Expose Regex memory usage info (fixes #943)

src/regex/bytes.rs

@@ -1482,6 +1482,15 @@ impl Regex {
     pub fn locations(&self) -> CaptureLocations {
         self.capture_locations()
     }
+
+    /// Return the total approximate heap memory, in bytes, used by this `Regex`.
+    ///
+    /// Note that this value is unrelated to [`RegexBuilder::size_limit`], and can
+    /// in many cases exceed it.
+    #[inline]
+    pub fn memory_usage(&self) -> usize {
+        self.meta.memory_usage() + self.pattern.len()
+    }
 }
 
 /// Represents a single match of a regex in a haystack.

src/regex/string.rs

@@ -1481,6 +1481,15 @@ impl Regex {
     pub fn locations(&self) -> CaptureLocations {
         self.capture_locations()
     }
+
+    /// Return the total approximate heap memory, in bytes, used by this `Regex`.
+    ///
+    /// Note that this value is unrelated to [`RegexBuilder::size_limit`], and can
+    /// in many cases exceed it.
+    #[inline]
+    pub fn memory_usage(&self) -> usize {
+        self.meta.memory_usage() + self.pattern.len()
+    }
 }
 
 /// Represents a single match of a regex in a haystack.