pcapGlobalHeader - default - @binstruct/pcap documentation

function pcapGlobalHeader



pcapGlobalHeader(endianness?: PcapEndianness): Coder<PcapGlobalHeader>

Creates a coder for the pcap global header in the requested byte order.

Examples

Encode and decode a little-endian global header

import { assertEquals } from "@std/assert";
import {
  pcapGlobalHeader,
  PCAP_MAGIC_MICROS,
  LINKTYPE,
} from "@binstruct/pcap";

const header = pcapGlobalHeader("le");
const value = {
  magic: PCAP_MAGIC_MICROS,
  versionMajor: 2,
  versionMinor: 4,
  thisZone: 0,
  sigFigs: 0,
  snapLen: 65535,
  network: LINKTYPE.ETHERNET,
};

const buffer = new Uint8Array(24);
const written = header.encode(value, buffer);
const [decoded, read] = header.decode(buffer);

assertEquals(written, 24);
assertEquals(read, 24);
assertEquals(decoded, value);

Big-endian header round trip

import { assertEquals } from "@std/assert";
import { pcapGlobalHeader, PCAP_MAGIC_MICROS } from "@binstruct/pcap";

const header = pcapGlobalHeader("be");
const value = {
  magic: PCAP_MAGIC_MICROS,
  versionMajor: 2,
  versionMinor: 4,
  thisZone: 0,
  sigFigs: 0,
  snapLen: 1500,
  network: 1,
};

const buffer = new Uint8Array(24);
const written = header.encode(value, buffer);
const [decoded] = header.decode(buffer);

assertEquals(written, 24);
assertEquals(decoded.magic, PCAP_MAGIC_MICROS);
assertEquals(decoded.snapLen, 1500);

Omitting the argument round-trips using the default byte order

import { assertEquals } from "@std/assert";
import {
  detectPcapMagic,
  LINKTYPE,
  PCAP_MAGIC_MICROS,
  pcapGlobalHeader,
} from "@binstruct/pcap";

const header = pcapGlobalHeader();
const value = {
  magic: PCAP_MAGIC_MICROS,
  versionMajor: 2,
  versionMinor: 4,
  thisZone: 0,
  sigFigs: 0,
  snapLen: 65535,
  network: LINKTYPE.ETHERNET,
};

const buffer = new Uint8Array(24);
const written = header.encode(value, buffer);
const [decoded, read] = header.decode(buffer);

assertEquals(written, 24);
assertEquals(read, 24);
assertEquals(decoded, value);
assertEquals(detectPcapMagic(buffer), { endianness: "le", nanos: false });

Parameters

optional



endianness: PcapEndianness = PCAP_DEFAULT_ENDIANNESS

Byte order used for the multi-byte fields. Pass "le" or "be" to match the file you are reading or producing. Defaults to PCAP_DEFAULT_ENDIANNESS. This coder is fixed to one byte order — to decode a header of unknown endianness, probe it with detectPcapMagic first, or use pcapFile, which does that for you.

Return Type

Coder<PcapGlobalHeader>

A coder that encodes/decodes a PcapGlobalHeader.