github.com/ylsgit/go-ethereum@v1.6.5/rlp/typecache.go (about)

     1  // Copyright 2014 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package rlp
    18  
    19  import (
    20  	"fmt"
    21  	"reflect"
    22  	"strings"
    23  	"sync"
    24  )
    25  
    26  var (
    27  	typeCacheMutex sync.RWMutex
    28  	typeCache      = make(map[typekey]*typeinfo)
    29  )
    30  
    31  type typeinfo struct {
    32  	decoder
    33  	writer
    34  }
    35  
    36  // represents struct tags
    37  type tags struct {
    38  	// rlp:"nil" controls whether empty input results in a nil pointer.
    39  	nilOK bool
    40  	// rlp:"tail" controls whether this field swallows additional list
    41  	// elements. It can only be set for the last field, which must be
    42  	// of slice type.
    43  	tail bool
    44  	// rlp:"-" ignores fields.
    45  	ignored bool
    46  }
    47  
    48  type typekey struct {
    49  	reflect.Type
    50  	// the key must include the struct tags because they
    51  	// might generate a different decoder.
    52  	tags
    53  }
    54  
    55  type decoder func(*Stream, reflect.Value) error
    56  
    57  type writer func(reflect.Value, *encbuf) error
    58  
    59  func cachedTypeInfo(typ reflect.Type, tags tags) (*typeinfo, error) {
    60  	typeCacheMutex.RLock()
    61  	info := typeCache[typekey{typ, tags}]
    62  	typeCacheMutex.RUnlock()
    63  	if info != nil {
    64  		return info, nil
    65  	}
    66  	// not in the cache, need to generate info for this type.
    67  	typeCacheMutex.Lock()
    68  	defer typeCacheMutex.Unlock()
    69  	return cachedTypeInfo1(typ, tags)
    70  }
    71  
    72  func cachedTypeInfo1(typ reflect.Type, tags tags) (*typeinfo, error) {
    73  	key := typekey{typ, tags}
    74  	info := typeCache[key]
    75  	if info != nil {
    76  		// another goroutine got the write lock first
    77  		return info, nil
    78  	}
    79  	// put a dummmy value into the cache before generating.
    80  	// if the generator tries to lookup itself, it will get
    81  	// the dummy value and won't call itself recursively.
    82  	typeCache[key] = new(typeinfo)
    83  	info, err := genTypeInfo(typ, tags)
    84  	if err != nil {
    85  		// remove the dummy value if the generator fails
    86  		delete(typeCache, key)
    87  		return nil, err
    88  	}
    89  	*typeCache[key] = *info
    90  	return typeCache[key], err
    91  }
    92  
    93  type field struct {
    94  	index int
    95  	info  *typeinfo
    96  }
    97  
    98  func structFields(typ reflect.Type) (fields []field, err error) {
    99  	for i := 0; i < typ.NumField(); i++ {
   100  		if f := typ.Field(i); f.PkgPath == "" { // exported
   101  			tags, err := parseStructTag(typ, i)
   102  			if err != nil {
   103  				return nil, err
   104  			}
   105  			if tags.ignored {
   106  				continue
   107  			}
   108  			info, err := cachedTypeInfo1(f.Type, tags)
   109  			if err != nil {
   110  				return nil, err
   111  			}
   112  			fields = append(fields, field{i, info})
   113  		}
   114  	}
   115  	return fields, nil
   116  }
   117  
   118  func parseStructTag(typ reflect.Type, fi int) (tags, error) {
   119  	f := typ.Field(fi)
   120  	var ts tags
   121  	for _, t := range strings.Split(f.Tag.Get("rlp"), ",") {
   122  		switch t = strings.TrimSpace(t); t {
   123  		case "":
   124  		case "-":
   125  			ts.ignored = true
   126  		case "nil":
   127  			ts.nilOK = true
   128  		case "tail":
   129  			ts.tail = true
   130  			if fi != typ.NumField()-1 {
   131  				return ts, fmt.Errorf(`rlp: invalid struct tag "tail" for %v.%s (must be on last field)`, typ, f.Name)
   132  			}
   133  			if f.Type.Kind() != reflect.Slice {
   134  				return ts, fmt.Errorf(`rlp: invalid struct tag "tail" for %v.%s (field type is not slice)`, typ, f.Name)
   135  			}
   136  		default:
   137  			return ts, fmt.Errorf("rlp: unknown struct tag %q on %v.%s", t, typ, f.Name)
   138  		}
   139  	}
   140  	return ts, nil
   141  }
   142  
   143  func genTypeInfo(typ reflect.Type, tags tags) (info *typeinfo, err error) {
   144  	info = new(typeinfo)
   145  	if info.decoder, err = makeDecoder(typ, tags); err != nil {
   146  		return nil, err
   147  	}
   148  	if info.writer, err = makeWriter(typ, tags); err != nil {
   149  		return nil, err
   150  	}
   151  	return info, nil
   152  }
   153  
   154  func isUint(k reflect.Kind) bool {
   155  	return k >= reflect.Uint && k <= reflect.Uintptr
   156  }