Device: Add disk read driver framework

Allow access to the device's logical disk.

At the moment, no drivers are implemented, so all devices have Access::None.

disk/diskreaddriver.cpp

@@ -0,0 +1,58 @@
+#include "icsneo/disk/diskreaddriver.h"
+#include <cstring>
+
+using namespace icsneo;
+
+optional<uint64_t> DiskReadDriver::readLogicalDisk(Communication& com, device_eventhandler_t report,
+	uint64_t pos, uint8_t* into, uint64_t amount, std::chrono::milliseconds timeout) {
+	optional<uint64_t> ret;
+
+	// Read into here if we can't read directly into the user buffer
+	// That would be the case either if we don't want some at the
+	// beginning or end of the block.
+	std::vector<uint8_t> alignedReadBuffer;
+
+	const uint32_t idealBlockSize = getBlockSizeBounds().second;
+	const uint64_t startBlock = pos / idealBlockSize;
+	const uint64_t posWithinFirstBlock = pos % idealBlockSize;
+	const uint64_t blocks = amount / idealBlockSize + (amount % idealBlockSize ? 1 : 0) + (posWithinFirstBlock ? 1 : 0);
+	uint64_t blocksProcessed = 0;
+
+	while(blocksProcessed < blocks && timeout >= std::chrono::milliseconds::zero()) {
+		const uint64_t currentBlock = startBlock + blocksProcessed;
+
+		const int intoOffset = std::min<int>((blocksProcessed * idealBlockSize) - posWithinFirstBlock, 0);
+		const auto posWithinCurrentBlock = (blocksProcessed ? 0 : posWithinFirstBlock);
+		auto curAmt = idealBlockSize - posWithinCurrentBlock;
+		const auto amountLeft = amount - *ret;
+		if(curAmt > amountLeft)
+			curAmt = amountLeft;
+
+		const bool useAlignedReadBuffer = (posWithinCurrentBlock != 0 || curAmt != idealBlockSize);
+		if(useAlignedReadBuffer && alignedReadBuffer.size() < idealBlockSize)
+			alignedReadBuffer.resize(idealBlockSize);
+
+		auto start = std::chrono::high_resolution_clock::now();
+		auto readAmount = readLogicalDiskAligned(com, report, currentBlock * idealBlockSize,
+			useAlignedReadBuffer ? alignedReadBuffer.data() : into + intoOffset, idealBlockSize, timeout);
+		timeout -= std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::high_resolution_clock::now() - start);
+
+		if(!readAmount.has_value() || *readAmount == 0) {
+			if(timeout < std::chrono::milliseconds::zero())
+				report(APIEvent::Type::Timeout, APIEvent::Severity::Error);
+			else
+				report(blocksProcessed ? APIEvent::Type::EOFReached : APIEvent::Type::ParameterOutOfRange, APIEvent::Severity::Error);
+			break;
+		}
+
+		if(useAlignedReadBuffer)
+			memcpy(into + intoOffset, alignedReadBuffer.data() + posWithinCurrentBlock, curAmt);
+
+		if(!ret)
+			ret.emplace();
+		*ret += *readAmount;
+		blocksProcessed++;
+	}
+
+	return ret;
+}

disk/nulldiskreaddriver.cpp

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+#include "icsneo/disk/nulldiskreaddriver.h"
+
+using namespace icsneo;
+
+optional<uint64_t> NullDiskReadDriver::readLogicalDisk(Communication& com, device_eventhandler_t report,
+	uint64_t pos, uint8_t* into, uint64_t amount, std::chrono::milliseconds timeout) {
+	report(APIEvent::Type::DiskNotSupported, APIEvent::Severity::Error);
+	return std::nullopt;
+}
+
+optional<uint64_t> NullDiskReadDriver::readLogicalDiskAligned(Communication& com, device_eventhandler_t report,
+	uint64_t pos, uint8_t* into, uint64_t amount, std::chrono::milliseconds timeout) {
+	report(APIEvent::Type::DiskNotSupported, APIEvent::Severity::Error);
+	return std::nullopt;
+}