mirror of
https://github.com/ivanizag/izapple2.git
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Iván Izaguirre
69da610b5a
Three things from the review. The overlay kept the file open from the first write, so it had an open with no close. It does not any more: read and applyTo open the file and close it, and openForWriting hands the caller a file to close where it writes. applyTo opens once for all the units instead of once per unit, and returns before opening anything when nothing has been saved yet. Identifying the image, which means reading all of it, happened whenever a DSK was loaded, even with no overlay in use, which is the usual case. Now the caller checks for a filename first. openOverlay no longer takes an empty one, both callers check before asking for it. blockDiskOverlay moves to its own file.
76 lines
2.1 KiB
Go
76 lines
2.1 KiB
Go
package storage
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import (
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"errors"
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)
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// Diskette represents a diskette and it's RW mechanism
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type Diskette interface {
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PowerOn(cycle uint64)
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PowerOff(cycle uint64)
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Read(quarterTrack int, cycle uint64) uint8
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Write(quarterTrack int, value uint8, cycle uint64)
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Is13Sectors() bool
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}
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// IsDiskette returns true if the files looks like a 5 1/4 diskette
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func IsDiskette(data []byte) bool {
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return isFileNib(data) || isFileDsk(data) || isFileWoz(data)
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}
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/*
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MakeDiskette returns a Diskette by detecting the format.
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With an overlayFilename, the changes the software writes are kept in that file
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and the image loaded is never modified. It also makes writable the diskettes
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that could not be written otherwise, the ones loaded from a compressed file, an
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URL or the embedded resources. An empty overlayFilename writes the changes back
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to the image, which only works for the DSK and PO files on disk.
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*/
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func MakeDiskette(data []byte, filename string, writeable bool, overlayFilename string) (Diskette, error) {
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if isFileD13(data) {
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return nil, errors.New("files with .d13 format are not supported for 13 sectors disk, use .nib or .woz")
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}
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if isFileNib(data) {
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var d disketteNib
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d.nib = newFileNib(data)
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return &d, nil
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}
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if isFileDsk(data) {
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var overlay *overlay
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if overlayFilename != "" {
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// Only now is it worth identifying the image, which means reading
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// all of it. The checksum is of the image as it was loaded, before
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// anything saved before is put back on top of it.
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var err error
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overlay, err = openOverlay(overlayFilename, bytesPerTrack, numberOfTracks,
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checksumOfBytes(data))
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if err != nil {
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return nil, err
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}
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if err := overlay.applyTo(data); err != nil {
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return nil, err
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}
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}
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var d disketteNibWritable
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d.nib = newFileDsk(data, filename)
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d.nib.overlay = overlay
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d.nib.supportsWrite = overlay != nil || (d.nib.supportsWrite && writeable)
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return &d, nil
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}
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if isFileWoz(data) {
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f, err := NewFileWoz(data)
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if err != nil {
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return nil, err
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}
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return newDisquetteWoz(f)
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}
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return nil, errors.New("diskette format not supported")
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}
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