client: don't output empty lines on configure commands

NEWS

@@ -1,6 +1,7 @@
 lldpd (1.0.17)
  * Fix:
    + Read overflow when parsing CDP addresses. Thanks to Matteo Memelli.
+   + Don't output empty lines on configure commands.
 
 lldpd (1.0.16)
  * Fix:

src/client/text_writer.c

@@ -17,6 +17,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdarg.h>
 #include <string.h>
 
 #include "writer.h"
@@ -29,8 +30,27 @@ struct txt_writer_private {
 	FILE *fh;
 	int level;
 	int attrs;
+	int lastnl;
 };
 
+static void
+txt_fprintf(struct txt_writer_private *p, const char *fmt, ...)
+{
+	va_list ap;
+
+	// Don't add a newline if we already had one.
+	while (p->lastnl && fmt[0] == '\n') {
+		fmt += 1;
+	}
+	if (fmt[0] == '\0') return;
+
+	va_start(ap, fmt);
+	vfprintf(p->fh, fmt, ap);
+	va_end(ap);
+
+	p->lastnl = (strlen(fmt) > 0 && fmt[strlen(fmt) - 1] == '\n');
+}
+
 static void
 txt_start(struct writer *w, const char *tag, const char *descr)
 {
@@ -39,19 +59,19 @@ txt_start(struct writer *w, const char *tag, const char *descr)
 	char buf[128];
 
 	if (p->level == 0) {
-		fprintf(p->fh, "%s\n", sep);
-	} else {
-		fprintf(p->fh, "\n");
+		txt_fprintf(p, "%s\n", sep);
+	} else if (!p->lastnl) {
+		txt_fprintf(p, "\n");
 	}
 
 	for (i = 1; i < p->level; i++) {
-		fprintf(p->fh, "  ");
+		txt_fprintf(p, "  ");
 	}
 
 	snprintf(buf, sizeof(buf), "%s:", descr);
-	fprintf(p->fh, "%-13s", buf);
+	txt_fprintf(p, "%-13s", buf);
 
-	if (p->level == 0) fprintf(p->fh, "\n%s", sep);
+	if (p->level == 0) txt_fprintf(p, "\n%s", sep);
 
 	p->level++;
 	p->attrs = 0;
@@ -63,10 +83,10 @@ txt_attr(struct writer *w, const char *tag, const char *descr, const char *value
 	struct txt_writer_private *p = w->priv;
 
 	if (descr == NULL || strlen(descr) == 0) {
-		fprintf(p->fh, "%s%s", (p->attrs > 0 ? ", " : " "),
+		txt_fprintf(p, "%s%s", (p->attrs > 0 ? ", " : " "),
 		    value ? value : "(none)");
 	} else {
-		fprintf(p->fh, "%s%s: %s", (p->attrs > 0 ? ", " : " "), descr,
+		txt_fprintf(p, "%s%s: %s", (p->attrs > 0 ? ", " : " "), descr,
 		    value ? value : "(none)");
 	}
 
@@ -81,24 +101,24 @@ txt_data(struct writer *w, const char *data)
 	char *v = begin = data ? strdup(data) : NULL;
 
 	if (v == NULL) {
-		fprintf(p->fh, " %s", data ? data : "(none)");
+		txt_fprintf(p, " %s", data ? data : "(none)");
 		return;
 	}
 
-	fprintf(p->fh, " ");
+	txt_fprintf(p, " ");
 	while ((nl = strchr(v, '\n')) != NULL) {
 		*nl = '\0';
-		fprintf(p->fh, "%s\n", v);
+		txt_fprintf(p, "%s\n", v);
 		v = nl + 1;
 
 		/* Indent */
 		int i;
 		for (i = 1; i < p->level - 1; i++) {
-			fprintf(p->fh, "  ");
+			txt_fprintf(p, "  ");
 		}
-		fprintf(p->fh, "%-14s", " ");
+		txt_fprintf(p, "%-14s", " ");
 	}
-	fprintf(p->fh, "%s", v);
+	txt_fprintf(p, "%s", v);
 	free(begin);
 }
 
@@ -109,7 +129,7 @@ txt_end(struct writer *w)
 	p->level--;
 
 	if (p->level == 1) {
-		fprintf(p->fh, "\n%s", sep);
+		txt_fprintf(p, "\n%s", sep);
 		fflush(p->fh);
 	}
 }
@@ -119,7 +139,7 @@ txt_finish(struct writer *w)
 {
 	struct txt_writer_private *p = w->priv;
 
-	fprintf(p->fh, "\n");
+	txt_fprintf(p, "\n");
 
 	free(w->priv);
 	w->priv = NULL;
@@ -143,6 +163,7 @@ txt_init(FILE *fh)
 	priv->fh = fh;
 	priv->level = 0;
 	priv->attrs = 0;
+	priv->lastnl = 1;
 
 	result = malloc(sizeof(struct writer));
 	if (!result) {