invert_map (for placeholder en/decode conversion)

implementations/rust/src/lib.rs

@@ -212,6 +212,7 @@ mod samples_tests {
     use crate::value::DecodePlaceholderMap;
     use crate::value::to_value;
     use crate::value::from_value;
+    use crate::value::invert_map;
     use std::collections::BTreeMap;
 
     #[derive(Debug, serde::Serialize, serde::Deserialize)]
@@ -236,16 +237,13 @@ mod samples_tests {
 
     #[test] fn run() {
         let mut d = Decoder::new(std::fs::File::open("../../tests/samples.bin").unwrap(), None);
-        let v = d.next().unwrap();
-        // println!("{:#?}", v);
+        let tests: TestCases = from_value(&d.next().unwrap()).unwrap();
+        let decode_placeholders = tests.decode_placeholders.0;
+        let encode_placeholders = invert_map(&decode_placeholders);
 
-        let tests: TestCases = from_value(&v).unwrap();
-        println!("{:#?}", tests);
-
-        // let mut buf = Vec::new();
-        // let mut e = Encoder::new(&mut buf, None);
-        // e.write(&v).unwrap();
-        // println!("{:?}", Value::from(buf))
+        // println!("{:#?}", tests);
+        println!("{:#?}", decode_placeholders);
+        println!("{:#?}", encode_placeholders);
     }
 
     #[test] fn simple_to_value() {

implementations/rust/src/value/mod.rs

@@ -18,3 +18,10 @@ pub use value::AValue;
 pub use value::Dictionary;
 pub use value::Set;
 pub use value::Value;
+
+pub fn invert_map<A, B>(m: &std::collections::BTreeMap<A, B>) -> std::collections::BTreeMap<B, A>
+    where A: Clone, B: Clone + Ord
+{
+    use std::iter::FromIterator;
+    std::collections::BTreeMap::from_iter(m.iter().map(|(a, b)| (b.clone(), a.clone())))
+}