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Make position non-static; add case for NULL data

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This commit is contained in:
Peter Evans 2017-12-14 23:08:33 -06:00
parent cebdedeff0
commit 4dffea1dda
1 changed files with 13 additions and 4 deletions
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17
src/apple2.dd.c
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@ -93,9 +93,18 @@ apple2dd_write_protect(apple2dd *drive, bool protect)
drive->write_protect = protect; drive->write_protect = protect;
} }
static int int
position(apple2dd *drive) apple2dd_position(apple2dd *drive)
{ {
// Special case: they didn't load any image data into the "drive".
// Return zero.
if (drive->data == NULL) {
return 0;
}
// This is a normative DOS 3.3 / ProDOS disk. (Except ProDOS is
// separated into 512 byte blocks which _shouldn't_ matter for our
// purposes but let's not talk about that here do-de-doo.)
if (drive->data->size == _140K_) { if (drive->data->size == _140K_) {
int track_offset; int track_offset;
@ -109,7 +118,7 @@ position(apple2dd *drive)
vm_8bit vm_8bit
apple2dd_read_byte(apple2dd *drive) apple2dd_read_byte(apple2dd *drive)
{ {
vm_8bit byte = vm_segment_get(drive->data, position(drive)); vm_8bit byte = vm_segment_get(drive->data, apple2dd_position(drive));
// We may have read the very last byte in a sector; if so let's // We may have read the very last byte in a sector; if so let's
// adjust the track_pos by two half tracks and reset the sector pos. // adjust the track_pos by two half tracks and reset the sector pos.
@ -125,7 +134,7 @@ apple2dd_read_byte(apple2dd *drive)
void void
apple2dd_write(apple2dd *drive, vm_8bit byte) apple2dd_write(apple2dd *drive, vm_8bit byte)
{ {
vm_segment_set(drive->data, position(drive), byte); vm_segment_set(drive->data, apple2dd_position(drive), byte);
drive->sector_pos++; drive->sector_pos++;
if (drive->sector_pos > MAX_SECTOR_POS) { if (drive->sector_pos > MAX_SECTOR_POS) {