Initial commit

.gitignore

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+/target
+/Cargo.lock

Cargo.toml

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+[package]
+name = "readformat"
+version = "0.1.0"
+edition = "2021"
+repository = "https://github.com/tudbut/readformat"
+license = "MIT"
+description = "Very small format reader"
+
+[dependencies]

src/lib.rs

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+
+pub fn readf(format: &str, mut s: &str) -> Option<Vec<String>> {
+    if !format.contains("{}") {
+        return if format == s { Some(vec![]) } else { None };
+    }
+    if format.contains("{}{}") {
+        panic!("Ambiguous argument: '{}' found in format string.", "{}{}");
+    }
+    let mut f = format;
+    let mut occurences = 0;
+    while let Some(idx) = f.find("{}") {
+        f = &f[(idx + 2)..];
+        occurences += 1;
+    }
+    let mut result: Vec<String> = Vec::with_capacity(occurences);
+
+    let mut f = format;
+    for n in 0..=occurences {
+        // shave off space until next {}
+        let i = if let Some(x) = f.find("{}") { x } else { f.len() };
+        if &f[0..i] != &s[0..i] {
+            return None;
+        }
+        if n == occurences {
+            break;
+        }
+        // abcde | a{}cd{} => bcde | cd{}
+        f = &f[(i + 2)..]; 
+        s = &s[i..];
+        // populate
+        match f.find("{}") { // has next
+            Some(x) => { // yes, append until next segment
+                // bcde | cd{}
+                // |      \ |
+                // gets the next segment, and appends everything until the beginning of it
+                result.push(s[0..s.find(&f[0..x])?].into());
+            },
+            None => { // no, append until last segment
+                // gets the last segment (last {} until end of string) and pushes up until it
+                result.push(s[0..(s.len() - (format.len() - format.rfind("{}").unwrap() - 2))].into())
+            },
+        }
+        // shave the appended string away
+        s = &s[result[n].len()..];
+    }
+    if result.len() != occurences {
+        None
+    } else {
+        Some(result)
+    }
+}
+
+pub fn readf1(format: &str, s: &str) -> Option<String> {
+    let r = readf(format, s);
+    r.map(|x| if x.len() == 0 { "".into() } else { x[0].clone() })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn t_readf1() {
+        assert_eq!(readf1("hello, {}", "hello, person"), Some("person".into()));
+        assert_eq!(readf1("hello, {}!", "hello, person!"), Some("person".into()));
+        assert_eq!(readf1("Hello, {}", "hello, person"), None);
+        assert_eq!(readf1("Hello, {}!", "hello, person"), None);
+        assert_eq!(readf1("hello!", "hello!"), Some("".into()));
+        assert_eq!(readf1("Hello!", "hello!"), None);
+    }
+
+    #[test]
+    fn t_readf() {
+        assert_eq!(readf("hello, {} and {}", "hello, person 1 and person 2"), Some(vec!["person 1".into(), "person 2".into()]));
+        assert_eq!(readf("hello, {} and {}!", "hello, person 1 and person 2!"), Some(vec!["person 1".into(), "person 2".into()]));
+        assert_eq!(readf("hello, {} and {}", "hello, person"), None);
+        assert_eq!(readf("hello, {} and {}!", "hello, person!"), None);
+        assert_eq!(readf("Hello, {} and {}", "hello, person 1 and person 2"), None);
+        assert_eq!(readf("Hello, {} and {}!", "hello, person 1 and person 2!"), None);
+        assert_eq!(readf("hello!", "hello!"), Some(vec![]));
+        assert_eq!(readf("Hello!", "hello!"), None);
+    }
+}