forked from cfenollosa/os-tutorial
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathscreen.c
More file actions
138 lines (116 loc) · 4.28 KB
/
screen.c
File metadata and controls
138 lines (116 loc) · 4.28 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
#include "screen.h"
#include "../drivers/ports.h"
/* Declaration of private functions */
int get_cursor_offset();
void set_cursor_offset(int offset);
int print_char(char c, int col, int row, char attr);
int get_offset(int col, int row);
int get_offset_row(int offset);
int get_offset_col(int offset);
/**********************************************************
* Public Kernel API functions *
**********************************************************/
/**
* Print a message on the specified location
* If col, row, are negative, we will use the current offset
*/
void kprint_at(char *message, int col, int row) {
/* Set cursor if col/row are negative */
int offset;
if (col >= 0 && row >= 0)
offset = get_offset(col, row);
else {
offset = get_cursor_offset();
row = get_offset_row(offset);
col = get_offset_col(offset);
}
/* Loop through message and print it */
int i = 0;
while (message[i] != 0) {
offset = print_char(message[i++], col, row, WHITE_ON_BLACK);
/* Compute row/col for next iteration */
row = get_offset_row(offset);
col = get_offset_col(offset);
}
}
void kprint(char *message) {
kprint_at(message, -1, -1);
}
/**********************************************************
* Private kernel functions *
**********************************************************/
/**
* Innermost print function for our kernel, directly accesses the video memory
*
* If 'col' and 'row' are negative, we will print at current cursor location
* If 'attr' is zero it will use 'white on black' as default
* Returns the offset of the next character
* Sets the video cursor to the returned offset
*/
int print_char(char c, int col, int row, char attr) {
unsigned char *vidmem = (unsigned char*) VIDEO_ADDRESS;
if (!attr) attr = WHITE_ON_BLACK;
/* Error control: print a red 'E' if the coords aren't right */
if (col >= MAX_COLS || row >= MAX_ROWS) {
vidmem[2*(MAX_COLS)*(MAX_ROWS)-2] = 'E';
vidmem[2*(MAX_COLS)*(MAX_ROWS)-1] = RED_ON_WHITE;
return get_offset(col, row);
}
int offset;
if (col >= 0 && row >= 0) offset = get_offset(col, row);
else offset = get_cursor_offset();
if (c == '\n') {
row = get_offset_row(offset);
offset = get_offset(0, row+1);
} else {
vidmem[offset] = c;
vidmem[offset+1] = attr;
offset += 2;
}
/* Check if the offset is over screen size and scroll */
if (offset >= MAX_ROWS * MAX_COLS * 2) {
int i;
for (i = 1; i < MAX_ROWS; i++)
memory_copy(get_offset(0, i) + VIDEO_ADDRESS,
get_offset(0, i-1) + VIDEO_ADDRESS,
MAX_COLS * 2);
/* Blank last line */
char *last_line = get_offset(0, MAX_ROWS-1) + VIDEO_ADDRESS;
for (i = 0; i < MAX_COLS * 2; i++) last_line[i] = 0;
offset -= 2 * MAX_COLS;
}
set_cursor_offset(offset);
return offset;
}
int get_cursor_offset() {
/* Use the VGA ports to get the current cursor position
* 1. Ask for high byte of the cursor offset (data 14)
* 2. Ask for low byte (data 15)
*/
port_byte_out(REG_SCREEN_CTRL, 14);
int offset = port_byte_in(REG_SCREEN_DATA) << 8; /* High byte: << 8 */
port_byte_out(REG_SCREEN_CTRL, 15);
offset += port_byte_in(REG_SCREEN_DATA);
return offset * 2; /* Position * size of character cell */
}
void set_cursor_offset(int offset) {
/* Similar to get_cursor_offset, but instead of reading we write data */
offset /= 2;
port_byte_out(REG_SCREEN_CTRL, 14);
port_byte_out(REG_SCREEN_DATA, (unsigned char)(offset >> 8));
port_byte_out(REG_SCREEN_CTRL, 15);
port_byte_out(REG_SCREEN_DATA, (unsigned char)(offset & 0xff));
}
void clear_screen() {
int screen_size = MAX_COLS * MAX_ROWS;
int i;
char *screen = VIDEO_ADDRESS;
for (i = 0; i < screen_size; i++) {
screen[i*2] = ' ';
screen[i*2+1] = WHITE_ON_BLACK;
}
set_cursor_offset(get_offset(0, 0));
}
int get_offset(int col, int row) { return 2 * (row * MAX_COLS + col); }
int get_offset_row(int offset) { return offset / (2 * MAX_COLS); }
int get_offset_col(int offset) { return (offset - (get_offset_row(offset)*2*MAX_COLS))/2; }