STXXL  1.4.1
 All Classes Namespaces Files Functions Variables Typedefs Enumerations Enumerator Friends Macros Groups Pages
Signed and Unsigned Integer Types

STXXL provides two very important types: stxxl::int_type and stxxl::unsigned_type. These should be used for general counting and indexing types, as they are defined to be the size of a register on the machines: on 32-bit machines the two types are 4 bytes size, while on a 64-bit machine the two types are 8 bytes in size!

The previous types are for general purpose counting. For real 64-bit integers, also on 32-bit machines, STXXL also provides a stxx::uint64 type (independent of other headers).

See the file common/types.h

uint40 and uint48 Unsigned Integer Types

When storing file offsets in external memory, one often does not require full 64-bit indexes. Mostly, 40-bit or 48-bit are sufficient, if only < 1 TiB or < 16 TiB of data are processed. If one stores theses integers in five or six bytes, the total I/O volume can be reduced significantly.

Since this issue occurs commonly in EM algorithms, STXXL provides two types: stxxl::uint40 and stxxl::uint48.

See the file common/uint_types.h