protobuf-codec/decode/reader.js

Minimal Protocol Buffers wire encoding/decoding

const assert = require('nanoassert')
const { decoders, tag } = require('./wire-types.js')

module.exports = function * reader (
  buf,
  byteOffset = 0,
  byteLength = buf.byteLength
) {
  let o = byteOffset
  const end = byteOffset + byteLength
  assert(end <= buf.byteLength)

  for (; o < end;) {
    const { wireType, fieldNumber } = tag(buf, o)
    const tagByteOffset = o
    const tagByteLength = tag.bytes
    o += tagByteLength

    const data = decoders[wireType](buf, o)
    const dataByteLength = decoders[wireType].bytes
    o += dataByteLength

    yield [fieldNumber, { tagByteOffset, tagByteLength, fieldNumber, wireType, dataByteLength, data }]
  }

  assert(o === end)
}