Function feed

packages/effect/src/unstable/encoding/Sse.ts:280–354

(chunk: string)

  }

  function feed(chunk: string): SseError | undefined {
    buffer = buffer ? buffer + chunk : chunk

    // Strip any UTF-8 byte order mark (BOM) at the start of the stream.
    // Note that we do not strip any non - UTF8 BOM, as eventsource streams are
    // always decoded as UTF8 as per the specification.
    if (isFirstChunk && buffer.startsWith(BOM)) {
      buffer = buffer.slice(BOM.length)
    }

    isFirstChunk = false

    // Set up chunk-specific processing state
    const length = buffer.length
    let position = 0

    // Read the current buffer byte by byte
    while (position < length) {
      // EventSource allows for carriage return + line feed, which means we
      // need to ignore a linefeed character if the previous character was a
      // carriage return
      // @todo refactor to reduce nesting, consider checking previous byte?
      // @todo but consider multiple chunks etc
      if (discardTrailingNewline) {
        if (buffer[position] === "\n") {
          ++position
        }
        discardTrailingNewline = false
      }

      let lineLength = -1
      let fieldLength = startingFieldLength
      let character: string

      for (let index = startingPosition; lineLength < 0 && index < length; ++index) {
        character = buffer[index]
        if (character === ":" && fieldLength < 0) {
          fieldLength = index - position
        } else if (character === "\r") {
          discardTrailingNewline = true
          lineLength = index - position
        } else if (character === "\n") {
          lineLength = index - position
        }
      }

      if (lineLength < 0) {
        startingPosition = length - position
        startingFieldLength = fieldLength
        break
      } else {
        startingPosition = 0
        startingFieldLength = -1
      }

      parseEventStreamLine(buffer, position, fieldLength, lineLength)

      position += lineLength + 1