Node.js Buffer.subarray()方法
原文:https://www . geesforgeks . org/node-js-buffer-subarray-method/
buffer.subarray()方法是缓冲模块的内置应用编程接口，用于裁剪数组的一部分，即从数组创建子数组。
语法:
Buffer.subarray( starting_index, ending_index )
参数:该方法有两个参数，如上所述，如下所述:
- starting _ index: This parameter specifies an integer value, indicating the starting address of the new buffer. Its default value is 0.
- [T0】 end _ index: 【T1] It specifies an integer value indicating the end address of the buffer where a new buffer is to be created. The default value is the length of the buffer.
返回值:该方法返回裁剪后的数组。该缓冲区指向相同的内存，但带有裁剪的开始和结束索引。如果参数中的 end _ index 大于缓冲区长度，则将缓冲区长度作为结束索引。
注意:如果新缓冲区被修改，那么当它们指向相同的内存时，相同的内容将反映在原始缓冲区中。
下面的例子说明了 buffer.subarray()方法在 Node.js 中的使用:
例 1:
// Node.js program to demonstrate the
// Buffer.subarray() method
// Allocating buffer
const buf = Buffer.from('GeeksforGeeks', 'ascii');
// Printing original buffer
console.log("Original buffer is: " + buf);
// Cropping buffer, here starting index
// is 5 and ending endex is 10
cropped_buf = buf.subarray(5, 10);
// Printing cropped buffer
console.log("Cropped buffer is: " + cropped_buf);
// Modifying cropped buffer
cropped_buf[0] = 70; // F
cropped_buf[1] = 79; // O
cropped_buf[2] = 82; // R
// Printing cropped buffer
console.log("Cropped buffer after modification is: " + cropped_buf);
// Printing original buffer
console.log("Original buffer after modification is: " + buf);
输出:
Original buffer is: GeeksforGeeks
Cropped buffer is: forGe
Cropped buffer after modification is: FORGe
Original buffer after modification is: GeeksFORGeeks
例 2:
// Node.js program to demonstrate the
// Buffer.subarray() method
// Allocating buffer
const buf = Buffer.from('GeeksforGeeks', 'ascii');
// Printing original buffer
console.log("Original buffer is: " + buf);
// Cropping buffer, here starting index
// is -10 and ending endex is -1
cropped_buf = buf.subarray(-12, -1);
// Printing cropped buffer
console.log("Cropped buffer is:" + cropped_buf);
// Cropping buffer again, here starting
// index is -10 and ending endex is -5
cropped_buf = buf.subarray(-10, -5);
// Printing cropped buffer
console.log("Cropped buffer is: " + cropped_buf);
// Cropping buffer again with no parameter
cropped_buf = buf.subarray();
// Printing cropped buffer
console.log("Cropped buffer is: " + cropped_buf);
输出:
Original buffer is: GeeksforGeeks
Cropped buffer is:eeksforGeek
Cropped buffer is: ksfor
Cropped buffer is: GeeksforGeeks
注意:以上程序使用node index.js命令编译运行。
参考:https://nodejs . org/API/buffer . html # buffer _ buf _ subarray _ start _ end
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