X-Git-Url: http://git.xonotic.org/?p=xonotic%2Fdarkplaces.git;a=blobdiff_plain;f=qdefs.h;h=5d0655f77f6e0b519bab330b08678166e20e639f;hp=463761e9b43a311993b6b182edf5f657c07b9a72;hb=b2a1a3ffa49a3f315f9f59aa011c5888ad4bea4b;hpb=1ff568a91b88652d1a12165607f5230e71e210e6

diff --git a/qdefs.h b/qdefs.h
index 463761e9..5d0655f7 100644
--- a/qdefs.h
+++ b/qdefs.h
@@ -208,4 +208,22 @@
 #define INT_LOSSLESS_FORMAT_CONVERT_U(x) ((uintmax_t)(x))
 #endif
 
+// simple safe library to handle integer overflows when doing buffer size calculations
+// Usage:
+//   - calculate data size using INTOVERFLOW_??? macros
+//   - compare: calculated-size <= INTOVERFLOW_NORMALIZE(buffersize)
+// Functionality:
+//   - all overflows (values > INTOVERFLOW_MAX) and errors are mapped to INTOVERFLOW_MAX
+//   - if any input of an operation is INTOVERFLOW_MAX, INTOVERFLOW_MAX will be returned
+//   - otherwise, regular arithmetics apply
+
+#define INTOVERFLOW_MAX 2147483647
+
+#define INTOVERFLOW_ADD(a,b) (((a) < INTOVERFLOW_MAX && (b) < INTOVERFLOW_MAX && (a) < INTOVERFLOW_MAX - (b)) ? ((a) + (b)) : INTOVERFLOW_MAX)
+#define INTOVERFLOW_SUB(a,b) (((a) < INTOVERFLOW_MAX && (b) < INTOVERFLOW_MAX && (b) <= (a))                  ? ((a) - (b)) : INTOVERFLOW_MAX)
+#define INTOVERFLOW_MUL(a,b) (((a) < INTOVERFLOW_MAX && (b) < INTOVERFLOW_MAX && (a) < INTOVERFLOW_MAX / (b)) ? ((a) * (b)) : INTOVERFLOW_MAX)
+#define INTOVERFLOW_DIV(a,b) (((a) < INTOVERFLOW_MAX && (b) < INTOVERFLOW_MAX && (b) > 0)                     ? ((a) / (b)) : INTOVERFLOW_MAX)
+
+#define INTOVERFLOW_NORMALIZE(a) (((a) < INTOVERFLOW_MAX) ? (a) : (INTOVERFLOW_MAX - 1))
+
 #endif