Node.js Buffer.readUIntBE()方法
原文:https://www . geesforgeks . org/node-js-buffer-readuintbe-method/
Buffer.readUIntBE()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的已分配缓冲区中读取指定数量的字节值。
语法:
Buffer.readUIntBE( offset, byteLength )
参数:该方法接受两个参数，如上所述，如下所述:
- Offset: It specifies the number of bytes to skip before reading, or simply indicates the index in the buffer. The value of offset is 0 < = offset < = buffer length–byte length . Its default value is 0.
- Byte Length: Specify the number of bytes to be read. The value of the byte length is 0 < The byte length < = 6 .
Return: 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.readUIntBE()方法:
例 1:
// Node program to demonstrate the
// Buffer.readUIntBE() Method
// Allocating buffer from array
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98]);
// Printing allocated buffer
console.log(buf);
// Reading data from the buffer
// and printing it as a string
console.log(buf.readUIntBE(0, 3).toString(16));
console.log(buf.readUIntBE(1, 3).toString(16));
console.log(buf.readUIntBE(2, 2).toString(16));
输出:
<Buffer 21 09 19 98>
210919
91998
1998
例 2:
// Node program to demonstrate the
// Buffer.readUIntBE() Method
// Allocating buffer from array
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98]);
// Printing allocated buffer
console.log(buf);
// Reading data from the buffer
// and printing it as a string
console.log(buf.readUIntBE(0, 3).toString(16));
console.log(buf.readUIntLE(0, 3).toString(16));
console.log(buf.readUIntBE(1, 2).toString(16));
console.log(buf.readUIntLE(1, 2).toString(16));
console.log(buf.readUIntBE(2, 1).toString(16));
console.log(buf.readUIntLE(2, 1).toString(16));
输出:
<Buffer 21 09 19 98>
210919
190921
919
1909
19
19
例 3:
// Node program to demonstrate the
// Buffer.readUIntBE() Method
// Allocating buffer from array
const buf = Buffer.from([0x21, 0x09, 0x19, 0x98]);
// Printing allocated buffer
console.log(buf);
// Reading data from the buffer
// and printing it as a string
console.log(buf.readUIntBE(0, 4).toString(16));
console.log(buf.readUIntBE(1, 2).toString(16));
console.log(buf.readUIntBE(2, 3).toString(16));
// Wrong index is provoded to produce error
console.log(buf.readUIntBE(3, 6).toString(16));
输出:
<Buffer 21 09 19 98>
21091998
919
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 <= 1\. Received 2
at boundsError (internal/buffer.js:49:9)
at readUInt24BE (internal/buffer.js:205:5)
at Buffer.readUIntBE (internal/buffer.js:148:12)
. . .
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 # buff _ readuintbe _ offset _ byte length
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