Function captureSnap

src/utils/sessionStoragePortable.ts:664–687

(
  s: LoadState,
  buf: Buffer,
  chunk: Buffer,
  lastSnapStart: number,
  lastSnapEnd: number,
)

// In-buf snap wins over straddle (later in file). carryBuf still valid here.
function captureSnap(
  s: LoadState,
  buf: Buffer,
  chunk: Buffer,
  lastSnapStart: number,
  lastSnapEnd: number,
): void {
  if (lastSnapStart !== -1) {
    s.lastSnapLen = lastSnapEnd - lastSnapStart
    if (s.lastSnapBuf === undefined || s.lastSnapLen > s.lastSnapBuf.length) {
      s.lastSnapBuf = Buffer.allocUnsafe(s.lastSnapLen)
    }
    buf.copy(s.lastSnapBuf, 0, lastSnapStart, lastSnapEnd)
    s.lastSnapSrc = s.lastSnapBuf
  } else if (s.straddleSnapCarryLen > 0) {
    s.lastSnapLen = s.straddleSnapCarryLen + s.straddleSnapTailEnd
    if (s.lastSnapBuf === undefined || s.lastSnapLen > s.lastSnapBuf.length) {
      s.lastSnapBuf = Buffer.allocUnsafe(s.lastSnapLen)
    }
    s.carryBuf!.copy(s.lastSnapBuf, 0, 0, s.straddleSnapCarryLen)
    chunk.copy(s.lastSnapBuf, s.straddleSnapCarryLen, 0, s.straddleSnapTailEnd)
    s.lastSnapSrc = s.lastSnapBuf
  }
}

function captureCarry(s: LoadState, buf: Buffer, trailStart: number): void {
  s.carryLen = buf.length - trailStart