Method readOrSkip

bolt/dwio/common/compression/PagedInputStream.cpp:126–226

Read into `data' if it is not null; otherwise skip some of the pending.

// Read into `data' if it is not null; otherwise skip some of the pending.
bool PagedInputStream::readOrSkip(const void** data, int32_t* size) {
  if (data) {
    BOLT_CHECK_EQ(pendingSkip_, 0);
  }
  // if the user pushed back, return them the partial buffer
  if (outputBufferLength_) {
    if (data) {
      *data = outputBufferPtr_;
    }
    *size = static_cast<int32_t>(outputBufferLength_);
    outputBufferPtr_ += outputBufferLength_;
    bytesReturned_ += outputBufferLength_;
    outputBufferLength_ = 0;
    // This is a rewind of previous output, does not count for
    // 'lastWindowSize_'.
    return true;
  }

  // release previous decryption buffer
  decryptionBuffer_ = nullptr;

  if (state_ == State::HEADER || remainingLength_ == 0) {
    readHeader();
  }
  if (state_ == State::END) {
    return false;
  }
  if (inputBufferPtr_ == inputBufferPtrEnd_) {
    readBuffer(true);
  }

  size_t availSize = std::min(
      static_cast<size_t>(inputBufferPtrEnd_ - inputBufferPtr_),
      remainingLength_);
  // in the case when decompression or decryption is needed, need to copy data
  // to input buffer if the input doesn't contain the entire block
  bool original = !decrypter_ && (state_ == State::ORIGINAL);
  const char* input = nullptr;
  // if no decompression or decryption is needed, simply adjust the output
  // pointer. Otherwise, make sure we have continuous block
  if (original) {
    if (data) {
      *data = inputBufferPtr_;
    }
    *size = static_cast<int32_t>(availSize);
    outputBufferPtr_ = inputBufferPtr_ + availSize;
    inputBufferPtr_ += availSize;
    remainingLength_ -= availSize;
  } else {
    input = ensureInput(availSize);
  }

  // perform decryption
  if (decrypter_) {
    decryptionBuffer_ =
        decrypter_->decrypt(folly::StringPiece{input, remainingLength_});
    input = reinterpret_cast<const char*>(decryptionBuffer_->data());
    remainingLength_ = decryptionBuffer_->length();