mirror of https://github.com/nmlgc/ReC98.git
88 lines
2.4 KiB
C++
88 lines
2.4 KiB
C++
/// Optimized byte-aligned sprite blitter
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/// -------------------------------------
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#include "planar.h"
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typedef void (* blit_func_t)(seg_t plane_seg, const void far* sprite);
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struct Blitter {
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blit_func_t write;
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blit_func_t or;
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};
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// Internals
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// ---------
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// Mainly here because BLITPERF needs access to them to implement custom
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// blitters.
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static const upixel_t UNROLL_H = 8;
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struct blit_state_t {
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vram_offset_t vo;
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// First blitted byte within the sprite. Can be nonzero if the sprite was
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// clipped at the left or top edge of VRAM.
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uint16_t sprite_offset;
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// Always set to the original width of the sprite. Can be larger than the
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// blitted width if the sprite is clipped.
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vram_byte_amount_t sprite_w;
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// 16-bit because it gets loaded into BX anyway.
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pixel_t loops_remainder;
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int16_t loops_unrolled;
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};
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extern blit_state_t blit_state;
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#define blitter_body(plane_seg, sprite, func_row, row_p1, row_p2) { \
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register int16_t loops_unrolled = blit_state.loops_unrolled; \
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_SI = FP_OFF(sprite); \
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_SI += blit_state.sprite_offset; \
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_DI = blit_state.vo; \
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_DX = blit_state.sprite_w; \
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_BX = blit_state.loops_remainder; \
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\
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/* Turbo C++ 4.0J does not back up DS if the function mutates it. */ \
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/* [blit_state] can't be accessed anymore beyond this point! */ \
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_asm { push ds; } \
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_DS = FP_SEG(sprite); \
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_ES = plane_seg; \
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\
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static_assert(UNROLL_H == 8); \
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switch(_BX) { \
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case 0: do { func_row(row_p1, row_p2) \
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case 7: func_row(row_p1, row_p2) \
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case 6: func_row(row_p1, row_p2) \
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case 5: func_row(row_p1, row_p2) \
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case 4: func_row(row_p1, row_p2) \
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case 3: func_row(row_p1, row_p2) \
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case 2: func_row(row_p1, row_p2) \
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case 1: func_row(row_p1, row_p2) \
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/* */} while(--loops_unrolled > 0); \
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} \
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\
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_asm { pop ds; } \
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}
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// ---------
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// Initialization
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// --------------
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// All of these set up blitting of a ([w]*8)×[h]-pixel sprite at the given VRAM
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// offset, cutting it at the respectively checked VRAM boundaries and assuming
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// that it does not touch the others. If the sprite would be cut to a width or
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// height of 0, they return a `nullptr` and leave the blitter in an invalid
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// state.
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// Checks all 4 edges of VRAM.
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const Blitter __ds* blitter_init_clip_lrtb(
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vram_x_t left, vram_y_t top, vram_byte_amount_t w, pixel_t h
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);
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// Checks the bottom edge of VRAM.
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const Blitter __ds* blitter_init_clip_b(
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vram_x_t left, vram_y_t top, vram_byte_amount_t w, pixel_t h
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);
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// --------------
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