lib/fold: Add text fold utility

We want to fold help text into the ncurses UI, so add a little module to
split text into lines.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/lib/fold/fold.c b/lib/fold/fold.c
new file mode 100644
index 0000000..ec10c8c
--- /dev/null
+++ b/lib/fold/fold.c
@@ -0,0 +1,44 @@
+
+#include "fold/fold.h"
+
+void fold_text(const char *text,
+		int linelen,
+		int line_cb(void *arg, const char *start, int len),
+		void *arg)
+{
+	const char *start, *end, *sep;
+	int rc = 0;
+
+	start = end = sep = text;
+
+	while (!rc) {
+
+		if (*end == '\n') {
+			rc = line_cb(arg, start, end - start);
+			start = sep = ++end;
+
+		} else if (*end == '\0') {
+			line_cb(arg, start, end - start);
+			rc = 1;
+
+		} else if (end - start >= linelen - 1) {
+			if (sep != start) {
+				/* split on a previous word boundary, if
+				 * possible */
+				rc = line_cb(arg, start, sep - start);
+				start = end = ++sep;
+			} else {
+				/* otherwise, break the word */
+				end++;
+				rc = line_cb(arg, start, end - start);
+				start = sep = end;
+			}
+
+		} else {
+			end++;
+			/* record our last separator */
+			if (*end == ' ')
+				sep = end;
+		}
+	}
+}