1 files changed, 119 insertions, 0 deletions
diff --git a/dom/encoding/TextDecoder.cpp b/dom/encoding/TextDecoder.cpp
new file mode 100644
index 0000000000..6718556868
--- /dev/null
+++ b/dom/encoding/TextDecoder.cpp
@@ -0,0 +1,119 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/UnionTypes.h"
+#include "mozilla/Encoding.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "nsContentUtils.h"
+
+#include <stdint.h>
+
+namespace mozilla::dom {
+
+void TextDecoder::Init(const nsAString& aLabel,
+                       const TextDecoderOptions& aOptions, ErrorResult& aRv) {
+  // Let encoding be the result of getting an encoding from label.
+  // If encoding is failure or replacement, throw a RangeError
+  // (https://encoding.spec.whatwg.org/#dom-textdecoder).
+  const Encoding* encoding = Encoding::ForLabelNoReplacement(aLabel);
+  if (!encoding) {
+    NS_ConvertUTF16toUTF8 label(aLabel);
+    label.Trim(" \t\n\f\r");
+    aRv.ThrowRangeError<MSG_ENCODING_NOT_SUPPORTED>(label);
+    return;
+  }
+  InitWithEncoding(WrapNotNull(encoding), aOptions);
+}
+
+void TextDecoder::InitWithEncoding(NotNull<const Encoding*> aEncoding,
+                                   const TextDecoderOptions& aOptions) {
+  aEncoding->Name(mEncoding);
+  // Store the flags passed via our options dictionary.
+  mFatal = aOptions.mFatal;
+  mIgnoreBOM = aOptions.mIgnoreBOM;
+
+  // Create a decoder object for mEncoding.
+  if (mIgnoreBOM) {
+    mDecoder = aEncoding->NewDecoderWithoutBOMHandling();
+  } else {
+    mDecoder = aEncoding->NewDecoderWithBOMRemoval();
+  }
+}
+
+void TextDecoderCommon::DecodeNative(Span<const uint8_t> aInput,
+                                     const bool aStream,
+                                     nsAString& aOutDecodedString,
+                                     ErrorResult& aRv) {
+  aOutDecodedString.Truncate();
+
+  CheckedInt<nsAString::size_type> needed =
+      mDecoder->MaxUTF16BufferLength(aInput.Length());
+  if (!needed.isValid()) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+
+  auto output = aOutDecodedString.GetMutableData(needed.value(), fallible);
+  if (!output) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+
+  uint32_t result;
+  size_t read;
+  size_t written;
+  if (mFatal) {
+    std::tie(result, read, written) =
+        mDecoder->DecodeToUTF16WithoutReplacement(aInput, *output, !aStream);
+    if (result != kInputEmpty) {
+      aRv.ThrowTypeError<MSG_DOM_DECODING_FAILED>();
+      return;
+    }
+  } else {
+    std::tie(result, read, written, std::ignore) =
+        mDecoder->DecodeToUTF16(aInput, *output, !aStream);
+  }
+  MOZ_ASSERT(result == kInputEmpty);
+  MOZ_ASSERT(read == aInput.Length());
+  MOZ_ASSERT(written <= aOutDecodedString.Length());
+
+  if (!aOutDecodedString.SetLength(written, fallible)) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+
+  // If the internal streaming flag of the decoder object is not set,
+  // then reset the encoding algorithm state to the default values
+  if (!aStream) {
+    if (mIgnoreBOM) {
+      mDecoder->Encoding()->NewDecoderWithoutBOMHandlingInto(*mDecoder);
+    } else {
+      mDecoder->Encoding()->NewDecoderWithBOMRemovalInto(*mDecoder);
+    }
+  }
+}
+
+void TextDecoder::Decode(const Optional<ArrayBufferViewOrArrayBuffer>& aBuffer,
+                         const TextDecodeOptions& aOptions,
+                         nsAString& aOutDecodedString, ErrorResult& aRv) {
+  if (!aBuffer.WasPassed()) {
+    DecodeNative(nullptr, aOptions.mStream, aOutDecodedString, aRv);
+    return;
+  }
+
+  ProcessTypedArrays(aBuffer.Value(), [&](const Span<uint8_t>& aData,
+                                          JS::AutoCheckCannotGC&&) {
+    DecodeNative(aData, aOptions.mStream, aOutDecodedString, aRv);
+  });
+}
+
+void TextDecoderCommon::GetEncoding(nsAString& aEncoding) {
+  CopyASCIItoUTF16(mEncoding, aEncoding);
+  nsContentUtils::ASCIIToLower(aEncoding);
+}
+
+}  // namespace mozilla::dom