From 56bc7721ecdaa63f078fad27f9a4be3e7bd88170 Mon Sep 17 00:00:00 2001
From: Luca Bacci <luca.bacci982@gmail.com>
Date: Thu, 29 Dec 2022 15:37:22 +0100
Subject: [PATCH] Add overflow check helpers

---
 babl/babl-util.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++
 babl/babl-util.h |  6 ++++++
 2 files changed, 61 insertions(+)

diff --git a/babl/babl-util.c b/babl/babl-util.c
index a4f482f..66a9290 100644
--- a/babl/babl-util.c
+++ b/babl/babl-util.c
@@ -17,6 +17,9 @@
  */
 
 #include "config.h"
+#include <stdarg.h>
+#include <limits.h>
+#include <assert.h>
 #include <stdio.h>
 #include <math.h>
 #include <sys/types.h>
@@ -106,6 +109,58 @@ babl_rel_avg_error (const double *imgA,
   return error;
 }
 
+size_t
+add_check_overflow (size_t numbers_count, ...)
+{
+  size_t result = 0;
+  va_list args;
+
+  assert (numbers_count > 0);
+
+  va_start (args, numbers_count);
+  while (numbers_count--)
+    {
+      size_t addendum = va_arg (args, size_t);
+
+      if ((SIZE_MAX - result) < addendum)
+        {
+          result = 0;
+          break;
+        }
+
+      result += addendum;
+    }
+  va_end (args);
+
+  return result;
+}
+
+size_t
+mul_check_overflow (size_t numbers_count, ...)
+{
+  size_t result = 1;
+  va_list args;
+
+  assert (numbers_count > 0);
+
+  va_start (args, numbers_count);
+  while (numbers_count--)
+    {
+      size_t factor = va_arg (args, size_t);
+
+      if ((SIZE_MAX / result) < factor)
+        {
+          result = 0;
+          break;
+        }
+
+      result *= factor;
+    }
+  va_end (args);
+
+  return result;
+}
+
 FILE *
 _babl_fopen (const char *path,
              const char *mode)
diff --git a/babl/babl-util.h b/babl/babl-util.h
index ad094e1..6c96540 100644
--- a/babl/babl-util.h
+++ b/babl/babl-util.h
@@ -38,6 +38,12 @@ babl_rel_avg_error (const double *imgA,
                     const double *imgB,
                     long          samples);
 
+size_t
+add_check_overflow (size_t numbers_count, ...);
+
+size_t
+mul_check_overflow (size_t numbers_count, ...);
+
 FILE *
 _babl_fopen (const char *path,
              const char *mode);
-- 
2.30.2