private static ReadOnlySpan <byte> GetUnescapedString(ReadOnlySpan <byte> utf8Source, int idx)
{
// The escaped name is always longer than the unescaped, so it is safe to use escaped name for the buffer length.
int length = utf8Source.Length;
byte[]? pooledName = null;
Span <byte> unescapedName = length <= JsonConstants.StackallocThreshold ?
stackalloc byte[length] :
(pooledName = ArrayPool <byte> .Shared.Rent(length));
JsonReaderHelper.Unescape(utf8Source, unescapedName, idx, out int written);
ReadOnlySpan <byte> propertyName = unescapedName.Slice(0, written).ToArray();
if (pooledName != null)
{
// We clear the array because it is "user data" (although a property name).
new Span <byte>(pooledName, 0, written).Clear();
ArrayPool <byte> .Shared.Return(pooledName);
}
return(propertyName);
}
private bool TryGetNamedPropertyValue(
int startIndex,
int endIndex,
ReadOnlySpan <byte> propertyName,
out JsonElement value)
{
ReadOnlySpan <byte> documentSpan = _utf8Json.Span;
// Move to the row before the EndObject
int index = endIndex - DbRow.Size;
while (index > startIndex)
{
DbRow row = _parsedData.Get(index);
Debug.Assert(row.TokenType != JsonTokenType.PropertyName);
// Move before the value
if (row.IsSimpleValue)
{
index -= DbRow.Size;
}
else
{
Debug.Assert(row.NumberOfRows > 0);
index -= DbRow.Size * (row.NumberOfRows + 1);
}
row = _parsedData.Get(index);
Debug.Assert(row.TokenType == JsonTokenType.PropertyName);
ReadOnlySpan <byte> currentPropertyName = documentSpan.Slice(row.Location, row.SizeOrLength);
if (row.HasComplexChildren)
{
// An escaped property name will be longer than an unescaped candidate, so only unescape
// when the lengths are compatible.
if (currentPropertyName.Length > propertyName.Length)
{
int idx = currentPropertyName.IndexOf(JsonConstants.BackSlash);
Debug.Assert(idx >= 0);
// If everything up to where the property name has a backslash matches, keep going.
if (propertyName.Length > idx &&
currentPropertyName.Slice(0, idx).SequenceEqual(propertyName.Slice(0, idx)))
{
int remaining = currentPropertyName.Length - idx;
int written = 0;
byte[] rented = null;
try
{
Span <byte> utf8Unescaped = remaining <= JsonConstants.StackallocThreshold ?
stackalloc byte[remaining] :
(rented = ArrayPool <byte> .Shared.Rent(remaining));
// Only unescape the part we haven't processed.
JsonReaderHelper.Unescape(currentPropertyName.Slice(idx), utf8Unescaped, 0, out written);
// If the unescaped remainder matches the input remainder, it's a match.
if (utf8Unescaped.Slice(0, written).SequenceEqual(propertyName.Slice(idx)))
{
// If the property name is a match, the answer is the next element.
value = new JsonElement(this, index + DbRow.Size);
return(true);
}
}
finally
{
if (rented != null)
{
rented.AsSpan(0, written).Clear();
ArrayPool <byte> .Shared.Return(rented);
}
}
}
}
}
else if (currentPropertyName.SequenceEqual(propertyName))
{
// If the property name is a match, the answer is the next element.
value = new JsonElement(this, index + DbRow.Size);
return(true);
}
// Move to the previous value
index -= DbRow.Size;
}
value = default;
return(false);
}
