Add attribute iterator (#14)

* Add attribute iterator

* remove copy-pasta comment

Author: JoeHowarth

examples/get_accounts.rs

@@ -20,18 +20,6 @@ use std::{
   str::FromStr
 };
 
-fn get_attr_str<'a,T>( ite: & mut T ) -> String
-where T : Iterator<Item=& 'a u8>
-{
-  let mut len = *ite.next().unwrap() as usize;
-  let mut val = String::with_capacity( len );
-  while len > 0 {
-    val.push( *ite.next().unwrap() as char );
-    len -= 1;
-  }
-  return val
-}
-
 fn get_price_type( ptype: &PriceType ) -> &'static str
 {
   match ptype {
@@ -78,13 +66,8 @@ fn main() {
 
       // print key and reference data for this Product
       println!( "product_account .. {:?}", prod_pkey );
-      let mut psz = prod_acct.size as usize - PROD_HDR_SIZE;
-      let mut pit = (&prod_acct.attr[..]).iter();
-      while psz > 0 {
-        let key = get_attr_str( &mut pit );
-        let val = get_attr_str( &mut pit );
+      for (key, val) in prod_acct.iter() {
         println!( "  {:.<16} {}", key, val );
-        psz -= 2 + key.len() + val.len();
       }
 
       // print all Prices that correspond to this Product

src/lib.rs

@@ -128,6 +128,12 @@ pub struct Product
   pub attr       : [u8;PROD_ATTR_SIZE]
 }
 
+impl Product {
+    pub fn iter(&self) -> AttributeIter {
+        AttributeIter { attrs: &self.attr }
+    }
+}
+
 #[cfg(target_endian = "little")]
 unsafe impl Zeroable for Product {}
 
@@ -387,3 +393,31 @@ pub fn load_price(data: &[u8]) -> Result<&Price, PythError> {
 
   return Ok(pyth_price);
 }
+
+struct AttributeIter<'a> {
+    attrs: &'a [u8],
+}
+
+impl<'a> Iterator for AttributeIter<'a> {
+    type Item = (&'a str, &'a str);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.attrs.is_empty() {
+            return None;
+        }
+        let (key, data) = get_attr_str(self.attrs);
+        let (val, data) = get_attr_str(data);
+        self.attrs = data;
+        return Some((key, val));
+    }
+}
+
+fn get_attr_str(buf: &[u8]) -> (&str, &[u8]) {
+    if buf.is_empty() {
+        return ("", &[]);
+    }
+    let len = buf[0] as usize;
+    let str = std::str::from_utf8(&buf[1..len + 1]).expect("attr should be ascii or utf-8");
+    let remaining_buf = &buf[len + 1..];
+    (str, remaining_buf)
+}