fcache.go

Documentation: github.com/bytedance/sonic/internal/caching

     1  /*
     2   * Copyright 2021 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 caching
    18  
    19  import (
    20      `strings`
    21      `unsafe`
    22  
    23      `github.com/bytedance/sonic/internal/rt`
    24  )
    25  
    26  type FieldMap struct {
    27      N uint64
    28      b unsafe.Pointer
    29      m map[string]int
    30  }
    31  
    32  type FieldEntry struct {
    33      ID   int
    34      Name string
    35      Hash uint64
    36  }
    37  
    38  const (
    39      FieldMap_N     = int64(unsafe.Offsetof(FieldMap{}.N))
    40      FieldMap_b     = int64(unsafe.Offsetof(FieldMap{}.b))
    41  	FieldEntrySize = int64(unsafe.Sizeof(FieldEntry{}))
    42  )
    43  
    44  func newBucket(n int) unsafe.Pointer {
    45      v := make([]FieldEntry, n)
    46      return (*rt.GoSlice)(unsafe.Pointer(&v)).Ptr
    47  }
    48  
    49  func CreateFieldMap(n int) *FieldMap {
    50      return &FieldMap {
    51          N: uint64(n * 2),
    52          b: newBucket(n * 2),    // LoadFactor = 0.5
    53          m: make(map[string]int, n * 2),
    54      }
    55  }
    56  
    57  func (self *FieldMap) At(p uint64) *FieldEntry {
    58      off := uintptr(p) * uintptr(FieldEntrySize)
    59      return (*FieldEntry)(unsafe.Pointer(uintptr(self.b) + off))
    60  }
    61  
    62  // Get searches FieldMap by name. JIT generated assembly does NOT call this
    63  // function, rather it implements its own version directly in assembly. So
    64  // we must ensure this function stays in sync with the JIT generated one.
    65  func (self *FieldMap) Get(name string) int {
    66      h := StrHash(name)
    67      p := h % self.N
    68      s := self.At(p)
    69  
    70      /* find the element;
    71       * the hash map is never full, so the loop will always terminate */
    72      for s.Hash != 0 {
    73          if s.Hash == h && s.Name == name {
    74              return s.ID
    75          } else {
    76              p = (p + 1) % self.N
    77              s = self.At(p)
    78          }
    79      }
    80  
    81      /* not found */
    82      return -1
    83  }
    84  
    85  func (self *FieldMap) Set(name string, i int) {
    86      h := StrHash(name)
    87      p := h % self.N
    88      s := self.At(p)
    89  
    90      /* searching for an empty slot;
    91       * the hash map is never full, so the loop will always terminate */
    92      for s.Hash != 0 {
    93          p = (p + 1) % self.N
    94          s = self.At(p)
    95      }
    96  
    97      /* set the value */
    98      s.ID   = i
    99      s.Hash = h
   100      s.Name = name
   101  
   102      /* add the case-insensitive version, prefer the one with smaller field ID */
   103      key := strings.ToLower(name)
   104      if v, ok := self.m[key]; !ok || i < v {
   105          self.m[key] = i
   106      }
   107  }
   108  
   109  func (self *FieldMap) GetCaseInsensitive(name string) int {
   110      if i, ok := self.m[strings.ToLower(name)]; ok {
   111          return i
   112      } else {
   113          return -1
   114      }
   115  }
   116
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