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| //Serialization of unsigned integers of 16, 32 or 64 bits
//16 bits (can't store more than 15 bits):
// range [ 0, 127] -> one byte
// range [ 128, 32767] -> two bytes
//
//|c|xxxxxxx| |xxxxxxxx|
// ^ 7 8
// 0 <--7-->
// 1 <-------15------->
//32 bits (can't store more than 30 bits):
// range [ 0, 63] -> one byte
// range [ 64, 16383] -> two bytes
// range [ 16384, 4194303] -> three bytes
// range [ 4194304, 1073741823] -> four bytes
//
//|cc|xxxxxx| |xxxxxxxx| |xxxxxxxx| |xxxxxxxx|
// ^^ 6 8 8 8
// 00 <--6->
// 01 <-------14------>
// 10 <------------22------------>
// 11 <------------------30----------------->
//64 bits (can't store more than 61 bits):
// range [ 0, 31] -> one byte
// range [ 32, 8191] -> two bytes
// range [ 8192, 2097151] -> three bytes
// range [ 2097152, 536870911] -> four bytes
// range [ 536870912, 137438953471] -> five bytes (up to 128 "Gigas")
// range [ 137438953472, 35184372088831] -> six bytes (up to 32768 "Gigas")
// range [ 35184372088831, ...] -> seven bytes (up to 8388608 "Gigas")
// ...
//
//|ccc|xxxxx| |xxxxxxxx| |xxxxxxxx| |xxxxxxxx| |xxxxxxxx| |xxxxxxxx|
// ^^^ 5 8 8 8 8 8
// 000 <-5->
// 001 <------13------>
// 010 <-----------21------------>
// 011 <-----------------29----------------->
// 100 <-----------------------37---------------------->
// 101 <----------------------------45---------------------------->
// 110 ... etc
template<typename U>
inline unsigned count_serial_unsigned(U u)
{
//U must be unsigned 16, 32 or 64 bits
unsigned const shift_bits=serializable_type<U>::log2;
unsigned const bytes=serializable_type<U>::bytes;
//loose the log2(sizeof(U)) most significant bits
u<<=shift_bits;
//count bytes
unsigned count_bytes=bytes-1;
while (count_bytes && (u & U(0xFF)<<((bytes-1)*8))==0)
{
u<<=8;
--count_bytes;
}
return count_bytes+1;
}
template<typename IT, typename U>
inline IT serialize_unsigned(IT it_out, U u)
{
//IT is meant to be a byte string iterator
//U must be unsigned 16, 32 or 64 bits
unsigned const shift_bits=serializable_type<U>::log2;
unsigned const bits=serializable_type<U>::bits;
unsigned const bytes=serializable_type<U>::bytes;
//loose the log2(sizeof(U)) most significant bits
u<<=shift_bits;
//count bytes
unsigned count_bytes=bytes-1;
while (count_bytes && (u & U(0xFF)<<((bytes-1)*8))==0)
{
u<<=8;
--count_bytes;
}
//reconstruct shifted value, add count bytes in front
u=(U(count_bytes)<<(bits-shift_bits)) | (u>>shift_bits);
//serialize most significant byte first
u=byte_swap(u);
do
{
*it_out=(unsigned char)u;//explicit truncation
++it_out;
u>>=8;
}
while (count_bytes--);
return it_out;
}
template<typename IT, typename U>
inline IT unserialize_unsigned(IT cit_in, U & ru)
{
//IT is meant to be a byte string iterator
//U must be unsigned 16, 32 or 64 bits
unsigned const shift_bits=serializable_type<U>::log2;
U u=(unsigned char)*cit_in;
++cit_in;
unsigned count_bytes=unsigned(u>>(8-shift_bits));
u&=(0xFF>>shift_bits);
while (count_bytes)
{
u<<=8;
u|=(unsigned char)*cit_in;
++cit_in;
--count_bytes;
}
ru=u;
return cit_in;
}
template<typename IT, typename U>
inline IT serialize_unsigned_inverted(IT it_out, U u)
{
//IT is meant to be a byte string iterator
//U must be unsigned 16, 32 or 64 bits
unsigned const shift_bits=serializable_type<U>::log2;
unsigned const bits=serializable_type<U>::bits;
unsigned const bytes=serializable_type<U>::bytes;
//loose the log2(sizeof(U)) most significant bits
u<<=shift_bits;
//count bytes
unsigned count_bytes=bytes-1;
while (count_bytes && (u & U(0xFF)<<((bytes-1)*8))==0)
{
u<<=8;
--count_bytes;
}
//reconstruct shifted value, add count bytes in front
u=(U(count_bytes)<<(bits-shift_bits)) | (u>>shift_bits);
//serialize most significant byte first
u=byte_swap(u);
do
{
*it_out=(unsigned char)u ^ 0xFF;//explicit truncation, inversion
++it_out;
u>>=8;
}
while (count_bytes--);
return it_out;
}
template<typename IT, typename U>
inline IT unserialize_unsigned_inverted(IT cit_in, U & ru)
{
//IT is meant to be a byte string iterator
//U must be unsigned 16, 32 or 64 bits
unsigned const shift_bits=serializable_type<U>::log2;
U u=(unsigned char)*cit_in ^ 0xFF;//restore inversion
++cit_in;
unsigned count_bytes=unsigned(u>>(8-shift_bits));
u&=(0xFF>>shift_bits);
while (count_bytes)
{
u<<=8;
u|=(unsigned char)*cit_in ^ 0xFF;//restore inversion
++cit_in;
--count_bytes;
}
ru=u;
return cit_in;
} |
