gmp_setbit
(PHP 4 >= 4.0.4, PHP 5, PHP 7)
gmp_setbit — Set bit
说明
&$a
, int $index
[, bool $bit_on = true
] )
Sets bit index in a.
参数
-
a -
The value to modify.
可以是一个 GMP 数据 resouce ，或一个可以转换为数值的字符串。
-
index -
The index of the bit to set. Index 0 represents the least significant bit.
-
bit_on -
True to set the bit (set it to 1/on); false to clear the bit (set it to 0/off).
返回值
GMP 数值 资源 .
范例
Example #1 gmp_setbit() example - 0 index
<?php
$a = gmp_init ( "2" ); //
echo gmp_strval ( $a ), ' -> 0b' , gmp_strval ( $a , 2 ), "\n" ;
gmp_setbit ( $a , 0 ); // 0b10 now becomes 0b11
echo gmp_strval ( $a ), ' -> 0b' , gmp_strval ( $a , 2 ), "\n" ;
?> 以上例程会输出：
2 -> 0b10 3 -> 0b11
Example #2 gmp_setbit() example - 1 index
<?php
$a = gmp_init ( "0xfd" );
echo gmp_strval ( $a ), ' -> 0b' , gmp_strval ( $a , 2 ), "\n" ;
gmp_setbit ( $a , 1 ); // index starts at 0
echo gmp_strval ( $a ), ' -> 0b' , gmp_strval ( $a , 2 ), "\n" ;
?> 以上例程会输出：
253 -> 0b11111101 255 -> 0b11111111
Example #3 gmp_setbit() example - clearing a bit
<?php
$a = gmp_init ( "0xff" );
echo gmp_strval ( $a ), ' -> 0b' , gmp_strval ( $a , 2 ), "\n" ;
gmp_setbit ( $a , 0 , false ); // clear bit at index 0
echo gmp_strval ( $a ), ' -> 0b' , gmp_strval ( $a , 2 ), "\n" ;
?> 以上例程会输出：
255 -> 0b11111111 254 -> 0b11111110
注释
Note:
Unlike most of the other GMP functions, gmp_setbit() must be called with a GMP resource that already exists (using gmp_init() for example). One will not be automatically created.
参见
- gmp_clrbit() - Clear bit
- gmp_testbit() - Tests if a bit is set
用户评论:
[#1] bluej100@gmail [2007-07-27 09:07:47]
The third parameter is somewhat confusingly named; it would probably be better described as "$set_state". If true, it sets the bit to 1. If false, it sets the bit to 0. Default is true.
<?php
$num = gmp_init(1);
gmp_setbit($num, 1);
echo 'gmp_setbit(1, 1): '.gmp_strval($num, 2)."\n"; // 11
$num = gmp_init(1);
gmp_setbit($num, 1, true);
echo 'gmp_setbit(1, 1, true): '.gmp_strval($num, 2)."\n"; // 11
$num = gmp_init(1);
gmp_setbit($num, 0, false);
echo 'gmp_setbit(1, 0, false): '.gmp_strval($num, 2)."\n"; // 0
?>