/// <summary>
/// Parses the next tag.
/// If the end of logical stream was reached, an invalid tag of 0 is returned.
/// </summary>
public static uint ParseTag(ref ReadOnlySpan <byte> buffer, ref ParserInternalState state)
{
// The "nextTag" logic is there only as an optimization for reading non-packed repeated / map
// fields and is strictly speaking not necessary.
// TODO(jtattermusch): look into simplifying the ParseTag logic.
if (state.hasNextTag)
{
state.lastTag = state.nextTag;
state.hasNextTag = false;
return(state.lastTag);
}
// Optimize for the incredibly common case of having at least two bytes left in the buffer,
// and those two bytes being enough to get the tag. This will be true for fields up to 4095.
if (state.bufferPos + 2 <= state.bufferSize)
{
int tmp = buffer[state.bufferPos++];
if (tmp < 128)
{
state.lastTag = (uint)tmp;
}
else
{
int result = tmp & 0x7f;
if ((tmp = buffer[state.bufferPos++]) < 128)
{
result |= tmp << 7;
state.lastTag = (uint)result;
}
else
{
// Nope, rewind and go the potentially slow route.
state.bufferPos -= 2;
state.lastTag = ParsingPrimitives.ParseRawVarint32(ref buffer, ref state);
}
}
}
else
{
if (SegmentedBufferHelper.IsAtEnd(ref buffer, ref state))
{
state.lastTag = 0;
return(0);
}
state.lastTag = ParsingPrimitives.ParseRawVarint32(ref buffer, ref state);
}
if (WireFormat.GetTagFieldNumber(state.lastTag) == 0)
{
// If we actually read a tag with a field of 0, that's not a valid tag.
throw InvalidProtocolBufferException.InvalidTag();
}
return(state.lastTag);
}
internal static void Initialize(ReadOnlySequence <byte> input, int recursionLimit, out ParseContext ctx)
{
ctx.buffer = default;
ctx.state = default;
ctx.state.lastTag = 0;
ctx.state.recursionDepth = 0;
ctx.state.sizeLimit = DefaultSizeLimit;
ctx.state.recursionLimit = recursionLimit;
ctx.state.currentLimit = int.MaxValue;
SegmentedBufferHelper.Initialize(input, out ctx.state.segmentedBufferHelper, out ctx.buffer);
ctx.state.bufferPos = 0;
ctx.state.bufferSize = ctx.buffer.Length;
ctx.state.DiscardUnknownFields = false;
ctx.state.ExtensionRegistry = null;
}
public static void Initialize(ReadOnlySequence <byte> sequence, out SegmentedBufferHelper instance, out ReadOnlySpan <byte> firstSpan)
{
instance.codedInputStream = null;
if (sequence.IsSingleSegment)
{
firstSpan = sequence.First.Span;
instance.totalLength = firstSpan.Length;
instance.readOnlySequenceEnumerator = default;
}
else
{
instance.readOnlySequenceEnumerator = sequence.GetEnumerator();
instance.totalLength = (int)sequence.Length;
// set firstSpan to the first segment
instance.readOnlySequenceEnumerator.MoveNext();
firstSpan = instance.readOnlySequenceEnumerator.Current.Span;
}
}
public static void ReadMessage(ref ParseContext ctx, IMessage message)
{
int length = ParsingPrimitives.ParseLength(ref ctx.buffer, ref ctx.state);
if (ctx.state.recursionDepth >= ctx.state.recursionLimit)
{
throw InvalidProtocolBufferException.RecursionLimitExceeded();
}
int oldLimit = SegmentedBufferHelper.PushLimit(ref ctx.state, length);
++ctx.state.recursionDepth;
ReadRawMessage(ref ctx, message);
CheckReadEndOfStreamTag(ref ctx.state);
// Check that we've read exactly as much data as expected.
if (!SegmentedBufferHelper.IsReachedLimit(ref ctx.state))
{
throw InvalidProtocolBufferException.TruncatedMessage();
}
--ctx.state.recursionDepth;
SegmentedBufferHelper.PopLimit(ref ctx.state, oldLimit);
}
internal static T Read <T>(ref ParseContext ctx, FieldCodec <T> codec)
{
int length = ctx.ReadLength();
int oldLimit = SegmentedBufferHelper.PushLimit(ref ctx.state, length);
uint tag;
T value = codec.DefaultValue;
while ((tag = ctx.ReadTag()) != 0)
{
if (tag == codec.Tag)
{
value = codec.Read(ref ctx);
}
else
{
ParsingPrimitivesMessages.SkipLastField(ref ctx.buffer, ref ctx.state);
}
}
ParsingPrimitivesMessages.CheckReadEndOfStreamTag(ref ctx.state);
SegmentedBufferHelper.PopLimit(ref ctx.state, oldLimit);
return(value);
}
public static void Initialize(CodedInputStream codedInputStream, out SegmentedBufferHelper instance)
{
instance.totalLength = codedInputStream.InternalInputStream == null ? (int?)codedInputStream.InternalBuffer.Length : null;
instance.readOnlySequenceEnumerator = default;
instance.codedInputStream = codedInputStream;
}
