Add pg_strnlen() a portable implementation of strlen.

As the OS version is likely going to be more optimized, fall back to
it if available, as detected by configure.

5 files changed, 43 insertions, 10 deletions

diff --git a/src/common/string.c b/src/common/string.c
index 159d9ea7b62..901821f3d87 100644
--- a/src/common/string.c
+++ b/src/common/string.c
@@ -41,3 +41,23 @@ pg_str_endswith(const char *str, const char *end)
 	str += slen - elen;
 	return strcmp(str, end) == 0;
 }
+
+
+/*
+ * Portable version of posix' strnlen.
+ *
+ * Returns the number of characters before a null-byte in the string pointed
+ * to by str, unless there's no null-byte before maxlen. In the latter case
+ * maxlen is returned.
+ */
+#ifndef HAVE_STRNLEN
+size_t
+pg_strnlen(const char *str, size_t maxlen)
+{
+	const char *p = str;
+
+	while (maxlen-- > 0 && *p)
+		p++;
+	return p - str;
+}
+#endif
diff --git a/src/include/common/string.h b/src/include/common/string.h
index 5f3ea71d613..3d46b80918c 100644
--- a/src/include/common/string.h
+++ b/src/include/common/string.h
@@ -12,4 +12,19 @@
 
 extern bool pg_str_endswith(const char *str, const char *end);
 
+/*
+ * Portable version of posix' strnlen.
+ *
+ * Returns the number of characters before a null-byte in the string pointed
+ * to by str, unless there's no null-byte before maxlen. In the latter case
+ * maxlen is returned.
+ *
+ * Use the system strnlen if provided, it's likely to be faster.
+ */
+#ifdef HAVE_STRNLEN
+#define pg_strnlen(str, maxlen) strnlen(str, maxlen)
+#else
+extern size_t pg_strnlen(const char *str, size_t maxlen);
+#endif
+
 #endif							/* COMMON_STRING_H */
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 368a297e6df..d20cc47fde0 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -496,6 +496,9 @@
 /* Define to 1 if you have the `strlcpy' function. */
 #undef HAVE_STRLCPY
 
+/* Define to 1 if you have the `strnlen' function. */
+#undef HAVE_STRNLEN
+
 /* Define to use have a strong random number source */
 #undef HAVE_STRONG_RANDOM
 
diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32
index 3537b6f7045..58eef0a538e 100644
--- a/src/include/pg_config.h.win32
+++ b/src/include/pg_config.h.win32
@@ -345,6 +345,9 @@
 /* Define to 1 if you have the <string.h> header file. */
 #define HAVE_STRING_H 1
 
+/* Define to 1 if you have the `strnlen' function. */
+#define HAVE_STRNLEN
+
 /* Define to use have a strong random number source */
 #define HAVE_STRONG_RANDOM 1
 
diff --git a/src/port/snprintf.c b/src/port/snprintf.c
index 231e5d6bdb4..531d2c5ee35 100644
--- a/src/port/snprintf.c
+++ b/src/port/snprintf.c
@@ -43,6 +43,8 @@
 #endif
 #include <sys/param.h>
 
+#include "common/string.h"
+
 #ifndef NL_ARGMAX
 #define NL_ARGMAX 16
 #endif
@@ -790,16 +792,6 @@ bad_format:
 	target->failed = true;
 }
 
-static size_t
-pg_strnlen(const char *str, size_t maxlen)
-{
-	const char *p = str;
-
-	while (maxlen-- > 0 && *p)
-		p++;
-	return p - str;
-}
-
 static void
 fmtstr(char *value, int leftjust, int minlen, int maxwidth,
 	   int pointflag, PrintfTarget *target)