FBB::Field(3bobcat) Number fields FBB::Field(3bobcat)
NAME
FBB::Field - sets and retrieves offset based number fields
SYNOPSIS
#include <bobcat/field>
DESCRIPTION
Numbers may contain offset-based sub-fields. E.g., a value like 12345
might consist of fields 12 and 345. Such fields can be considered
offset-based, using end- and begin offsets in the number
representations. In this example 345 begins at digit position 0
(indicating the least significant digit of 12345) and at digit position
3 the next field starts. Likewise, the field 12 begins at digit
position 3 and has ended at digit position 5.
The Field class template provides facilities for retrieving and
assigning position based values of existing numeric values of
(currently) at most 64 bits.
To represent such fields the following format is used:
Field<base, end, begin>::function(argument(s))
where base specifies the number system's base value, end specifies the
(0-based) index position where the number field ends, and begin
specifies the index position where the number field begins. Here are
two examples, using the decimal number system:
Field<10, 3, 0>::get(12345) // returns 345
Field<10, 5, 3>::get(12345) // returns 12
The decision to specify the end offset before (i.e., left of) the begin
offset is based on the consideration that this corresponds to the
standard way of looking at digit positions in numbers, where the end
offset is found to the left of the begin offset.
Values of fields can be retrieved, but they can also be set: to set a
field's value the following format is used:
Field<10, 3, 1>::set(12345, 99) // returns 12995
Field<10, 1, 0>::set(12345, 0) // returns 12450
When values are assigned to fields the maximum width of the destination
field is taken into account. When specifying 9999 instead of 99 in the
above example the returned value will still be 12995, as the
destination field has a width of two digit positions. Likewise,
specifying a smaller value sets the remaining (more significant) digits
to 0:
Field<10, 3, 1>::set(12345, 9) // returns 12095
The class templates themselves are unaware of bases of number systems.
Since 0xdeaf equals the decimal value 57007 and 0xd equals 13, calling
the above function as
Field<16, 1, 0>::set(76007, 13)
returns the hexadecimal value 0xdead'.
The Field class template requires three non-type numeric arguments:
o base, specifying the base of the number system;
o end, specifying the 0-based offset of the digit position where
the field has ended;
o begin, specifying the 0-based offset of the digit position where
the field begins;
The class template is specialized for situations where base is a mere
power of 2 (like 2, 4, 8, 16, ...) because in those cases
bit-operations can be used which are faster than multiplications,
divisions and modulo computation which are required when other number
system bases are used.
NAMESPACE
FBB
All constructors, members, operators and manipulators, mentioned in
this man-page, are defined in the namespace FBB.
INHERITS FROM
-
MEMBER FUNCTIONS
o uint64_t Field<base, end, begin>::get(uint64_t value):
value is interpreted as a value in the base number system, and
using digit positions in that number system the value of the
digits from offset begin to (but not including) offset end is
returned;
o uint64_t Field<base, end, begin>::set(uint64_t value, uint64_t
field):
value is interpreted as a value in the base number system, and
using digit positions in that number system the digits from
offset begin to (but not including) offset end are replaced by
field's value. When the number of fields's digits (also using
number system base) exceeds end - begin then those excess digits
are ignored.
EXAMPLE
See the examples in the DESCRIPTION section
FILES
bobcat/field - defines the class interface
SEE ALSO
bobcat(7)
BUGS
None Reported.
BOBCAT PROJECT FILES
o https://fbb-git.gitlab.io/bobcat/: gitlab project page;
o bobcat_6.06.02-x.dsc: detached signature;
o bobcat_6.06.02-x.tar.gz: source archive;
o bobcat_6.06.02-x_i386.changes: change log;
o libbobcat1_6.06.02-x_*.deb: debian package containing the
libraries;
o libbobcat1-dev_6.06.02-x_*.deb: debian package containing the
libraries, headers and manual pages;
BOBCAT
Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.
COPYRIGHT
This is free software, distributed under the terms of the GNU General
Public License (GPL).
AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl).
libbobcat-dev_6.06.02 2005-2024 FBB::Field(3bobcat)