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CSHARP-5611: Eliminate the temporary byte array allocation in ObjectId.ToString #1706

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CSHARP-5611: Eliminate the temporary byte array allocation in ObjectId.ToString #1706

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CSHARP-5611: Eliminate the temporary byte array allocation in ObjectI…
ugurpelister Jun 7, 2025
b3ab8b1
CSHARP-5611: Eliminate the temporary byte array allocation in ObjectI…
ugurpelister Jun 7, 2025
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75 changes: 75 additions & 0 deletions src/MongoDB.Bson/ObjectModel/ObjectId.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -449,12 +449,86 @@ public void ToByteArray(byte[] destination, int offset)
destination[offset + 11] = (byte)(_c);
}

#if NET6_0_OR_GREATER || NETSTANDARD2_1_OR_GREATER
/// <summary>
/// Converts the ObjectId to a byte buffer provided by the input span.
/// </summary>
/// <param name="destination">The destination byte span.</param>
/// <exception cref="ArgumentException">Not enough room in destination span.</exception>
public void ToByteSpan(Span<byte> destination)
{
if (destination.Length < 12)
{
throw new ArgumentException("Not enough room in destination span.", "destination");
}

destination[0] = (byte)(_a >> 24);
destination[1] = (byte)(_a >> 16);
destination[2] = (byte)(_a >> 8);
destination[3] = (byte)(_a);
destination[4] = (byte)(_b >> 24);
destination[5] = (byte)(_b >> 16);
destination[6] = (byte)(_b >> 8);
destination[7] = (byte)(_b);
destination[8] = (byte)(_c >> 24);
destination[9] = (byte)(_c >> 16);
destination[10] = (byte)(_c >> 8);
destination[11] = (byte)(_c);
}

/// <summary>
/// Fills a character span with the characters corresponding to the string representation of the value.
/// </summary>
/// <param name="destination">The span to fill the characters in.</param>
/// <exception cref="ArgumentException">Not enough room in destination span.</exception>
public void ToCharSpan(Span<char> destination)
{
if (destination.Length < 24)
{
throw new ArgumentException("Not enough room in destination span.", "destination");
}

Span<byte> span = stackalloc byte[12];
ToByteSpan(span);
destination[0] = BsonUtils.ToHexChar(span[0] >> 4);
destination[1] = BsonUtils.ToHexChar(span[0] & 0xF);
destination[2] = BsonUtils.ToHexChar(span[1] >> 4);
destination[3] = BsonUtils.ToHexChar(span[1] & 0xF);
destination[4] = BsonUtils.ToHexChar(span[2] >> 4);
destination[5] = BsonUtils.ToHexChar(span[2] & 0xF);
destination[6] = BsonUtils.ToHexChar(span[3] >> 4);
destination[7] = BsonUtils.ToHexChar(span[3] & 0xF);
destination[8] = BsonUtils.ToHexChar(span[4] >> 4);
destination[9] = BsonUtils.ToHexChar(span[4] & 0xF);
destination[10] = BsonUtils.ToHexChar(span[5] >> 4);
destination[11] = BsonUtils.ToHexChar(span[5] & 0xF);
destination[12] = BsonUtils.ToHexChar(span[6] >> 4);
destination[13] = BsonUtils.ToHexChar(span[6] & 0xF);
destination[14] = BsonUtils.ToHexChar(span[7] >> 4);
destination[15] = BsonUtils.ToHexChar(span[7] & 0xF);
destination[16] = BsonUtils.ToHexChar(span[8] >> 4);
destination[17] = BsonUtils.ToHexChar(span[8] & 0xF);
destination[18] = BsonUtils.ToHexChar(span[9] >> 4);
destination[19] = BsonUtils.ToHexChar(span[9] & 0xF);
destination[20] = BsonUtils.ToHexChar(span[10] >> 4);
destination[21] = BsonUtils.ToHexChar(span[10] & 0xF);
destination[22] = BsonUtils.ToHexChar(span[11] >> 4);
destination[23] = BsonUtils.ToHexChar(span[11] & 0xF);
}
#endif

/// <summary>
/// Returns a string representation of the value.
/// </summary>
/// <returns>A string representation of the value.</returns>
public override string ToString()
{
#if NET6_0_OR_GREATER || NETSTANDARD2_1_OR_GREATER
return string.Create(24, this, static (span, input) =>
{
input.ToCharSpan(span);
});
#else
var c = new char[24];
c[0] = BsonUtils.ToHexChar((_a >> 28) & 0x0f);
c[1] = BsonUtils.ToHexChar((_a >> 24) & 0x0f);
Expand All @@ -481,6 +555,7 @@ public override string ToString()
c[22] = BsonUtils.ToHexChar((_c >> 4) & 0x0f);
c[23] = BsonUtils.ToHexChar(_c & 0x0f);
return new string(c);
#endif
}

// explicit IConvertible implementation
Expand Down
10 changes: 10 additions & 0 deletions tests/MongoDB.Bson.Tests/ObjectModel/ObjectIdTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,11 @@ public void TestByteArrayConstructor()
Assert.Equal(BsonConstants.UnixEpoch.AddSeconds(0x01020304), objectId.CreationTime);
Assert.Equal("0102030405060708090a0b0c", objectId.ToString());
Assert.True(bytes.SequenceEqual(objectId.ToByteArray()));
#if NET6_0_OR_GREATER || NETSTANDARD2_1_OR_GREATER
Span<byte> span = new byte[12];
objectId.ToByteSpan(span);
Assert.True(span.SequenceEqual(bytes));
#endif
}

[Fact]
Expand All @@ -101,6 +106,11 @@ public void TestStringConstructor()
Assert.Equal(BsonConstants.UnixEpoch.AddSeconds(0x01020304), objectId.CreationTime);
Assert.Equal("0102030405060708090a0b0c", objectId.ToString());
Assert.True(bytes.SequenceEqual(objectId.ToByteArray()));
#if NET6_0_OR_GREATER || NETSTANDARD2_1_OR_GREATER
Span<char> span = new char[24];
objectId.ToCharSpan(span);
Assert.True(span.SequenceEqual("0102030405060708090a0b0c"));
#endif
}

[Fact]
Expand Down