidChar :: Int -> ConversionError

-- | This error covers the case where the end of the input has trailing
--   bytes that are the initial bytes of a valid character in the input
--   encoding. In other words, it looks like the input ended in the middle
--   of a multi-byte character. This would often be an indication that the
--   input was somehow truncated. Again, the Int parameter is the byte
--   offset in the input where the incomplete character starts.
IncompleteChar :: Int -> ConversionError

-- | An unexpected iconv error. The iconv spec lists a number of possible
--   expected errors but does not guarantee that there might not be other
--   errors.
--   
--   This error can occur either immediately, which might indicate that the
--   iconv installation is messed up somehow, or it could occur later which
--   might indicate resource exhaustion or some other internal iconv error.
--   
--   Use <a>errnoToIOError</a> to get slightly more information on what the
--   error could possibly be.
UnexpectedError :: Errno -> ConversionError
reportConversionError :: ConversionError -> IOError

-- | Output spans from encoding conversion. When nothing goes wrong we
--   expect just a bunch of <a>Span</a>s. If there are conversion errors we
--   get other span types.
data Span

-- | An ordinary output span in the target encoding
Span :: !ByteString -> Span

-- | An error in the conversion process. If this occurs it will be the last
--   span.
ConversionError :: !ConversionError -> Span