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Add documentation; plus set sector/track pos to 0 on eject

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Peter Evans 2018-01-01 17:26:29 -06:00
parent 2aeef09f97
commit d53b6df7a4
1 changed files with 58 additions and 0 deletions
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58
src/apple2.dd.c
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@ -4,6 +4,11 @@
#include "apple2.dd.h"
/*
* Create a new disk drive. We do not create a memory segment for the
* drive right away, as the size of said data can be variable based on
* the disk format.
*/
apple2dd *
apple2dd_create()
{
@ -29,6 +34,11 @@ apple2dd_create()
return drive;
}
/*
* Insert a "disk" into the drive, such that a disk is delivered to us
* through a FILE stream. Return an error code if the disk format is
* something we cannot accept.
*/
int
apple2dd_insert(apple2dd *drive, FILE *stream)
{
@ -68,6 +78,10 @@ apple2dd_insert(apple2dd *drive, FILE *stream)
return OK;
}
/*
* Return the segment position that the drive is currently at, based
* upon track and sector position.
*/
int
apple2dd_position(apple2dd *drive)
{
@ -90,6 +104,10 @@ apple2dd_position(apple2dd *drive)
return 0;
}
/*
* Read a single byte from the disk drive, at its current position, and
* then shift the head by 1 byte.
*/
vm_8bit
apple2dd_read(apple2dd *drive)
{
@ -99,6 +117,10 @@ apple2dd_read(apple2dd *drive)
return byte;
}
/*
* Here we mean to "empty" the drive, essentially freeing the segment
* memory and resetting the head position.
*/
void
apple2dd_eject(apple2dd *drive)
{
@ -106,8 +128,14 @@ apple2dd_eject(apple2dd *drive)
vm_segment_free(drive->data);
drive->data = NULL;
}
drive->track_pos = 0;
drive->sector_pos = 0;
}
/*
* Free the memory taken up by the disk drive.
*/
void
apple2dd_free(apple2dd *drive)
{
@ -118,6 +146,10 @@ apple2dd_free(apple2dd *drive)
free(drive);
}
/*
* Set the disk drive mode, which is either read or write. (It can only
* be one or the other at a time.)
*/
void
apple2dd_set_mode(apple2dd *drive, int mode)
{
@ -128,6 +160,11 @@ apple2dd_set_mode(apple2dd *drive, int mode)
drive->mode = mode;
}
/*
* Shift the head position in the drive by the given positions, which is
* in bytes. Pos may be a negative number; if so, the head essentially
* moves further away from the center of the magnetic wafer.
*/
void
apple2dd_shift(apple2dd *drive, int pos)
{
@ -143,6 +180,13 @@ apple2dd_shift(apple2dd *drive, int pos)
}
}
/*
* When you step the drive, you are essentially moving the head in
* track positions. It's not really faster for _us_, but it's faster for
* a mechanical drive than a bunch of shifts if you know the data is far
* away track-wise. This function also safeguards (as the drive did!)
* against stepping too far out or too far in.
*/
void
apple2dd_step(apple2dd *drive, int steps)
{
@ -155,12 +199,20 @@ apple2dd_step(apple2dd *drive, int steps)
}
}
/*
* A really simple function to turn the drive "on".
*/
void
apple2dd_turn_on(apple2dd *drive, bool online)
{
drive->online = online;
}
/*
* Write a byte to the disk in the drive. This is pretty similar to the
* read function in that, once we do what we need with the segment, we
* shift the drive position forward by one byte.
*/
void
apple2dd_write(apple2dd *drive, vm_8bit byte)
{
@ -168,6 +220,12 @@ apple2dd_write(apple2dd *drive, vm_8bit byte)
apple2dd_shift(drive, 1);
}
/*
* Set the write-protect status for the disk. Note that it was _disks_
* that were write-protected in the past, sometimes by taping over a
* chunk that was clipped out of the disk. So this function is somewhat
* similar to just taping over or removing that tape.
*/
void
apple2dd_write_protect(apple2dd *drive, bool protect)
{