gecko-dev/dom/encoding/TextDecoder.cpp

/* 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 "mozilla/dom/TextDecoder.h"
#include "mozilla/dom/EncodingUtils.h"
#include "nsContentUtils.h"
#include "nsICharsetConverterManager.h"
#include "nsServiceManagerUtils.h"

namespace mozilla {
namespace dom {

static const PRUnichar kReplacementChar = static_cast<PRUnichar>(0xFFFD);

void
TextDecoder::Init(const nsAString& aEncoding, const bool aFatal,
                  ErrorResult& aRv)
{
  nsAutoString label(aEncoding);
  EncodingUtils::TrimSpaceCharacters(label);

  // Let encoding be the result of getting an encoding from label.
  // If encoding is failure, throw a TypeError.
  if (!EncodingUtils::FindEncodingForLabel(label, mEncoding)) {
    aRv.ThrowTypeError(MSG_ENCODING_NOT_SUPPORTED, &label);
    return;
  }

  // If the constructor is called with an options argument,
  // and the fatal property of the dictionary is set,
  // set the internal fatal flag of the decoder object.
  mFatal = aFatal;

  // Create a decoder object for mEncoding.
  nsCOMPtr<nsICharsetConverterManager> ccm =
    do_GetService(NS_CHARSETCONVERTERMANAGER_CONTRACTID);
  if (!ccm) {
    aRv.Throw(NS_ERROR_UNEXPECTED);
    return;
  }

  ccm->GetUnicodeDecoderRaw(mEncoding.get(), getter_AddRefs(mDecoder));
  if (!mDecoder) {
    aRv.Throw(NS_ERROR_UNEXPECTED);
    return;
  }

  if (mFatal) {
    mDecoder->SetInputErrorBehavior(nsIUnicodeDecoder::kOnError_Signal);
  }
}

void
TextDecoder::Decode(const char* aInput, const int32_t aLength,
                    const bool aStream, nsAString& aOutDecodedString,
                    ErrorResult& aRv)
{
  aOutDecodedString.Truncate();

  // Run or resume the decoder algorithm of the decoder object's encoder.
  int32_t outLen;
  nsresult rv = mDecoder->GetMaxLength(aInput, aLength, &outLen);
  if (NS_FAILED(rv)) {
    aRv.Throw(rv);
    return;
  }
  // Need a fallible allocator because the caller may be a content
  // and the content can specify the length of the string.
  static const fallible_t fallible = fallible_t();
  nsAutoArrayPtr<PRUnichar> buf(new (fallible) PRUnichar[outLen + 1]);
  if (!buf) {
    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
    return;
  }

  int32_t length = aLength;
  rv = mDecoder->Convert(aInput, &length, buf, &outLen);
  MOZ_ASSERT(mFatal || rv != NS_ERROR_ILLEGAL_INPUT);
  buf[outLen] = 0;
  aOutDecodedString.Append(buf, outLen);

  // If the internal streaming flag of the decoder object is not set,
  // then reset the encoding algorithm state to the default values
  if (!aStream) {
    mDecoder->Reset();
    if (rv == NS_OK_UDEC_MOREINPUT) {
      if (mFatal) {
        aRv.Throw(NS_ERROR_DOM_ENCODING_DECODE_ERR);
      } else {
        // Need to emit a decode error manually
        // to simulate the EOF handling of the Encoding spec.
        aOutDecodedString.Append(kReplacementChar);
      }
    }
  }

  if (NS_FAILED(rv)) {
    aRv.Throw(NS_ERROR_DOM_ENCODING_DECODE_ERR);
  }
}

void
TextDecoder::GetEncoding(nsAString& aEncoding)
{
  CopyASCIItoUTF16(mEncoding, aEncoding);
  nsContentUtils::ASCIIToLower(aEncoding);
}

} // dom
} // mozilla