95 lines
3.3 KiB
C
95 lines
3.3 KiB
C
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// Manages ROM data loaded from file in an efficient manner
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// Game_Music_Emu $vers
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#ifndef ROM_DATA_H
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#define ROM_DATA_H
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#include "blargg_common.h"
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#include "Data_Reader.h"
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/* Loads a ROM file into memory and allows access to it in page-sized chunks.
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* ROM file consists of header followed by ROM data. Instead of storing the entire
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ROM contents, the file only stores the occupied portion, with the bytes before and
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after that cleared to some value. The size and format of the header is up to the
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caller, as is the starting address of the ROM data following it. File loading is
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performed with a single read, rather than two or more that might otherwise be
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required.
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* Once ROM data is loaded and its address specified, a pointer to any "page" can
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be obtained. ROM data is mirrored using smallest power of 2 that contains it.
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Addresses not aligned to pages can also be used, but this might cause unexpected
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results.
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Example with file data of size 0x0C put at address 0x0F, with page size of 8:
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---------------0123456789AB--------------------0123456789AB---------...
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^ ^ ^ ^ ^ ^ ^ ^ ^
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0 0x08 0x10 0x18 0x20 0x28 0x30 0x38 0x40
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at_addr(0x00) = pointer to 8 bytes of fill.
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at_addr(0x08) = pointer to 7 bytes of fill, followed by first byte of file.
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at_addr(0x10) = pointer to next 8 bytes of file.
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at_addr(0x18) = pointer to last 3 bytes of file, followed by 5 bytes of fill.
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at_addr(0x20) = pointer to 8 bytes of fill.
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at_addr(0x28) = pointer to 7 bytes of fill, followed by first byte of file.
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etc. */
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class Rom_Data {
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enum { pad_extra = 8 };
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public:
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typedef unsigned char byte;
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// Page_size should be a power of 2
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Rom_Data( int page_size );
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// Loads file into memory, then copies header to *header_out and fills
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// unmapped bank and file data padding with fill. Returns blargg_err_file_type
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// if in.remain() <= header_size.
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blargg_err_t load( Data_Reader& in, int header_size, void* header_out, int fill );
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// Below, "file data" refers to data AFTER the header
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// Size of file data
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int file_size() const { return file_size_; }
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// Pointer to beginning of file data
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byte * begin() { return rom.begin() + pad_size; }
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byte const* begin() const { return rom.begin() + pad_size; }
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// Pointer to unmapped page cleared with fill value
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byte* unmapped() { return rom.begin(); }
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// Sets address that file data will start at. Must be set before using following
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// functions, and cannot be set more than once.
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void set_addr( int addr );
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// Address of first empty page (file size + addr rounded up to multiple of page_size)
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int size() const { return rom.size() - pad_extra + rom_addr; }
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// Masks address to nearest power of two greater than size()
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int mask_addr( int addr ) const { return addr & mask; }
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// Pointer to page beginning at addr, or unmapped() if outside data.
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// Mirrored using mask_addr().
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byte* at_addr( int addr );
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// Frees memory
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void clear();
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// Implementation
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public:
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~Rom_Data();
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protected:
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blargg_vector<byte> rom;
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int mask;
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int rom_addr;
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int const pad_size;
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int file_size_;
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blargg_err_t load_( Data_Reader& in, int header_size, int file_offset );
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};
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#endif
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