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Merge pull request #4963 from maxpat78/master
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Ehanced DetectGeometry
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@joncampbell123
joncampbell123 authored Apr 15, 2024
2 parents d5743d4 + 6829b21 commit 652aa25
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Showing 2 changed files with 15 additions and 19 deletions.
1 change: 1 addition & 0 deletions include/bios_disk.h
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Original file line number Diff line number Diff line change
Expand Up @@ -358,6 +358,7 @@ class imageDiskVHD : public imageDisk {
static uint32_t CreateDifferencing(const char* filename, const char* basename);
uint32_t CreateSnapshot();
void DetectGeometry(Bitu sizes[]);
static void DetectGeometry(uint8_t* buf, Bitu sizes[], uint64_t currentSize);
static uint64_t scanMBR(uint8_t* mbr, Bitu sizes[], uint64_t disksize=0);
bool MergeSnapshot(uint32_t* totalSectorsMerged, uint32_t* totalBlocksUpdated);
static void SizeToCHS(uint64_t size, uint16_t* c, uint8_t* h, uint8_t* s);
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33 changes: 14 additions & 19 deletions src/ints/bios_vhd.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -92,10 +92,6 @@ imageDiskVHD::ErrorCodes imageDiskVHD::Open(const char* fileName, const bool rea
}
//check that uniqueId matches
if (matchUniqueId && memcmp(matchUniqueId, footer.uniqueId, 16)) { fclose(file); return INVALID_MATCH; }
//calculate disk size
// WRONG! Max pseudo-CHS is 65535*16*255 or ~127GB, but a VHD can reach 2040GB!
//uint64_t calcDiskSize = (uint64_t)footer.geometry.cylinders * (uint64_t)footer.geometry.heads * (uint64_t)footer.geometry.sectors * (uint64_t)512;
//if (!calcDiskSize) { fclose(file); return INVALID_DATA; }

//set up imageDiskVHD here
imageDiskVHD* vhd = new imageDiskVHD();
Expand All @@ -107,7 +103,6 @@ imageDiskVHD::ErrorCodes imageDiskVHD::Open(const char* fileName, const bool rea
vhd->heads = footer.geometry.heads;
vhd->sectors = footer.geometry.sectors;
vhd->sector_size = 512;
//vhd->diskSizeK = calcDiskSize / 1024;
vhd->diskSizeK = footer.currentSize / 1024;
vhd->diskimg = file;
vhd->diskname = fileName;
Expand All @@ -118,7 +113,6 @@ imageDiskVHD::ErrorCodes imageDiskVHD::Open(const char* fileName, const bool rea
//if fixed image, store a plain imageDisk also
if (footer.diskType == VHD_TYPE_FIXED) {
//make sure that the image size is at least as big as the geometry
//if (calcDiskSize > footerPosition) {
if (footer.currentSize > footerPosition) {
fclose(file);
return INVALID_DATA;
Expand All @@ -128,13 +122,11 @@ imageDiskVHD::ErrorCodes imageDiskVHD::Open(const char* fileName, const bool rea
if(fseeko64(file, 0, SEEK_SET)) { fclose(file); return INVALID_DATA; }
if(fread(&buf, sizeof(uint8_t), 512, file) != 512) { fclose(file); return INVALID_DATA; }
//detect real DOS geometry (MBR, BPB or default X-255-63)
imageDiskVHD::scanMBR(buf, sizes, footer.currentSize);
vhd->cylinders = sizes[3];
vhd->heads = sizes[2];
vhd->sectors = sizes[1];
vhd->fixedDisk = new imageDisk(file, fileName, vhd->cylinders, vhd->heads, vhd->sectors, 512, true);
//now possible FAT geometry can be detected (in Windows 11, those two can differ!)
vhd->DetectGeometry(sizes);
uint64_t lba = imageDiskVHD::scanMBR(buf, sizes, footer.currentSize);
//load boot sector
if(fseeko64(file, lba, SEEK_SET)) { fclose(file); return INVALID_DATA; }
if(fread(&buf, sizeof(uint8_t), 512, file) != 512) { fclose(file); return INVALID_DATA; }
imageDiskVHD::DetectGeometry(buf, sizes, footer.currentSize);
vhd->cylinders = sizes[3];
vhd->heads = sizes[2];
vhd->sectors = sizes[1];
Expand Down Expand Up @@ -201,7 +193,6 @@ imageDiskVHD::ErrorCodes imageDiskVHD::Open(const char* fileName, const bool rea
+ 7) / 8) /* convert to bytes and round up to nearest byte; 4096/8 = 512 bytes required */
+ 511) / 512); /* convert to sectors and round up to nearest sector; 512/512 = 1 sector */
//check that the BAT is large enough for the disk
//uint32_t tablesRequired = (uint32_t)((calcDiskSize + (dynHeader.blockSize - 1)) / dynHeader.blockSize);
uint32_t tablesRequired = (uint32_t)((footer.currentSize + (dynHeader.blockSize - 1)) / dynHeader.blockSize);
if (dynHeader.maxTableEntries < tablesRequired) { delete vhd; return INVALID_DATA; }
//check that the BAT is contained within the file
Expand Down Expand Up @@ -810,7 +801,6 @@ uint32_t imageDiskVHD::ConvertFixed(const char* filename) {
footer.SetDefaults();
footer.dataOffset = 0xFFFFFFFFFFFFFFFF;
footer.originalSize = footer.currentSize = size;
//c = size / 512 / (h * s);
footer.geometry.cylinders = (uint16_t)c;
footer.geometry.heads = (uint8_t)h;
footer.geometry.sectors = (uint8_t)s;
Expand Down Expand Up @@ -933,14 +923,20 @@ void imageDiskVHD::DetectGeometry(Bitu sizes[]) {
//load and check MBR
Read_AbsoluteSector(0, buf);
uint64_t lba = scanMBR(buf, sizes, footer.currentSize);
if(lba < 512 || lba > (footer.currentSize - 512)) {
if(lba < 512 || lba >(footer.currentSize - 512)) {
LOG_MSG("Bad CHS partition start in MBR");
lba = 0;
}

if (lba) {
if(lba) {
//load FAT boot sector and scan BPB
Read_AbsoluteSector(lba / 512, buf);
DetectGeometry(buf, sizes, footer.currentSize);
}
}

void imageDiskVHD::DetectGeometry(uint8_t* buf, Bitu sizes[], uint64_t currentSize) {
//scan BPB
uint16_t s2 = *((uint16_t*)(buf + 0x18));
uint16_t h2 = *((uint16_t*)(buf + 0x1A));
if(!s2 || !h2 || s2 > 63 || h2 > 255) {
Expand All @@ -950,9 +946,8 @@ void imageDiskVHD::DetectGeometry(Bitu sizes[]) {
sizes[0] = 512;
sizes[1] = s2;
sizes[2] = h2;
sizes[3] = footer.currentSize / 512 / s2 / h2;
sizes[3] = currentSize / 512 / s2 / h2;
}
}
}

//scans a MBR and returns
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1 comment on commit 652aa25

@BridgeHeadland
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I created dynamic VHD files with VHDMAKE last weekend, if I create dynamic VHD files in the same way (same size) today, will the new VHD files be different from the ones I created last weekend?

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