Add waveform.proto under ni/protobuf/types (#40)

* Add waveform.proto under ni/protobuf/types

* Define a precisiontime proto file and use the new messages in the waveform.

* Fix syntax error.

* Address review comments.

* Delete the unused precision_duration.proto and README.md files. Place the DoubleWaveform datatype at the top of the waveform.proto file.

* Address Brad's comments.

* Rename DoubleWaveform -> DoubleAnalogWaveform

ni/protobuf/types/precision_timestamp.proto

@@ -0,0 +1,33 @@
+//---------------------------------------------------------------------
+//---------------------------------------------------------------------
+syntax = "proto3";
+
+//---------------------------------------------------------------------
+//---------------------------------------------------------------------
+package ni.protobuf.types;
+
+//---------------------------------------------------------------------
+//---------------------------------------------------------------------
+option csharp_namespace = "NationalInstruments.Protobuf.Types";
+option go_package = "types";
+option java_multiple_files = true;
+option java_outer_classname = "PrecisionTimeProto";
+option java_package = "com.ni.protobuf.types";
+option objc_class_prefix = "NIPT";
+option php_namespace = "NI\\PROTOBUF\\TYPES";
+option ruby_package = "NI::Protobuf::Types";
+
+// A PrecisionTimestamp represents a point in time expressed in NI Binary Time Format (NI-BTF).
+// https://www.ni.com/docs/en-US/bundle/labwindows-cvi/page/cvi/libref/ni-btf.htm
+// NI-BTF stores time values in Coordinated Universal Time (UTC) format.
+// A PrecisionTimestamp is encoded as a count of seconds and fractions of seconds at
+// 2^-64 resolution. The count is relative to an epoch of January 1, 1904.
+message PrecisionTimestamp
+{
+  // Represents the number of seconds since the epoch
+  // 1904-01-01T00:00:00Z.
+  int64 seconds = 1;
+
+  // Non-negative fractions of a second at 2^-64 resolution.
+  uint64 fractional_seconds = 2;
+}

ni/protobuf/types/waveform.proto

@@ -0,0 +1,64 @@
+//---------------------------------------------------------------------
+//---------------------------------------------------------------------
+syntax = "proto3";
+
+//---------------------------------------------------------------------
+//---------------------------------------------------------------------
+package ni.protobuf.types;
+
+import "ni/protobuf/types/precision_timestamp.proto";
+
+//---------------------------------------------------------------------
+//---------------------------------------------------------------------
+option csharp_namespace = "NationalInstruments.Protobuf.Types";
+option go_package = "types";
+option java_multiple_files = true;
+option java_outer_classname = "WaveformProto";
+option java_package = "com.ni.protobuf.types";
+option objc_class_prefix = "NIPT";
+option php_namespace = "NI\\PROTOBUF\\TYPES";
+option ruby_package = "NI::Protobuf::Types";
+
+// DoubleAnalogWaveform datatype.
+message DoubleAnalogWaveform
+{
+  // The trigger time of the waveform.
+  PrecisionTimestamp t0 = 1;
+
+  // The time interval in seconds between data points in the waveform.
+  double dt = 2;
+
+  // The data values of the waveform.
+  repeated double y_data = 3;
+
+  // The names and values of all waveform attributes.
+  // A waveform attribute is metadata attached to a waveform.
+  // It is represented in this message as a map associating the name of the attribute with the value described by WaveformAttributeValue.
+  // The NI-DAQmx driver sets the following string attributes:
+  // NI_ChannelName: the name of the virtual channel producing the waveform.
+  // NI_LineNames: the name of the digital line in the waveform.
+  // NI_UnitDescription: the units of measure for the waveform.
+  // NI_dBReference: the reference value to use when converting measurement levels to decibel.
+  // For additional information on waveform attributes, please visit https://www.ni.com/docs/en-US/bundle/labview-api-ref/page/functions/get-waveform-attribute.html
+  map<string, WaveformAttributeValue> attributes = 4;
+}
+
+// Waveform Attribute Value
+message WaveformAttributeValue
+{
+  // The kind of attribute value.
+  oneof attribute
+  {
+    // Represents a bool attribute.
+    bool bool_value = 1;
+
+    // Represents an integer attribute.
+    int32 integer_value = 2;
+
+    // Represents a double attribute.
+    double double_value = 3;
+
+    // Represents a string attribute.
+    string string_value = 4;
+  }
+}