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DiskDump should now automatically shrink a disk image whose logical format is smaller than its physical format

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This commit is contained in:
Jeff Parsons 2017-07-04 15:25:54 -07:00 • committed by Jeff Parsons
commit 3ba2f569b9
6 changed files with 33 additions and 39 deletions
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56
modules/diskdump/lib/diskdump.js
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@ -2768,26 +2768,32 @@ DiskDump.prototype.convertToJSON = function()
}
}
}
var nLogicalSectorsPerTrack = nSectorsPerTrack;
if (iBPB >= 0) {
/*
* Sometimes we come across a physical 360Kb disk image that contains a logical 320Kb image (and similarly,
* a physical 180Kb disk image that contains a logical 160Kb disk image), presumably because it was possible
* for someone to take a diskette formatted with 9 sectors/track and then use FORMAT or DISKCOPY to create
* a smaller file system on it (ie, using only 8 sectors/track).
*/
if (!bMediaIDBPB) bMediaIDBPB = this.bufDisk.readUInt8(offBootSector + 512);
if (iBPB >= 2 && bMediaIDBPB == DiskAPI.FAT.MEDIA_320KB && bMediaID == DiskAPI.FAT.MEDIA_360KB || bMediaIDBPB == DiskAPI.FAT.MEDIA_160KB && bMediaID == DiskAPI.FAT.MEDIA_180KB) {
iBPB -= 2;
bMediaID = DiskDump.aDefaultBPBs[iBPB][DiskAPI.BPB.MEDIA_ID];
nLogicalSectorsPerTrack = DiskDump.aDefaultBPBs[iBPB][DiskAPI.BPB.TRACK_SECS];
DiskDump.logWarning("shrinking track size to " + nLogicalSectorsPerTrack + " sectors/track");
}
if (fBPBExists) {
/*
* In deference to the PC-DOS 2.0 BPB behavior discussed above, we stop our BPB verification
* after the first word of HIDDEN_SECS.
*
* Also, we permit a physical 360Kb disk image to contain a logical 320Kb image (and similarly, a physical
* 180Kb disk image to contain a logical 160Kb disk image), because it was entirely possible for someone to
* take a diskette formatted with 9 sectors/track and "DISKCOPY" another disk with only 8 sectors/track onto it.
* When we imaged the physical disk, we likely read all readable sectors, regardless of whether the file system
* contained within used them all or not.
*/
if ((bMediaIDBPB != DiskAPI.FAT.MEDIA_320KB || bMediaID != DiskAPI.FAT.MEDIA_360KB) && (bMediaIDBPB != DiskAPI.FAT.MEDIA_160KB || bMediaID != DiskAPI.FAT.MEDIA_180KB)) {
for (i = DiskAPI.BPB.SECTOR_BYTES; i < DiskAPI.BPB.HIDDEN_SECS + 2; i++) {
var bDefault = DiskDump.aDefaultBPBs[iBPB][i];
var bActual = this.bufDisk.readUInt8(offBootSector + i);
if (bDefault != bActual) {
DiskDump.logWarning("BPB byte " + str.toHexByte(i) + " default (" + str.toHexByte(bDefault) + ") does not match actual byte: " + str.toHexByte(bActual));
fBPBExists = false;
}
for (i = DiskAPI.BPB.SECTOR_BYTES; i < DiskAPI.BPB.HIDDEN_SECS + 2; i++) {
var bDefault = DiskDump.aDefaultBPBs[iBPB][i];
var bActual = this.bufDisk.readUInt8(offBootSector + i);
if (bDefault != bActual) {
DiskDump.logWarning("BPB byte " + str.toHexByte(i) + " default (" + str.toHexByte(bDefault) + ") does not match actual byte: " + str.toHexByte(bActual));
fBPBExists = false;
}
}
}
@ -2806,19 +2812,7 @@ DiskDump.prototype.convertToJSON = function()
*
* However, if --forceBPB is specified, all those concerns go out the window: the goal is assumed to
* be a mountable disk, not a bootable disk. So the BPB copy starts at offset 0 instead of SECTOR_BYTES.
