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KhooHaoYitKhooHaoYit
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patterns: Add support for exFAT (#398)
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‎README.md‎

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| DTED | | [`patterns/dted.hexpat`](patterns/dted.hexpat) | Digital Terrain Elevation Data (DTED) |
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| ELF | `application/x-executable` | [`patterns/elf.hexpat`](patterns/elf.hexpat) | ELF header in elf binaries |
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| EVTX | `application/x-ms-evtx` | [`patterns/evtx.hexpat`](patterns/evtx.hexpat) | MS Windows Vista Event Log |
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| EXFAT | | [`patterns/exfat.hexpat`](patterns/exfat.hexpat) | Extensible File Allocation Table (exFAT) |
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| EXT4 | | [`patterns/ext4.hexpat`](patterns/ext4.hexpat) | Ext4 filesystem |
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| FAS | | [`patterns/fas_oskasoftware.hexpat`](patterns/fas_oskasoftware.hexpat) [`patterns/fas_oskasoftware_old.hexpat`](patterns/fas_oskasoftware_old.hexpat) (Old versions of Oska DeskMate) | Oska Software DeskMates FAS (Frames and Sequences) file |
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| FBX | | [`patterns/fbx.hexpat`](patterns/fbx.hexpat) | Kaydara FBX Binary |

‎patterns/exfat.hexpat‎

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#pragma magic [45 58 46 41 54 20 20 20] @ 0x03
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#pragma description Extensible File Allocation Table (exFAT)
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#pragma author Khoo Hao Yit
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import std.mem;
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import std.string;
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import std.core;
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struct BootSector {
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std::mem::Bytes<3> jumpBoot;
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char fileSystemName[8];
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std::mem::Bytes<53> mustBeZero;
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u64 partitionOffset;
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u64 volumeLength;
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u32 fatOffset;
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u32 fatLength;
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u32 clusterHeapOffset;
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u32 clusterCount;
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u32 firstClusterOfRootDirectory;
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u32 volumeSerialNumber;
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u16 fileSystemRevision;
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u16 volumeFlags;
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u8 bytesPerSectorShift;
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u8 sectorsPerClusterShift;
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u8 numberOfFats;
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u8 driveSelect;
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u8 percentInUse;
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std::mem::Bytes<7> reserved;
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std::mem::Bytes<390> bootCode;
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std::mem::Bytes<2> bootSignature;
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};
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struct ExtendedBootSector {
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std::mem::Bytes<bytesPerSector - 4> bootCode;
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std::mem::Bytes<4> bootSignature;
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};
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struct Parameter {
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std::mem::Bytes<16> guid;
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std::mem::Bytes<32> data;
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};
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struct OemParameter {
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Parameter parameters[10];
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std::mem::Bytes<bytesPerSector - 480> reserved;
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};
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u64 bytesPerSector;
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u64 startOfClusterHeap;
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u64 bytesPerCluster;
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u64 fatAddress;
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struct BootRegion {
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BootSector bootSector;
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bytesPerSector = 1 << bootSector.bytesPerSectorShift;
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bytesPerCluster = bytesPerSector << bootSector.sectorsPerClusterShift;
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ExtendedBootSector extendedBootSectors[8];
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OemParameter oemParameter;
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std::mem::Bytes<bytesPerSector> reservedSector;
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std::mem::Bytes<bytesPerSector> bootChecksum;
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};
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struct VolumeLabelEntry {
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u8 entryType;
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u8 characterCount;
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char volumeLabel[22];
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std::mem::Bytes<8> reserved;
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};
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bitfield FileAttribute {
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readOnly : 1;
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hidden : 1;
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system : 1;
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reserved : 1;
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directory : 1;
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archive : 1;
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reserved1 : 10;
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};
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auto currentClusterIndex = -1;
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auto currentClusterSize = -1;
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auto currentIsDirectory = -1;
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struct FileEntry {
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u8 entryType;
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u8 secondayEntryCount;
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u16 checksum;
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FileAttribute attributes;
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std::mem::Bytes<2> reserved;
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u32 creationDatetime;
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u32 modificationDatetime;
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u32 accessDatetime;
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u8 creationTimeHundredths;
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u8 modificationTimeHundredths;
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u8 creationUtcOffset;
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u8 modificationUtcOffset;
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u8 accessUtcOffset;
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std::mem::Bytes<7> reserved1;
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currentIsDirectory = attributes.directory;
