text: add mem{r,}chr(3) based byte search functions

These are generally implemented efficiently in libc.
While memrchr(3) is non-standard, it is a common extension.
If it is not available, we use a simple C implementation from musl.

1 files changed, 29 insertions, 0 deletions

diff --git a/text.c b/text.c
index f789339..1bf1940 100644
--- a/text.c
+++ b/text.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE // memrchr(3) is non-standard
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -1455,6 +1456,34 @@ bool text_iterator_byte_prev(Iterator *it, char *b) {
 	return true;
 }
 
+bool text_iterator_byte_find_prev(Iterator *it, char b) {
+	while (it->text) {
+		const char *match = memrchr(it->start, b, it->text - it->start);
+		if (match) {
+			it->pos -= it->text - match;
+			it->text = match;
+			return true;
+		}
+		text_iterator_prev(it);
+	}
+	text_iterator_next(it);
+	return false;
+}
+
+bool text_iterator_byte_find_next(Iterator *it, char b) {
+	while (it->text) {
+		const char *match = memchr(it->text, b, it->end - it->text);
+		if (match) {
+			it->pos += match - it->text;
+			it->text = match;
+			return true;
+		}
+		text_iterator_next(it);
+	}
+	text_iterator_prev(it);
+	return false;
+}
+
 bool text_iterator_codepoint_next(Iterator *it, char *c) {
 	while (text_iterator_byte_next(it, NULL)) {
 		if (ISUTF8(*it->text)) {