dom/encoding/TextDecoder.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "mozilla/dom/TextDecoder.h"
   8 #include "mozilla/dom/UnionTypes.h"
   9 #include "mozilla/Encoding.h"
  10 #include "mozilla/UniquePtrExtensions.h"
  11 #include "nsContentUtils.h"
  12
  13 #include <stdint.h>
  14
  15 namespace mozilla::dom {
  16
  17 void TextDecoder::Init(const nsAString& aLabel,
  18                        const TextDecoderOptions& aOptions, ErrorResult& aRv) {
  19   // Let encoding be the result of getting an encoding from label.
  20   // If encoding is failure or replacement, throw a RangeError
  21   // (https://encoding.spec.whatwg.org/#dom-textdecoder).
  22   const Encoding* encoding = Encoding::ForLabelNoReplacement(aLabel);
  23   if (!encoding) {
  24     NS_ConvertUTF16toUTF8 label(aLabel);
  25     label.Trim(" \t\n\f\r");
  26     aRv.ThrowRangeError<MSG_ENCODING_NOT_SUPPORTED>(label);
  27     return;
  28   }
  29   InitWithEncoding(WrapNotNull(encoding), aOptions);
  30 }
  31
  32 void TextDecoder::InitWithEncoding(NotNull<const Encoding*> aEncoding,
  33                                    const TextDecoderOptions& aOptions) {
  34   aEncoding->Name(mEncoding);
  35   // Store the flags passed via our options dictionary.
  36   mFatal = aOptions.mFatal;
  37   mIgnoreBOM = aOptions.mIgnoreBOM;
  38
  39   // Create a decoder object for mEncoding.
  40   if (mIgnoreBOM) {
  41     mDecoder = aEncoding->NewDecoderWithoutBOMHandling();
  42   } else {
  43     mDecoder = aEncoding->NewDecoderWithBOMRemoval();
  44   }
  45 }
  46
  47 void TextDecoderCommon::DecodeNative(Span<const uint8_t> aInput,
  48                                      const bool aStream,
  49                                      nsAString& aOutDecodedString,
  50                                      ErrorResult& aRv) {
  51   aOutDecodedString.Truncate();
  52
  53   CheckedInt<nsAString::size_type> needed =
  54       mDecoder->MaxUTF16BufferLength(aInput.Length());
  55   if (!needed.isValid()) {
  56     aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
  57     return;
  58   }
  59
  60   auto output = aOutDecodedString.GetMutableData(needed.value(), fallible);
  61   if (!output) {
  62     aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
  63     return;
  64   }
  65
  66   uint32_t result;
  67   size_t read;
  68   size_t written;
  69   if (mFatal) {
  70     std::tie(result, read, written) =
  71         mDecoder->DecodeToUTF16WithoutReplacement(aInput, *output, !aStream);
  72     if (result != kInputEmpty) {
  73       aRv.ThrowTypeError<MSG_DOM_DECODING_FAILED>();
  74       return;
  75     }
  76   } else {
  77     std::tie(result, read, written, std::ignore) =
  78         mDecoder->DecodeToUTF16(aInput, *output, !aStream);
  79   }
  80   MOZ_ASSERT(result == kInputEmpty);
  81   MOZ_ASSERT(read == aInput.Length());
  82   MOZ_ASSERT(written <= aOutDecodedString.Length());
  83
  84   if (!aOutDecodedString.SetLength(written, fallible)) {
  85     aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
  86     return;
  87   }
  88
  89   // If the internal streaming flag of the decoder object is not set,
  90   // then reset the encoding algorithm state to the default values
  91   if (!aStream) {
  92     if (mIgnoreBOM) {
  93       mDecoder->Encoding()->NewDecoderWithoutBOMHandlingInto(*mDecoder);
  94     } else {
  95       mDecoder->Encoding()->NewDecoderWithBOMRemovalInto(*mDecoder);
  96     }
  97   }
  98 }
  99
 100 void TextDecoder::Decode(const Optional<ArrayBufferViewOrArrayBuffer>& aBuffer,
 101                          const TextDecodeOptions& aOptions,
 102                          nsAString& aOutDecodedString, ErrorResult& aRv) {
 103   if (!aBuffer.WasPassed()) {
 104     DecodeNative(nullptr, aOptions.mStream, aOutDecodedString, aRv);
 105     return;
 106   }
 107
 108   ProcessTypedArrays(aBuffer.Value(), [&](const Span<uint8_t>& aData,
 109                                           JS::AutoCheckCannotGC&&) {
 110     DecodeNative(aData, aOptions.mStream, aOutDecodedString, aRv);
 111   });
 112 }
 113
 114 void TextDecoderCommon::GetEncoding(nsAString& aEncoding) {
 115   CopyASCIItoUTF16(mEncoding, aEncoding);
 116   nsContentUtils::ASCIIToLower(aEncoding);
 117 }
 118
 119 }  // namespace mozilla::dom