More sophisticated error handling

[libs/core.git] / source / codec.h

diff --git a/source/codec.h b/source/codec.h
index 8ea99915c2451fc161fc53d16e482ebef77a28a7..7acd88f89008e6e50b72333f4437172907dd7b55 100644 (file)
--- a/source/codec.h
+++ b/source/codec.h
@@ -17,16 +17,24 @@ public:
 };
 
 /**
-Base class for string codecs.  Mostly abstract.  Use one of the derived classes
-or the function create_codec to create a specific codec.
+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 std::wstring is considered to contain
 Unicode characters and an std::string is considered to be an encoded sequence
-of bytes.  Codecs are able to determine if an encoded string could be 
+of bytes.  A codec is able to determine if an encoded string could be decoded
+with it.
 */
 class StringCodec
 {
 public:
+       enum ErrorMode
+       {
+               THROW_ON_ERROR,
+               IGNORE_ERRORS,
+               REPLACE_ERRORS
+       };
+
        /**
        Base class for string encoder.  Each codec class should contain an Encoder
        class derived from this.
@@ -39,13 +47,13 @@ public:
                function to put the result into the internal buffer.
                */
                virtual void encode_char(wchar_t) =0;
-               
+
                /**
                Encodes a string.
                */
                virtual void encode(const std::wstring &s)
                { for(std::wstring::const_iterator i=s.begin(); i!=s.end(); ++i) encode_char(*i); }
-               
+
                /**
                Brings the encoder back to its initial state.  This allows the encoded
                sequence to be extracted or flushed without loss of integrity.
@@ -62,7 +70,7 @@ public:
                Returns the number of bytes in the output buffer.
                */
                unsigned size() const { return buffer_.size(); }
-               
+
                /**
                Clears the encoded sequence.  Encoder state is left intact.
                */
@@ -70,11 +78,14 @@ public:
 
                virtual ~Encoder() { }
        protected:
-               Encoder() { }
+               Encoder(ErrorMode em=THROW_ON_ERROR): err_mode_(em) { }
                void append(char c) { buffer_+=c; }
                void append(const char *s, unsigned l) { buffer_.append(s, l); }
                void append(const std::string &s) { buffer_+=s; }
+               void error(const std::string &);
+               virtual void append_replacement() { }
        private:
+               ErrorMode err_mode_;
                std::string buffer_;
        };
 
@@ -90,8 +101,8 @@ public:
                { for(std::string::const_iterator i=s.begin(); i!=s.end(); ) decode_char(s, i); }
 
                /**
-               Ensures that all input has been processed.  An exception is thrown if
-               this is not the case.
+               Ensures that all input has been processed.  If this is not the case any
+               buffers are cleared and an error is triggered.
                */
                virtual void sync() { }
 
@@ -100,15 +111,17 @@ public:
                void flush() { buffer_.clear(); }
                virtual ~Decoder() { }
        protected:
-               Decoder() { }
+               Decoder(ErrorMode em): err_mode_(em) { }
                void append(wchar_t c) { buffer_+=c; }
                void append(const std::wstring &s) { buffer_+=s; }
+               void error(const std::string &);
        private:
+               ErrorMode err_mode_;
                std::wstring buffer_;
        };
 
-       virtual Encoder *create_encoder() const =0;
-       virtual Decoder *create_decoder() const =0;
+       virtual Encoder *create_encoder(ErrorMode =THROW_ON_ERROR) const =0;
+       virtual Decoder *create_decoder(ErrorMode =THROW_ON_ERROR) const =0;
        virtual bool    detect(const std::string &) const;
        virtual ~StringCodec() { }
 protected:
@@ -116,7 +129,7 @@ protected:
 };
 
 /**
-Convenience function that decodes a string using the given codec. 
+Convenience function that decodes a string using the given codec.
 */
 template<class C>
 std::wstring decode(const std::string &s)