@foxglove/omgidl-serialization

@foxglove/omgidl-serialization

OMG IDL message serialization, for reading and writing CDR and XCDR2 messages based on .idl schema

MessageReader

Message reader deserializes CDR, XCDR1 and XCDR2 messages into plain objects. The messages are fully deserialized.

import { parseIDL } from "@foxglove/omgidl-parser";
import { MessageReader } from "@foxglove/omgidl-serialization";

const msgDef = `
  module geometry_msgs {
    struct PointStamped {
      Header header;
      Point point;
    };
  };
  struct Header {
    uint32 seq;
    Time stamp;
    string frame_id;
  };
  struct Time {
    uint32 sec;
    uint64 nsec;
  };
  struct Point {
    float x;
    float y;
    float z;
  };
`;

const messageDefinition = parseIDL(msgDef);
const reader = new MessageReader("geometry_msgs::PointStamped", messageDefinition);

// deserialize a buffer into an object
const message = reader.readMessage([0x00, 0x01, ...]);

// access message fields
message.header.stamp;

MessageWriter

Convert an object, array, or primitive value into binary data using CDR message serialization. (XCDR1 and XCDR2 writing is not yet supported.)

import { MessageWriter } from "@foxglove/omgidl-serialization";

const msgDef = `
  module geometry_msgs {
    struct PointStamped {
      Header header;
      Point point;
    };
  };
  struct Header {
    uint32 seq;
    Time stamp;
    string frame_id;
  };
  struct Time {
    uint32 sec;
    uint64 nsec;
  };
  struct Point {
    float x;
    float y;
    float z;
  };
`;

const messageDefinition = parseIDL(msgDef);

const writer = new MessageWriter("geometry_msgs::PointStamped", messageDefinition, cdrOptions);

// serialize the passed in object to a Uint8Array as a PointStamped message
const uint8Array = writer.writeMessage({
  header: {
    stamp: { sec: 0, nsec: 0 },
    frame_id: ""
  },
  x: 1,
  y: 0,
  z: 0
});

Known Limitations

MessageReader does not support:

• arrays of variable-size arrays. parseIDL will error if this is detected in the schema to prevent incorrect deserialization.

MessageWriter does not support:

• does not support writing XCDR1 (PL_CDR) or XCDR2 (PL_CDR2, DELIMITED_CDR2) encoded messages utilizing extensible types. However we can deserialize these encapsulation kinds in MessageReader.

Both do not support:

• wchar and wstring - These are written and read using custom implementations that are specific to someone's environment. If encountered during deserialization, they will throw an error saying that they are unsupported.

Also see the current IDL parser schema limitations here