public static int CountTimestamps(byte[] b, int startindex, int len)
{
if (b == null || b.Length < startindex + len)
{
return(0);
}
// Encoding type is stored in the 4 high bits of the first byte
byte encoding = (byte)(b[startindex] >> 4);
switch (encoding)
{
case TimeEncoder.timeUncompressed:
// Uncompressed timestamps are just 8 bytes each
return((len - 1) / 8);
case TimeEncoder.timeCompressedRLE:
// First 9 bytes are the starting timestamp and scaling factor, skip over them
int j = startindex + 9;
// Next 1-10 bytes is our (scaled down by factor of 10) run length values
ulong value;
j += Varint.Read(b, j, out value);
// Last 1-10 bytes is how many times the value repeats
Varint.Read(b, j, out value);
return((int)value);
case TimeEncoder.timeCompressedPackedSimple:
// First 9 bytes are the starting timestamp and scaling factor, skip over them
var count = Simple8bDecoder.CountBytes(b, startindex + 9, len - 9);
return(count.Item1 + 1); // +1 is for the first uncompressed timestamp, starting timestamep in b[1:9]
default:
return(0);
}
}
private void decodePacked()
{
if (bytes == null || byteIndex >= endIndex)
{
return;
}
if (endIndex - byteIndex < 8)
{
err = "IntegerDecoder: not enough data to decode packed value";
return;
}
ulong v = BitConverter.ToUInt64(bytes, byteIndex);
// The first value is always unencoded
if (first)
{
first = false;
n = 1;
values[0] = v;
}
else
{
var m = Simple8bDecoder.Decode(values, v);
if (m.error != null)
{
// Should never happen, only error that could be returned is if the the value to be decoded was not
// actually encoded by simple8b encoder.
err = string.Format("failed to decode value {0}: {1}", v, m.error);
}
n = m.Item1;
}
i = 0;
byteIndex += 8;
}
public (int, string) DecodeAll(Span <byte> b, Span <ulong> dst)
{
if (b.Length == 0)
{
return(0, null);
}
byte encoding = (byte)(b[0] >> 4);
ulong div = (ulong)Math.Pow(10, b[0] & 0xF);
b = b.Slice(1);
if (encoding == timeUncompressed)
{
if ((b.Length & 0x7) != 0)
{
return(0, "timeArrayDecodeAll: expected multiple of 8 bytes");
}
int count = b.Length / 8;
ulong prev = 0;
for (int i = 0; i < count; i++)
{
prev += BitConverter.ToUInt64(b);
dst[i] = prev;
b = b.Slice(8);
}
return(count, null);
}//uncompressed
else if (encoding == timeCompressedPackedSimple)
{
if (b.Length < 8)
{
return(0, "timeArrayDecodeAll: not enough data to decode packed value");
}
(int count, string err) = Simple8bDecoder.CountBytes(b.Slice(8));
if (err != null)
{
return(0, err);
}
count++;
ulong[] bufarray = ArrayPool <ulong> .Shared.Rent(count);
Span <ulong> buf = new Span <ulong>(bufarray, 0, count);
//first value
dst[0] = BitConverter.ToUInt64(b);
var nerr = Simple8bDecoder.DecodeAll(buf.Slice(1), b.Slice(8));
if (nerr.error != null)
{
ArrayPool <ulong> .Shared.Return(bufarray);
return(0, err);
}
if (nerr.Item1 != count - 1)
{
ArrayPool <ulong> .Shared.Return(bufarray);
return(0, String.Format("timeArrayDecodeAll: unexpected number of values decoded; got={0}, exp={1}", nerr.Item1, count - 1));
}
// Compute the prefix sum and scale the deltas back up
var last = dst[0];
if (div > 1)
{
for (int i = 1; i < count; i++)
{
var dgap = buf[i] * div;
dst[i] = last + dgap;
last = dst[i];
}
}
else
{
for (int i = 1; i < count; i++)
{
dst[i] = buf[i] + last;
last = dst[i];
}
}
ArrayPool <ulong> .Shared.Return(bufarray);
return(count, null);
}//simple.
