jspurefix/src/buffer/ascii/ascii-parser.ts

pure node js fix engine

import { FixDefinitions } from '../../dictionary/definition'
import { Ascii } from '../ascii'
import { AsciiView } from './ascii-view'
import { AsciiSegmentParser } from './ascii-segment-parser'
import { AsciiParserState, ParseState } from './ascii-parser-state'
import { Structure } from '../structure'
import { Tags } from '../tags'
import { MsgParser } from '../msg-parser'
import { MsgView } from '../msg-view'
import { Readable } from 'stream'
import { ElasticBuffer } from '../elastic-buffer'
import { SegmentDescription, SegmentType } from '../segment-description'

export class AsciiParser extends MsgParser {
  private static nextId: number = 0
  public readonly id: number
  public readonly state: AsciiParserState
  private readonly receivingBuffer: ElasticBuffer
  private readonly segmentParser: AsciiSegmentParser

  // allocate enough in receive buffer so buffer does not constant resize back after large messages
  // want to keep one slice of memory and constantly reuse it

  constructor (public readonly definitions: FixDefinitions,
               public readonly readStream: Readable,
               public readonly delimiter: number,
               public readonly writeDelimiter: number = delimiter,
               public readonly maxMessageLen: number = 160 * 1024) {
    super()
    this.id = AsciiParser.nextId++
    this.segmentParser = new AsciiSegmentParser(definitions)
    this.receivingBuffer = new ElasticBuffer(maxMessageLen)
    this.state = new AsciiParserState(this.receivingBuffer)
    this.state.locations = new Tags(definitions, maxMessageLen / 10)
    this.state.beginMessage()
    this.subscribe()
  }

  private subscribe (): void {
    const inst: AsciiParser = this
    const Writable = require('stream').Writable
    const stream = this.readStream

    const receiver = new Writable({
      write: (data: Buffer, _: any, done: Function) => {
        try {
          inst.parse(data, data.length)
          done()
        } catch (e) {
          done(e)
        }
      }
    })
    receiver.on('error', (e: Error) => {
      this.emit('error', e)
    })

    // receive from say a socket or file and pipe to parser which discovers messages
    stream.pipe(receiver).on('finish', () => {
      this.emit('done')
    })
    stream.on('error', (e) => {
      this.emit('error', e)
    })
    stream.on('end', () => {
      this.emit('end')
    })
  }

  private msg (ptr: number): void {
    const receivingBuffer: ElasticBuffer = this.receivingBuffer
    const state = this.state
    if (this.listeners('decoded')) {
      this.emit('decoded', state.msgType, receivingBuffer, ptr)
    }
    this.emit('msg', state.msgType, this.getView(ptr))
    state.beginMessage()
  }

  private parse (readBuffer: Buffer, end: number): void {
    const state = this.state
    const eq: number = Ascii.Eq
    const zero: number = Ascii.Zero
    const nine: number = Ascii.Nine
    const delimiter: number = this.delimiter
    const writeDelimiter: number = this.writeDelimiter
    const receivingBuffer: ElasticBuffer = this.receivingBuffer
    const switchDelimiter = writeDelimiter !== delimiter
    let readPtr: number = 0

    while (readPtr < end) {
      let charAtPos: number = readBuffer[readPtr]

      const writePtr = receivingBuffer.saveChar(charAtPos) - 1
      switch (state.parseState) {

        case ParseState.MsgComplete: {
          this.msg(writePtr)
          continue
        }

        case ParseState.BeginField: {
          const atDigit: boolean = charAtPos >= zero && charAtPos <= nine
          if (atDigit) {
            state.beginTag(writePtr)
          }
          break
        }

        case ParseState.ParsingTag: {
          const isEquals: boolean = charAtPos === eq
          if (isEquals) {
            state.endTag(writePtr)
          }
          break
        }

        case ParseState.ParsingRawData: {
          // keep skipping until length read, regardless of delimiter or not
          if (state.incRaw()) {
            // having consumed the raw field expecting delimiter
            if (charAtPos === delimiter) {
              if (switchDelimiter) {
                receivingBuffer.switchChar(writeDelimiter)
              }
              state.store()
            } else {
              throw new Error(`delimiter (${delimiter}) expected at position ${readPtr} when value is ${charAtPos}`)
            }
          }
          break
        }

        case ParseState.ParsingRawDataLength:
        case ParseState.ParsingValue: {
          if (charAtPos === delimiter) {
            if (switchDelimiter) {
              receivingBuffer.switchChar(writeDelimiter)
            }
            state.store()
          }
          break
        }

        default: {
          throw new Error(`fix parser in unknown state ${state}`)
        }
      }
      readPtr++
    }

    switch (state.parseState) {
      case ParseState.MsgComplete: {
        this.msg(receivingBuffer.getPos())
        break
      }
    }
  }

  private getView (ptr: number): MsgView {
    const state = this.state
    const locations = state.locations
    const source = this.receivingBuffer
    const delimiter = this.delimiter
    const replace = this.writeDelimiter
    if (state.message) {
      const structure: Structure = this.segmentParser.parse(state.msgType, locations,
        locations.nextTagPos - 1)
      return new AsciiView(structure.msg(),
        source,
        structure,
        ptr,
        delimiter,
        replace)
    }

    const structure = new Structure(locations, [])
    const segment = new SegmentDescription('unknown', locations.tagPos[0].tag, null, 0, 1, SegmentType.Unknown)
    segment.endPosition = locations.nextTagPos - 1
    return new AsciiView(segment, source, structure, ptr, delimiter, replace)
  }
}