gecko-dev/netwerk/base/ArrayBufferInputStream.cpp

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include <algorithm>
#include "ArrayBufferInputStream.h"
#include "nsStreamUtils.h"
#include "js/ArrayBuffer.h"  // JS::{GetArrayBuffer{ByteLength,Data},IsArrayBufferObject}
#include "js/RootingAPI.h"  // JS::{Handle,Rooted}
#include "js/Value.h"       // JS::Value
#include "mozilla/UniquePtrExtensions.h"
#include "mozilla/dom/ScriptSettings.h"

using mozilla::dom::RootingCx;

NS_IMPL_ISUPPORTS(ArrayBufferInputStream, nsIArrayBufferInputStream,
                  nsIInputStream);

ArrayBufferInputStream::ArrayBufferInputStream()
    : mBufferLength(0), mPos(0), mClosed(false) {}

NS_IMETHODIMP
ArrayBufferInputStream::SetData(JS::Handle<JS::Value> aBuffer,
                                uint32_t aByteOffset, uint32_t aLength) {
  NS_ASSERT_OWNINGTHREAD(ArrayBufferInputStream);

  if (!aBuffer.isObject()) {
    return NS_ERROR_FAILURE;
  }
  JS::Rooted<JSObject*> arrayBuffer(RootingCx(), &aBuffer.toObject());
  if (!JS::IsArrayBufferObject(arrayBuffer)) {
    return NS_ERROR_FAILURE;
  }

  uint32_t buflen = JS::GetArrayBufferByteLength(arrayBuffer);
  uint32_t offset = std::min(buflen, aByteOffset);
  uint32_t bufferLength = std::min(buflen - offset, aLength);

  mArrayBuffer = mozilla::MakeUniqueFallible<char[]>(bufferLength);
  if (!mArrayBuffer) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  mBufferLength = bufferLength;

  JS::AutoCheckCannotGC nogc;
  bool isShared;
  char* src =
      (char*)JS::GetArrayBufferData(arrayBuffer, &isShared, nogc) + offset;
  memcpy(&mArrayBuffer[0], src, mBufferLength);
  return NS_OK;
}

NS_IMETHODIMP
ArrayBufferInputStream::Close() {
  mClosed = true;
  return NS_OK;
}

NS_IMETHODIMP
ArrayBufferInputStream::Available(uint64_t* aCount) {
  if (mClosed) {
    return NS_BASE_STREAM_CLOSED;
  }
  if (mArrayBuffer) {
    *aCount = mBufferLength ? mBufferLength - mPos : 0;
  } else {
    *aCount = 0;
  }
  return NS_OK;
}

NS_IMETHODIMP
ArrayBufferInputStream::Read(char* aBuf, uint32_t aCount,
                             uint32_t* aReadCount) {
  return ReadSegments(NS_CopySegmentToBuffer, aBuf, aCount, aReadCount);
}

NS_IMETHODIMP
ArrayBufferInputStream::ReadSegments(nsWriteSegmentFun writer, void* closure,
                                     uint32_t aCount, uint32_t* result) {
  NS_ASSERTION(result, "null ptr");
  NS_ASSERTION(mBufferLength >= mPos, "bad stream state");

  if (mClosed) {
    return NS_BASE_STREAM_CLOSED;
  }

  MOZ_ASSERT(mArrayBuffer || (mPos == mBufferLength),
             "stream inited incorrectly");

  *result = 0;
  while (mPos < mBufferLength) {
    uint32_t remaining = mBufferLength - mPos;
    MOZ_ASSERT(mArrayBuffer);

    uint32_t count = std::min(aCount, remaining);
    if (count == 0) {
      break;
    }

    uint32_t written;
    nsresult rv = writer(this, closure, &mArrayBuffer[0] + mPos, *result, count,
                         &written);
    if (NS_FAILED(rv)) {
      // InputStreams do not propagate errors to caller.
      return NS_OK;
    }

    NS_ASSERTION(written <= count,
                 "writer should not write more than we asked it to write");
    mPos += written;
    *result += written;
    aCount -= written;
  }

  return NS_OK;
}

NS_IMETHODIMP
ArrayBufferInputStream::IsNonBlocking(bool* aNonBlocking) {
  *aNonBlocking = true;
  return NS_OK;
}