*
* And again, we must also deal with a physical 360Kb disk image containing a logical 320Kb image (and
* similarly, a physical 180Kb disk image containing a logical 160Kb disk image). So we check the FAT ID
* byte to make sure we're using a BPB that matches the logical disk image.
*/
bMediaIDBPB = this.bufDisk.readUInt8(offBootSector + 512);
if (bMediaIDBPB == DiskAPI.FAT.MEDIA_320KB && bMediaID == DiskAPI.FAT.MEDIA_360KB) {
if (iBPB == 3) iBPB = 1;
}
else if (bMediaIDBPB == DiskAPI.FAT.MEDIA_160KB && bMediaID == DiskAPI.FAT.MEDIA_180KB) {
if (iBPB == 2) iBPB = 0;
}
bMediaID = DiskDump.aDefaultBPBs[iBPB][DiskAPI.BPB.MEDIA_ID];
for (i = this.forceBPB? 0 : DiskAPI.BPB.SECTOR_BYTES; i < DiskAPI.BPB.LARGE_SECS+4; i++) {
this.bufDisk.writeUInt8(DiskDump.aDefaultBPBs[iBPB][i] || 0, offBootSector + i);
}
@ -2878,13 +2872,13 @@ DiskDump.prototype.convertToJSON = function()
cbSector = cbSectorDSK;
nHeads = this.bufDisk.readUInt8(offBootSector + 0x01);
nCylinders = this.bufDisk.readUInt16LE(offBootSector + 0x02);
nSectorsPerTrack= this.bufDisk.readUInt16LE(offBootSector + 0x04);
nLogicalSectorsPerTrack = nSectorsPerTrack = this.bufDisk.readUInt16LE(offBootSector + 0x04);
var nTracks = nHeads * nCylinders;
cbTrack = nSectorsPerTrack * cbSector;
offTrack = 0x08;
if (!cbTrack) {
for (iTrack = 0; iTrack < nTracks; iTrack++) {
nSectorsPerTrack = this.bufDisk.readUInt16LE(offTrack);
nLogicalSectorsPerTrack = nSectorsPerTrack = this.bufDisk.readUInt16LE(offTrack);
cbSectorDSK = this.bufDisk.readUInt16LE(offTrack+2);
cbTrack = nSectorsPerTrack * cbSectorDSK;
offSector = this.bufDisk.readUInt32LE(offTrack+4);
@ -2923,7 +2917,7 @@ DiskDump.prototype.convertToJSON = function()
if (aTracks.length) {
var aTrack = aTracks[iTrack++];
nSectorsPerTrack = aTrack[0];
nLogicalSectorsPerTrack = nSectorsPerTrack = aTrack[0];
cbSector = aTrack[1];
bufTrack = aTrack[2];
cbTrack = nSectorsPerTrack * cbSector;
@ -2933,7 +2927,7 @@ DiskDump.prototype.convertToJSON = function()
var aSectors;
if (this.fJSONNative) {
aSectors = new Array(nSectorsPerTrack);
aSectors = new Array(nLogicalSectorsPerTrack);
aHeads[iHead] = aSectors;
} else {
json += this.dumpLine(2, "[", "head:" + this.sJSONWhitespace + iHead + ", track:" + this.sJSONWhitespace + iCylinder);
@ -2947,7 +2941,7 @@ DiskDump.prototype.convertToJSON = function()
* be unnecessary.
*/
var cbSectorThisTrack = cbSector;
var nSectorsThisTrack = nSectorsPerTrack;
var nSectorsThisTrack = nLogicalSectorsPerTrack;
/*
* Notes regarding XDF track layouts, from http://forum.kryoflux.com/viewtopic.php?f=3&t=234: