将4个二进制字节转换为单精度浮点数

Question

I have a single-precision, big-endian floating point number stored in 4 binary bytes that I'd like to decode into a JS Number . The bytes were generated using Ruby's Array#pack method like:

[100.32].pack('g')  # "\x42\xC8\xA3\xD7"

Using the npm binary package I can decode these bytes as a 32-bit unsigned integer:

let binary = require('binary');  // npm install binary
let buf = new Buffer([0x42,0xc8,0xa3,0xd7]);
let val = binary.parse(buf).word32bu('foo').vars.foo;
console.log(val);
// 1120445399

…but that doesn't help me. How can I convert either 1120445399 or [0x42,0xc8,0xa3,0xd7] into the floating point number 100.32 ?

Answer 1

It looks like it's stored as a float, which is 32-bit. Node can already handle these common number parsing/writing scenarios. In this particular case, you can just use buf.readFloatBE(0) to convert the 4 bytes.