refactor: optional-chain size-cap options instead of a {} default

Drops the options = {} default on the streaming decode/encode functions and
guards each cap check with options?.x. Avoids allocating a throwaway empty
object per readCid/readBlockHead call when no caps are passed, and the param
type now matches the optional [options] annotation. No behavior change.

Author: tabcat

src/decoder.js

@@ -26,12 +26,12 @@ import { CarV1HeaderOrV2Pragma } from './header-validator.js'
  * @param {CarCodecOptions} [options]
  * @returns {Promise<CarHeader|CarV2Header>}
  */
-export async function readHeader (reader, strictVersion, options = {}) {
+export async function readHeader (reader, strictVersion, options) {
   const length = decodeVarint(await reader.upTo(8), reader)
   if (length === 0) {
     throw new Error('Invalid CAR header (zero length)')
   }
-  if (options.maxHeaderLength != null && length > options.maxHeaderLength) {
+  if (options?.maxHeaderLength != null && length > options.maxHeaderLength) {
     throw new RangeError(`CAR header of length ${length} exceeds maxHeaderLength of ${options.maxHeaderLength}`)
   }
   const header = await reader.exactly(length, true)
@@ -64,7 +64,7 @@ export async function readHeader (reader, strictVersion, options = {}) {
  * @param {CarCodecOptions} [options]
  * @returns {Promise<CID>}
  */
-async function readCid (reader, options = {}) {
+async function readCid (reader, options) {
   const cidStart = reader.pos
   const first = await reader.exactly(2, false)
   if (first[0] === CIDV0_BYTES.SHA2_256 && first[1] === CIDV0_BYTES.LENGTH) {
@@ -82,7 +82,7 @@ async function readCid (reader, options = {}) {
   const mhLength = getMultihashLength(await reader.upTo(8))
   // full CID = version + codec varints (already consumed) + multihash
   const cidLength = Number(reader.pos - cidStart) + mhLength
-  if (options.maxCidLength != null && cidLength > options.maxCidLength) {
+  if (options?.maxCidLength != null && cidLength > options.maxCidLength) {
     throw new RangeError(`CID of length ${cidLength} exceeds maxCidLength of ${options.maxCidLength}`)
   }
   const bytes = await reader.exactly(mhLength, true)
@@ -101,7 +101,7 @@ async function readCid (reader, options = {}) {
  * @param {CarCodecOptions} [options]
  * @returns {Promise<BlockHeader>}
  */
-export async function readBlockHead (reader, options = {}) {
+export async function readBlockHead (reader, options) {
   // length includes a CID + Binary, where CID has a variable length
   // we have to deal with
   const start = reader.pos
@@ -112,7 +112,7 @@ export async function readBlockHead (reader, options = {}) {
   length += (reader.pos - start)
   const cid = await readCid(reader, options)
   const blockLength = length - Number(reader.pos - start) // subtract CID length
-  if (options.maxBlockLength != null && blockLength > options.maxBlockLength) {
+  if (options?.maxBlockLength != null && blockLength > options.maxBlockLength) {
     throw new RangeError(`CAR block of length ${blockLength} exceeds maxBlockLength of ${options.maxBlockLength}`)
   }
 
@@ -124,7 +124,7 @@ export async function readBlockHead (reader, options = {}) {
  * @param {CarCodecOptions} [options]
  * @returns {Promise<Block>}
  */
-async function readBlock (reader, options = {}) {
+async function readBlock (reader, options) {
   const { cid, blockLength } = await readBlockHead(reader, options)
   const bytes = await reader.exactly(blockLength, true)
   return { bytes, cid }
@@ -135,7 +135,7 @@ async function readBlock (reader, options = {}) {
  * @param {CarCodecOptions} [options]
  * @returns {Promise<BlockIndex>}
  */
-async function readBlockIndex (reader, options = {}) {
+async function readBlockIndex (reader, options) {
   const offset = reader.pos
   const { cid, length, blockLength } = await readBlockHead(reader, options)
   const index = { cid, length, blockLength, offset, blockOffset: reader.pos }
@@ -153,7 +153,7 @@ async function readBlockIndex (reader, options = {}) {
  * @param {CarCodecOptions} [options]
  * @returns {CarDecoder}
  */
-export function createDecoder (reader, options = {}) {
+export function createDecoder (reader, options) {
   const headerPromise = (async () => {
     const header = await readHeader(reader, undefined, options)
     if (header.version === 2) {

src/encoder.js

@@ -18,9 +18,9 @@ const CAR_V1_VERSION = 1
  * @param {CarCodecOptions} [options]
  * @returns {Uint8Array}
  */
-export function createHeader (roots, options = {}) {
+export function createHeader (roots, options) {
   const headerBytes = dagCborEncode({ version: CAR_V1_VERSION, roots })
-  if (options.maxHeaderLength != null && headerBytes.length > options.maxHeaderLength) {
+  if (options?.maxHeaderLength != null && headerBytes.length > options.maxHeaderLength) {
     throw new RangeError(`CAR header of length ${headerBytes.length} exceeds maxHeaderLength of ${options.maxHeaderLength}`)
   }
   const varintBytes = varint.encode(headerBytes.length)
@@ -35,7 +35,7 @@ export function createHeader (roots, options = {}) {
  * @param {CarCodecOptions} [options]
  * @returns {CarEncoder}
  */
-function createEncoder (writer, options = {}) {
+function createEncoder (writer, options) {
   // none of this is wrapped in a mutex, that needs to happen above this to
   // avoid overwrites
 
@@ -55,10 +55,10 @@ function createEncoder (writer, options = {}) {
      */
     async writeBlock (block) {
       const { cid, bytes } = block
-      if (cid.version === 1 && options.maxCidLength != null && cid.bytes.length > options.maxCidLength) {
+      if (cid.version === 1 && options?.maxCidLength != null && cid.bytes.length > options.maxCidLength) {
         throw new RangeError(`CID of length ${cid.bytes.length} exceeds maxCidLength of ${options.maxCidLength}`)
       }
-      if (options.maxBlockLength != null && bytes.length > options.maxBlockLength) {
+      if (options?.maxBlockLength != null && bytes.length > options.maxBlockLength) {
         throw new RangeError(`CAR block of length ${bytes.length} exceeds maxBlockLength of ${options.maxBlockLength}`)
       }
       await writer.write(new Uint8Array(varint.encode(cid.bytes.length + bytes.length)))