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Fixes for Gutenberg, Jr. disks

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Also added some observations about the file format.
This commit is contained in:
Andy McFadden 2015-01-09 22:25:14 -08:00
parent 125d128b36
commit 3d3c19d67f
1 changed files with 56 additions and 29 deletions
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85
diskimg/Gutenberg.cpp
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@ -4,8 +4,8 @@
* See the file LICENSE for distribution terms.
*/
/*
* Implementation of DiskFSGutenberg and A2FileGutenberg classes.
*
* Implementation of Gutenberg disk format (used by the Gutenberg and
* Gutenberg Jr. word processors).
*/
#include "StdAfx.h"
#include "DiskImgPriv.h"
@ -17,6 +17,53 @@
* ===========================================================================
*/
/*
The Gutenberg disk format embeds the file structure meta-data into the disk
sectors themselves, rather than having a separate track/sector list. The
first six bytes in every sector are:
+00 previous track in this file (+$80 indicates link not valid?)
+01 previous sector
+02 current track (+$80 indicates start of file)
+03 current sector
+04 next track (+$80 indicates end of file)
+05 next sector
The files are circular -- the "next" and "previous" links will wrap around --
so you have to test the high bit to see if you've reached an end.
The disk catalog works the same way, and is present as the first file on
the disk (called "DIR"). (It's not quite the same -- the "previous" pointer
in the first sector just points to the first sector.) The catalog begins
at track 17 sector 7, and skips around the disk.
The boot area is not represented by a file, and does not include the
embedded T/S links.
Each directory entry is 16 bytes, and lays out rather nicely in the sector
editor:
00: 11 07 11 87 15 0e c7 c2 af cd c1 d3 d4 c5 d2 8d ......GB/MASTER.
10: c4 c9 d2 a0 a0 a0 a0 a0 a0 a0 a0 a0 11 07 cc 8d DIR ..L.
20: c3 cf d0 d9 a0 a0 a0 a0 a0 a0 a0 a0 10 40 d0 8d COPY .@P.
30: c3 cf d0 d9 c1 cc cc a0 a0 a0 a0 a0 10 04 d0 8d COPYALL ..P.
This shows the six T/S bytes, followed by a nine-character volume name.
The fact that each entry ends in 0x8d is likely a deliberate attempt to
make the file readable as high-ASCII text, with one entry per line.
The regular directory entries start at 0x10. The file name is 12 bytes,
followed by the track and sector of the start of the file. Note "DIR"
starts at track 17 sector 7, as expected. The next entry, COPY, has 0x40 for
its sector number, indicating that it has been deleted. (Some entries on
Gutenberg Jr. disks use 0x40 for the track number instead?)
The next value is one of 'L', 'P', 'M', or ' ' (0xcc, 0xd0, 0xcd, 0xa0).
Some files have text, some have fonts, some have executable code (a short
header followed by 6502 instructions). There's no apparent link between
the value and the type of data in the file.
*/
const int kMaxSectors = 32;
const int kMaxVolNameLen = 9;
const int kSctSize = 256;
@ -51,7 +98,6 @@ static DIError TestImage(DiskImg* pImg, DiskImg::SectorOrder imageOrder,
{
DIError dierr = kDIErrNone;
uint8_t sctBuf[kSctSize];
// int numTracks, numSectors;
int catTrack = kVTOCTrack;
int catSect = kVTOCSector;
int foundGood = 0;
@ -70,10 +116,8 @@ static DIError TestImage(DiskImg* pImg, DiskImg::SectorOrder imageOrder,
dierr = kDIErrNone;
break; /* allow it if earlier stuff was okay */
}
#ifdef TRY_THIS
// This allowed Gutenberg_Jr_f1.dsk to be read, but it doesn't look
// quite right... leaving it alone for the moment.
if (catTrack == sctBuf[2] & 0x7f && catSect == sctBuf[3] & 0x7f) {
// current-sector values matched, check for the end-of-entry bits
foundGood++;
if (sctBuf[0x0f] == 0x8d && sctBuf[0x1f] == 0x8d &&
sctBuf[0x2f] == 0x8d && sctBuf[0x3f] == 0x8d &&
@ -90,24 +134,6 @@ static DIError TestImage(DiskImg* pImg, DiskImg::SectorOrder imageOrder,
// full circle
break;
}
#else
if (catTrack == sctBuf[0] && catSect == sctBuf[1]) {
foundGood++;
if (sctBuf[0x0f] == 0x8d && sctBuf[0x1f] == 0x8d &&
sctBuf[0x2f] == 0x8d && sctBuf[0x3f] == 0x8d &&
sctBuf[0x4f] == 0x8d && sctBuf[0x5f] == 0x8d &&
sctBuf[0x6f] == 0x8d && sctBuf[0x7f] == 0x8d &&
sctBuf[0x8f] == 0x8d && sctBuf[0x9f] == 0x8d)
foundGood++;
}
else if (catTrack >0x80) {
LOGI(" Gutenberg detected end-of-catalog on cat (%d,%d)",
catTrack, catSect);
break;
}
catTrack = sctBuf[0x04];
catSect = sctBuf[0x05];
#endif
iterations++; // watch for infinite loops
}
if (iterations >= DiskFSGutenberg::kMaxCatalogSectors) {
@ -223,15 +249,15 @@ DIError DiskFSGutenberg::ReadCatalog(void)
int catTrack, catSect;
int iterations;
catTrack = 17;
catSect = 7;
catTrack = kVTOCTrack;
catSect = kVTOCSector;
iterations = 0;
memset(fCatalogSectors, 0, sizeof(fCatalogSectors));
while (catTrack < 35 && catSect < 16 && iterations < kMaxCatalogSectors)
{
LOGI(" Gutenberg reading catalog sector T=%d S=%d", catTrack, catSect);
LOGD(" Gutenberg reading catalog sector T=%d S=%d", catTrack, catSect);
dierr = fpImg->ReadTrackSector(catTrack, catSect, sctBuf);
if (dierr != kDIErrNone)
goto bail;
@ -278,7 +304,9 @@ DIError DiskFSGutenberg::ProcessCatalogSector(int catTrack, int catSect,
pEntry = &sctBuf[kCatalogEntryOffset];
for (i = 0; i < kCatalogEntriesPerSect; i++) {
if (pEntry[0x0d] != kEntryDeleted && pEntry[0x00] != 0xa0 && pEntry[0x00] != 0x00) {
if (pEntry[0x0c] != kEntryDeleted && pEntry[0x0d] != kEntryDeleted &&
pEntry[0x00] != 0xa0 && pEntry[0x00] != 0x00)
{
pFile = new A2FileGutenberg(this);
pFile->SetQuality(A2File::kQualityGood);
@ -290,7 +318,6 @@ DIError DiskFSGutenberg::ProcessCatalogSector(int catTrack, int catSect,
pFile->fFileName[A2FileGutenberg::kMaxFileName] = '\0';
pFile->FixFilename();
//pFile->fCatTS.track = catTrack;
//pFile->fCatTS.sector = catSect;
pFile->fCatEntryNum = i;