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#include <stdbool.h>
#include <stdint.h>
#define VGA_COLUMNS 80
#define VGA_ROWS 25
#define VGA_START (uint16_t *)0x000b8000
#define VGA_END (VGA_START + VGA_COLUMNS * VGA_ROWS)
static uint16_t *cursor = VGA_START;
static uint16_t mask;
void vga_set_color(uint8_t new_color) {
mask = new_color << 8;
}
void vga_swap_color(uint16_t pos) {
uint8_t *color_byte = (uint8_t *)(VGA_START + (pos >> 8) * VGA_COLUMNS + (pos & 0xff)) + 1;
*color_byte = (*color_byte << 4) + (*color_byte >> 4);
}
static void vga_scroll() {
for (uint32_t *i = (uint32_t *)VGA_START; i < (uint32_t *)(VGA_END - VGA_COLUMNS); ++i)
*i = *(i + VGA_COLUMNS / 2);
uint32_t f = (mask | (uint8_t)' ') * 0x00010001;
for (uint32_t *i = (uint32_t *)(VGA_END - VGA_COLUMNS); i < (uint32_t *)VGA_END; ++i)
*i = f;
cursor -= VGA_COLUMNS;
}
void vga_blank() {
uint32_t f = (mask | (uint8_t)' ') * 0x00010001;
uint32_t *p = (uint32_t *)VGA_START;
while (p < (uint32_t *)VGA_END)
*p++ = f;
cursor = VGA_END - VGA_COLUMNS;
}
void vga_printch(char ch) {
if (ch == '\n')
cursor = ((cursor - VGA_START) / VGA_COLUMNS + 1) * VGA_COLUMNS + VGA_START;
else if (ch == '\b')
*--cursor = mask | ' ';
else
*cursor++ = mask | (uint8_t)ch;
if (cursor == VGA_END)
vga_scroll();
}
void vga_print_at(uint16_t pos, const char *sz) {
cursor = VGA_START + (pos >> 8) * VGA_COLUMNS + (pos & 0xff);
while (*sz)
vga_printch(*sz++);
}
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