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};
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bitfield GeneralSecondaryFlags {
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allocationPossible : 1;
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noFatChain : 1;
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customDefined : 6;
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};
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struct FileNameEntry {
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u8 entryType;
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u8 flags;
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char16 name[15];
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};
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fn divideCeil(auto a, auto b) {
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auto result = a / b;
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auto remain = a % b;
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if (remain) {
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result += 1;
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}
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return result;
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};
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struct ContinuousFatRange<auto ClusterIndex, auto ClusterSize> {
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u32 fatRange[ClusterSize] @ fatAddress + ClusterIndex * 4 [[sealed]];
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} [[name(std::format("ContinuousFatRange<{}, {}>", ClusterIndex, ClusterSize))]];
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struct FatChain {
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auto clusterIndex = currentClusterIndex;
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auto clusterSize = currentClusterSize;
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currentClusterIndex = -1;
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currentClusterSize = -1;
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if (clusterIndex == -1) {
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std::error(std::format("Invalid cluster index: {}", clusterIndex));
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}
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if (clusterSize == -1) {
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auto startingFatRange = fatAddress + clusterIndex * 4;
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u32 clusters[while(
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$ == startingFatRange
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|| $ == fatAddress + std::mem::read_unsigned($ - 4, 4) * 4
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)] @ startingFatRange [[hidden]];
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clusterSize = std::core::member_count(clusters);
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}
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ContinuousFatRange<clusterIndex, clusterSize> data @ 0;
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try {
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auto nextClusterIndex = clusters[clusterSize - 1];
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if (nextClusterIndex != 0xffffffff && nextClusterIndex != 0) {
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currentClusterIndex = nextClusterIndex;
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FatChain next @ 0 [[inline]];
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}
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}
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} [[name(std::format("FatChain<{}>", clusterIndex))]];
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struct ContinuousDataRange<auto ClusterIndex, auto ClusterSize> {
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std::mem::Bytes<ClusterSize * bytesPerCluster> dataRange @
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startOfClusterHeap + ClusterIndex * bytesPerCluster;
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} [[name(std::format("ContinuousDataRange<{}, {}>", ClusterIndex, ClusterSize))]];
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struct DataChain {
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auto clusterIndex = currentClusterIndex;
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auto clusterSize = currentClusterSize;
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currentClusterIndex = -1;
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currentClusterSize = -1;
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if (clusterIndex == -1) {
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std::error(std::format("Invalid cluster index: {}", clusterIndex));
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}
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if (clusterSize == -1) {
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auto startingFatRange = fatAddress + clusterIndex * 4;
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u32 clusters[while(
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$ == startingFatRange
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|| $ == fatAddress + std::mem::read_unsigned($ - 4, 4) * 4
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)] @ startingFatRange [[hidden]];
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clusterSize = std::core::member_count(clusters);
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}
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ContinuousDataRange<clusterIndex, clusterSize> data @ 0;
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try {
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auto nextClusterIndex = clusters[clusterSize - 1];
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if (nextClusterIndex != 0xffffffff && nextClusterIndex != 0) {
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currentClusterIndex = nextClusterIndex;
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DataChain next @ 0 [[inline]];
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}
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}
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} [[name(std::format("DataChain<{}>", clusterIndex))]];
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struct UpcaseTableEntry {
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u8 entryType;
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std::mem::Bytes<3> reserved;
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u32 tableChecksum;
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std::mem::Bytes<12> reserved1;
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u32 firstCluster;
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u64 dataLength;
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ContinuousFatRange<firstCluster, 1> fatRange;
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ContinuousDataRange<firstCluster, 1> dataRange;
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};
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struct AllocationBitmapEntry {
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u8 entryType;
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u8 bitmapFlags;
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std::mem::Bytes<18> reserved;
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u32 firstCluster;
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u64 dataLength;
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ContinuousFatRange<firstCluster, 1> fatRange;
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ContinuousDataRange<firstCluster, 1> dataRange;
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};
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using StreamExtensionEntry;
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struct DirectoryEntry {
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u8 entryType @ addressof(this) [[hidden]];
