buf.subarray([start[, end]])

• start <integer> 新的 Buffer 将开始的位置。 默认值: 0。
• end <integer> 新的 Buffer 将结束的位置（不包括在内）。 默认值: buf.length.
• 返回: <Buffer>

返回新的 Buffer，其引用与原始缓冲区相同的内存，但由 start 和 end 索引进行偏移和裁剪。

指定 end 大于 buf.length 将返回与 end 等于 buf.length 相同的结果。

该方法继承自 TypedArray.prototype.subarray()。

修改新的 Buffer 切片会修改原来 Buffer 中的内存，因为两个对象分配的内存是重叠的。

// 用 ASCII 字母创建 `Buffer`，取一个切片，并从原来的 `Buffer` 修改一个字节。

const buf1 = Buffer.allocUnsafe(26);

for (let i = 0; i < 26; i++) {
  // 97 是 'a' 的十进制 ASCII 值。
  buf1[i] = i + 97;
}

const buf2 = buf1.subarray(0, 3);

console.log(buf2.toString('ascii', 0, buf2.length));
// 打印: abc

buf1[0] = 33;

console.log(buf2.toString('ascii', 0, buf2.length));
// 打印: !bc

指定负索引会导致相对于 buf 的末尾而不是开头生成切片。

const buf = Buffer.from('buffer');

console.log(buf.subarray(-6, -1).toString());
// 打印: buffe
// (相当于 buf.subarray(0, 5).)

console.log(buf.subarray(-6, -2).toString());
// 打印: buff
// (相当于 buf.subarray(0, 4).)

console.log(buf.subarray(-5, -2).toString());
// 打印: uff
// (相当于 buf.subarray(1, 4).)

• start <integer> Where the new Buffer will start. Default: 0.
• end <integer> Where the new Buffer will end (not inclusive). Default: buf.length.
• Returns: <Buffer>

Returns a new Buffer that references the same memory as the original, but offset and cropped by the start and end indices.

Specifying end greater than buf.length will return the same result as that of end equal to buf.length.

This method is inherited from TypedArray.prototype.subarray().

Modifying the new Buffer slice will modify the memory in the original Buffer because the allocated memory of the two objects overlap.

// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte
// from the original `Buffer`.

const buf1 = Buffer.allocUnsafe(26);

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf1[i] = i + 97;
}

const buf2 = buf1.subarray(0, 3);

console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: abc

buf1[0] = 33;

console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: !bc

Specifying negative indexes causes the slice to be generated relative to the end of buf rather than the beginning.

const buf = Buffer.from('buffer');

console.log(buf.subarray(-6, -1).toString());
// Prints: buffe
// (Equivalent to buf.subarray(0, 5).)

console.log(buf.subarray(-6, -2).toString());
// Prints: buff
// (Equivalent to buf.subarray(0, 4).)

console.log(buf.subarray(-5, -2).toString());
// Prints: uff
// (Equivalent to buf.subarray(1, 4).)