126 lines
2.5 KiB
C
126 lines
2.5 KiB
C
#include <stddef.h>
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#include <stdint.h>
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// Make sure we are using the right compiler
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#if defined(__linux__)
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#error "You are using the wrong compiler."
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#endif
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// Color constants
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enum vgaColor
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{
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COLOR_BLACK = 0,
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COLOR_BLUE = 1,
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COLOR_GREEN = 2,
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COLOR_CYAN = 3,
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COLOR_RED = 4,
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COLOR_MAGENTA = 5,
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COLOR_BROWN = 6,
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COLOR_LIGHT_GREY = 7,
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COLOR_DARK_GREY = 8,
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COLOR_LIGHT_BLUE = 9,
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COLOR_LIGHT_GREEN = 10,
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COLOR_LIGHT_CYAN = 11,
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COLOR_LIGHT_RED = 12,
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COLOR_LIGHT_MAGENTA = 13,
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COLOR_LIGHT_BROWN = 14,
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COLOR_WHITE = 15
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};
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uint8_t makeColor(enum vgaColor fg, enum vgaColor bg)
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{
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return fg | bg << 4;
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}
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uint16_t makeVGAEntry(char c, uint8_t color)
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{
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uint16_t c16 = c;
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uint16_t color16 = color;
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return c16 | color16 << 8;
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}
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size_t strlen(const char *str)
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{
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size_t len = 0;
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while (str[len] != 0)
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len++;
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return len;
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}
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static const size_t VGA_WIDTH = 80;
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static const size_t VGA_HEIGHT = 24;
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size_t terminalRow, terminalCol;
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uint8_t terminalColor;
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uint16_t *terminalBuf;
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void terminalInit()
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{
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terminalRow = terminalCol = 0;
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terminalColor = makeColor(COLOR_LIGHT_GREY, COLOR_BLACK);
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terminalBuf = (uint16_t *) 0xB8000;
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for (size_t x = 0; x < VGA_WIDTH; x++) {
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for (size_t y = 0; y < VGA_HEIGHT; y++) {
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const size_t index = y * VGA_WIDTH + x;
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terminalBuf[index] = makeVGAEntry(' ', terminalColor);
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}
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}
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}
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void terminalSetColor(uint8_t color)
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{
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terminalColor = color;
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}
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void terminalPutEntryAt(char c, uint8_t color, size_t x, size_t y)
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{
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const size_t index = y * VGA_WIDTH + x;
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terminalBuf[index] = makeVGAEntry(c, color);
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}
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void terminalScroll()
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{
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for (size_t i = 1; i < VGA_HEIGHT; i++) {
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for (size_t j = 0; j < VGA_WIDTH; j++) {
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const size_t index = i * VGA_WIDTH + j;
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const size_t indexBelow = (i - 1) * VGA_WIDTH + j;
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terminalBuf[indexBelow] = terminalBuf[index];
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}
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}
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for (size_t i = 0; i < VGA_WIDTH; i++) {
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const size_t index = (VGA_HEIGHT - 1) * VGA_WIDTH + i;
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terminalBuf[index] = ' ';
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}
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}
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void terminalPutChar(char c)
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{
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if (c == '\n')
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terminalCol = VGA_WIDTH - 1;
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else
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terminalPutEntryAt(c, terminalColor, terminalCol, terminalRow);
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if (terminalCol++ == VGA_WIDTH) {
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terminalCol = 0;
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if (terminalRow++ == VGA_HEIGHT) {
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terminalRow--;
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terminalScroll();
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}
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}
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}
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void terminalWriteString(const char *data)
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{
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size_t dataLen = strlen(data);
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for (size_t i = 0; i < dataLen; i++)
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terminalPutChar(data[i]);
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}
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void brados_main()
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{
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terminalInit();
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terminalWriteString("Welcome to BRaDOS!\n");
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}
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