Merge pull request #64489 from MewPurPur/fast-string-repeat

Improved performance of `String.repeat()`

1 files changed, 13 insertions, 12 deletions

diff --git a/core/string/ustring.cpp b/core/string/ustring.cpp
index 13be7516d5..c02be9e5b7 100644
--- a/core/string/ustring.cpp
+++ b/core/string/ustring.cpp
@@ -3451,18 +3451,19 @@ String String::replacen(const String &p_key, const String &p_with) const {
 String String::repeat(int p_count) const {
 	ERR_FAIL_COND_V_MSG(p_count < 0, "", "Parameter count should be a positive number.");
 
-	String new_string;
-	const char32_t *src = this->get_data();
-
-	new_string.resize(length() * p_count + 1);
-	new_string[length() * p_count] = 0;
-
-	for (int i = 0; i < p_count; i++) {
-		for (int j = 0; j < length(); j++) {
-			new_string[i * length() + j] = src[j];
-		}
-	}
-
+	int len = length();
+	String new_string = *this;
+	new_string.resize(p_count * len + 1);
+
+	char32_t *dst = new_string.ptrw();
+	int offset = 1;
+	int stride = 1;
+	while (offset < p_count) {
+		memcpy(dst + offset * len, dst, stride * len * sizeof(char32_t));
+		offset += stride;
+		stride = MIN(stride * 2, p_count - offset);
+	}
+	dst[p_count * len] = _null;
 	return new_string;
 }