Node.js Buffer.readUInt32BE() 方法

Buffer.readUInt32BE() 方法是 Buffer 模块中 Buffer 类的内置应用程序编程接口，用于从指定偏移量的已分配缓冲区中读取 32 位值。

句法：

Buffer.readUInt32BE( offset )

参数：此方法接受单个参数偏移量，它指定在读取之前要跳过的字节数，或者只是表示缓冲区中的索引。 offset 的值是0 <= offset <= Buffer.length – 4 。它的默认值为 0。

返回值：此方法返回一个整数值，它以大端格式从缓冲区读取。

下面的示例说明了在 Node.js 中使用 Buffer.readUInt32BE() 方法：

示例 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：

21091998
9199816
19981609
98160919
16091996

示例 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：

21091998
98190921
9199834
34981909
199834ae
ae349819
9834aee8
e8ae3498
34aee8ff
ffe8ae34

示例 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：

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：以上程序将使用node index.js命令编译运行。

参考： https://nodejs.org/api/buffer.html#buffer_buf_readuint32be_offset