[Performous-commit] Lasse Kärkkäinen : Some MIDI writer support

[Lasse Kärkkäi. <tr...@us...>]

Author: Lasse Kärkkäinen <tronic+ndrm at trn.iki.fi>
Date:   Thu Feb 24 17:34:41 2011 +0100

Some MIDI writer support

---

 midifile.cc |   14 +++++++-------
 midifile.hh |   46 ++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 49 insertions(+), 11 deletions(-)

diff --git a/midifile.cc b/midifile.cc
index d359dc5..b4f7102 100644
--- a/midifile.cc
+++ b/midifile.cc
@@ -33,16 +33,16 @@ bool Reader::nextTrack() {
 void Reader::parseRiff(char const* name) {
 	if (!std::equal(name, name + 4, m_pos)) throw std::runtime_error("MIDI header " + std::string(name) + " not found, instead found " + std::string(m_pos, m_pos + 4));
 	m_pos += 4;
-	unsigned size = read<uint32_t>();
+	unsigned size = read<4>();
 	if (m_fileEnd - m_pos < size) throw std::runtime_error("Unexpected end of file within MIDI header " + std::string(name));
 	m_riffEnd = m_pos + size;
 }
 
 void Reader::parseMThd() {
 	parseRiff("MThd");
-	unsigned fmt = read<uint16_t>();
-	m_tracks = read<uint16_t>();
-	m_division = read<uint16_t>();
+	unsigned fmt = read<2>();
+	m_tracks = read<2>();
+	m_division = read<2>();
 	if (fmt == 2) throw std::runtime_error("MIDI format 2 not supported.");
 	if (fmt == 0 && m_tracks == 1) return;  // Old single track format
 	if (fmt == 1 && m_tracks > 1) return;  // New format (timing info on first track)
@@ -61,7 +61,7 @@ bool Reader::parseEvent(Event& ev) {
 	// Event header
 	{
 		ev.timecode = read_varlen();
-		unsigned event = read<uint8_t>();
+		unsigned event = read<1>();
 		if (event & 0x80) {
 			if (event < 0xF0) m_runningStatus = event;  // Stored for regular (0x00..0xEF)
 			else if (event < 0xF8) m_runningStatus = 0;  // Cleared for System Common Category (0xF0..0xF7)
@@ -74,7 +74,7 @@ bool Reader::parseEvent(Event& ev) {
 		ev.type = static_cast<Event::Type>(event & 0xF0);
 		ev.channel = event & 0x0F;
 	}
-	if (ev.type != Event::SPECIAL || ev.channel >= 8) ev.arg1 = read<uint8_t>();  // Everything except System Common takes one argument
+	if (ev.type != Event::SPECIAL || ev.channel >= 8) ev.arg1 = read<1>();  // Everything except System Common takes one argument
 	unsigned tmp;
 	switch (ev.type) {
 	case Event::NOTE_ON:
@@ -82,7 +82,7 @@ bool Reader::parseEvent(Event& ev) {
 	case Event::NOTE_AFTERTOUCH:
 	case Event::CONTROLLER:
 	case Event::PITCH_BEND:
-		ev.arg2 = read<uint8_t>();
+		ev.arg2 = read<1>();
 		break;
 	case Event::PROGRAM_CHANGE:
 	case Event::CHANNEL_AFTERTOUCH:
diff --git a/midifile.hh b/midifile.hh
index 3d90431..6dd7718 100644
--- a/midifile.hh
+++ b/midifile.hh
@@ -66,9 +66,9 @@ namespace mid {
 		void parseMThd();
 		void parseMTrk();
 		void parseRiff(char const* name);
-		template <typename T> T read() {
-			T value = 0;
-			for (int i = sizeof(T) - 1; i >= 0; --i) value |= *m_pos++ << (8 * i);
+		template <unsigned N> unsigned read() {
+			unsigned value = 0;
+			for (unsigned i = N - 1; i < N; --i) value |= *m_pos++ << (8 * i);
 			return value;
 		}
 
@@ -91,6 +91,44 @@ namespace mid {
 		unsigned m_division;
 		unsigned m_runningStatus;
 	};
-	
+
+	class Writer {
+	public:
+	private:
+		void writeMThd(unsigned tracks, unsigned division) {
+			beginRiff("MThd");
+			write<2>(1); // fmt	1 (multitrack)
+			write<2>(tracks);
+			write<2>(division);
+			endRiff();
+		}
+		void writeMTrk() {
+			beginRiff("MTrk");
+		}
+		void beginRiff(char const* name) {
+			m_riffBegin = m_data.size();
+			m_data.resize(m_riffBegin + 8);  // Add space for header
+			std::copy(name, name + 4, m_data.begin() + m_riffBegin);  // Set RIFF name
+		}
+		void endRiff() {
+			unsigned size = m_data.size() - 8 - m_riffBegin;
+			m_data[m_riffBegin + 4] = size >> 24;
+			m_data[m_riffBegin + 5] = size >> 16;
+			m_data[m_riffBegin + 6] = size >> 8;
+			m_data[m_riffBegin + 7] = size;
+		}
+		template <unsigned N> void write(unsigned value) {
+			for (unsigned i = N - 1; i < N; --i) m_data.push_back(value >> (8 * i));
+		}
+		void write_varlen(unsigned value) {
+			if (value >= 0x10000000U) throw std::logic_error("Value cannot be MIDI varlen encoded");
+			if (value >= 0x200000U) m_data.push_back(0x80 | (value >> 21));
+			if (value >= 0x4000U) m_data.push_back(0x80 | (value >> 14));
+			if (value >= 0x80U) m_data.push_back(0x80 | (value >> 7));
+			m_data.push_back(value & 0x7F);
+		}
+		std::vector<value_type> m_data;
+		unsigned m_riffBegin;
+	};
 }