Add CircularBufferBlock

WIP: only writes

Author: danngreen

tests/circular_buffer_block_tests.cc

@@ -0,0 +1,35 @@
+#include "doctest.h"
+
+#include "util/circular_buffer_block.hh"
+
+TEST_CASE("Basic usage") {
+
+	CircularBufferBlock<char, 8> buf;
+
+	std::array<char, 6> a{1, 2, 3, 4, 5, 6};
+
+	buf.write(a, 0);
+	CHECK(buf.data[0] == a[0]);
+	CHECK(buf.data[1] == a[1]);
+	CHECK(buf.data[2] == a[2]);
+	CHECK(buf.data[3] == a[3]);
+	CHECK(buf.data[4] == a[4]);
+	CHECK(buf.data[5] == a[5]);
+
+	std::array<char, 6> b{7, 8, 9, 10, 11, 12};
+	buf.write(b, 6);
+	CHECK(buf.data[6] == b[0]);
+	CHECK(buf.data[7] == b[1]);
+	CHECK(buf.data[0] == b[2]);
+	CHECK(buf.data[1] == b[3]);
+	CHECK(buf.data[2] == b[4]);
+	CHECK(buf.data[3] == b[5]);
+
+	std::array<char, 1> c{99};
+	buf.write(c, 8);
+	CHECK(buf.data[0] == 99);
+
+	std::array<char, 1> d{88};
+	buf.write(d, 7);
+	CHECK(buf.data[7] == 88);
+}

util/circular_buffer_block.hh

@@ -0,0 +1,31 @@
+#pragma once
+#include "util/math.hh"
+#include <cstdint>
+#include <cstdio>
+#include <cstring>
+#include <span>
+
+template<typename T, size_t SIZE>
+struct CircularBufferBlock {
+	static_assert(MathTools::is_power_of_2(SIZE));
+	static constexpr unsigned SIZEMASK = (SIZE - 1);
+
+	std::array<T, SIZE> data;
+
+	void write(std::span<const T> block, unsigned start_pos) {
+		unsigned offset = start_pos & SIZEMASK;
+		auto begin = data.begin() + offset;
+
+		if (offset + block.size() <= size()) {
+			std::memcpy(&*begin, block.data(), block.size());
+		} else {
+			int space_avail = size() - offset;
+			std::memcpy(&*begin, block.data(), space_avail);
+			std::memcpy(data.data(), block.data() + space_avail, block.size() - space_avail);
+		}
+	}
+
+	constexpr size_t size() {
+		return data.size();
+	}
+};