<?php
/*************************************************************************************************
This example demonstrates the use of the BitString and BitStringIterator classes on a
simple example string, "ABCDEF", which will be considered as a string of bits.
*************************************************************************************************/
require_once ( 'BitString.phpclass' ) ;
if ( php_sapi_name ( ) != 'cli' )
echo '<pre>' ;
// getbits -
// This function simply outputs bits from the specified value, up to $count.
function getbits ( $value, $count )
{
$result = '' ;
for ( $i = 0 ; $i < $count ; $i ++, $value >>= 1 )
$result .= ( $value & 1 ) ? '1' : '0' ;
return ( $result ) ;
}
// Our example string
$data = "ABCDEF" ;
// Create a bit string from it
$bs = new BitString ( $data ) ;
// Try the ToHex() and ToBin() functions. Note that ToBin (0) will print the bits in exactly the same order
// as they are stored (least significant bit first), while ToBin(1) will print them in the order they are
// printed by ToHex()
echo "ToHex() : " ; print_r ( $bs -> ToHex ( ) ) ; echo "\n" ;
echo "ToBin(1) : " ; print_r ( $bs -> ToBin ( 1 ) ) ; echo "\n" ;
echo "ToBin(0) : " ; print_r ( $bs -> ToBin ( 0 ) ) ; echo "\n" ;
// Use the ArrayAccess interface to retrieve and display each individual bit
echo "Bit per bit (for) : " ;
for ( $i = 0 ; $i < count ( $bs ) ; $i ++ )
echo $bs [$i] ;
// Use the Iterator interface to display each individual bit
echo "\nBit per bit (foreach) : " ;
foreach ( $bs as $bit )
echo $bit ;
// Now, use the BitString::GetBits() function to display bits by group of x bits, from 1 to 32.
// Note that the getbits() function defined here will add trailing zeroes for bit counts that are
// not a denominator of the machine's word size - this is not a bug, this inconvenience was aimed
// at making this example simpler
for ( $bit_count = 1 ; $bit_count <= 32 ; $bit_count ++ )
{
echo sprintf ( "\nTaking by %2d bits : ", $bit_count ) ;
for ( $i = 0 ; $i < count ( $bs ) ; $i += $bit_count )
{
$value = $bs -> GetBits ( $i, $bit_count ) ;
if ( $value === false )
output ( "FALSE for offset $i, count $bit_count" ) ;
echo getbits ( $value, $bit_count ) ;
}
}
// Now use a BitStringIterator object : extract bits from the bit string by groups of
// 3 components having 8 bits each. It should display the hexadecimal translation of
// "ABCDEF" which is : "414243444546"
echo "\nBitStringIterator(8,3) : " ;
foreach ( new BitStringIterator ( $bs, 8, 3 ) as $values )
{
foreach ( $values as $value )
echo ( sprintf ( "%02X", $value ) ) ;
}
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