third_party/blink/renderer/modules/encoding/text_decoder.cc

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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#include "third_party/blink/renderer/modules/encoding/text_decoder.h"

#include "third_party/blink/renderer/bindings/core/v8/v8_union_arraybuffer_arraybufferview.h"
#include "third_party/blink/renderer/core/typed_arrays/dom_array_buffer.h"
#include "third_party/blink/renderer/core/typed_arrays/dom_array_buffer_view.h"
#include "third_party/blink/renderer/modules/encoding/encoding.h"
#include "third_party/blink/renderer/platform/bindings/exception_state.h"
#include "third_party/blink/renderer/platform/wtf/text/strcat.h"
#include "third_party/blink/renderer/platform/wtf/text/string_view.h"
#include "third_party/blink/renderer/platform/wtf/text/text_encoding_registry.h"

namespace blink {

TextDecoder* TextDecoder::Create(const String& label,
                                 const TextDecoderOptions* options,
                                 ExceptionState& exception_state) {
  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() ||
      EqualIgnoringASCIICase(encoding.GetName(), "replacement")) {
    exception_state.ThrowRangeError(
        StrCat({"The encoding label provided ('", label, "') is invalid."}));
    return nullptr;
  }

  return MakeGarbageCollected<TextDecoder>(encoding, options->fatal(),
                                           options->ignoreBOM());
}

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

TextDecoder::~TextDecoder() = default;

String TextDecoder::encoding() const {
  String name = encoding_.GetName().GetString().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(std::optional<base::span<const uint8_t>> input,
                           const TextDecodeOptions* options,
                           ExceptionState& exception_state) {
  DCHECK(options);
  base::span<const uint8_t> input_span =
      input.value_or(base::span<const uint8_t>());
  if (input_span.size() > std::numeric_limits<uint32_t>::max()) {
    exception_state.ThrowRangeError(
        "Buffer size exceeds maximum heap object size.");
    return String();
  }

  return Decode(input_span, options, exception_state);
}

String TextDecoder::Decode(base::span<const uint8_t> input,
                           const TextDecodeOptions* options,
                           ExceptionState& exception_state) {
  DCHECK(options);
  if (!do_not_flush_) {
    if (!codec_) {
      // In the spec, a new decoder is created unconditionally here, but that
      // requires an extra allocation. Since the TextCodec would be flushed
      // here by the previous call if `!do_not_flush` (sorry about the double
      // negatives), then we don't need a new TextCodec to match the spec
      // behavior.
      // https://encoding.spec.whatwg.org/#dom-textdecoder-decode
      codec_ = NewTextCodec(encoding_);
    }
    bom_seen_ = false;
  }

  DCHECK(codec_);
  do_not_flush_ = options->stream();
  FlushBehavior flush =
      do_not_flush_ ? FlushBehavior::kDoNotFlush : FlushBehavior::kDataEOF;

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

  if (fatal_ && saw_error) {
    if (!do_not_flush_) {
      // If flushing, the error should not persist.
      codec_.reset();
    }
    exception_state.ThrowTypeError("The encoded data was not valid.");
    return String();
  }

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

  return s;
}

String TextDecoder::decode(ExceptionState& exception_state) {
  TextDecodeOptions* options = TextDecodeOptions::Create();
  return Decode({}, options, exception_state);
}

}  // namespace blink