Use 'Cow' to remove unnecessary allocations

1 files changed, 45 insertions, 41 deletions

diff --git a/src/value.rs b/src/value.rs
index a887104..ad173e8 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -1,49 +1,53 @@
 use std::convert::From;
 use std::collections::HashMap;
+use std::borrow::Cow;
 
 /// A configuration value.
 ///
 /// Has an underlying or native type that comes from the configuration source
 /// but will be coerced into the requested type.
 #[derive(Debug, Clone)]
-pub enum Value {
-    String(String),
+pub enum Value<'a> {
+    String(Cow<'a, str>),
     Integer(i64),
     Float(f64),
     Boolean(bool),
-    Table(HashMap<String, Value>),
-    Array(Vec<Value>),
+    Table(HashMap<String, Value<'a>>),
+    Array(Vec<Value<'a>>),
 }
 
-impl Value {
-    /// Gets the underyling value as a string, performing a conversion only if neccessary.
-    pub fn as_str(self) -> Option<String> {
-        if let Value::String(value) = self {
-            Some(value)
-        } else if let Value::Integer(value) = self {
-            Some(value.to_string())
-        } else if let Value::Float(value) = self {
-            Some(value.to_string())
-        } else if let Value::Boolean(value) = self {
-            Some(value.to_string())
+impl<'a> Value<'a> {
+    /// Gets the underlying value as a string, performing a conversion only if neccessary.
+    pub fn as_str(&'a self) -> Option<Cow<'a, str>> {
+        if let Value::String(ref value) = *self {
+            Some(match *value {
+                Cow::Borrowed(v) => Cow::Borrowed(v),
+                Cow::Owned(ref v) => Cow::Borrowed(v),
+            })
+        } else if let Value::Integer(value) = *self {
+            Some(Cow::Owned(value.to_string()))
+        } else if let Value::Float(value) = *self {
+            Some(Cow::Owned(value.to_string()))
+        } else if let Value::Boolean(value) = *self {
+            Some(Cow::Owned(value.to_string()))
         } else {
             None
         }
     }
 
     /// Gets the underlying type as a boolean, performing a conversion only if neccessary.
-    pub fn as_bool(self) -> Option<bool> {
-        if let Value::Boolean(value) = self {
+    pub fn as_bool(&self) -> Option<bool> {
+        if let Value::Boolean(value) = *self {
             Some(value)
-        } else if let Value::String(ref value) = self {
+        } else if let Value::String(ref value) = *self {
             match value.to_lowercase().as_ref() {
                 "1" | "true" | "on" | "yes" => Some(true),
                 "0" | "false" | "off" | "no" => Some(false),
                 _ => None,
             }
-        } else if let Value::Integer(value) = self {
+        } else if let Value::Integer(value) = *self {
             Some(value != 0)
-        } else if let Value::Float(value) = self {
+        } else if let Value::Float(value) = *self {
             Some(value != 0.0)
         } else {
             None
@@ -51,14 +55,14 @@ impl Value {
     }
 
     /// Gets the underlying type as an integer, performing a conversion only if neccessary.
-    pub fn as_int(self) -> Option<i64> {
-        if let Value::Integer(value) = self {
+    pub fn as_int(&self) -> Option<i64> {
+        if let Value::Integer(value) = *self {
             Some(value)
-        } else if let Value::String(ref value) = self {
+        } else if let Value::String(ref value) = *self {
             value.parse().ok()
-        } else if let Value::Boolean(value) = self {
+        } else if let Value::Boolean(value) = *self {
             Some(if value { 1 } else { 0 })
-        } else if let Value::Float(value) = self {
+        } else if let Value::Float(value) = *self {
             Some(value.round() as i64)
         } else {
             None
@@ -66,14 +70,14 @@ impl Value {
     }
 
     /// Gets the underlying type as a floating-point, performing a conversion only if neccessary.
-    pub fn as_float(self) -> Option<f64> {
-        if let Value::Float(value) = self {
+    pub fn as_float(&self) -> Option<f64> {
+        if let Value::Float(value) = *self {
             Some(value)
-        } else if let Value::String(ref value) = self {
+        } else if let Value::String(ref value) = *self {
             value.parse().ok()
-        } else if let Value::Integer(value) = self {
+        } else if let Value::Integer(value) = *self {
             Some(value as f64)
-        } else if let Value::Boolean(value) = self {
+        } else if let Value::Boolean(value) = *self {
             Some(if value { 1.0 } else { 0.0 })
         } else {
             None
@@ -84,32 +88,32 @@ impl Value {
 // Generalized construction from type into variant is needed
 // for setting configuration values
 
-impl From<String> for Value {
-    fn from(value: String) -> Value {
-        Value::String(value)
+impl<'a> From<String> for Value<'a> {
+    fn from(value: String) -> Value<'a> {
+        Value::String(value.into())
     }
 }
 
-impl<'a> From<&'a str> for Value {
-    fn from(value: &'a str) -> Value {
+impl<'a> From<&'a str> for Value<'a> {
+    fn from(value: &'a str) -> Value<'a> {
         Value::String(value.into())
     }
 }
 
-impl From<i64> for Value {
-    fn from(value: i64) -> Value {
+impl<'a> From<i64> for Value<'a> {
+    fn from(value: i64) -> Value<'a> {
         Value::Integer(value)
     }
 }
 
-impl From<f64> for Value {
-    fn from(value: f64) -> Value {
+impl<'a> From<f64> for Value<'a> {
+    fn from(value: f64) -> Value<'a> {
         Value::Float(value)
     }
 }
 
-impl From<bool> for Value {
-    fn from(value: bool) -> Value {
+impl<'a> From<bool> for Value<'a> {
+    fn from(value: bool) -> Value<'a> {
         Value::Boolean(value)
     }
 }