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

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);
+}