fragments

util/include/rusefi/fragments.h

@@ -0,0 +1,31 @@
+/*
+ * FragmentEntry.h
+ *
+ *  Created on: Jan 5, 2022
+ * @author Andrey Belomutskiy, (c) 2012-2022
+ */
+
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+
+struct FragmentEntry {
+	template <typename TData>
+	FragmentEntry(const TData* data)
+		: data(reinterpret_cast<const uint8_t*>(data))
+		, size(sizeof(TData))
+	{
+	}
+
+	const uint8_t* const data;
+	const size_t size;
+};
+
+struct FragmentList {
+	const FragmentEntry* fragments;
+	const size_t count;
+};
+
+// copy `size` of fragmented outputs in to destination, skipping the first `skip` bytes
+void copyRange(uint8_t* destination, FragmentList src, size_t skip, size_t size);

util/src/fragments.cpp

@@ -0,0 +1,44 @@
+/*
+ * FragmentEntry.cpp
+ *
+ *  Created on: Jan 5, 2022
+ * @author Andrey Belomutskiy, (c) 2012-2022
+ */
+
+#include <rusefi/fragments.h>
+
+#include <rusefi/math.h>
+#include <cstring>
+
+void copyRange(uint8_t* destination, FragmentList src, size_t skip, size_t size) {
+	int fragmentIndex = 0;
+
+	// Find which fragment to start - skip any full fragments smaller than `skip` parameter
+	while (skip > src.fragments[fragmentIndex].size && fragmentIndex <= src.count) {
+		skip -= src.fragments[fragmentIndex].size;
+		fragmentIndex++;
+	}
+
+	int destinationIndex = 0;
+
+	while (size > 0) {
+		if (fragmentIndex >= src.count) {
+			// somehow we are past the end of fragments - fill with zeros
+			memset(destination + destinationIndex, 0, size);
+			return;
+		}
+
+		int copyNowSize = minI(size, src.fragments[fragmentIndex].size - skip);
+		const uint8_t* fromBase = src.fragments[fragmentIndex].data;
+		if (!fromBase) {
+			// we have no buffer for this fragment - fill with zeroes
+			memset(destination + destinationIndex, 0, copyNowSize);
+		} else {
+			memcpy(destination + destinationIndex, fromBase + skip, copyNowSize);
+		}
+		destinationIndex += copyNowSize;
+		skip = 0;
+		size -= copyNowSize;
+		fragmentIndex++;
+	}
+}

util/test/test_fragments.cpp

@@ -0,0 +1,88 @@
+#include <rusefi/fragments.h>
+
+struct obj1 {
+	const uint8_t x[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+};
+
+static_assert(sizeof(obj1) == 10);
+
+struct obj2 {
+	const uint8_t x[5] = { 11, 12, 13, 14, 15 };
+};
+
+static_assert(sizeof(obj2) == 5);
+
+obj1 buffer10;
+obj2 buffer5;
+
+static FragmentEntry fragmentBuffer[] = {
+		&buffer10,
+		&buffer5,
+		reinterpret_cast<obj2*>(0),	// null fragment for fun
+		&buffer10
+};
+
+static uint8_t buffer[120];
+static void resetBuffer() {
+	memset(buffer, 0xFF, sizeof(buffer));
+}
+
+TEST(outputs, fragments) {
+	static_assert(4 == efi::size(fragmentBuffer));
+
+	FragmentList fragments{ fragmentBuffer, efi::size(fragmentBuffer) };
+
+	resetBuffer();
+
+	{
+		// Check overlap between first and second fragments
+		uint8_t expected[] = {9, 10, 11, 12, 13};
+		copyRange(buffer, fragments, 8, 5);
+		EXPECT_TRUE( 0 == std::memcmp(buffer, expected, sizeof(expected)));
+	}
+
+	resetBuffer();
+
+	{
+		// Check partial of only second fragment
+		uint8_t expected[] = {13, 14, 15};
+		copyRange(buffer, fragments, 12, 3);
+		EXPECT_TRUE( 0 == std::memcmp(buffer, expected, sizeof(expected)));
+	}
+
+	resetBuffer();
+
+	{
+		// Check overlap between second fragment and null fragment
+		uint8_t expected[] = {15, 0, 0};
+		copyRange(buffer, fragments, 14, 3);
+		EXPECT_TRUE( 0 == std::memcmp(buffer, expected, sizeof(expected)));
+	}
+
+	resetBuffer();
+
+	{
+		// Check overlap between null fragment and 4th fragment
+		uint8_t expected[] = {0, 1, 2};
+		copyRange(buffer, fragments, 19, 3);
+		EXPECT_TRUE( 0 == std::memcmp(buffer, expected, sizeof(expected)));
+	}
+
+	resetBuffer();
+
+	{
+		// Check overlap between last fragment and off-end of buffer (off-buffer should give 0s)
+		uint8_t expected[] = {9, 10, 0, 0};
+		copyRange(buffer, fragments, 28, 4);
+		EXPECT_TRUE( 0 == std::memcmp(buffer, expected, sizeof(expected)));
+	}
+
+	resetBuffer();
+
+	{
+		// Check way off the end of the buffer
+		uint8_t expected[] = {0, 0, 0};
+		copyRange(buffer, fragments, 1000, 3);
+		EXPECT_TRUE( 0 == std::memcmp(buffer, expected, sizeof(expected)));
+	}
+}

util/util.mk

@@ -3,9 +3,11 @@ RUSEFI_LIB_INC += $(RUSEFI_LIB)/util/include
 RUSEFI_LIB_CPP += \
 	$(RUSEFI_LIB)/util/src/util_dummy.cpp \
 	$(RUSEFI_LIB)/util/src/crc.cpp \
+	$(RUSEFI_LIB)/util/src/fragments.cpp \
 	$(RUSEFI_LIB)/util/src/math.cpp \
 
 RUSEFI_LIB_CPP_TEST += \
 	$(RUSEFI_LIB)/util/test/test_arrays.cpp \
+	$(RUSEFI_LIB)/util/test/test_framgents.cpp \
 	$(RUSEFI_LIB)/util/test/test_math.cpp \