Zend: Introduce inline helpers for raw C-string concatenation

Zend/zend_string.h

@@ -316,6 +316,43 @@ static zend_always_inline zend_string *zend_string_safe_realloc(zend_string *s,
 	return ret;
 }
 
+static zend_always_inline char *zend_cstr_append_char(const char *str, size_t len, char c) {
+    char *res = (char *)safe_emalloc(len, 1, 2);
+    if (len > 0) {
+        zend_mempcpy(res, str, len);
+    }
+    res[len] = c;
+    res[len + 1] = '\0';
+    return res;
+}
+
+static zend_always_inline char *zend_cstr_concat(const char *s1, size_t len1, const char *s2, size_t len2) {
+    char *res = (char *)safe_emalloc(len1, 1, len2 + 1);
+    if (len1 > 0) {
+        zend_mempcpy(res, s1, len1);
+    }
+    if (len2 > 0) {
+        zend_mempcpy(res + len1, s2, len2);
+    }
+    res[len1 + len2] = '\0';
+    return res;
+}
+
+static zend_always_inline char *zend_cstr_concat3(const char *s1, size_t len1, const char *s2, size_t len2, const char *s3, size_t len3) {
+    char *res = (char *)safe_emalloc(len1, 1, len2 + len3 + 1);
+    if (len1 > 0) {
+        zend_mempcpy(res, s1, len1);
+    }
+    if (len2 > 0) {
+        zend_mempcpy(res + len1, s2, len2);
+    }
+    if (len3 > 0) {
+        zend_mempcpy(res + len1 + len2, s3, len3);
+    }
+    res[len1 + len2 + len3] = '\0';
+    return res;
+}
+
 static zend_always_inline void zend_string_free(zend_string *s)
 {
 	if (!ZSTR_IS_INTERNED(s)) {