PHP - Ds Sequence::allocate() 函数

PHP 的 Ds\Sequence::allocate() 函数用于为 Sequence 的所需容量分配足够的内存。Sequence 的容量是指 Sequence 可以容纳的内存或元素数量。

如果 Sequence 的当前容量大于已分配的容量，则旧容量保持不变，不会分配新的容量。可以使用 capacity() 函数检查 Sequence 的当前容量。

语法

以下是 PHP Ds\Sequence::allocate() 函数的语法：

abstract public Ds\Sequence::allocate(int $capacity): void

参数

此函数接受一个参数，如下所述：

• capacity - 需要分配的容量。

返回值

此函数不返回任何值。

示例 1

以下是 PHP Ds\Sequence::allocate() 函数的基本示例：

<?php 
   $seq = new \Ds\Vector([]);
   echo "The sequence elements are: \n";
   print_r($seq);
   #using allocate() function
   $capacity = 30;
   echo "The capacity to be allocated: ".$capacity;
   $seq->allocate($capacity);
   echo "\nThe capacity after allocated: ";
   print_r($seq->capacity());
?>

输出

以上程序输出如下：

The sequence elements are:
Ds\Vector Object
(
)
The capacity to be allocated: 30
The capacity after allocated: 30

示例 2

以下是 PHP Ds\Sequence::allocate() 函数的另一个示例。我们使用此函数为此序列 ([10, 20, 30, 40, 50]) 分配新的容量 64：

<?php 
   $seq = new \Ds\Stack([10, 20, 30, 40, 50]);
   echo "The sequence elements are: \n";
   print_r($seq);
   echo "The current capacity before allocation: ";
   print_r($seq->capacity());
   $capacity = 64;
   echo "\nThe capacity need to be allocated: ".$capacity;
   #using allocate() function
   $seq->allocate($capacity);
   echo "\nThe capacity after allocated: ";
   print_r($seq->capacity());
?>

输出

执行上述程序后，将显示以下输出：

The sequence elements are:
Ds\Stack Object
(
    [0] => 50
    [1] => 40
    [2] => 30
    [3] => 20
    [4] => 10
)
The current capacity before allocation: 8
The capacity need to be allocated: 64
The capacity after allocated: 64

示例 3

如果已分配的容量小于 Sequence 的当前容量，则旧容量将保持不变：

<?php 
   $seq = new \Ds\Set(['a', 'e', 'i', 'o', 'u']);
   echo "The sequence elements are: \n";
   print_r($seq);
   echo "The current capacity before allocation: ";
   print_r($seq->capacity());
   $capacity = 4;
   echo "\nThe capacity need to be allocated: ".$capacity;
   #using allocate() function
   $seq->allocate($capacity);
   echo "\nThe capacity after allocated: ";
   print_r($seq->capacity());
?>

输出

执行上述程序后，将显示以下输出：

The sequence elements are:
Ds\Set Object
(
    [0] => a
    [1] => e
    [2] => i
    [3] => o
    [4] => u
)
The current capacity before allocation: 8
The capacity need to be allocated: 4
The capacity after allocated: 8