/ 
Bit-Manip-PP-1.05
River stage one • 1 direct dependent • 2 total dependents
/ Bit::Manip::PP

NAME

Bit::Manip::PP - Pure Perl functions to simplify bit string manipulation

Coverage Status

SYNOPSIS

use Bit::Manip::PP qw(:all);

my $b;    # bit string
$b = 128; # 10000000

$b = bit_toggle($b, 4); # 10010000
$b = bit_toggle($b, 4); # 10000000

bit_toggle(\$b, 4); # same as above, but with a reference

$b = bit_off($b, 7);    # 0 
$b = bit_on($b, 7);     # 10000000 

bit_off(\$b, 7);
bit_on(\$b, 7);

# get the value of a range of bits...
# in this case, we'll print the value of bits 4-3

$b = 0b00111000; (56)

print bit_get($b, 4, 3); # 3

# set a range of bits...
# let's set bits 4-2 to binary 101

$b = 0b10000000;

$b = bit_set($b, 2, 3, 0b101); # 10010100

bit_set(\$b, 2, 3, 0b101); # reference

# clear some bits

$b = 0b11111111;

$num_bits = 3;
$lsb = 3;

$b = bit_clr($b, $lsb, $num_bits); # 11000111

bit_clr(\$b, $lsb, $num_bits); # reference

# helpers

my ($num_bits, $lsb) = (3, 2);
print bit_mask($num_bits, $lsb); # 28, or 11100

print bit_bin(255); # 11111111 (same as printf("%b", 255);)

DESCRIPTION

This is the Pure Perl version of the XS-based Bit::Manip distribution.

Provides functions to aid in bit manipulation (set, unset, toggle, shifting) etc. Particularly useful for embedded programming and writing device communication software.

In functions that modify your data, you can pass your data by value and get the modified value returned, or pass it in as a scalar reference and we'll modify the data inline.

Currently, up to 32-bit integers are supported.

EXPORT_OK

Use the :all tag (eg: use Bit::Manip::PP qw(:all);) to import the following functions into your namespace, or pick and choose individually:

bit_get 
bit_set
bit_clr
bit_toggle
bit_on
bit_off
bit_bin
bit_count
bit_mask

FUNCTIONS

bit_get

Retrieves the value of specified bits within a bit string.

Parameters:

$data

Mandatory: Integer, the bit string you want to send in. Eg: 255 for 11111111 (or 0xFF).

$msb

Mandatory: Integer, the Most Significant Bit (leftmost) of the group of bits to collect the value for (starting from 0 from the right, so with 1000, so you'd send in 3 as the start parameter for the bit set to 1). Must be 1

$lsb

Optional: Integer, the Least Significant Bit (rightmost) of the group of bits to collect the value for (starting at 0 from the right). A value of 0 means return the value from $msb through to the very end of the bit string. A value of 1 will capture from $msb through to bit 1 (second from right). This value must be equal to or lower than $msb.

Return: Integer, the modified $data param.

bit_set

Allows you to set a value for specific bits in your bit string.

Parameters:

$data

Mandatory: Integer, the bit string you want to manipulate bits in. Optionally, send in a reference to the scalar, and we'll work directly on it instead of passing by value and getting the updated value returned.

$lsb

Mandatory: Integer, the least significant bit (rightmost) in the bit range you want to manipulate. For example, if you wanted to set a new value for bits 7-5, you'd send in 5.

$bits

Mandatory: Integer, the number of bits you plan on setting. This is so that any leading zeros are honoured.

$value

Mandatory: Integer, the value that you want to change the specified bits to. Easiest if you send in a binary string (eg: 0b1011 in Perl).

Return: Integer, the modified $data param if <C$data> is passed in by value, or 0 if passed in by reference.

Example:

You have an 8-bit register where the MSB is a start bit, and the rest of the bits are zeroed out:

my $data = 0b10000000; # (0x80, or 128)

The datasheet for the hardware you're writing to requires you to set bits 6-4 to 111 in binary (always start from bit 0, not 1):

10000000
 ^^^   ^
 6-4   0

Code:

my $x = bit_set($data, 4, 3, 0b111); # (0x07, or 7)
printf("%b\n", $x); # prints 11110000

bit_clr

Clear (unset to 0) specific bits in the bit string.

Parameters:

$data

Mandatory: Integer, the bit string you want to manipulate bits in. Optionally, send in a reference to the scalar, and we'll work directly on it instead of passing by value and getting the updated value returned.

$lsb

Mandatory: Integer, the least significant bit (rightmost) in the bit range you want to manipulate. For example, if you wanted to clear bits 7-5, you'd send in 5.

$nbits

Mandatory: Integer, the number of bits you're wanting to clear, starting from the $lsb bit, and clearing the number of bits to the left.

Return: Integer, the modified $data param if <C$data> is passed in by value, or 0 if passed in by reference.

bit_toggle

Toggles a single bit. If it's 0 it'll toggle to 1 and vice-versa.

Parameters:

$data

Mandatory: Integer, the number/bit string to toggle a bit in. Optionally, send in a reference to the scalar, and we'll work directly on it instead of passing by value and getting the updated value returned.

$bit

Mandatory: Integer, the bit number counting from the right-most (LSB) bit starting from 0.

Return: Integer, the modified $data param if <C$data> is passed in by value, or 0 if passed in by reference.

bit_on

Sets a single bit (sets to 1), regardless of its current state.

Parameters:

$data

Mandatory: Integer, the number/bit string to toggle a bit in. Optionally, send in a reference to the scalar, and we'll work directly on it instead of passing by value and getting the updated value returned.

$bit

Mandatory: Integer, the bit number counting from the right-most (LSB) bit starting from 0.

Return: Integer, the modified $data param if <C$data> is passed in by value, or 0 if passed in by reference.

bit_off

Unsets a single bit (sets to 0), regardless of its current state.

Parameters:

$data

Mandatory: Integer, the number/bit string to toggle a bit in. Optionally, send in a reference to the scalar, and we'll work directly on it instead of passing by value and getting the updated value returned.

$bit

Mandatory: Integer, the bit number counting from the right-most (LSB) bit starting from 0.

Return: Integer, the modified $data param if <C$data> is passed in by value, or 0 if passed in by reference.

bit_mask

Generates a bit mask for the specific bits you specify.

Parameters:

$bits

Mandatory: Integer, the number of bits to get the mask for.

$lsb

Mandatory: Integer, the LSB at which you plan on implementing your change.

Return: Integer, the bit mask ready to be applied.

bit_bin

Returns the binary representation of a number as a string of ones and zeroes.

Parameters:

$data

Mandatory: Integer, the number you want to convert.

bit_count

Returns either the total count of bits in a number, or just the number of set bits (if the $set, parameter is sent in and is true).

Parameters:

$num

Mandatory: Unsigned integer, the number to retrieve the total number of bits for. For example, if you send in 15, the total number of bits would be 4, likewise, for 255, the number of bits would be 16.

$set

Optional: Integer. If this is sent and is a true value, we'll return the number of *set* bits only. For example, for 255, the set bits will be 8 (ie. all of them), and for 8, the return will be 1 (as only the MSB is set out of all four of the total).

Return: Integer, the number of bits that make up the number if $set is 0, and the number of set bits (1's) if $set is true.

AUTHOR

Steve Bertrand, <steveb at cpan.org>

LICENSE AND COPYRIGHT

Copyright 2017 Steve Bertrand.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.