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fix(video): memory overflow in cursor handling #11

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fix(video): memory overflow in cursor handling #11

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9 changes: 7 additions & 2 deletions src/video.c
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Original file line number Diff line number Diff line change
Expand Up @@ -249,8 +249,13 @@ static void video_poll(void) {
}

// update cursor on screen
const unsigned int cursor_position =
crtc_cursorPosition() - crtc_startAddress();
unsigned int cursor_position = crtc_cursorPosition();
const unsigned int start_address = crtc_startAddress();
// avoid underflows in case of cursor position wrap
cursor_position = cursor_position > start_address
? cursor_position - start_address
: start_address - cursor_position;

const unsigned int row = cursor_position / VIDEO_COLUMNS;
const unsigned int column = cursor_position % VIDEO_COLUMNS;
unsigned int blink_period = 0; // [fields]
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