internal bool TryGetNamedPropertyValue(int index, ReadOnlySpan <byte> propertyName, out JsonElement value)
{
CheckNotDisposed();
DbRow row = _parsedData.Get(index);
CheckExpectedType(JsonTokenType.StartObject, row.TokenType);
// Only one row means it was EndObject.
if (row.NumberOfRows == 1)
{
value = default;
return(false);
}
int endIndex = checked (row.NumberOfRows * DbRow.Size + index);
return(TryGetNamedPropertyValue(
index + DbRow.Size,
endIndex,
propertyName,
out value));
}
private bool AppendDbRow(JsonObject.JsonValueType type, int valueIndex, int LengthOrNumberOfRows = DbRow.UnknownNumberOfRows)
{
var newIndex = _dbIndex + DbRow.Size;
if (newIndex >= _db.Length) {
ResizeDb();
}
var dbRow = new DbRow(type, valueIndex, LengthOrNumberOfRows);
_db.Span.Slice(_dbIndex).Write(dbRow);
_dbIndex = newIndex;
return true;
}
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);
}
internal bool TryGetNamedPropertyValue(int index, ReadOnlySpan <char> propertyName, out JsonElement value)
{
CheckNotDisposed();
DbRow row = _parsedData.Get(index);
CheckExpectedType(JsonTokenType.StartObject, row.TokenType);
// Only one row means it was EndObject.
if (row.NumberOfRows == 1)
{
value = default;
return(false);
}
int maxBytes = JsonReaderHelper.s_utf8Encoding.GetMaxByteCount(propertyName.Length);
int startIndex = index + DbRow.Size;
int endIndex = checked (row.NumberOfRows * DbRow.Size + index);
if (maxBytes < JsonConstants.StackallocThreshold)
{
Span <byte> utf8Name = stackalloc byte[JsonConstants.StackallocThreshold];
int len = JsonReaderHelper.GetUtf8FromText(propertyName, utf8Name);
utf8Name = utf8Name.Slice(0, len);
return(TryGetNamedPropertyValue(
startIndex,
endIndex,
utf8Name,
out value));
}
// Unescaping the property name will make the string shorter (or the same)
// So the first viable candidate is one whose length in bytes matches, or
// exceeds, our length in chars.
//
// The maximal escaping seems to be 6 -> 1 ("\u0030" => "0"), but just transcode
// and switch once one viable long property is found.
int minBytes = propertyName.Length;
// Move to the row before the EndObject
int candidateIndex = endIndex - DbRow.Size;
while (candidateIndex > index)
{
int passedIndex = candidateIndex;
row = _parsedData.Get(candidateIndex);
Debug.Assert(row.TokenType != JsonTokenType.PropertyName);
// Move before the value
if (row.IsSimpleValue)
{
candidateIndex -= DbRow.Size;
}
else
{
Debug.Assert(row.NumberOfRows > 0);
candidateIndex -= DbRow.Size * (row.NumberOfRows + 1);
}
row = _parsedData.Get(candidateIndex);
Debug.Assert(row.TokenType == JsonTokenType.PropertyName);
if (row.SizeOrLength >= minBytes)
{
byte[] tmpUtf8 = ArrayPool <byte> .Shared.Rent(maxBytes);
Span <byte> utf8Name = default;
try
{
int len = JsonReaderHelper.GetUtf8FromText(propertyName, tmpUtf8);
utf8Name = tmpUtf8.AsSpan(0, len);
return(TryGetNamedPropertyValue(
startIndex,
passedIndex + DbRow.Size,
utf8Name,
out value));
}
finally
{
// While property names aren't usually a secret, they also usually
// aren't long enough to end up in the rented buffer transcode path.
//
// On the basis that this is user data, go ahead and clear it.
utf8Name.Clear();
ArrayPool <byte> .Shared.Return(tmpUtf8);
}
}
// Move to the previous value
candidateIndex -= DbRow.Size;
}
// None of the property names were within the range that the UTF-8 encoding would have been.
value = default;
return(false);
}
