1 files changed, 71 insertions, 0 deletions
diff --git a/somebar/src/line_buffer.hpp b/somebar/src/line_buffer.hpp
new file mode 100644
index 0000000..a5497bf
--- /dev/null
+++ b/somebar/src/line_buffer.hpp
@@ -0,0 +1,71 @@
+// somebar - dwl bar
+// See LICENSE file for copyright and license details.
+
+#pragma once
+#include <array>
+#include <algorithm>
+#include <sys/types.h>
+
+// reads data from Reader, and passes complete lines to Consumer.
+template<size_t BufSize>
+class LineBuffer {
+	using Iterator = typename std::array<char, BufSize>::iterator;
+	std::array<char, BufSize> _buffer;
+	Iterator _bufferedTo;
+	Iterator _consumedTo;
+	bool _discardLine {false};
+public:
+	LineBuffer()
+		: _bufferedTo {_buffer.begin()}
+		, _consumedTo {_buffer.begin()}
+	{
+	}
+
+	template<typename Reader, typename Consumer>
+	ssize_t readLines(const Reader& reader, const Consumer& consumer)
+	{
+		while (true) {
+			auto bytesRead = reader(_bufferedTo, _buffer.end() - _bufferedTo);
+			if (bytesRead <= 0) {
+				return bytesRead;
+			}
+			_bufferedTo += bytesRead;
+			dispatchLines(consumer);
+			resetBuffer();
+		}
+	}
+private:
+	template<typename Consumer>
+	void dispatchLines(const Consumer& consumer)
+	{
+		while (true) {
+			auto separator = std::find(_consumedTo, _bufferedTo, '\n');
+			if (separator == _bufferedTo) {
+				break;
+			}
+			size_t lineLength = separator - _consumedTo;
+			if (!_discardLine) {
+				consumer(_consumedTo, lineLength);
+			}
+			_consumedTo = separator + 1;
+			_discardLine = false;
+		}
+	}
+
+	void resetBuffer()
+	{
+		size_t bytesRemaining = _bufferedTo - _consumedTo;
+		if (bytesRemaining == _buffer.size()) {
+			// line too long
+			_discardLine = true;
+			_consumedTo = _buffer.begin();
+			_bufferedTo = _buffer.begin();
+		} else {
+			// move the last partial message to the front of the buffer, so a full-sized
+			// message will fit
+			std::copy(_consumedTo, _bufferedTo, _buffer.begin());
+			_consumedTo = _buffer.begin();
+			_bufferedTo = _consumedTo + bytesRemaining;
+		}
+	}
+};