Representation Codes

RP66 V1 defines 27 representation codes that specify how a value is encoded in the binary stream. The RC object exported by the library maps each mnemonic to its numeric code.

import { RC, RC_SIZE } from '@geoharkat/dlis-parser';

console.log(RC.FSINGL);   // 2
console.log(RC.SNORM);    // 13
console.log(RC_SIZE[RC.FDOUBL]); // 8  (bytes per value)

Complete table

Code	Mnemonic	Bytes	Description
1	`FSHORT`	2	RP66 proprietary 16-bit float (not IEEE half-float). Exponent in bits 14-11, mantissa in bits 10-0.
2	`FSINGL`	4	IEEE 754 single-precision float (most common scalar type).
3	`FSING1`	8	IEEE single + 4-byte validity/exponent field. Only the float is returned; the extra field is skipped.
4	`FSING2`	12	IEEE single + 8-byte lower/upper bounds. Only the float is returned.
5	`ISINGL`	4	IBM base-16 single-precision float.
6	`VSINGL`	4	VAX F-float (word-swapped byte pairs).
7	`FDOUBL`	8	IEEE 754 double-precision float (common for depth/time index channels).
8	`FDOUB1`	12	IEEE double + 4-byte exponent field.
9	`FDOUB2`	16	IEEE double + 8-byte bounds.
10	`CSINGL`	8	Complex single: real (4 B) + imaginary (4 B). Returned as `{ re, im }`.
11	`CDOUBL`	16	Complex double: real (8 B) + imaginary (8 B). Returned as `{ re, im }`.
12	`SSHORT`	1	Signed 8-bit integer.
13	`SNORM`	2	Signed 16-bit integer (big-endian). Used by waveform/array channels (VDL, sonic, FMI).
14	`SLONG`	4	Signed 32-bit integer (big-endian).
15	`USHORT`	1	Unsigned 8-bit integer. Used internally in EFLR templates to store representation codes.
16	`UNORM`	2	Unsigned 16-bit integer (big-endian).
17	`ULONG`	4	Unsigned 32-bit integer (big-endian).
18	`UVARI`	1–4	Variable-length unsigned integer. 1 byte if value < 128, 2 bytes if < 16384, otherwise 4 bytes.
19	`IDENT`	1+N	Short ASCII string: 1-byte length prefix + N bytes of text.
20	`ASCII`	4+N	Long ASCII string: 4-byte (ULONG) length prefix + N bytes.
21	`DTIME`	8	Date and time: year (1B) + month (1B) + day (1B) + hour (1B) + minute (1B) + second (1B) + milliseconds (2B BE). Year is offset from 1900. Parsed into a JavaScript `Date`.
22	`ORIGIN`	1–4	Origin reference. Encoded as UVARI.
23	`OBNAME`	variable	Object name triplet: UVARI origin + USHORT copy + IDENT name.
24	`OBJREF`	variable	Object reference: IDENT type + OBNAME name.
25	`ATTREF`	variable	Attribute reference: IDENT label + OBNAME name.
26	`STATUS`	1	Boolean status byte. Returned as JavaScript `boolean`.
27	`UNITS`	1+N	Unit expression. Same encoding as IDENT.

Variable-size codes

Codes with variable byte size (UVARI, IDENT, ASCII, OBNAME, OBJREF, ATTREF, UNITS) return 0 from RC_SIZE since their length is not known without reading the data.

import { RC, RC_SIZE } from '@geoharkat/dlis-parser';

RC_SIZE[RC.SNORM]  // 2
RC_SIZE[RC.FDOUBL] // 8
RC_SIZE[RC.IDENT]  // 0  (variable)
RC_SIZE[RC.UVARI]  // 0  (variable)

Checking a channel’s type

import { RC } from '@geoharkat/dlis-parser';

const ch = lf.getChannel('VDL');

if (ch.repcode === RC.SNORM) {
  // 16-bit signed waveform — stride = ch.dimension[0] samples per row
  console.log('VDL is a signed-16 waveform,', ch.dimension[0], 'samples/row');
}

if (ch.repcode === RC.FSINGL) {
  console.log('Scalar IEEE float channel');
}