2 files changed, 30 insertions, 0 deletions
diff --git a/src/common/strlib.c b/src/common/strlib.c
index d0b312f0a..db47c969b 100644
--- a/src/common/strlib.c
+++ b/src/common/strlib.c
@@ -316,6 +316,31 @@ size_t safestrnlen(const char* string, size_t maxlen)
 	return ( string != NULL ) ? strnlen(string, maxlen) : 0;
 }
 
+/// Works like snprintf, but always nul-terminates the buffer.
+/// Returns the size of the string (without nul-terminator)
+/// or -1 if the buffer is too small.
+///
+/// @param buf Target buffer
+/// @param sz Size of the buffer (including nul-terminator)
+/// @param fmt Format string
+/// @param ... Format arguments
+/// @return The size of the string or -1 if the buffer is too small
+int safesnprintf(char* buf, size_t sz, const char* fmt, ...)
+{
+	va_list ap;
+	int ret;
+
+	va_start(ap,fmt);
+	ret = vsnprintf(buf, sz, fmt, ap);
+	va_end(ap);
+	if( ret < 0 || (size_t)ret >= sz )
+	{// overflow
+		buf[sz-1] = '\0';// always nul-terminate
+		return -1;
+	}
+	return ret;
+}
+
 /// Returns the line of the target position in the string.
 /// Lines start at 1.
 int strline(const char* str, size_t pos)
diff --git a/src/common/strlib.h b/src/common/strlib.h
index 4df5a51d2..31e364e2a 100644
--- a/src/common/strlib.h
+++ b/src/common/strlib.h
@@ -37,6 +37,11 @@ char* safestrncpy(char* dst, const char* src, size_t n);
 /// doesn't crash on null pointer
 size_t safestrnlen(const char* string, size_t maxlen);
 
+/// Works like snprintf, but always nul-terminates the buffer.
+/// Returns the size of the string (without nul-terminator)
+/// or -1 if the buffer is too small.
+int safesnprintf(char* buf, size_t sz, const char* fmt, ...);
+
 /// Returns the line of the target position in the string.
 /// Lines start at 1.
 int strline(const char* str, size_t pos);