68 lines
1.9 KiB
C
68 lines
1.9 KiB
C
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// Reworked sample code from OSDev! Stripped down some of the extra stuff to leave as an exercise.
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//Headers provided by GCC :). No need for libs! We don't even have those yet.
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#include <stddef.h>
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#include <stdint.h>
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//VGA buffer is the easiest way to write to the screen at this stage. it's just a massive array with two datapoints: what color, and what character?
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//array starts at the absolute address 0xB8000
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volatile uint16_t* vga_buffer = (uint16_t*)0xB8000;
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//the VGA buffer is 80x25 to represent the screen.
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const int GRID_COLS = 80;
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const int GRID_ROWS = 25;
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//grid is top left origin. This is our cursor!
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int cursor_col = 0;
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int cursor_row = 0;
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uint16_t term_color = 0x0F00; // Black background, White foreground
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//wipe the screen
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void term_clear() {
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for (int col = 0; col < GRID_COLS; col ++) {
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for (int row = 0; row < GRID_ROWS; row ++) {
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//works out to iterating every cell
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const size_t index = (GRID_COLS * row) + col;
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//vga buffer looks something like xxxxyyyyzzzzzzzz
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//x=bg color
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//y=fg color
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//c=character to use
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//Therefore, to write, we just take our color data and tack on the character to the end.
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vga_buffer[index] = term_color | ' '; //blank out
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}
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}
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}
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//
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void term_printc(char c)
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{
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const size_t index = (GRID_COLS * cursor_row) + cursor_col; //where am i puttin it
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vga_buffer[index] = term_color | c; //put it there by putting color+char into that spot in the array
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cursor_col++; //next time put it in the next spot.
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}
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//print a string!
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void term_println(const char* out)
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{
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for (int i = 0; out[i] != '\0'; i++)
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term_printc(out[i]);
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//go to the next line for a println func.
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cursor_col = 0;
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cursor_row++;
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}
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//finally, main.
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void kern_main()
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{
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//wipe the screen
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term_clear();
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//IT IS TIME. TO PRINT.
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term_println("hello my chungus world");
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term_println(":100:");
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}
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