#define MSP_STRINGS_CODEC_H_
#include <string>
-#include <msp/core/error.h>
+#include <msp/core/except.h>
namespace Msp {
namespace Codecs {
Base class for string codecs. Use one of the derived classes or the function
create_codec to create a specific codec.
-For the purposes of this class, an ustring is considered to contain
-Unicode characters and 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.
+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.
+ 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() { }
- virtual void encode_char(UnicodeChar ch, std::string &buf) =0;
+ /** 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:
- ErrorMode err_mode;
+ /** Handles an error depending on the error mode.
- Encoder(ErrorMode em): err_mode(em) { }
- void error(UnicodeChar, std::string &, const std::string &);
- virtual void transliterate(UnicodeChar, std::string &) { }
+ 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.
+ 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. In case a
- decoding error occurs, behavior depends on the error mode specified for
- the decoder:
-
- For THROW_ON_ERROR, an exception is thrown and the iterator is left at
- the erroneous character.
+ /** 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;
- For IGNORE_ERRORS, -1 is returned and the iterator is advanced.
+ /** Decodes a string. */
+ virtual void decode(const std::string &str, ustring &buf);
- For TRANSLITERATE, 0xFFFE is returned and the iterator is advanced.
- */
- virtual UnicodeChar decode_char(const std::string &str, std::string::const_iterator &i) =0;
+ ustring decode(const std::string &);
- virtual void decode(const std::string &str, ustring &buf);
+ /** Resets the decoder to the initial state. */
virtual void reset() { }
- protected:
- ErrorMode err_mode;
- Decoder(ErrorMode em): err_mode(em) { }
- UnicodeChar error(const std::string &);
+ 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() { }
- /**
- Creates an encoder for this codec.
- */
- virtual Encoder *create_encoder(ErrorMode err_mode=THROW_ON_ERROR) const =0;
+ /** Returns the name of the encoding handled by this codec. */
+ virtual const char *get_name() const = 0;
- /**
- Creates a decoder for this codec.
- */
- virtual Decoder *create_decoder(ErrorMode err_mode=THROW_ON_ERROR) const =0;
+ /** Creates an encoder for this codec. */
+ virtual Encoder *create_encoder(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.
- */
+ /** 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;
-protected:
- Codec() { }
};
typedef Codec::Encoder Encoder;
typedef Codec::Decoder Decoder;
-/**
-Convenience function that decodes a string using the given codec.
-*/
+/** Convenience function that decodes a string. */
template<class C>
ustring decode(const std::string &s)
{
return result;
}
+/** Convenience function that encodes a string. */
template<class C>
std::string encode(const ustring &s)
{
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)
{
return result;
}
-/**
-Creates a codec for an encoding by name. The caller is responsible for
-deleting the codec when it's no longer needed.
-*/
+/** 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
projects / libs / core.git / blobdiff