OMG IDL schema parser

OMG IDL parser to flattened message definitions for (de)serialization

This package provides functions to parse raw .idl schemas into resolved, flattened message definitions.

Output definitions can be passed to serializers along with a specified root schema name string in @lichtblick/omgidl-serialization to read and write CDR, XCDR1 and XCDR2 messages.

Example

const schemaString = `
// Generated by https://github.com/foxglove/schemas

module foxglove {
// A vector in 3D space that represents a direction only
struct Vector3 {
  double x;
  double y;
  double z;
};
};

module foxglove {
struct Quaternion {
  double x;
  double y;
  double z;
  @default(1.0)
  double w;
};
};

module foxglove {
// A position and orientation for an object or reference frame in 3D space
struct Pose {
  // Point denoting position in 3D space
  Vector3 position;
  // Quaternion denoting orientation in 3D space
  Quaternion orientation;
};
};
`;

const definitions = parseIDL(schemaString);

definitions results in:

[
  {
    name: "foxglove::Vector3",
    aggregatedKind: "struct",
    definitions: [
      {
        name: "x",
        isComplex: false,
        type: "float64",
      },
      {
        name: "y",
        isComplex: false,
        type: "float64",
      },
      {
        name: "z",
        isComplex: false,
        type: "float64",
      },
    ],
  },
  {
    name: "foxglove::Quaternion",
    aggregatedKind: "struct",
    definitions: [
      {
        name: "x",
        isComplex: false,
        type: "float64",
      },
      {
        name: "y",
        isComplex: false,
        type: "float64",
      },
      {
        name: "z",
        isComplex: false,
        type: "float64",
      },
      {
        name: "w",
        annotations: {
          default: {
            name: "default",
            type: "const-param",
            value: 1,
          },
        },
        defaultValue: 1,
        isComplex: false,
        type: "float64",
      },
    ],
  },
  {
    name: "foxglove::Pose",
    aggregatedKind: "struct",
    definitions: [
      {
        isComplex: true,
        name: "position",
        type: "foxglove::Vector3",
      },
      {
        isComplex: true,
        name: "orientation",
        type: "foxglove::Quaternion",
      },
    ],
  },
]

API

parseIDL(schema: string) - parses raw .idl schema string to resolved, flattened definitions.

TypeScript types for the output definitions are also available.

OMG IDL Subset Support

NOTE: numbers like 7.4.1 refer to sections of the OMG IDL specification.

• Generally supported features

  • 7.4.1 Building Block Core Data Types (with exceptions below)
  • support for extended numeric types uint8, int8 ... uint64, int64
    • Note 7.4.13 Building Block Extended Data-Types is not fully supported
  • Literals (with some hexadecimal, character and wide-type exceptions)
  • Blanks, horizontal and vertical tabs, newlines, form feeds, and comments (collective, "white space") as described below are ignored except as they serve to separate tokens
  • Parse generic annotations (only defaultValue is read in to AST)
  • unions and cases
  • enumerator overrides with @value annotation

• Unsupported features

  • native declarations
  • forward declarations
  • Constant expressions
  • unary operators
  • default value annotation type checking
  • identifiers prefixed with :: scope
  • 7.2.6.1 - Octal and hexadecimal integers are not supported (014 and 0xC)
  • 7.2.6.2.1 wide character and wide string has limited support
    • can be read in to schema but only considered uint8
    • wide character and string literals are not supported (L'X')
  • 7.2.6.3 - wide string literals are not supported
  • 7.2.3.1 - we do not check collision explicitly and we use case-sensitive identifiers whereas IDL requires identifiers to be case insensitive.
  • 7.4.2-7.4.16 extended IDL building blocks not supported
  • Composing variable-sized array typedefs with other array typedefs or struct member nodes.
  • const Color color = RED; not supported. However const Color color = Color::RED; is supported.

• Unsupported reference and type resolution features

  • numeric type checking for constant usage
  • we do not enforce type-based value ranges on constants in schema