// Decodes and consumes a variable-length integer consisting of "length" bytes
// in little-endian format. Returns false if not enough bytes are available.
//
// REQUIRES: T is an unsigned integer type.
// REQUIRES: 2 <= sizeof(T) <= 8
// REQUIRES: 0 <= length <= sizeof(T)
public static bool DecodeUintWithLength(int length, Decoder decoder, out UInt64 result)
{
result = default;
if (decoder.Avail() < length)
{
return(false);
}
result = EncodedUintVector_UInt64.GetUintWithLength(decoder.Buffer, decoder.Offset, length);
decoder.Skip(length);
return(true);
}
// Initializes the EncodedS2PointVector.
//
// REQUIRES: The Decoder data buffer must outlive this object.
public bool Init(Decoder decoder)
{
if (decoder.Avail() < 1)
{
return(false);
}
// Peek at the format but don't advance the decoder; the format-specific
// Init functions will do that.
format_ = (Format)(decoder.Get8() & kEncodingFormatMask);
return(format_ switch
{
Format.UNCOMPRESSED => InitUncompressedFormat(decoder),
Format.CELL_IDS => InitCellIdsFormat(decoder),
_ => false,
});
// Initializes the EncodedS2CellIdVector.
//
// REQUIRES: The Decoder data buffer must outlive this object.
public bool Init(Decoder decoder)
{
// All encodings have at least 2 bytes (one for our header and one for the
// EncodedUintVector header), so this is safe.
if (decoder.Avail() < 2)
{
return(false);
}
// Invert the encoding of (shift_code, base_len) described above.
int code_plus_len = decoder.Get8();
int shift_code = code_plus_len >> 3;
if (shift_code == 31)
{
shift_code = 29 + decoder.Get8();
if (shift_code > 56)
{
return(false); // Valid range 0..56
}
}
// Decode the "base_len" most-significant bytes of "base".
int base_len = code_plus_len & 7;
if (!EncodedUintVector.DecodeUintWithLength(base_len, decoder, out base_))
{
return(false);
}
base_ <<= 64 - 8 * Math.Max(1, base_len);
// Invert the encoding of "shift_code" described above.
if (shift_code >= 29)
{
shift_ = (byte)(2 * (shift_code - 29) + 1);
base_ |= 1UL << (shift_ - 1);
}
else
{
shift_ = (byte)(2 * shift_code);
}
return(deltas_.Init(decoder));
}
// Initializes the EncodedUintVector. Returns false on errors, leaving the
// vector in an unspecified state.
//
// REQUIRES: The Decoder data buffer must outlive this object.
public bool Init(Decoder decoder)
{
if (!decoder.TryGetVarUInt64(out var size_len))
{
return(false);
}
Count = (int)(size_len / sizeof(UInt16)); // Optimized into bit shift.
len_ = (Byte)((size_len & ((UInt16)(sizeof(UInt16) - 1))) + 1);
if (Count > int.MaxValue / sizeof(UInt16))
{
return(false);
}
int bytes = Count * len_;
if (decoder.Avail() < bytes)
{
return(false);
}
data_ = decoder.Buffer;
decoder.Skip(bytes);
return(true);
}