3 files changed, 98 insertions, 17 deletions

diff --git a/usr/src/lib/libcmdutils/common/custr.c b/usr/src/lib/libcmdutils/common/custr.c
index 1ec72de9dd..8da7b98ac2 100644
--- a/usr/src/lib/libcmdutils/common/custr.c
+++ b/usr/src/lib/libcmdutils/common/custr.c
@@ -14,19 +14,27 @@
  */
 
 /*
- * Copyright 2014, Joyent, Inc.
+ * Copyright 2015 Joyent, Inc.
  */
 
 #include <stdlib.h>
 #include <err.h>
 #include <string.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <sys/debug.h>
 
 #include "libcmdutils.h"
 
+typedef enum {
+	CUSTR_FIXEDBUF	= 0x01
+} custr_flags_t;
+
 struct custr {
 	size_t cus_strlen;
 	size_t cus_datalen;
 	char *cus_data;
+	custr_flags_t cus_flags;
 };
 
 #define	STRING_CHUNK_SIZE	64
@@ -50,26 +58,28 @@ custr_len(custr_t *cus)
 const char *
 custr_cstr(custr_t *cus)
 {
-	return (cus->cus_data);
-}
+	if (cus->cus_data == NULL) {
+		VERIFY(cus->cus_strlen == 0);
+		VERIFY(cus->cus_datalen == 0);
 
-int
-custr_appendc(custr_t *cus, char newc)
-{
-	char news[2];
-
-	news[0] = newc;
-	news[1] = '\0';
-
-	return (custr_append(cus, news));
+		/*
+		 * This function should never return NULL.  If no buffer has
+		 * been allocated, return a pointer to a zero-length string.
+		 */
+		return ("");
+	}
+	return (cus->cus_data);
 }
 
-int
-custr_append(custr_t *cus, const char *news)
+static int
+custr_append_vprintf(custr_t *cus, const char *fmt, va_list ap)
 {
-	size_t len = strlen(news);
+	int len = vsnprintf(NULL, 0, fmt, ap);
 	size_t chunksz = STRING_CHUNK_SIZE;
 
+	if (len == -1)
+		return (len);
+
 	while (chunksz < len) {
 		chunksz *= 2;
 	}
@@ -78,6 +88,11 @@ custr_append(custr_t *cus, const char *news)
 		char *new_data;
 		size_t new_datalen = cus->cus_datalen + chunksz;
 
+		if (cus->cus_flags & CUSTR_FIXEDBUF) {
+			errno = EOVERFLOW;
+			return (-1);
+		}
+
 		/*
 		 * Allocate replacement memory:
 		 */
@@ -104,13 +119,41 @@ custr_append(custr_t *cus, const char *news)
 	/*
 	 * Append new string to existing string:
 	 */
-	(void) memcpy(cus->cus_data + cus->cus_strlen, news, len + 1);
+	len = vsnprintf(cus->cus_data + cus->cus_strlen,
+	    (uintptr_t)cus->cus_data - (uintptr_t)cus->cus_strlen, fmt, ap);
+	if (len == -1)
+		return (len);
 	cus->cus_strlen += len;
 
 	return (0);
 }
 
 int
+custr_appendc(custr_t *cus, char newc)
+{
+	return (custr_append_printf(cus, "%c", newc));
+}
+
+int
+custr_append_printf(custr_t *cus, const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+
+	va_start(ap, fmt);
+	ret = custr_append_vprintf(cus, fmt, ap);
+	va_end(ap);
+
+	return (ret);
+}
+
+int
+custr_append(custr_t *cus, const char *name)
+{
+	return (custr_append_printf(cus, "%s", name));
+}
+
+int
 custr_alloc(custr_t **cus)
 {
 	custr_t *t;
@@ -124,12 +167,35 @@ custr_alloc(custr_t **cus)
 	return (0);
 }
 
+int
+custr_alloc_buf(custr_t **cus, void *buf, size_t buflen)
+{
+	int ret;
+
+	if (buflen == 0 || buf == NULL) {
+		errno = EINVAL;
+		return (-1);
+	}
+
+	if ((ret = custr_alloc(cus)) != 0)
+		return (ret);
+
+	(*cus)->cus_data = buf;
+	(*cus)->cus_datalen = buflen;
+	(*cus)->cus_strlen = 0;
+	(*cus)->cus_flags = CUSTR_FIXEDBUF;
+	(*cus)->cus_data[0] = '\0';
+
+	return (0);
+}
+
 void
 custr_free(custr_t *cus)
 {
 	if (cus == NULL)
 		return;
 
-	free(cus->cus_data);
+	if ((cus->cus_flags & CUSTR_FIXEDBUF) == 0)
+		free(cus->cus_data);
 	free(cus);
 }
diff --git a/usr/src/lib/libcmdutils/common/mapfile-vers b/usr/src/lib/libcmdutils/common/mapfile-vers
index 640959e4b5..3106695eb0 100644
--- a/usr/src/lib/libcmdutils/common/mapfile-vers
+++ b/usr/src/lib/libcmdutils/common/mapfile-vers
@@ -43,8 +43,10 @@ SYMBOL_VERSION SUNWprivate_1.1 {
     global:
 	add_tnode;
 	custr_alloc;
+	custr_alloc_buf;
 	custr_append;
 	custr_appendc;
+	custr_append_printf;
 	custr_cstr;
 	custr_free;
 	custr_len;
diff --git a/usr/src/lib/libcmdutils/libcmdutils.h b/usr/src/lib/libcmdutils/libcmdutils.h
index bbc03475dc..e0c97178dc 100644
--- a/usr/src/lib/libcmdutils/libcmdutils.h
+++ b/usr/src/lib/libcmdutils/libcmdutils.h
@@ -156,6 +156,12 @@ extern int custr_alloc(custr_t **);
 extern void custr_free(custr_t *);
 
 /*
+ * Allocate a "custr_t" dynamic string object that operates on a fixed external
+ * buffer.
+ */
+extern int custr_alloc_buf(custr_t **, void *, size_t);
+
+/*
  * Append a single character, or a NUL-terminated string of characters, to a
  * dynamic string.  Returns 0 on success and -1 otherwise.  The dynamic string
  * will be unmodified if the function returns -1.
@@ -164,6 +170,13 @@ extern int custr_appendc(custr_t *, char);
 extern int custr_append(custr_t *, const char *);
 
 /*
+ * Append a format string and arguments as though the contents were being parsed
+ * through snprintf. Returns 0 on success and -1 otherwise.  The dynamic string
+ * will be unmodified if the function returns -1.
+ */
+extern int custr_append_printf(custr_t *, const char *, ...);
+
+/*
  * Determine the length in bytes, not including the NUL terminator, of the
  * dynamic string.
  */