From d96f70b49d24d5c61f8fd47b58d5ae28cb156ffe Mon Sep 17 00:00:00 2001
From: Brian Smith <brian@briansmith.org>
Date: Fri, 29 Sep 2023 19:01:59 -0700
Subject: [PATCH] NFC: DRY in budget.

---
 src/budget.rs | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/src/budget.rs b/src/budget.rs
index 4585b9b2..266548d3 100644
--- a/src/budget.rs
+++ b/src/budget.rs
@@ -23,23 +23,26 @@ pub(super) struct Budget {
 impl Budget {
     #[inline]
     pub fn consume_signature(&mut self) -> Result<(), InternalError> {
-        self.signatures = self
-            .signatures
-            .checked_sub(1)
-            .ok_or(InternalError::MaximumSignatureChecksExceeded)?;
-        Ok(())
+        checked_sub(
+            &mut self.signatures,
+            InternalError::MaximumSignatureChecksExceeded,
+        )
     }
 
     #[inline]
     pub fn consume_build_chain_call(&mut self) -> Result<(), InternalError> {
-        self.build_chain_calls = self
-            .build_chain_calls
-            .checked_sub(1)
-            .ok_or(InternalError::MaximumPathBuildCallsExceeded)?;
-        Ok(())
+        checked_sub(
+            &mut self.build_chain_calls,
+            InternalError::MaximumPathBuildCallsExceeded,
+        )
     }
 }
 
+fn checked_sub(value: &mut usize, underflow_error: InternalError) -> Result<(), InternalError> {
+    *value = value.checked_sub(1).ok_or(underflow_error)?;
+    Ok(())
+}
+
 impl Default for Budget {
     fn default() -> Self {
         Self {