christoph/lecture-operating-system-development
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simplify cga memory manipulation

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This commit is contained in:
churl
2022-05-09 14:02:44 +02:00
parent 27d8f13b5e
commit 5b16da23ed
3 changed files with 46 additions and 20 deletions
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25
c_os/devices/CGA.cc
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@ -73,14 +73,14 @@ void CGA::show(int x, int y, char character, unsigned char attrib) {
/* Hier muess Code eingefuegt werden */
if (x > COLUMNS || y > ROWS) {
if (x >= COLUMNS || y >= ROWS) {
// Out of bounds
return;
}
char* pos = (char*)(CGA_START + 2 * (x + y * COLUMNS)); // cast to char* to make writable
*pos = character;
*(pos + 1) = attrib;
cga_char_t* pos = (cga_char_t*)(CGA_START + 2 * (x + y * COLUMNS)); // cast to char* to make writable
pos->cga_char = character;
pos->cga_attribute = attrib;
}
/*****************************************************************************
@ -147,19 +147,13 @@ void CGA::print(char* string, int n, unsigned char attrib) {
*****************************************************************************/
void CGA::scrollup() {
/* Hier muess Code eingefuegt werden */
// TODO: I really want a scrollback buffer
/* Hier muss Code eingefuegt werden */
// Move up
for (unsigned short byte = 2 * COLUMNS * 1; byte < 2 * COLUMNS * ROWS; ++byte) {
*((char*)(CGA_START + byte - 2 * COLUMNS * 1)) = *(CGA_START + byte);
}
mymemcpy<cga_line_t>((cga_line_t*)CGA_START, (cga_line_t*)CGA_START + 1, ROWS - 1);
// Clear last line
for (unsigned short byte = 2 * COLUMNS * (ROWS - 1); byte < 2 * COLUMNS * ROWS; ++byte) {
*((char*)(CGA_START + byte)) = '\0';
}
myzero<cga_line_t>((cga_line_t*)CGA_START + ROWS - 1);
}
/*****************************************************************************
@ -171,10 +165,7 @@ void CGA::clear() {
/* Hier muess Code eingefuegt werden */
for (unsigned short byte = 2 * COLUMNS * 0; byte < 2 * COLUMNS * ROWS; ++byte) {
*((char*)(CGA_START + byte)) = '\0';
}
myzero<cga_page_t>((cga_page_t*)CGA_START);
this->setpos(0, 0);
}