From e8546cff07a4d252e3669bf37407669f838a150e Mon Sep 17 00:00:00 2001
From: gaetbout <gaetan.ansotte@hotmail.com>
Date: Wed, 7 Aug 2024 15:37:49 +0200
Subject: [PATCH] overflowing to checked where possible

---
 packages/bytes/src/storage.cairo            | 35 ++++++++++-----------
 packages/data_structures/src/span_ext.cairo | 21 ++-----------
 2 files changed, 19 insertions(+), 37 deletions(-)

diff --git a/packages/bytes/src/storage.cairo b/packages/bytes/src/storage.cairo
index 94db2d31..25fb3801 100644
--- a/packages/bytes/src/storage.cairo
+++ b/packages/bytes/src/storage.cairo
@@ -1,5 +1,5 @@
 use alexandria_bytes::bytes::{Bytes, BytesTrait, BYTES_PER_ELEMENT};
-use core::num::traits::OverflowingAdd;
+use core::num::traits::CheckedAdd;
 use starknet::SyscallResult;
 use starknet::storage_access::{
     Store, StorageAddress, StorageBaseAddress, storage_address_from_base,
@@ -88,15 +88,13 @@ fn inner_read_bytes(address_domain: u32, address: StorageAddress) -> SyscallResu
         data.append(value);
         remaining_full_words -= 1;
 
-        let (tmp, did_overflow) = index_in_chunk.overflowing_add(1);
-        if did_overflow {
-            // After reading 256 `uint128`s `index_in_chunk` will overflow and we move to the
-            // next chunk.
-            chunk += 1;
-            chunk_base = inner_bytes_pointer(address, chunk);
-            index_in_chunk = 0;
-        } else {
-            index_in_chunk = tmp;
+        match index_in_chunk.checked_add(1) {
+            Option::Some(x) => { index_in_chunk = x; },
+            Option::None => {
+                chunk += 1;
+                chunk_base = inner_bytes_pointer(address, chunk);
+                index_in_chunk = 0;
+            },
         }
     }?;
     if last_word_len != 0 {
@@ -133,15 +131,14 @@ fn inner_write_bytes(
             Result::Ok(_) => {},
             Result::Err(err) => { break Result::Err(err); },
         };
-        let (tmp, did_overflow) = index_in_chunk.overflowing_add(1);
-        if did_overflow {
-            // After writing 256 `uint128`s `index_in_chunk` will overflow and we move to the
-            // next chunk.
-            chunk += 1;
-            chunk_base = inner_bytes_pointer(address, chunk);
-            index_in_chunk = 0;
-        } else {
-            index_in_chunk = tmp;
+
+        match index_in_chunk.checked_add(1) {
+            Option::Some(x) => { index_in_chunk = x; },
+            Option::None => {
+                chunk += 1;
+                chunk_base = inner_bytes_pointer(address, chunk);
+                index_in_chunk = 0;
+            },
         }
     }?;
     Result::Ok(())
diff --git a/packages/data_structures/src/span_ext.cairo b/packages/data_structures/src/span_ext.cairo
index 75e81c21..211b1ec5 100644
--- a/packages/data_structures/src/span_ext.cairo
+++ b/packages/data_structures/src/span_ext.cairo
@@ -1,7 +1,6 @@
 use core::clone::Clone;
 use core::cmp::min;
-use core::num::traits::OverflowingSub;
-use core::option::OptionTrait;
+use core::num::traits::CheckedSub;
 use super::array_ext::ArrayTraitExt;
 
 pub trait SpanTraitExt<T> {
@@ -52,14 +51,7 @@ impl SpanImpl<T, +Clone<T>, +Drop<T>> of SpanTraitExt<T> {
     fn pop_back_n(ref self: Span<T>, n: usize) -> Span<T> {
         let span_len = self.len();
         // Saturating substraction
-        let separator = {
-            let (value, overflow) = span_len.overflowing_sub(n);
-            if overflow {
-                0
-            } else {
-                value
-            }
-        };
+        let separator = span_len.checked_sub(n).unwrap_or(0);
 
         let res = self.slice(separator, span_len - separator);
         self = self.slice(0, separator);
@@ -77,14 +69,7 @@ impl SpanImpl<T, +Clone<T>, +Drop<T>> of SpanTraitExt<T> {
     fn remove_back_n(ref self: Span<T>, mut n: usize) {
         let span_len = self.len();
         // Saturating substraction
-        let separator = {
-            let (value, overflow) = span_len.overflowing_sub(n);
-            if overflow {
-                0
-            } else {
-                value
-            }
-        };
+        let separator = span_len.checked_sub(n).unwrap_or(0);
 
         self = self.slice(0, separator);
     }