feat: add fn allocation_size to BigUint and BigInt

Cargo.toml

@@ -73,3 +73,8 @@ default-features = false
 optional = true
 version = "1"
 default-features = false
+
+[dev-dependencies]
+
+[dev-dependencies.dhat]
+version = "0.3.3"

src/bigint.rs

@@ -1153,6 +1153,15 @@ impl BigInt {
         // The top bit may have been cleared, so normalize
         self.normalize();
     }
+
+    /// Returns the total amount of memory allocated internally by the
+    /// big int, in bytes.
+    ///
+    /// The returned number is informational only. It is intended to be
+    /// primarily used for memory profiling.
+    pub fn allocation_size(&self) -> usize {
+        self.data.allocation_size()
+    }
 }
 
 impl num_traits::FromBytes for BigInt {

src/biguint.rs

@@ -1042,6 +1042,15 @@ impl BigUint {
             self.normalize();
         }
     }
+
+    /// Returns the total amount of memory allocated internally by the
+    /// big uint, in bytes.
+    ///
+    /// The returned number is informational only. It is intended to be
+    /// primarily used for memory profiling.
+    pub fn allocation_size(&self) -> usize {
+        self.data.capacity() * std::mem::size_of::<BigDigit>()
+    }
 }
 
 impl num_traits::FromBytes for BigUint {

tests/bigint_allocation_size.rs

@@ -0,0 +1,12 @@
+use num_bigint::BigInt;
+
+#[global_allocator]
+static ALLOC: dhat::Alloc = dhat::Alloc;
+
+#[test]
+fn test_biguint_allocation_size() {
+    let _profiler = dhat::Profiler::builder().testing().build();
+    let big: BigInt = "-1234567898765432123456789876543212345678987654321".parse().unwrap();
+    let stats = dhat::HeapStats::get();
+    assert_eq!(stats.curr_bytes, big.allocation_size());
+}

tests/biguint_allocation_size.rs

@@ -0,0 +1,12 @@
+use num_bigint::BigUint;
+
+#[global_allocator]
+static ALLOC: dhat::Alloc = dhat::Alloc;
+
+#[test]
+fn test_biguint_allocation_size() {
+    let _profiler = dhat::Profiler::builder().testing().build();
+    let big: BigUint = "1234567898765432123456789876543212345678987654321".parse().unwrap();
+    let stats = dhat::HeapStats::get();
+    assert_eq!(stats.curr_bytes, big.allocation_size());
+}