1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/src/Chunk.h	Sun Sep 20 20:39:24 2009 -0700
     1.3 @@ -0,0 +1,97 @@
     1.4 +/*
     1.5 + *  Chunk.h
     1.6 + *  Ottoman
     1.7 + *
     1.8 + *  Created by Jens Alfke on 8/27/09.
     1.9 + *  Copyright 2009 Jens Alfke. All rights reserved.
    1.10 + *  BSD-Licensed: See the file "LICENSE.txt" for details.
    1.11 + */
    1.12 +
    1.13 +#ifndef _MOOSEYARD_CHUNK_
    1.14 +#define _MOOSEYARD_CHUNK_
    1.15 +#include "File.h"
    1.16 +
    1.17 +namespace Mooseyard {
    1.18 +    
    1.19 +    class KeyValueChunk;
    1.20 +    
    1.21 +#pragma pack(2)
    1.22 +    
    1.23 +    /** An item stored in a file. It's prefixed with its length, so that the entire file
    1.24 +        can be scanned for chunks easily. */
    1.25 +    class Chunk {
    1.26 +    public:
    1.27 +        uint32_t size() const                       {return _size;}
    1.28 +        uint16_t type() const;
    1.29 +        
    1.30 +        /** If this is a KeyValueChunk, returns itself cast to that type, else NULL. */
    1.31 +        const KeyValueChunk* asKeyValue() const;
    1.32 +        
    1.33 +        /** Write a Chunk to the file, in pieces a la writev. */
    1.34 +        static size_t writeMultiple (File *file, uint16_t type,
    1.35 +                                     Blob blobs[], int count)  throw(File::Error);
    1.36 +        
    1.37 +        static size_t writePadding (File *file);
    1.38 +
    1.39 +        static const uint16_t kChunkTypePadding = 0;
    1.40 +
    1.41 +        const void* end() const                     {return offsetBy(this,_size);}
    1.42 +
    1.43 +    protected:
    1.44 +        Chunk (uint32_t size, uint16_t type)        :_size(size), _keyLength(0xFFFF), _type(type) { }
    1.45 +
    1.46 +    private:
    1.47 +        // This is mapped to data in the file! Don't mess with it!
    1.48 +        LittleEndian<uint32_t> _size;
    1.49 +        LittleEndian<uint16_t> _keyLength;          // Used by KeyValueChunk; else 0xFFFF
    1.50 +        LittleEndian<uint16_t> _type;               // Not used by KeyValueChunk
    1.51 +        friend class KeyValueChunk;
    1.52 +    };
    1.53 +    
    1.54 +    
    1.55 +    /** A key/value pair as stored in the memory-mapped file. */
    1.56 +    class KeyValueChunk :public Chunk {
    1.57 +    public:
    1.58 +        Blob key() const;
    1.59 +        Blob value() const;
    1.60 +        
    1.61 +        bool hasKey (Blob key) const;
    1.62 +        
    1.63 +        void validate() const  throw(File::Error);
    1.64 +        
    1.65 +        /** Write a KeyValueChunk to a file. */
    1.66 +        static size_t write (File* file, FilePosition pos, Blob key, Blob value)  throw(File::Error);
    1.67 +
    1.68 +        static const uint16_t kChunkType = 1;
    1.69 +
    1.70 +    private:
    1.71 +        const char* valuePtr() const;
    1.72 +    };    
    1.73 +   
    1.74 +#pragma options align=reset
    1.75 +    
    1.76 +    
    1.77 +    /** An iterator over all the Chunks in a file. */
    1.78 +    class ChunkIterator {
    1.79 +    public:
    1.80 +        ChunkIterator (File*, FilePosition start);
    1.81 +        
    1.82 +        const Chunk* chunk() const              {return _chunk;}
    1.83 +        FilePosition position() const           {return _pos;}
    1.84 +        bool atEOF() const;
    1.85 +        bool next();
    1.86 +        
    1.87 +        operator const Chunk*() const           {return _chunk;}
    1.88 +        virtual bool hasValue() const           {return _chunk != NULL;}
    1.89 +        operator bool() const                   {return hasValue();}
    1.90 +        ChunkIterator& operator++()             {next(); return *this;}
    1.91 +    private:
    1.92 +        void _loadChunk();
    1.93 +        File *_file;
    1.94 +        FilePosition _pos, _length;
    1.95 +        const Chunk* _chunk;
    1.96 +    };
    1.97 +    
    1.98 +}
    1.99 +
   1.100 +#endif _MOOSEYARD_CHUNK_