Implement utility functions for dynamic strings

Introduce support for strings which support concatenating the current
value with a printf-style formatted value, thereby growing in size
dynamically.

Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

src/Makefile.am

@@ -32,6 +32,7 @@ calcurse_SOURCES = \
 	recur.c \
 	sha1.c \
 	sigs.c \
+	strings.c \
 	todo.c \
 	ui-calendar.c \
 	ui-day.c \

src/calcurse.h

@@ -601,6 +601,13 @@ struct nbar {
 	pthread_mutex_t mutex;
 };
 
+/* Dynamic strings. */
+struct string {
+	char *buf;
+	int bufsize;
+	int len;
+};
+
 /* Return codes for the getstring() function. */
 enum getstr {
 	GETSTRING_VALID,
@@ -982,6 +989,15 @@ unsigned sigs_set_hdlr(int, void (*)(int));
 void sigs_ignore(void);
 void sigs_unignore(void);
 
+/* strings.c */
+void string_init(struct string *);
+void string_reset(struct string *);
+int string_grow(struct string *, int);
+char *string_buf(struct string *);
+int string_catf(struct string *, const char *, ...);
+int string_vcatf(struct string *, const char *, va_list);
+int string_printf(struct string *, const char *, ...);
+
 /* todo.c */
 extern llist_t todolist;
 struct todo *todo_get_item(int);

src/strings.c

@@ -0,0 +1,112 @@
+/*
+ * Calcurse - text-based organizer
+ *
+ * Copyright (c) 2004-2016 calcurse Development Team <misc@calcurse.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the
+ *        following disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the
+ *        following disclaimer in the documentation and/or other
+ *        materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Send your feedback or comments to : misc@calcurse.org
+ * Calcurse home page : http://calcurse.org
+ *
+ */
+
+#include "calcurse.h"
+
+#define STRING_INITIAL_BUFSIZE 128
+
+void string_init(struct string *sb)
+{
+	sb->buf = mem_malloc(STRING_INITIAL_BUFSIZE);
+	sb->bufsize = STRING_INITIAL_BUFSIZE;
+	sb->len = 0;
+}
+
+void string_reset(struct string *sb)
+{
+	if (sb->buf)
+		mem_free(sb->buf);
+	string_init(sb);
+}
+
+int string_grow(struct string *sb, int minsize)
+{
+	if (sb->bufsize >= minsize)
+		return 0;
+
+	while (sb->bufsize < minsize)
+		sb->bufsize *= 2;
+
+	sb->buf = mem_realloc(sb->buf, 1, sb->bufsize);
+	return 1;
+}
+
+char *string_buf(struct string *sb)
+{
+	return sb->buf;
+}
+
+int string_vcatf(struct string *sb, const char *format, va_list ap)
+{
+	va_list ap2;
+	int n;
+
+	va_copy(ap2, ap);
+
+	n = vsnprintf(sb->buf + sb->len, sb->bufsize - sb->len, format, ap);
+	if (string_grow(sb, sb->len + n + 1)) {
+		n = vsnprintf(sb->buf + sb->len, sb->bufsize - sb->len, format,
+			      ap2);
+	}
+	sb->len += n;
+
+	return n;
+}
+
+int string_catf(struct string *sb, const char *format, ...)
+{
+	va_list	ap;
+	int n;
+
+	va_start(ap, format);
+	n = string_vcatf(sb, format, ap);
+	va_end(ap);
+
+	return n;
+}
+
+int string_printf(struct string *sb, const char *format, ...)
+{
+	va_list	ap;
+	int n;
+
+	va_start(ap, format);
+	string_reset(sb);
+	n = string_vcatf(sb, format, ap);
+	va_end(ap);
+
+	return n;
+}