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Diffstat (limited to 'main.h')
| -rw-r--r-- | main.h | 98 |
1 files changed, 98 insertions, 0 deletions
@@ -0,0 +1,98 @@ +#ifndef MAIN_H +#define MAIN_H + +#include <limits.h> +#include <stdbool.h> +#include "lookup.h" + +bool render = false; + +uint8_t V[16];//all the registers + +#define WIDTH 64 +#define HEIGHT 32 + +#define BITMASK(b) (1 << ((b) % CHAR_BIT)) +#define BITSLOT(b) ((b) / CHAR_BIT) +#define BITSET(a, b) ((a)[BITSLOT(b)] |= BITMASK(b)) +#define BITCLEAR(a, b) ((a)[BITSLOT(b)] &= ~BITMASK(b)) +#define BITTEST(a, b) ((a)[BITSLOT(b)] & BITMASK(b)) + +//bittest that works with pointers +#define CHECK_BIT(var,pos) ((var) & (1<<(pos))) + +char *program; //program is defined here so it can be accessed in main.h +char *I; //left wild to be set later + +int *pixels = NULL;//used SQL pixel setting + +int returnPos[12];//the position to return to when the end of a subroute is reached (e.g. 0x00EE is reached). There's meant to be a 48 byte stack, but as on the COSMAC VIP there was 12, we do that. + + +//value of lower four bits of 8 bit string +int lowerFour(char s[]) +{ +return s[0] & 0x0F; +} + +//value of upper four bits of 8 bit string +int upperFour(char s[]) +{ +return (s[0] & 0xF0) >> 4; +} + +//Draws a sprite at coordinate (VX, VY) that has a width of 8 pixels and a height of N +//pixels. Each row of 8 pixels is read as bit-coded starting from memory location I; +//I value doesn’t change after the execution of this instruction. +//As described above, VF is set to 1 if any screen pixels are flipped from set to unset +//when the sprite is drawn, and to 0 if that doesn’t happen +int draw(uint8_t VX, uint8_t VY, int N) +{ +render = true; +int bitPosition;//the bits read from I need to be bittested from bit 7 to 0. x can't be used since it goes from 0 to 7. + +V[0xF] = 0;//0 by default, since if we don't unset pixels, then VF equals 0 +bitPosition = 8; +for (int x=0; x<8; ++x) + { + --bitPosition; + if (bitPosition == -1){printf("No\n"); exit(1);} + for (int y=0; y<N; ++y) + { + //only draw if place to draw is within bounds + if ((VX+x < WIDTH) && (VY+y < HEIGHT))//position of x is correct + { + if(CHECK_BIT(*(I+y),bitPosition))//draw white xor if bit in I+y is set, do not draw anything if pixel is black though + { + if (pixels[display[VY+y][VX+x]] == 0xFFFFFFFF){V[0xF] = 1;}//set VF to 1 if pixel to draw is already set + pixels[display[VY+y][VX+x]] ^= 0xFFFFFFFF;//draw with XOR + } + } + else + { + //use modulus make out of range writes start again at 0 + if(CHECK_BIT(*(I+y),bitPosition))//draw white xor if bit in I+y is set, do not draw anything if pixel is black though + { + if (pixels[display[(VY+y)%HEIGHT][(VX+x)%WIDTH]] == 0xFFFFFFFF){V[0xF] = 1;} + pixels[display[(VY+y)%HEIGHT][(VX+x)%WIDTH]] ^= 0xFFFFFFFF; + } + } + } + + } +} + +void display_clear() +{ +render = true; +for (int x = 0; x<WIDTH; ++x) + { + for (int y = 0; y<HEIGHT; ++y) + { + pixels[display[y][x]] = 0x00000000; + } + } +} + + +#endif |