PDO MySQL: Use mysqlnd column names

mysqlnd already creates interned zend_strings for us, so let's
make use of them.

This also required updating the PDO case changing code to work
with potentially shared strings. For the lowercasing, use the
optimized zend_string_tolower() implementation.

Author: nikic

Zend/zend_string.h

@@ -195,6 +195,19 @@ static zend_always_inline zend_string *zend_string_dup(zend_string *s, bool pers
 	}
 }
 
+static zend_always_inline zend_string *zend_string_separate(zend_string *s, bool persistent)
+{
+	if (ZSTR_IS_INTERNED(s) || GC_REFCOUNT(s) > 1) {
+		if (!ZSTR_IS_INTERNED(s)) {
+			GC_DELREF(s);
+		}
+		return zend_string_init(ZSTR_VAL(s), ZSTR_LEN(s), persistent);
+	}
+
+	zend_string_forget_hash_val(s);
+	return s;
+}
+
 static zend_always_inline zend_string *zend_string_realloc(zend_string *s, size_t len, bool persistent)
 {
 	zend_string *ret;

ext/pdo/pdo_stmt.c

@@ -138,23 +138,22 @@ int pdo_stmt_describe_columns(pdo_stmt_t *stmt) /* {{{ */
 
 		/* if we are applying case conversions on column names, do so now */
 		if (stmt->dbh->native_case != stmt->dbh->desired_case && stmt->dbh->desired_case != PDO_CASE_NATURAL) {
-			char *s = ZSTR_VAL(stmt->columns[col].name);
-
+			zend_string *orig_name = stmt->columns[col].name;
 			switch (stmt->dbh->desired_case) {
-				case PDO_CASE_UPPER:
-					while (*s != '\0') {
-						*s = toupper(*s);
-						s++;
-					}
-					break;
 				case PDO_CASE_LOWER:
+					stmt->columns[col].name = zend_string_tolower(orig_name);
+					zend_string_release(orig_name);
+					break;
+				case PDO_CASE_UPPER: {
+					stmt->columns[col].name = zend_string_separate(orig_name, 0);
+					char *s = ZSTR_VAL(stmt->columns[col].name);
 					while (*s != '\0') {
-						*s = tolower(*s);
+						*s = toupper(*s);
 						s++;
 					}
 					break;
-				default:
-					;
+				}
+				EMPTY_SWITCH_DEFAULT_CASE()
 			}
 		}
 

ext/pdo_mysql/mysql_statement.c

@@ -619,7 +619,11 @@ static int pdo_mysql_stmt_describe(pdo_stmt_t *stmt, int colno) /* {{{ */
 		if (S->H->fetch_table_names) {
 			cols[i].name = strpprintf(0, "%s.%s", S->fields[i].table, S->fields[i].name);
 		} else {
+#ifdef PDO_USE_MYSQLND
+			cols[i].name = zend_string_copy(S->fields[i].sname);
+#else
 			cols[i].name = zend_string_init(S->fields[i].name, S->fields[i].name_length, 0);
+#endif
 		}
 
 		cols[i].precision = S->fields[i].decimals;