1 files changed, 52 insertions, 3 deletions

diff --git a/src/ion.rs b/src/ion.rs
index 65f5d23..26b54b9 100644
--- a/src/ion.rs
+++ b/src/ion.rs
@@ -81,7 +81,6 @@ impl IonValue {
     }
 
     pub fn len(&self) -> usize {
-        // TODO: Should this read the type length?
         self.0.len()
     }
 
@@ -116,15 +115,65 @@ impl IonValue {
         self.reader().next_symbol_id()
     }
 
+    pub fn get_field(&self, field_id: usize) -> Option<IonValue> {
+        let mut reader = self.reader();
+        reader.step_in();
+        while reader.offset() < self.len() {
+            let value = reader.next_value();
+            if Some(field_id) == reader.field_id() {
+                return Some(value);
+            }
+        }
+        None
+    }
 }
 
 impl From<Vec<u8>> for IonValue {
     fn from(value: Vec<u8>) -> Self {
-        if value.len() > 0 {
+        if value.is_empty() {
+            IonValue(vec![0x0F])
+        } else {
             IonValue(value)
+        }
+    }
+}
+
+impl From<Vec<(usize, IonValue)>> for IonValue {
+    fn from(values: Vec<(usize, IonValue)>) -> Self {
+        let mut buf = Vec::new();
+        for (k, v) in values {
+            push_varuint(&mut buf, k);
+            buf.extend(v.0);
+        }
+        let len = buf.len();
+        if len < 14 {
+            buf.insert(0, 0xD0 | len as u8);
         } else {
-            IonValue(vec![0x0F])
+            let oldbuf = buf;
+            buf = Vec::with_capacity(oldbuf.len() + 9);
+            buf.push(0xDE);
+            push_varuint(&mut buf, len);
+            buf.extend(oldbuf);
+        }
+        IonValue(buf)
+    }
+}
+
+impl From<Vec<IonValue>> for IonValue {
+    fn from(values: Vec<IonValue>) -> Self {
+        let len: usize = values.iter().map(|v| v.len()).sum();
+        let lenlen = ((usize::BITS - len.leading_zeros() + 6) / 7) as usize;
+        let mut buf = Vec::with_capacity(1 + len + lenlen);
+        if len < 14 {
+            buf.push(0xB0 | len as u8);
+        } else {
+            buf.push(0xBE);
+            push_varuint(&mut buf, len);
         }
+        for v in values {
+            buf.extend(v.0);
+        }
+        IonValue(buf)
     }
 }