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Add JsonEncodedText with Utf8JsonWriter overloads that accept it (#37323
) * Initial impl of JsonEncodedText with tests. * Auto-generate the reference assembly. * Update tests and ref assembly to include dummy field. * Add JsonEncodedText overloads to Utf8JsonWriter with tests. * Auto-gen the ref * Address PR feedback. * Fix typo - dispose the Utf8JsonWriter within serializer. * Add XML comments to the new APIs and types. * Alpha order the csproj.
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src/System.Text.Json/src/System/Text/Json/JsonEncodedText.cs
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|---|---|---|
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| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
| // See the LICENSE file in the project root for more information. | ||
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| using System.Buffers; | ||
| using System.Diagnostics; | ||
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| namespace System.Text.Json | ||
| { | ||
| /// <summary> | ||
| /// Provides a way to transform UTF-8 or UTF-16 encoded text into a form that is suitable for JSON. | ||
| /// </summary> | ||
| /// <remarks> | ||
| /// This can be used to cache and store known strings used for writing JSON ahead of time by pre-encoding them up front. | ||
| /// </remarks> | ||
| public readonly struct JsonEncodedText : IEquatable<JsonEncodedText> | ||
| { | ||
| private readonly byte[] _utf8Value; | ||
| private readonly string _value; | ||
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| /// <summary> | ||
| /// Returns the UTF-8 encoded representation of the pre-encoded JSON text. | ||
| /// </summary> | ||
| public ReadOnlySpan<byte> EncodedUtf8Bytes => _utf8Value; | ||
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| private JsonEncodedText(byte[] utf8Value) | ||
| { | ||
| Debug.Assert(utf8Value != null); | ||
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| _value = JsonReaderHelper.GetTextFromUtf8(utf8Value); | ||
| _utf8Value = utf8Value; | ||
| } | ||
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| /// <summary> | ||
| /// Encodes the string text value as a JSON string. | ||
| /// </summary> | ||
| /// <param name="value">The UTF-16 encoded value to be transformed as JSON encoded text.</param> | ||
| /// <exception cref="ArgumentNullException"> | ||
| /// Thrown if value is null. | ||
| /// </exception> | ||
| /// <exception cref="ArgumentException"> | ||
| /// Thrown when the specified value is too large or if it contains invalid UTF-16 characters. | ||
| /// </exception> | ||
| public static JsonEncodedText Encode(string value) | ||
| { | ||
| if (value == null) | ||
| throw new ArgumentNullException(nameof(value)); | ||
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| return Encode(value.AsSpan()); | ||
| } | ||
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| /// <summary> | ||
| /// Encodes the UTF-16 text value as a JSON string. | ||
| /// </summary> | ||
| /// <param name="value">The UTF-16 encoded value to be transformed as JSON encoded text.</param> | ||
| /// <exception cref="ArgumentException"> | ||
| /// Thrown when the specified value is too large or if it contains invalid UTF-16 characters. | ||
| /// </exception> | ||
| public static JsonEncodedText Encode(ReadOnlySpan<char> value) | ||
| { | ||
| if (value.Length == 0) | ||
| { | ||
| return new JsonEncodedText(Array.Empty<byte>()); | ||
| } | ||
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| return TranscodeAndEncode(value); | ||
| } | ||
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| private static JsonEncodedText TranscodeAndEncode(ReadOnlySpan<char> value) | ||
| { | ||
| JsonWriterHelper.ValidateValue(value); | ||
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| int expectedByteCount = JsonReaderHelper.GetUtf8ByteCount(value); | ||
| byte[] utf8Bytes = ArrayPool<byte>.Shared.Rent(expectedByteCount); | ||
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| JsonEncodedText encodedText; | ||
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| // Since GetUtf8ByteCount above already throws on invalid input, the transcoding | ||
| // to UTF-8 is guaranteed to succeed here. Therefore, there's no need for a try-catch-finally block. | ||
| int actualByteCount = JsonReaderHelper.GetUtf8FromText(value, utf8Bytes); | ||
| Debug.Assert(expectedByteCount == actualByteCount); | ||
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| encodedText = EncodeHelper(utf8Bytes.AsSpan(0, actualByteCount)); | ||
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| // On the basis that this is user data, go ahead and clear it. | ||
| utf8Bytes.AsSpan(0, expectedByteCount).Clear(); | ||
