This is decoded string from bytes, they are always different. Am not using it in the code, its just for shown what is all about.

"Background:Sunfire Topo;Base:Eagle;Accessory3:None;Patch:Oreo;Jacket:Pink Bonez;Eyes:BloodShot;Beak:Drool;Accessory2:Nose Ring;Accessory1:None;Item:Knife;tags:Dope Eagles,ELEMENT-HYDRO,ATTACK-10,DEFENSE-5,HIGHNESS-4,SWAG-1;metadata:QmU7JcFDoGcUvNkDgsPz9cy13md4xHdNyD6itwmgVLuo7x/860.json"

This is array of bytes from above string which i get as input.

[66, 97, 99, 107, 103, 114, 111, 117, 110, 100, 58, 83, 117, 110, 102, 105, 114, 101, 32, 84, 111, 112, 111, 59, 66, 97, 115, 101, 58, 69, 97, 103, 108, 101, 59, 65, 99, 99, 101, 115, 115, 111, 114, 121, 51, 58, 78, 111, 110, 101, 59, 80, 97, 116, 99, 104, 58, 79, 114, 101, 111, 59, 74, 97, 99, 107, 101, 116, 58, 80, 105, 110, 107, 32, 66, 111, 110, 101, 122, 59, 69, 121, 101, 115, 58, 66, 108, 111, 111, 100, 83, 104, 111, 116, 59, 66, 101, 97, 107, 58, 68, 114, 111, 111, 108, 59, 65, 99, 99, 101, 115, 115, 111, 114, 121, 50, 58, 78, 111, 115, 101, 32, 82, 105, 110, 103, 59, 65, 99, 99, 101, 115, 115, 111, 114, 121, 49, 58, 78, 111, 110, 101, 59, 73, 116, 101, 109, 58, 75, 110, 105, 102, 101, 59, 116, 97, 103, 115, 58, 68, 111, 112, 101, 32, 69, 97, 103, 108, 101, 115, 44, 69, 76, 69, 77, 69, 78, 84, 45, 72, 89, 68, 82, 79, 44, 65, 84, 84, 65, 67, 75, 45, 49, 48, 44, 68, 69, 70, 69, 78, 83, 69, 45, 53, 44, 72, 73, 71, 72, 78, 69, 83, 83, 45, 52, 44, 83, 87, 65, 71, 45, 49, 59, 109, 101, 116, 97, 100, 97, 116, 97, 58, 81, 109, 85, 55, 74, 99, 70, 68, 111, 71, 99, 85, 118, 78, 107, 68, 103, 115, 80, 122, 57, 99, 121, 49, 51, 109, 100, 52, 120, 72, 100, 78, 121, 68, 54, 105, 116, 119, 109, 103, 86, 76, 117, 111, 55, 120, 47, 56, 54, 48, 46, 106, 115, 111, 110]

What i need is get the values from ELEMENT, ATTACK,DEFENSE,HIGHNESS,SWAG. While every byte in the array is changing. but some bytes are always same. I was thinking if there is any way how to extract it without using any Strings... Thanks for any ideas

so the output would look like this:

let element = [72, 89, 68, 82, 79];
let attack = [49, 48];
let defense = [53];
let highness = [52];
let swag = [49];

CodePudding user response：

You can do all this without allocating any extra space using rusts iterators, using split and related functions

At the top level, your data is of the form (key:value;)* This suggests first splitting on ; Then splitting each of these pieces into key and value using :

In your case, all the information is when the key is "tags".

Then within the tags section, you again have (mostly) key-value pairs of the form (key-value,)* so we need to split on , then break into key-value pairs using -.

An example that does this but only prints all the tag key-value pairs is:

fn split_kv(v: &[u8], c: u8) -> Option<(&[u8], &[u8])> {
    let n = v.iter().position(|&b| b == c)?;
    let w = v.split_at(n);
    Some((w.0, &(w.1)[1..]))
}

fn main() {
    let s: &str = "Background:Sunfire Topo;Base:Eagle;Accessory3:None;Patch:Oreo;Jacket:Pink Bonez;Eyes:BloodShot;Beak:Drool;Accessory2:Nose Ring;Accessory1:None;Item:Knife;tags:Dope Eagles,ELEMENT-HYDRO,ATTACK-10,DEFENSE-5,HIGHNESS-4,SWAG-1;metadata:QmU7JcFDoGcUvNkDgsPz9cy13md4xHdNyD6itwmgVLuo7x/860.json";
    let ss: &[u8] = s.as_bytes();

    let tags = ss
        .split(|&b| b == b';') // Break up at ';'
        .filter_map(|s| split_kv(s, b':')) // Split each piece into key-value pairs using ':'
        .filter_map(|(k, v)| { // Only keep the tags entry.
            if k == "tags".as_bytes() {
                Some(v)
            } else {
                None
            }
        }) 
        .next() // And just take the first of those.
        .unwrap(); 

    // Split the tags by ','
    for t in tags.split(|&b| b == b',') {
        // Then try to convert each to a key-value using '-' as seperator.
        if let Some((k, v)) = split_kv(t, b'-') {       
            println!(
                "k={:?} v={:?}",
                std::str::from_utf8(k).unwrap(),
                std::str::from_utf8(v).unwrap()
            );
        } else {
            println!("t={:?}", std::str::from_utf8(t).unwrap());
        }
    }
}

You can run this here