List from_be_bytes as Alternative in Transmute Docs

[domenukk]

Many code bases I see use transmute to convert raw bytes (&[u8]) to u32, f64, etc. - while they could, and probably should, use from_le_bytes or from_be_bytes.
The transmute docs include a lengthy section about Alternatives, but this obvious one seems to be missing.

[huangjiahua]

@domenukk I've used from_le_bytes and from_be_bytes several times in my little project. I want to have a try. Will this code snippet work?

    let raw_data = &[0x78, 0x56, 0x34, 0x12];
    
    let num = unsafe {
        std::mem::transmute::<[u8; 4], u32>(*raw_data)
    };
    // This result depends on your machine
    assert_eq!(num, 0x12345678);


    // use from_be_bytes and from_le_bytes instead to produce predictable result
    let num = u32::from_le_bytes(*raw_data);
    assert_eq!(num, 0x12345678);
    
    let num = u32::from_be_bytes(*raw_data);
    assert_eq!(num, 0x78563412);

[Duddino]

@huangjiahua maybe you can also add u32::from_ne_bytes() as an alternative to transmute but without unsafe
also you can show that u32::from_ne_bytes() is equal to mem::trasmute with an assertion

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[Alexendoo]

Closed by #71315