| ArrayPool<byte>.Shared.Return(utf8Bytes); | ||
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| return encodedText; | ||
| } | ||
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| /// <summary> | ||
| /// Encodes the UTF-8 text value as a JSON string. | ||
| /// </summary> | ||
| /// <param name="utf8Value">The UTF-8 encoded value to be transformed as JSON encoded text.</param> | ||
| /// <exception cref="ArgumentException"> | ||
| /// Thrown when the specified value is too large or if it contains invalid UTF-8 bytes. | ||
| /// </exception> | ||
| public static JsonEncodedText Encode(ReadOnlySpan<byte> utf8Value) | ||
| { | ||
| if (utf8Value.Length == 0) | ||
| { | ||
| return new JsonEncodedText(Array.Empty<byte>()); | ||
| } | ||
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| JsonWriterHelper.ValidateValue(utf8Value); | ||
| return EncodeHelper(utf8Value); | ||
| } | ||
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| private static JsonEncodedText EncodeHelper(ReadOnlySpan<byte> utf8Value) | ||
| { | ||
| int idx = JsonWriterHelper.NeedsEscaping(utf8Value); | ||
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| if (idx != -1) | ||
| { | ||
| return new JsonEncodedText(GetEscapedString(utf8Value, idx)); | ||
| } | ||
| else | ||
| { | ||
| return new JsonEncodedText(utf8Value.ToArray()); | ||
| } | ||
| } | ||
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| private static byte[] GetEscapedString(ReadOnlySpan<byte> utf8Value, int firstEscapeIndexVal) | ||
| { | ||
| Debug.Assert(int.MaxValue / JsonConstants.MaxExpansionFactorWhileEscaping >= utf8Value.Length); | ||
| Debug.Assert(firstEscapeIndexVal >= 0 && firstEscapeIndexVal < utf8Value.Length); | ||
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| byte[] valueArray = null; | ||
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| int length = JsonWriterHelper.GetMaxEscapedLength(utf8Value.Length, firstEscapeIndexVal); | ||
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| Span<byte> escapedValue = length <= JsonConstants.StackallocThreshold ? | ||
| stackalloc byte[length] : | ||
| (valueArray = ArrayPool<byte>.Shared.Rent(length)); | ||
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| JsonWriterHelper.EscapeString(utf8Value, escapedValue, firstEscapeIndexVal, out int written); | ||
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| byte[] escapedString = escapedValue.Slice(0, written).ToArray(); | ||
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| if (valueArray != null) | ||
| { | ||
| ArrayPool<byte>.Shared.Return(valueArray); | ||
| } | ||
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| return escapedString; | ||
| } | ||
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| /// <summary> | ||
| /// Determines whether this instance and another specified <see cref="JsonEncodedText"/> instance have the same value. | ||
| /// </summary> | ||
| /// <remarks> | ||
| /// Default instances of <see cref="JsonEncodedText"/> are treated as equal. | ||
| /// </remarks> | ||
| public bool Equals(JsonEncodedText other) | ||
| { | ||
| if (_value == null) | ||
| { | ||
| return other._value == null; | ||
| } | ||
| else | ||
| { | ||
| return _value.Equals(other._value); | ||
| } | ||
| } | ||
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| /// <summary> | ||
| /// Determines whether this instance and a specified object, which must also be a <see cref="JsonEncodedText"/> instance, have the same value. | ||
| /// </summary> | ||
| /// <remarks> | ||
| /// If <paramref name="obj"/> is null, the method returns false. | ||
| /// </remarks> | ||
| public override bool Equals(object obj) | ||
| { | ||
| if (obj is JsonEncodedText encodedText) | ||
| { | ||
| return Equals(encodedText); | ||
| } | ||
| return false; | ||
| } | ||
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| /// <summary> | ||
| /// Converts the value of this instance to a <see cref="string"/>. | ||
| /// </summary> | ||
| /// <remarks> | ||
| /// Returns the underlying UTF-16 encoded string. | ||
| /// </remarks> | ||
| /// <remarks> | ||
| /// Returns an empty string on a default instance of <see cref="JsonEncodedText"/>. | ||
| /// </remarks> | ||
| public override string ToString() | ||
| => _value ?? string.Empty; | ||
|
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| /// <summary> | ||
| /// Returns the hash code for this <see cref="JsonEncodedText"/>. | ||
| /// </summary> | ||
| /// <remarks> | ||
| /// Returns 0 on a default instance of <see cref="JsonEncodedText"/>. | ||
| /// </remarks> | ||
| public override int GetHashCode() | ||
| => _value == null ? 0 : _value.GetHashCode(); | ||
| } | ||
| } |
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