1 files changed, 73 insertions, 2 deletions
diff --git a/src/include/common/int.h b/src/include/common/int.h
index fedf7b39992..7fc046e78af 100644
--- a/src/include/common/int.h
+++ b/src/include/common/int.h
@@ -1,7 +1,7 @@
 /*-------------------------------------------------------------------------
  *
  * int.h
- *	  Routines to perform integer math, while checking for overflows.
+ *	  Overflow-aware integer math and integer comparison routines.
  *
  * The routines in this file are intended to be well defined C, without
  * relying on compiler flags like -fwrapv.
@@ -22,7 +22,7 @@
 
 
 /*---------
- * The following guidelines apply to all the routines:
+ * The following guidelines apply to all the overflow routines:
  * - If a + b overflows, return true, otherwise store the result of a + b
  * into *result. The content of *result is implementation defined in case of
  * overflow.
@@ -438,4 +438,75 @@ pg_mul_u64_overflow(uint64 a, uint64 b, uint64 *result)
 #endif
 }
 
+/*------------------------------------------------------------------------
+ *
+ * Comparison routines for integer types.
+ *
+ * These routines are primarily intended for use in qsort() comparator
+ * functions and therefore return a positive integer, 0, or a negative
+ * integer depending on whether "a" is greater than, equal to, or less
+ * than "b", respectively.  These functions are written to be as efficient
+ * as possible without introducing overflow risks, thereby helping ensure
+ * the comparators that use them are transitive.
+ *
+ * Types with fewer than 32 bits are cast to signed integers and
+ * subtracted.  Other types are compared using > and <, and the results of
+ * those comparisons (which are either (int) 0 or (int) 1 per the C
+ * standard) are subtracted.
+ *
+ * NB: If the comparator function is inlined, some compilers may produce
+ * worse code with these helper functions than with code with the
+ * following form:
+ *
+ *     if (a < b)
+ *         return -1;
+ *     if (a > b)
+ *         return 1;
+ *     return 0;
+ *
+ *------------------------------------------------------------------------
+ */
+
+static inline int
+pg_cmp_s16(int16 a, int16 b)
+{
+	return (int32) a - (int32) b;
+}
+
+static inline int
+pg_cmp_u16(uint16 a, uint16 b)
+{
+	return (int32) a - (int32) b;
+}
+
+static inline int
+pg_cmp_s32(int32 a, int32 b)
+{
+	return (a > b) - (a < b);
+}
+
+static inline int
+pg_cmp_u32(uint32 a, uint32 b)
+{
+	return (a > b) - (a < b);
+}
+
+static inline int
+pg_cmp_s64(int64 a, int64 b)
+{
+	return (a > b) - (a < b);
+}
+
+static inline int
+pg_cmp_u64(uint64 a, uint64 b)
+{
+	return (a > b) - (a < b);
+}
+
+static inline int
+pg_cmp_size(size_t a, size_t b)
+{
+	return (a > b) - (a < b);
+}
+
 #endif							/* COMMON_INT_H */