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match (entryType) {
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(0x83 | 0x03): VolumeLabelEntry;
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(0x81): AllocationBitmapEntry;
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(0x82): UpcaseTableEntry;
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(0x85 | 0x05): FileEntry;
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(0xc0 | 0x40): StreamExtensionEntry;
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(0xc1 | 0x41): FileNameEntry;
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(_): std::mem::Bytes<32> [[name(std::format("UnknownEntry @ {:#X}", addressof(this)))]];
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}
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} [[inline]];
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struct ContinuousDirectoryEntry<auto ClusterIndex, auto ClusterSize> {
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DirectoryEntry entry[ClusterSize * bytesPerCluster / 32] @
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startOfClusterHeap + ClusterIndex * bytesPerCluster
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[[inline]];
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} [[name(std::format("ContinuousDirectoryEntry<{}, {}>", ClusterIndex, ClusterSize))]];
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struct DirectoryEntryChain {
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auto clusterIndex = currentClusterIndex;
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auto clusterSize = currentClusterSize;
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currentClusterIndex = -1;
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currentClusterSize = -1;
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if (clusterIndex == -1) {
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std::error(std::format("Invalid cluster index: {}", clusterIndex));
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}
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if (clusterSize == -1) {
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auto startingFatRange = fatAddress + clusterIndex * 4;
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u32 clusters[while(
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$ == startingFatRange
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|| $ == fatAddress + std::mem::read_unsigned($ - 4, 4) * 4
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)] @ startingFatRange [[hidden]];
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clusterSize = std::core::member_count(clusters);
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}
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try {
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ContinuousDirectoryEntry<clusterIndex, clusterSize> data @ 0;
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} catch {
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std::warning(std::format("Error trying to parse ContinuousDirectoryEntry at {:#x} (Cluster index {} with cluster size of {})", startOfClusterHeap + clusterIndex * bytesPerCluster, clusterIndex, clusterSize));
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}
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try {
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auto nextClusterIndex = clusters[clusterSize - 1];
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if (nextClusterIndex != 0xffffffff && nextClusterIndex != 0) {
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currentClusterIndex = nextClusterIndex;
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DirectoryEntryChain next @ 0 [[inline]];
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}
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}
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currentIsDirectory = -1;
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} [[name(std::format("DirectoryEntryChain<{}>", clusterIndex))]];
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struct StreamExtensionEntry {
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u8 entryType;
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GeneralSecondaryFlags secondaryFlags;
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std::mem::Bytes<1> reserved;
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u8 nameLength;
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u16 nameHash;
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std::mem::Bytes<2> reserved1;
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u64 validDateLength;
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std::mem::Bytes<4> reserved2;
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u32 firstCluster;
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u64 dataLength;
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if (entryType & 0x80 && currentIsDirectory == 1) {
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currentClusterIndex = firstCluster;
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if (secondaryFlags.noFatChain) {
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currentClusterSize = divideCeil(dataLength, bytesPerCluster);
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}
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FatChain fatChain;
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currentClusterIndex = firstCluster;
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if (secondaryFlags.noFatChain) {
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currentClusterSize = divideCeil(dataLength, bytesPerCluster);
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}
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DirectoryEntryChain directoryChain;
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}
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else if (dataLength) {
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currentClusterIndex = firstCluster;
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if (secondaryFlags.noFatChain) {
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currentClusterSize = divideCeil(dataLength, bytesPerCluster);
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}
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FatChain fatChain;
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currentClusterIndex = firstCluster;
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if (secondaryFlags.noFatChain) {
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currentClusterSize = divideCeil(dataLength, bytesPerCluster);
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}
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DataChain data @ 0;
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}
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};
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BootRegion bootRegion @ 0 [[name("BootRegion")]];
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BootRegion backupBootRegion @ 12 * bytesPerSector [[name("BackupBootRegion")]];
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startOfClusterHeap =
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bootRegion.bootSector.clusterHeapOffset * bytesPerSector
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- 2 * bytesPerCluster;
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fatAddress =
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bootRegion.bootSector.fatOffset * bytesPerSector;
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std::mem::Bytes<bootRegion.bootSector.fatLength * bytesPerSector> fat @ fatAddress [[hidden]];
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currentClusterIndex = bootRegion.bootSector.firstClusterOfRootDirectory;
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FatChain rootDirectoryFatChain @ 0;
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currentClusterIndex = bootRegion.bootSector.firstClusterOfRootDirectory;
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DirectoryEntryChain rootDirectory @ 0;

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