text-motion: introduce text_line_{up,down}

2 files changed, 15 insertions, 0 deletions

diff --git a/text-motions.c b/text-motions.c
index 9089371..43077e9 100644
--- a/text-motions.c
+++ b/text-motions.c
@@ -183,6 +183,18 @@ size_t text_line_char_prev(Text *txt, size_t pos) {
 	return it.pos;
 }
 
+size_t text_line_up(Text *txt, size_t pos) {
+	size_t bol = text_line_begin(txt, pos);
+	size_t prev = text_line_prev(txt, bol);
+	return text_line_offset(txt, prev, pos - bol);
+}
+
+size_t text_line_down(Text *txt, size_t pos) {
+	size_t bol = text_line_begin(txt, pos);
+	size_t next = text_line_next(txt, bol);
+	return text_line_offset(txt, next, pos - bol);
+}
+
 static size_t text_customword_start_next(Text *txt, size_t pos, int (*isboundry)(int)) {
 	char c;
 	Iterator it = text_iterator_get(txt, pos);
diff --git a/text-motions.h b/text-motions.h
index 3c7c9c5..438a42f 100644
--- a/text-motions.h
+++ b/text-motions.h
@@ -39,6 +39,9 @@ size_t text_line_offset(Text*, size_t pos, size_t off);
 /* move to the next/previous character on the same line */
 size_t text_line_char_next(Text*, size_t pos);
 size_t text_line_char_prev(Text*, size_t pos);
+/* move to same offset in previous/next line */
+size_t text_line_up(Text*, size_t pos);
+size_t text_line_down(Text*, size_t pos);
 /*
  * A longword consists of a sequence of non-blank characters, separated with
  * white space. TODO?: An empty line is also considered to be a word.