Add support for snprintf() to libstand.

Reviewed by:	brooks @
Sponsored by:	DARPA, AFRL

2 files changed, 54 insertions, 6 deletions

diff --git a/lib/libstand/printf.c b/lib/libstand/printf.c
index 977c026..1a86e93 100644
--- a/lib/libstand/printf.c
+++ b/lib/libstand/printf.c
@@ -56,8 +56,16 @@ __FBSDID("$FreeBSD$");
 
 #define MAXNBUF (sizeof(intmax_t) * CHAR_BIT + 1)
 
+typedef void (kvprintf_fn_t)(int, void *);
+
 static char	*ksprintn (char *buf, uintmax_t num, int base, int *len, int upper);
-static int	kvprintf(char const *fmt, void (*func)(int), void *arg, int radix, va_list ap);
+static int	kvprintf(char const *fmt, kvprintf_fn_t *func, void *arg, int radix, va_list ap);
+
+static void
+putchar_wrapper(int cc, void *arg)
+{
+	putchar(cc);
+}
 
 int
 printf(const char *fmt, ...)
@@ -66,7 +74,7 @@ printf(const char *fmt, ...)
 	int retval;
 
 	va_start(ap, fmt);
-	retval = kvprintf(fmt, putchar, NULL, 10, ap);
+	retval = kvprintf(fmt, putchar_wrapper, NULL, 10, ap);
 	va_end(ap);
 	return retval;
 }
@@ -74,8 +82,7 @@ printf(const char *fmt, ...)
 void
 vprintf(const char *fmt, va_list ap)
 {
-
-	kvprintf(fmt, putchar, NULL, 10, ap);
+	kvprintf(fmt, putchar_wrapper, NULL, 10, ap);
 }
 
 int
@@ -91,6 +98,46 @@ sprintf(char *buf, const char *cfmt, ...)
 	return retval;
 }
 
+struct print_buf {
+	char *buf;
+	size_t size;
+};
+
+static void
+snprint_func(int ch, void *arg)
+{
+	struct print_buf *pbuf = arg;
+
+	if (pbuf->size < 2) {
+		/*
+		 * Reserve last buffer position for the terminating
+		 * character:
+		 */
+		return;
+	}
+	*(pbuf->buf)++ = ch;
+	pbuf->size--;
+}
+
+int
+snprintf(char *buf, size_t size, const char *cfmt, ...)
+{
+	int retval;
+	va_list ap;
+	struct print_buf arg;
+
+	arg.buf = buf;
+	arg.size = size;
+
+	va_start(ap, cfmt);
+	retval = kvprintf(cfmt, &snprint_func, &arg, 10, ap);
+	va_end(ap);
+
+	if (arg.size >= 1)
+		*(arg.buf)++ = 0;
+	return retval;
+}
+
 void
 vsprintf(char *buf, const char *cfmt, va_list ap)
 {
@@ -149,9 +196,9 @@ ksprintn(char *nbuf, uintmax_t num, int base, int *lenp, int upper)
  *		("%*D", len, ptr, " " -> XX XX XX XX ...
  */
 static int
-kvprintf(char const *fmt, void (*func)(int), void *arg, int radix, va_list ap)
+kvprintf(char const *fmt, kvprintf_fn_t *func, void *arg, int radix, va_list ap)
 {
-#define PCHAR(c) {int cc=(c); if (func) (*func)(cc); else *d++ = cc; retval++; }
+#define PCHAR(c) {int cc=(c); if (func) (*func)(cc, arg); else *d++ = cc; retval++; }
 	char nbuf[MAXNBUF];
 	char *d;
 	const char *p, *percent, *q;
diff --git a/lib/libstand/stand.h b/lib/libstand/stand.h
index 2a1e9a9..2808722 100644
--- a/lib/libstand/stand.h
+++ b/lib/libstand/stand.h
@@ -238,6 +238,7 @@ extern void	mallocstats(void);
 extern int	printf(const char *fmt, ...) __printflike(1, 2);
 extern void	vprintf(const char *fmt, __va_list);
 extern int	sprintf(char *buf, const char *cfmt, ...) __printflike(2, 3);
+extern int	snprintf(char *buf, size_t size, const char *cfmt, ...) __printflike(3, 4);
 extern void	vsprintf(char *buf, const char *cfmt, __va_list);
 
 extern void	twiddle(void);