private static bool TryReadPrefixLength(Stream source, PrefixStyle style, int tag, out uint length, Getter <int, bool> processField)
{
MethodStart:
switch (style)
{
case PrefixStyle.None:
length = uint.MaxValue;
return(true);
case PrefixStyle.Base128:
if (tag <= 0)
{
return(SerializationContext.TryDecodeUInt32(source, out length));
}
uint expected = GetFieldToken(tag, WireType.String), actual;
if (!SerializationContext.TryDecodeUInt32(source, out actual))
{
length = 0;
return(false);
}
WireType wireType;
int actualTag;
ParseFieldToken(actual, out wireType, out actualTag);
if (processField != null)
{
if (processField(actualTag))
{
length = SerializationContext.DecodeUInt32(source);
return(true);
}
}
else if (expected == actual)
{
length = SerializationContext.DecodeUInt32(source);
return(true);
}
switch (wireType)
{
case WireType.String:
SerializationContext.SkipStringData(source);
goto MethodStart;
default:
throw new ProtoException("A record with a different tag could not be jumped because of the wire-type: " + wireType);
}
case PrefixStyle.Fixed32:
return(SerializationContext.TryDecodeUInt32Fixed(source, out length));
default:
throw new NotSupportedException("Invalid prefix style: " + style);
}
}
private static bool TryReadPrefixLength(SerializationContext context, PrefixStyle style, int tag, out uint length)
{
MethodStart:
switch (style)
{
case PrefixStyle.None:
length = uint.MaxValue;
return(true);
case PrefixStyle.Base128:
if (tag <= 0)
{
return(context.TryDecodeUInt32(out length));
}
uint expected = GetFieldToken(tag, WireType.String), actual;
if (!context.TryDecodeUInt32(out actual))
{
length = 0;
return(false);
}
if (expected == actual)
{
length = context.DecodeUInt32();
return(true);
}
WireType wireType;
int actualTag;
ParseFieldToken(actual, out wireType, out actualTag);
SkipData(context, actualTag, wireType);
goto MethodStart;
case PrefixStyle.Fixed32:
return(context.TryDecodeUInt32Fixed(out length));
default:
throw new NotSupportedException("Invalid prefix style: " + style);
}
}
/// <summary>Indicates the number of bytes expected for the next message.</summary>
/// <param name="buffer">The buffer containing the data to investigate for a length.</param>
/// <param name="index">The offset of the first byte to read from the buffer.</param>
/// <param name="count">The number of bytes to read from the buffer.</param>
/// <param name="style">The algorithm used to encode the length.</param>
/// <param name="length">The length of the message, if it could be identified.</param>
/// <returns>True if a length could be obtained, false otherwise.</returns>
public static bool TryReadLengthPrefix(byte[] buffer, int index, int count, PrefixStyle style, out int length)
{
using (Stream source = new MemoryStream(buffer, index, count))
{
uint len;
bool result;
switch (style)
{
case PrefixStyle.Fixed32:
result = SerializationContext.TryDecodeUInt32Fixed(source, out len);
break;
case PrefixStyle.Base128:
result = SerializationContext.TryDecodeUInt32Fixed(source, out len);
break;
default:
throw new ArgumentOutOfRangeException("style", "Invalid prefix style: " + style);
}
length = (int)len;
return(result);
}
}