#@mplx/d64

Read, write, create and format Commodore 1541 D64 disk images.

A D64 is the blocks of a 5.25" floppy stored back to back: 683 blocks of 256 bytes, no header. Inside them is CBM DOS 2.6 - a Block Availability Map in sector 18/0, a chain of 32-byte directory slots from 18/1, one linked list of blocks per file. This deck implements all of it in pure Jennifer.

Four BAM layouts: stock 35-track Cbm, plus the three 40-track extensions SpeedDos, DolphinDos and PrologicDos.

#Import

use io;
import "@mplx/d64/" as d64;

def img as d64.Image init d64.formatDisk("sample disk", "01");
$img = d64.writeText($img, "readme", d64.FileType.Seq, "hello\n");
io.printf("%s", d64.directoryText($img));
d64.save($img, "sample.d64");

The trailing slash resolves to the entry module.

#Value semantics

Every function that changes the disk returns a fresh Image and leaves its argument untouched.

def before as d64.Image init d64.formatDisk("work", "01");
def after as d64.Image init d64.writeText($before, "readme", d64.FileType.Seq, "hi\n");

len(d64.listFiles($before));   # 0
len(d64.listFiles($after));    # 1

So the calling shape is $img = something($img, ...). A failed multi-step operation cannot leave a half-written disk.

#Case

PETSCII $41-$5a are the unshifted letters, shown upper case on a C64; ASCII spells the same codes A-Z. The transcoder swaps case, the petcat convention. Write names lower case for the classic look.

d64.toPetscii("hello");   # $48 $45 $4c $4c $4f - "HELLO" on screen

fromPetscii(toPetscii(s)) == s for anything PETSCII can spell. See PETSCII.

#Errors

Every failure is an Error with kind "d64".

try {
    $img = d64.writeFile($img, "toobig", d64.FileType.Prg, $huge);
} catch (e) {
    io.printf("%s\n", $e.message);
}

Raised on: a name over 16 PETSCII characters, a name already present, a full disk, a full directory, an address outside the image, a scratch of a locked file, a chain that loops, an image whose length is not a D64 size.

#Contents

Runnable programs: examples/.