173 lines
3.4 KiB
C
Executable File
173 lines
3.4 KiB
C
Executable File
#include "devices/vga.h"
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#include <round.h>
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#include <stdint.h>
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#include <stddef.h>
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#include <string.h>
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#include "devices/speaker.h"
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#include "threads/io.h"
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#include "threads/interrupt.h"
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#include "threads/vaddr.h"
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/* VGA text screen support. See [FREEVGA] for more information. */
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/* Number of columns and rows on the text display. */
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#define COL_CNT 80
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#define ROW_CNT 25
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/* Current cursor position. (0,0) is in the upper left corner of
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the display. */
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static size_t cx, cy;
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/* Attribute value for gray text on a black background. */
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#define GRAY_ON_BLACK 0x07
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/* Framebuffer. See [FREEVGA] under "VGA Text Mode Operation".
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The character at (x,y) is fb[y][x][0].
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The attribute at (x,y) is fb[y][x][1]. */
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static uint8_t (*fb)[COL_CNT][2];
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static void clear_row (size_t y);
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static void cls (void);
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static void newline (void);
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static void move_cursor (void);
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static void find_cursor (size_t *x, size_t *y);
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/* Initializes the VGA text display. */
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static void
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init (void)
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{
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/* Already initialized? */
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static bool inited;
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if (!inited)
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{
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fb = ptov (0xb8000);
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find_cursor (&cx, &cy);
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inited = true;
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}
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}
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/* Writes C to the VGA text display, interpreting control
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characters in the conventional ways. */
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void
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vga_putc (int c)
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{
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/* Disable interrupts to lock out interrupt handlers
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that might write to the console. */
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enum intr_level old_level = intr_disable ();
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init ();
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switch (c)
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{
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case '\n':
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newline ();
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break;
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case '\f':
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cls ();
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break;
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case '\b':
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if (cx > 0)
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cx--;
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break;
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case '\r':
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cx = 0;
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break;
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case '\t':
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cx = ROUND_UP (cx + 1, 8);
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if (cx >= COL_CNT)
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newline ();
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break;
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case '\a':
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intr_set_level (old_level);
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speaker_beep ();
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intr_disable ();
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break;
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default:
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fb[cy][cx][0] = c;
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fb[cy][cx][1] = GRAY_ON_BLACK;
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if (++cx >= COL_CNT)
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newline ();
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break;
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}
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/* Update cursor position. */
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move_cursor ();
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intr_set_level (old_level);
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}
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/* Clears the screen and moves the cursor to the upper left. */
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static void
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cls (void)
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{
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size_t y;
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for (y = 0; y < ROW_CNT; y++)
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clear_row (y);
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cx = cy = 0;
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move_cursor ();
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}
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/* Clears row Y to spaces. */
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static void
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clear_row (size_t y)
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{
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size_t x;
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for (x = 0; x < COL_CNT; x++)
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{
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fb[y][x][0] = ' ';
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fb[y][x][1] = GRAY_ON_BLACK;
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}
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}
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/* Advances the cursor to the first column in the next line on
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the screen. If the cursor is already on the last line on the
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screen, scrolls the screen upward one line. */
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static void
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newline (void)
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{
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cx = 0;
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cy++;
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if (cy >= ROW_CNT)
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{
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cy = ROW_CNT - 1;
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memmove (&fb[0], &fb[1], sizeof fb[0] * (ROW_CNT - 1));
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clear_row (ROW_CNT - 1);
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}
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}
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/* Moves the hardware cursor to (cx,cy). */
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static void
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move_cursor (void)
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{
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/* See [FREEVGA] under "Manipulating the Text-mode Cursor". */
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uint16_t cp = cx + COL_CNT * cy;
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outw (0x3d4, 0x0e | (cp & 0xff00));
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outw (0x3d4, 0x0f | (cp << 8));
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}
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/* Reads the current hardware cursor position into (*X,*Y). */
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static void
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find_cursor (size_t *x, size_t *y)
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{
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/* See [FREEVGA] under "Manipulating the Text-mode Cursor". */
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uint16_t cp;
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outb (0x3d4, 0x0e);
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cp = inb (0x3d5) << 8;
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outb (0x3d4, 0x0f);
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cp |= inb (0x3d5);
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*x = cp % COL_CNT;
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*y = cp / COL_CNT;
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}
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