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Merge pull request #296 from hharte/northstar_mixed_density

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Northstar: Handle mixed-density disks
This commit is contained in:
David Given
2021-07-09 22:47:55 +01:00
committed by GitHub
parent 7f95f6b43f cc79977ac0
commit 155e8c2a4b
1 changed files with 25 additions and 1 deletions
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26
lib/imagewriter/nsiimagewriter.cc
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@@ -24,10 +24,16 @@ public:
unsigned autoSides;
unsigned autoSectors;
unsigned autoBytes;
bool mixedDensity = false;
sectors.calculateSize(autoTracks, autoSides, autoSectors, autoBytes);
size_t trackSize = autoSectors * autoBytes;
if (autoTracks * trackSize == 0) {
std::cout << "No sectors in output; skipping .nsi image file generation." << std::endl;
return;
}
std::cout << fmt::format("Writing {} cylinders, {} heads, {} sectors, {} ({} bytes/sector), {} kB total",
autoTracks, autoSides,
autoSectors, autoBytes == 256 ? "SD" : "DD", autoBytes,
@@ -56,7 +62,25 @@ public:
(sectorId * autoBytes); /* Sector offset from beginning of track. */
}
outputFile.seekp(sectorFileOffset, std::ios::beg);
sector->data.slice(0, autoBytes).writeTo(outputFile);
if ((autoBytes == 512) && (sector->data.size() == 256)) {
/* North Star DOS provided an upgrade path for disks formatted as single-
* density to hold double-density data without reformatting. In this
* case, the four directory blocks will be single-density but other areas
* of the disk are double-density. This cannot be accurately represented
* using a .nsi file, so in these cases, we pad the sector to 512-bytes,
* filling with spaces.
*/
char fill[256];
memset(fill, ' ', sizeof(fill));
if (mixedDensity == false) {
std::cout << "Warning: Disk contains mixed single/double-density sectors." << std::endl;
}
mixedDensity = true;
sector->data.slice(0, 256).writeTo(outputFile);
outputFile.write(fill, sizeof(fill));
} else {
sector->data.slice(0, autoBytes).writeTo(outputFile);
}
}
}
}