Data_Reader.h

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// Data reader interface for uniform access
 
// File_Extractor 0.4.0
#ifndef DATA_READER_H
#define DATA_READER_H
 
#include "blargg_common.h"
 
// Supports reading and finding out how many bytes are remaining
class Data_Reader {
public:
        virtual ~Data_Reader() { }
        
        static const char eof_error []; // returned by read() when request goes beyond end
        
        // Read at most count bytes and return number actually read, or <= 0 if error
        virtual long read_avail( void*, long n ) = 0;
        
        // Read exactly count bytes and return error if they couldn't be read
        virtual blargg_err_t read( void*, long count );
        
        // Number of bytes remaining until end of file
        virtual long remain() const = 0;
        
        // Read and discard count bytes
        virtual blargg_err_t skip( long count );
        
public:
        Data_Reader() { }
        typedef blargg_err_t error_t; // deprecated
private:
        // noncopyable
        Data_Reader( const Data_Reader& );
        Data_Reader& operator = ( const Data_Reader& );
};
 
// Supports seeking in addition to Data_Reader operations
class File_Reader : public Data_Reader {
public:
        // Size of file
        virtual long size() const = 0;
        
        // Current position in file
        virtual long tell() const = 0;
        
        // Go to new position
        virtual blargg_err_t seek( long ) = 0;
        
        long remain() const;
        blargg_err_t skip( long n );
};
 
// Disk file reader
class Std_File_Reader : public File_Reader {
public:
        blargg_err_t open( const char* path );
        void close();
        
public:
        Std_File_Reader();
        ~Std_File_Reader();
        long size() const;
        blargg_err_t read( void*, long );
        long read_avail( void*, long );
        long tell() const;
        blargg_err_t seek( long );
private:
        void* file_;
};
 
// Treats range of memory as a file
class Mem_File_Reader : public File_Reader {
public:
        Mem_File_Reader( const void*, long size );
        
public:
        long size() const;
        long read_avail( void*, long );
        long tell() const;
        blargg_err_t seek( long );
private:
        const char* const begin;
        const long size_;
        long pos;
};
 
// Makes it look like there are only count bytes remaining
class Subset_Reader : public Data_Reader {
public:
        Subset_Reader( Data_Reader*, long count );
 
public:
        long remain() const;
        long read_avail( void*, long );
private:
        Data_Reader* in;
        long remain_;
};
 
// Joins already-read header and remaining data into original file (to avoid seeking)
class Remaining_Reader : public Data_Reader {
public:
        Remaining_Reader( void const* header, long size, Data_Reader* );
 
public:
        long remain() const;
        long read_avail( void*, long );
        blargg_err_t read( void*, long );
private:
        char const* header;
        char const* header_end;
        Data_Reader* in;
        long read_first( void* out, long count );
};
 
// Invokes callback function to read data. Size of data must be specified in advance.
class Callback_Reader : public Data_Reader {
public:
        typedef const char* (*callback_t)( void* data, void* out, int count );
        Callback_Reader( callback_t, long size, void* data = 0 );
public:
        long read_avail( void*, long );
        blargg_err_t read( void*, long );
        long remain() const;
private:
        callback_t const callback;
        void* const data;
        long remain_;
};
 
#ifdef HAVE_ZLIB_H
#include <zlib.h>
 
// Gzip compressed file reader
class Gzip_File_Reader : public File_Reader {
public:
        blargg_err_t open( const char* path );
        void close();
        
public:
        Gzip_File_Reader();
        ~Gzip_File_Reader();
        long size() const;
        long read_avail( void*, long );
        long tell() const;
        blargg_err_t seek( long );
private:
        gzFile file_;
        long size_;
};
#endif
 
#endif