Device: Find the VSA offset for Disk::Access::EntireDisk

CMakeLists.txt

@@ -154,6 +154,7 @@ set(SRC_FILES
 	disk/nulldiskdriver.cpp
 	disk/neomemorydiskreaddriver.cpp
 	disk/plasiondiskreaddriver.cpp
+	disk/fat.cpp
 	${PLATFORM_SRC}
 )
 

device/device.cpp

@@ -4,6 +4,7 @@
 #include "icsneo/communication/command.h"
 #include "icsneo/device/extensions/deviceextension.h"
 #include "icsneo/platform/optional.h"
+#include "icsneo/disk/fat.h"
 #include <string.h>
 #include <iostream>
 #include <sstream>
@@ -532,6 +533,20 @@ optional<uint64_t> Device::getLogicalDiskSize() {
 	return info->getReportedSize();
 }
 
+optional<uint64_t> Device::getVSAOffsetInLogicalDisk() {
+	if(!isOpen()) {
+		report(APIEvent::Type::DeviceCurrentlyClosed, APIEvent::Severity::Error);
+		return nullopt;
+	}
+
+	if (diskReadDriver->getAccess() == Disk::Access::VSA || diskReadDriver->getAccess() == Disk::Access::None)
+		return 0ull;
+	
+	return Disk::FindVSAInFAT([this](uint64_t pos, uint8_t *into, uint64_t amount) {
+		return readLogicalDisk(pos, into, amount);
+	});
+}
+
 optional<bool> Device::getDigitalIO(IO type, size_t number /* = 1 */) {
 	if(number == 0) { // Start counting from 1
 		report(APIEvent::Type::ParameterOutOfRange, APIEvent::Severity::Error);

disk/fat.cpp

@@ -0,0 +1,48 @@
+#include "icsneo/disk/fat.h"
+#include "icsneo/disk/diskdriver.h"
+#include "ff.h"
+#include "diskio.h"
+#include <mutex>
+
+using namespace icsneo;
+
+// The FAT driver can only be accessed by one caller at a time, since it relies on globals
+static std::mutex fatDriverMutex;
+static std::function< optional<uint64_t>(uint64_t pos, uint8_t* into, uint64_t amount) > diskReadFn;
+
+extern "C" DRESULT disk_read(BYTE, BYTE* buff, LBA_t sector, UINT count) {
+	static_assert(Disk::SectorSize == 512, "FatFs expects 512 byte sectors");
+
+	const uint64_t expected = count * uint64_t(Disk::SectorSize);
+	const auto res = diskReadFn(sector * uint64_t(Disk::SectorSize), buff, expected);
+	if (!res.has_value())
+		return RES_NOTRDY;
+	return res == expected ? RES_OK : RES_ERROR;
+}
+
+extern "C" DSTATUS disk_initialize(BYTE) {
+	return RES_OK;
+}
+
+extern "C" DSTATUS disk_status(BYTE) {
+	return RES_OK;
+}
+
+static uint64_t ClusterToSector(const FATFS& fs, DWORD cluster) {
+	return fs.database + (LBA_t)fs.csize * (cluster - 2);
+}
+
+optional<uint64_t> Disk::FindVSAInFAT(std::function< optional<uint64_t>(uint64_t pos, uint8_t* into, uint64_t amount) > diskRead) {
+	std::lock_guard<std::mutex> lk(fatDriverMutex);
+	diskReadFn = diskRead;
+
+	FATFS fs = {};
+	if (f_mount(&fs, "", 0) != FR_OK)
+		return nullopt;
+
+	FIL logData = {};
+	if (f_open(&logData, "0:\\LOG_DATA.VSA", FA_READ) != FR_OK)
+		return nullopt;
+
+	return ClusterToSector(fs, logData.obj.sclust) * uint64_t(Disk::SectorSize);
+}

include/icsneo/device/device.h

@@ -198,6 +198,18 @@ public:
 	 */
 	optional<uint64_t> getLogicalDiskSize();
 
+	/**
+	 * Get the offset to the VSA filesystem within the logical disk, represented
+	 * in bytes.
+	 * 
+	 * This method is synchronous and consacts the device for the latest status
+	 * if necessary.
+	 * 
+	 * `icsneo::nullopt` will be returned if the device does not respond in a
+	 * timely manner, or if the disk is disconnected/improperly configured.
+	 */
+	optional<uint64_t> getVSAOffsetInLogicalDisk();
+
 	/**
 	 * Retrieve the number of Ethernet (DoIP) Activation lines present
 	 * on this device.

include/icsneo/disk/fat.h

@@ -0,0 +1,22 @@
+#ifndef __FAT_H__
+#define __FAT_H__
+
+#ifdef __cplusplus
+
+#include "icsneo/platform/optional.h"
+#include <cstdint>
+#include <functional>
+
+namespace icsneo {
+
+namespace Disk {
+
+optional<uint64_t> FindVSAInFAT(std::function< optional<uint64_t>(uint64_t pos, uint8_t* into, uint64_t amount) > diskRead);
+
+} // namespace Disk
+
+} // namespace icsneo
+
+#endif // __cplusplus
+
+#endif // __FAT_H__