Node.js Buffer.readUInt32BE()方法
原文:https://www . geesforgeks . org/node-js-buffer-readuint 32 be-method/
Buffer.readUInt32BE()方法是 Buffer 模块中类 Buffer 的内置应用编程接口，用于从指定偏移量处分配的缓冲区中读取 32 位值。
语法:
Buffer.readUInt32BE( offset )
参数:该方法接受单参数偏移量，该偏移量指定读取前要跳过的字节数，或者简单地表示缓冲区中的索引。偏移量的值为 0 < =偏移量< =缓冲区长度–4。其默认值为 0。
返回值:这个方法返回一个从缓冲区读取的大端格式的整数值。
下面的例子说明了在 Node.js 中使用 Buffer.readUInt32BE()方法:
例 1:
// Node program to demonstrate the
// Buffer.readUInt32LE() Method
// Allocating buffer from array
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98,
0x16, 0x09, 0x19, 0x96]);
// Printing allocated buffer
console.log(buf);
// Reading 32 bits data from the buffer
// and printing it as a string
console.log(buf.readUInt32BE(0).toString(16));
console.log(buf.readUInt32BE(1).toString(16));
console.log(buf.readUInt32BE(2).toString(16));
console.log(buf.readUInt32BE(3).toString(16));
console.log(buf.readUInt32BE(4).toString(16));
输出:
<Buffer 21 09 19 98 16 09 19 96>
21091998
9199816
19981609
98160919
16091996
例 2:
// Node program to demonstrate the
// Buffer.readUInt32LE() Method
// Allocating buffer from array
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98,
0x34, 0xae, 0xe8, 0xff]);
// Printing allocated buffer
console.log(buf);
// Reading 16bits data from the
// buffer and printing it as a string
console.log(buf.readUInt32BE(0).toString(16));
console.log(buf.readUInt32LE(0).toString(16));
console.log(buf.readUInt32BE(1).toString(16));
console.log(buf.readUInt32LE(1).toString(16));
console.log(buf.readUInt32BE(2).toString(16));
console.log(buf.readUInt32LE(2).toString(16));
console.log(buf.readUInt32BE(3).toString(16));
console.log(buf.readUInt32LE(3).toString(16));
console.log(buf.readUInt32BE(4).toString(16));
console.log(buf.readUInt32LE(4).toString(16));
输出:
<Buffer 21 09 19 98 34 ae e8 ff>
21091998
98190921
9199834
34981909
199834ae
ae349819
9834aee8
e8ae3498
34aee8ff
ffe8ae34
例 3:
// Node program to demonstrate the
// Buffer.readUInt32LE() Method
// Allocating buffer from array
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98]);
// Printing allocated buffer
console.log(buf);
// Reading 16bits data from the buffer
// and printing it as a string
console.log(buf.readUInt32BE(0).toString(16));
// Wrong index is provoded to produce error
console.log(buf.readUInt32BE(1).toString(16));
输出:
<Buffer 21 09 19 98>
21091998
internal/buffer.js:49
throw new ERR_OUT_OF_RANGE(type || 'offset',
^
RangeError [ERR_OUT_OF_RANGE]: The value of "offset" is out of range.
It must be >= 0 and <= 0\. Received 1
at boundsError (internal/buffer.js:49:9)
at Buffer.readUInt32BE (internal/buffer.js:192:5)
. . .
注意:以上程序使用node index.js命令编译运行。
参考:T2【https://nodejs . org/API/buffer . html # buffer _ buf _ readuint 32 be _ offset
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