third_party/WebKit/Source/modules/encoding/TextDecoder.cpp

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#include "modules/encoding/TextDecoder.h"

#include "bindings/core/v8/ExceptionState.h"
#include "core/typed_arrays/DOMArrayBuffer.h"
#include "core/typed_arrays/DOMArrayBufferView.h"
#include "modules/encoding/Encoding.h"
#include "platform/wtf/StringExtras.h"
#include "platform/wtf/text/TextEncodingRegistry.h"

namespace blink {

TextDecoder* TextDecoder::Create(const String& label,
                                 const TextDecoderOptions& options,
                                 ExceptionState& exception_state) {
  WTF::TextEncoding encoding(
      label.StripWhiteSpace(&Encoding::IsASCIIWhiteSpace));
  // The replacement encoding is not valid, but the Encoding API also
  // rejects aliases of the replacement encoding.
  if (!encoding.IsValid() || !strcasecmp(encoding.GetName(), "replacement")) {
    exception_state.ThrowRangeError("The encoding label provided ('" + label +
                                    "') is invalid.");
    return nullptr;
  }

  return new TextDecoder(encoding, options.fatal(), options.ignoreBOM());
}

TextDecoder::TextDecoder(const WTF::TextEncoding& encoding,
                         bool fatal,
                         bool ignore_bom)
    : encoding_(encoding),
      codec_(NewTextCodec(encoding)),
      fatal_(fatal),
      ignore_bom_(ignore_bom),
      bom_seen_(false) {}

TextDecoder::~TextDecoder() {}

String TextDecoder::encoding() const {
  String name = String(encoding_.GetName()).DeprecatedLower();
  // Where possible, encoding aliases should be handled by changes to Chromium's
  // ICU or Blink's WTF.  The same codec is used, but WTF maintains a different
  // name/identity for these.
  if (name == "iso-8859-1" || name == "us-ascii")
    return "windows-1252";
  return name;
}

String TextDecoder::decode(const BufferSource& input,
                           const TextDecodeOptions& options,
                           ExceptionState& exception_state) {
  DCHECK(!input.IsNull());
  if (input.IsArrayBufferView()) {
    const char* start = static_cast<const char*>(
        input.GetAsArrayBufferView().View()->BaseAddress());
    size_t length = input.GetAsArrayBufferView().View()->byteLength();
    return decode(start, length, options, exception_state);
  }
  DCHECK(input.IsArrayBuffer());
  const char* start =
      static_cast<const char*>(input.GetAsArrayBuffer()->Data());
  size_t length = input.GetAsArrayBuffer()->ByteLength();
  return decode(start, length, options, exception_state);
}

String TextDecoder::decode(const char* start,
                           size_t length,
                           const TextDecodeOptions& options,
                           ExceptionState& exception_state) {
  WTF::FlushBehavior flush =
      options.stream() ? WTF::kDoNotFlush : WTF::kDataEOF;

  bool saw_error = false;
  String s = codec_->Decode(start, length, flush, fatal_, saw_error);

  if (fatal_ && saw_error) {
    exception_state.ThrowTypeError("The encoded data was not valid.");
    return String();
  }

  if (!ignore_bom_ && !bom_seen_ && !s.IsEmpty()) {
    bom_seen_ = true;
    String name(encoding_.GetName());
    if ((name == "UTF-8" || name == "UTF-16LE" || name == "UTF-16BE") &&
        s[0] == 0xFEFF)
      s.Remove(0);
  }

  if (flush)
    bom_seen_ = false;

  return s;
}

String TextDecoder::decode(ExceptionState& exception_state) {
  TextDecodeOptions options;
  return decode(nullptr, 0, options, exception_state);
}

}  // namespace blink