add txt_range_equal()

3 files changed, 39 insertions, 4 deletions

diff --git a/main.c b/main.c
index 15188f4..0923324 100644
--- a/main.c
+++ b/main.c
@@ -138,7 +138,8 @@ int shell_replace(TxtLoc start, TxtLoc end, const char *cmd) {
 		end = t;
 	}
 
-	u32 cur_ofs = txt_range_len(cur, end);
+	int cur_ofs = txt_before(cur, start) || txt_after(cur, end)
+	    ? -1 : txt_range_len(cur, end);
 
 	int in, out;
 	int p = popen2(cmd, &in, &out);
@@ -151,7 +152,6 @@ int shell_replace(TxtLoc start, TxtLoc end, const char *cmd) {
 	Str wrs = txt_collect_range(start, end, &scratch);
 	DYNARR(char) rds = { 0 };
 	u32 wr_i = 0;
-	cur = txt_delete_range(start, end);
 	while ((pfds[0].fd >= 0 || pfds[1].fd >= 0) && poll(pfds, 2, 200) >= 0) {
 		const u32 chunksz = 8L << 10;
 		if (pfds[0].revents & POLLOUT) {
@@ -182,8 +182,15 @@ int shell_replace(TxtLoc start, TxtLoc end, const char *cmd) {
 			pfds[1].fd = -1;
 		}
 	}
-	cur = txt_insert(cur, rds.v, rds.n);
-	while (cur_ofs--) cur = cprev(cur);
+
+	if (!txt_range_equal(start, end, (Str){rds.v,rds.n})) {
+		start = txt_delete_range(start, end);
+		start = txt_insert(start, rds.v, rds.n);
+		if (cur_ofs != -1) {
+			cur = start;
+			while (cur_ofs--) cur = cprev(cur);
+		}
+	}
 	return 0;
 }
 
diff --git a/txt.c b/txt.c
index 038140d..b4b4f54 100644
--- a/txt.c
+++ b/txt.c
@@ -323,6 +323,32 @@ u32 txt_read_chunk(TxtLoc *lo, TxtLoc hi, char *buf, u32 sz) {
 	return n;
 }
 
+Str txt_next_chunk(TxtLoc *l) {
+	TxtPiece *p = &l->t->ptbl.v[l->p];
+	Str s = { l->t->buf[p->buf].s + p->ofs + l->i, p->n - l->i };
+	if (l->p + 1 < l->t->ptbl.n) {
+		l->p++;
+		l->i = 0;
+	} else {
+		l->i = p->n;
+	}
+	return s;
+}
+
+int txt_range_equal(TxtLoc lo, TxtLoc hi, Str cmp) {
+	u32 i = 0;
+	while (txt_before(lo, hi)) {
+		Str s = txt_next_chunk(&lo);
+		u32 n = cmp.n - i;
+		if (s.n < n) n = s.n;
+		if (memcmp(s.s, cmp.s + i, n)) {
+			return 0;
+		}
+		i += s.n;
+	}
+	return 1;
+}
+
 /* navigation */
 
 int txt_valid_loc(TxtLoc l) {
diff --git a/txt.h b/txt.h
index 3b62e04..d7c5685 100644
--- a/txt.h
+++ b/txt.h
@@ -43,6 +43,8 @@ void txt_free(Txt *b);
 
 Str txt_collect_range(TxtLoc lo, TxtLoc hi, Arena *a);
 u32 txt_read_chunk(TxtLoc *lo, TxtLoc hi, char *buf, u32 sz);
+Str txt_next_chunk(TxtLoc *l);
+int txt_range_equal(TxtLoc lo, TxtLoc hi, Str s);
 
 /* insertion & deletion */