mirror of https://github.com/nmlgc/ReC98.git
47 lines
1.7 KiB
C++
47 lines
1.7 KiB
C++
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// Redefined versions of master.lib's grcg_setmode() and grcg_setcolor().
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void near grcg_setmode_rmw_seg1(void);
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void near grcg_setmode_tdw(void);
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// In contrast to master.lib's own grcg_setcolor(), these keep the current
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// GRCG mode, and reenable interrupts before returning.
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#define grcg_setcolor_direct_seg1(col) \
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_AH = col; \
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grcg_setcolor_direct_seg1_raw();
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void near grcg_setcolor_direct_seg1_raw(void);
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void near grcg_setcolor_direct_seg3_raw(void);
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// Implementation macros
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// ---------------------
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#define grcg_setmode_rmw_inlined() { \
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outportb2(0x7C, 0xC0); \
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}
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// Builds the contents of a GRCG tile register from the x86 carry flag by
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// extending its value to a full byte (CF=0 → 0x00, CF=1 → 0xFF).
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//
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// (Technically returns a dots8_t, but why add a planar.h dependency just for
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// one type.)
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inline uint8_t tile_register_from_carry(uint8_t unused) {
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__emit__(0x1A, 0xC0); // SBB AL, AL
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return _AL;
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}
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// And this is why [col] is stored in AH: x86 simply only supports AL as the
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// source operand for OUT. By shifting each successive bit of [col] into the
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// carry flag and using the function above, we get the minimum of three
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// instructions (SHR, SBB, OUT) per bitplane, with no register spills. Quite a
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// beautiful optimization!
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#define grcg_setcolor_direct_inlined(col) { \
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disable(); \
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_DX = 0x7E; \
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/* Just in case people want to call this with an immediate color value… */ \
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_AH = col; \
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outportb(_DX, tile_register_from_carry(_AH >>= 1)); \
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outportb(_DX, tile_register_from_carry(_AH >>= 1)); \
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outportb(_DX, tile_register_from_carry(_AH >>= 1)); \
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outportb(_DX, tile_register_from_carry(_AH >>= 1)); \
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enable(); \
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}
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// ---------------------
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