else if (encoding == timeCompressedRLE)
{
if (b.Length < 8)
{
return(0, "timeArrayDecodeAll: not enough data to decode RLE starting value");
}
// Lower 4 bits hold the 10 based exponent so we can scale the values back up
var mod = div;
ulong first = BitConverter.ToUInt64(b);
b = b.Slice(8);
// Next 1-10 bytes is our (scaled down by factor of 10) run length delta
int n = Varint.Read(b, out ulong delta);
if (n <= 0)
{
return(0, "timeArrayDecodeAll: invalid RLE delta value");
}
b = b.Slice(n);
// Scale the delta back up
delta *= mod;
// Last 1-10 bytes is how many times the value repeats
n = Varint.Read(b, out int count);
if (n <= 0)
{
return(0, "timeDecoder: invalid repeat value in decodeRLE");
}
var acc = first;
for (int i = 0; i < count; i++)
{
dst[i] = acc;
acc += delta;
}
return(count, null);
}//rle
else
{
return(0, string.Format("unknown encoding {0:X2}", encoding));
}
}
public (int, string) DecodeAll(Span <byte> b, Span <long> dst)
{
if (b.Length == 0)
{
return(0, null);
}
byte encoding = (byte)(b[0] >> 4);
b = b.Slice(1);
if (encoding == intUncompressed)
{
if ((b.Length & 0x7) != 0)
{
return(0, "integerArrayDecodeAll: expected multiple of 8 bytes");
}
int count = b.Length / 8;
long prev = 0;
for (int i = 0; i < count; i++)
{
prev += Encoding.ZigZagDecode(BitConverter.ToUInt64(b));
dst[i] = prev;
b = b.Slice(8);
}
return(count, null);
}//uncompressed
else if (encoding == intCompressedSimple)
{
if (b.Length < 8)
{
return(0, "integerArrayDecodeAll: not enough data to decode packed value");
}
(int count, string err) = Simple8bDecoder.CountBytes(b.Slice(8));
if (err != null)
{
return(0, err);
}
count++;
//first value
dst[0] = Encoding.ZigZagDecode(BitConverter.ToUInt64(b));
ulong[] bufarray = ArrayPool <ulong> .Shared.Rent(count);
Span <ulong> buf = new Span <ulong>(bufarray, 0, count);
var nerr = Simple8bDecoder.DecodeAll(buf.Slice(1), b.Slice(8));
if (nerr.error != null)
{
ArrayPool <ulong> .Shared.Return(bufarray);
return(0, err);
}
if (nerr.Item1 != count - 1)
{
ArrayPool <ulong> .Shared.Return(bufarray);
return(0, String.Format("integerArrayDecodeAll: unexpected number of values decoded; got={0}, exp={1}", nerr.Item1, count - 1));
}
// calculate prefix sum
var prev = dst[0];
for (int i = 1; i < count; i++)
{
prev += Encoding.ZigZagDecode(buf[i]);
dst[i] = prev;
}
ArrayPool <ulong> .Shared.Return(bufarray);
return(count, null);
}//simple.
else if (encoding == intCompressedRLE)
{
if (b.Length < 8)
{
return(0, "integerArrayDecodeAll: not enough data to decode RLE starting value");
}
long first = Encoding.ZigZagDecode(BitConverter.ToUInt64(b));
b = b.Slice(8);
// Next 1-10 bytes is the delta value
int n = Varint.Read(b, out ulong value);
if (n <= 0)
{
return(0, "integerArrayDecodeAll: invalid RLE delta value");
}
b = b.Slice(n);
long delta = Encoding.ZigZagDecode(value);
// Last 1-10 bytes is how many times the value repeats
n = Varint.Read(b, out int count);
if (n <= 0)
{
return(0, "integerArrayDecodeAll: invalid RLE repeat value");
}
count++;
if (delta == 0)
{
for (int i = 0; i < count; i++)
{
dst[i] = first;
}
}
else
{
long acc = first;
for (int i = 0; i < count; i++)
{
dst[i] = acc;
acc += delta;
}
}
return(count, null);
}//rle
else
{
return(0, string.Format("unknown encoding {0:X2}", encoding));
}
}
public TimeDecoder()
{
ts = new List <ulong>();
dec = new Simple8bDecoder();
}