+++ /dev/null
-/* $Id$
-
-This file is part of libmspstrings
-Copyright © 2006-2007 Mikko Rasa
-Distributed under the LGPL
-*/
-
-#ifndef MSP_STRINGS_CODEC_H_
-#define MSP_STRINGS_CODEC_H_
-
-#include <string>
-#include <msp/core/except.h>
-
-namespace Msp {
-namespace Codecs {
-
-typedef int UnicodeChar;
-
-typedef std::basic_string<UnicodeChar> ustring;
-
-enum ErrorMode
-{
- THROW_ON_ERROR,
- IGNORE_ERRORS,
- TRANSLITERATE
-};
-
-/**
-An exception thrown for all kinds of problems encountered while encoding or
-decoding strings.
-*/
-class CodecError: public Exception
-{
-public:
- CodecError(const std::string &w_): Exception(w_) { }
-};
-
-/**
-Base class for string codecs. Use one of the derived classes or the function
-create_codec to create a specific codec.
-
-Unicode strings are represented as ustrings. An std::string is considered to
-be an encoded sequence of bytes. A codec is able to determine if an encoded
-string could be decoded with it.
-*/
-class Codec
-{
-public:
- /**
- Base class for string encoder.
-
- Each codec class should contain an Encoder class derived from this. The
- encode_char and transliterate functions must be overloaded. Some encoders
- may find it useful or necessary to implement some other functions too
- (particularly sync and reset for stateful codecs).
- */
- class Encoder
- {
- protected:
- ErrorMode err_mode;
-
- Encoder(ErrorMode em): err_mode(em) { }
- public:
- virtual ~Encoder() { }
-
- /** Encodes a single unicode character. If the character can't be
- represented in this encoding, error() should be called. */
- virtual void encode_char(UnicodeChar ch, std::string &buf) = 0;
-
- /** Encodes a unicode string. This is equivalent to calling encode_char
- for each character in the string with the same buffer. */
- virtual void encode(const ustring &str, std::string &buf);
-
- std::string encode(const ustring &);
-
- /** Procuces a sequence of bytes that will bring the encoder back to the
- initial state. */
- virtual void sync(std::string &buf) { (void)buf; }
-
- /** Resets the encoder to the initial state without producing output. */
- virtual void reset() { }
-
- protected:
- /** Handles an error depending on the error mode.
-
- THROW_ON_ERROR: throws CodecError(msg)
- IGNORE_ERRORS: does nothing
- TRANSLITERATE: calls transliterate(ch, buf) */
- void error(UnicodeChar ch, std::string &buf, const std::string &msg);
-
- /** Attempts to produce an alternative encoding for a unicode character.
- Typically this includes dropping accent marks or romanizing letters. */
- virtual void transliterate(UnicodeChar ch, std::string &buf) = 0;
- };
-
- /**
- Base class for string decoder.
-
- Each codec class should contain an Decoder class derived from this.
- */
- class Decoder
- {
- protected:
- ErrorMode err_mode;
-
- Decoder(ErrorMode em): err_mode(em) { }
- public:
- virtual ~Decoder() { }
-
- /** Decodes a single character from a string. The iterator is advanced
- to the next character. For stateful codecs, -1 may be returned if a
- state change sequence was decoded but no character followed it. If
- invalid input is encountered, the error() function should be called and
- the iterator advanced only if it doesn't throw. */
- virtual UnicodeChar decode_char(const std::string &str, std::string::const_iterator &i) = 0;
-
- /** Decodes a string. */
- virtual void decode(const std::string &str, ustring &buf);
-
- ustring decode(const std::string &);
-
- /** Resets the decoder to the initial state. */
- virtual void reset() { }
-
- protected:
- /** Handles an error depending on the error mode. The return value is
- suitable for returning from decode_char.
-
- THROW_ON_ERROR: throws CodecError(msg)
- IGNORE_ERRORS: returns -1
- TRANSLITERATE: return 0xFFFE */
- UnicodeChar error(const std::string &msg);
- };
-
-protected:
- Codec() { }
-public:
- virtual ~Codec() { }
-
- /** Returns the name of the encoding handled by this codec. */
- virtual const char *get_name() const = 0;
-
- /** Creates an encoder for this codec. */
- virtual Encoder *create_encoder(ErrorMode err_mode = THROW_ON_ERROR) const = 0;
-
- /** Creates a decoder for this codec. */
- virtual Decoder *create_decoder(ErrorMode err_mode = THROW_ON_ERROR) const = 0;
-
- /** Determines whether the given string can be successfully decoded with
- this codec. Note that this function returning true does not guarantee that
- the string was actually encoded with this codec. In particular, many 8-bit
- encodings are indistinguishable. */
- virtual bool detect(const std::string &) const;
-};
-
-typedef Codec::Encoder Encoder;
-typedef Codec::Decoder Decoder;
-
-/** Convenience function that decodes a string. */
-template<class C>
-ustring decode(const std::string &s)
-{
- typename C::Decoder dec;
- ustring result;
- dec.decode(s, result);
- return result;
-}
-
-/** Convenience function that encodes a string. */
-template<class C>
-std::string encode(const ustring &s)
-{
- typename C::Encoder enc;
- std::string result;
- enc.encode(s, result);
- enc.sync(result);
- return result;
-}
-
-/** Convenience function that transcodes a string from one codec to another. */
-template<class F, class T>
-std::string transcode(const std::string &s)
-{
- typename F::Decoder from;
- typename T::Encoder to;
- ustring temp;
- from.decode(s, temp);
- std::string result;
- to.encode(temp, result);
- to.sync(result);
- return result;
-}
-
-/** Creates a codec for an encoding by name. The caller is responsible for
-deleting the codec when it's no longer needed. */
-Codec *create_codec(const std::string &);
-
-/** Automatically detects the encoding of a string and creates a codec for it.
-The codec must be deleted when it's no longer needed. */
-Codec *detect_codec(const std::string &);
-
-} // namespace Codecs
-} // namespace Msp
-
-#endif
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