++ed by:
TYLDUM KES STEVEB

3 PAUSE users

Steve Bertrand

NAME

Bit::Manip - Functions to simplify bit string manipulation

SYNOPSIS

    use Bit::Manip qw(:all);

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

    $b = bit_toggle($b, 4); # 10010000
    $b = bit_toggle($b, 4); # 10000000
    
    $b = bit_off($b, 7);    # 0 
    $b = bit_on($b, 7);     # 10000000 

    # 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;
    my $num_bits = 3; # 0b101 in the call is 3 bits

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

    # clear some bits

    $b = 0b11111111;

    $num_bits = 3;
    $lsb = 3;

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

    # 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

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

Currently, up to 32-bit integers are supported.

EXPORT_OK

Use the :all tag (eg: use Bit::Manip 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 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.

    $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.

    $nbits

Mandatory: Integer, the number of bits you're sending in. We need this param in the event your leading bit is a zero. For example, if you're sending in 0b111 or 0b001, this param would be 3.

    $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.

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.

    $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.

Returns the modified bit string.

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.

    $bit

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

Return: Integer, the modified $data param.

bit_on

Sets a single bit (sets to 1), regardless of its current state. This is just a short form of setting a single bit with bit_set.

Parameters:

    $data

Mandatory: Integer, the number/bit string to toggle a bit in.

    $bit

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

Return: Integer, the modified $data param.

bit_off

Unsets a single bit (sets to 0), regardless of its current state. This is just a short form of clearing a single bit with bit_set.

Parameters:

    $data

Mandatory: Integer, the number/bit string to toggle a bit in.

    $bit

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

Return: Integer, the modified $data param.

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.

bit_mask

Generates a bit mask for the specific bits you specify.

Parameters:

    $nbits

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.

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.