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src/sql/engine/expr/ob_expr_reverse.cpp

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+/**
+ * Copyright (c) 2021 OceanBase
+ * OceanBase CE is licensed under Mulan PubL v2.
+ * You can use this software according to the terms and conditions of the Mulan PubL v2.
+ * You may obtain a copy of Mulan PubL v2 at:
+ *          http://license.coscl.org.cn/MulanPubL-2.0
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PubL v2 for more details.
+ */
+
+#define USING_LOG_PREFIX SQL_ENG
+#include "ob_expr_reverse.h"
+#include <string.h>
+#include "lib/charset/ob_charset.h"
+#include "share/object/ob_obj_cast.h"
+#include "sql/parser/ob_item_type.h"
+#include "sql/session/ob_sql_session_info.h"
+
+namespace oceanbase {
+using namespace common;
+namespace sql {
+
+ObExprReverse::ObExprReverse(ObIAllocator& alloc) : ObStringExprOperator(alloc, T_FUN_SYS_REVERSE, "reverse", 1)
+{}
+
+ObExprReverse::~ObExprReverse()
+{}
+
+int ObExprReverse::calc_result1(common::ObObj& result, const common::ObObj& obj1, common::ObExprCtx& expr_ctx) const
+{
+  int ret = OB_SUCCESS;
+  if (obj1.is_null()) {
+    result.set_null();
+  } else {
+    TYPE_CHECK(obj1, ObVarcharType);
+    ObString res_str;
+    if (OB_FAIL(do_reverse(obj1.get_string(), obj1.get_collation_type(), expr_ctx.calc_buf_, res_str))) {
+      LOG_WARN("Failed to calc", K(ret));
+    } else {
+      result.set_varchar(res_str);
+      result.set_collation(result_type_);
+    }
+  }
+  return ret;
+}
+
+int ObExprReverse::do_reverse(const ObString& input_str, const ObCollationType& cs_type,
+    ObIAllocator* allocator,  // make sure alloc() is called once
+    ObString& res_str)
+{
+  int ret = OB_SUCCESS;
+  const char* input_start = input_str.ptr();
+  int64_t input_length = input_str.length();
+  char* buf = NULL;
+  if (OB_ISNULL(allocator)) {
+    LOG_WARN("nullptr allocator.", K(allocator));
+  } else if (OB_UNLIKELY(input_length == 0)) {
+    res_str.reset();
+  } else if (OB_ISNULL(input_start)) {
+    ret = OB_INVALID_ARGUMENT;
+    LOG_WARN("Invalid string, buf is null", K(ret));
+  } else if (OB_ISNULL(buf = static_cast<char*>(allocator->alloc(input_length)))) {
+    ret = OB_ALLOCATE_MEMORY_FAILED;
+    LOG_ERROR("alloc memory failed. ", "size", input_length);
+  } else {
+    int64_t converted_length = 0;
+    int64_t char_begin = 0;
+    int64_t char_length = 0;
+    char* buf_tail = buf + input_length;
+    while (OB_SUCC(ret) && (converted_length < input_length)) {
+      if (OB_FAIL(ObCharset::first_valid_char(
+              cs_type, input_start + char_begin, input_length - converted_length, char_length))) {
+        LOG_WARN("Get first valid char failed ", K(ret));
+      } else {
+        MEMCPY(buf_tail - char_length, input_start + char_begin, char_length);
+        buf_tail -= char_length;
+        converted_length += char_length;
+        char_begin += char_length;
+      }
+    }
+    if (OB_SUCC(ret)) {
+      res_str.assign_ptr(buf, static_cast<int32_t>(input_length));
+    }
+  }
+  return ret;
+}
+
+int calc_reverse_expr(const ObExpr& expr, ObEvalCtx& ctx, ObDatum& res_datum)
+{
+  int ret = OB_SUCCESS;
+  ObDatum* arg = NULL;
+  if (OB_FAIL(expr.args_[0]->eval(ctx, arg))) {
+    LOG_WARN("eval arg failed", K(ret));
+  } else if (arg->is_null()) {
+    res_datum.set_null();
+  } else {
+    const ObString& arg_str = arg->get_string();
+    const ObCollationType& arg_cs_type = expr.args_[0]->datum_meta_.cs_type_;
+    ObString res_str;
+    ObExprStrResAlloc res_alloc(expr, ctx);
+    if (OB_FAIL(ObExprReverse::do_reverse(arg_str, arg_cs_type, &res_alloc, res_str))) {
+      LOG_WARN("do_reverse failed", K(ret), K(arg_str), K(arg_cs_type));
+    } else {
+      // expr reverse is in mysql mode. no need to check res_str.empty()
+      res_datum.set_string(res_str);
+    }
+  }
+  return ret;
+}
+
+int ObExprReverse::cg_expr(ObExprCGCtx& expr_cg_ctx, const ObRawExpr& raw_expr, ObExpr& rt_expr) const
+{
+  int ret = OB_SUCCESS;
+  UNUSED(expr_cg_ctx);
+  UNUSED(raw_expr);
+  rt_expr.eval_func_ = calc_reverse_expr;
+  return ret;
+}
+}  // namespace sql
+}  // namespace oceanbase