github.com/cloudwego/frugal@v0.1.15/internal/binary/defs/defaults.go (about)

     1  /*
     2   * Copyright 2022 ByteDance Inc.
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package defs
    18  
    19  import (
    20      `fmt`
    21      `reflect`
    22      `unsafe`
    23  )
    24  
    25  type DefaultInitializer interface {
    26      InitDefault()
    27  }
    28  
    29  func GetDefaultInitializer(vt reflect.Type) (unsafe.Pointer, error) {
    30      var ok bool
    31      var mt reflect.Method
    32  
    33      /* element type and pointer type */
    34      et := vt
    35      pt := reflect.PtrTo(vt)
    36  
    37      /* dereference the type */
    38      for et.Kind() == reflect.Ptr {
    39          pt = et
    40          et = et.Elem()
    41      }
    42  
    43      /* find the default initializer method */
    44      if mt, ok = et.MethodByName("InitDefault"); ok {
    45          return nil, fmt.Errorf("implementation of `InitDefault()` must have a pointer receiver: %s", mt.Type)
    46      } else if mt, ok = pt.MethodByName("InitDefault"); !ok {
    47          return nil, nil
    48      } else if mt.Type.NumIn() != 1 || mt.Type.NumOut() != 0 {
    49          return nil, fmt.Errorf("invalid implementation of `InitDefault()`: %s", mt.Type)
    50      } else {
    51          return *(*[2]*unsafe.Pointer)(unsafe.Pointer(&mt.Func))[1], nil
    52      }
    53  }