github.com/goshafaq/sonic@v0.0.0-20231026082336-871835fb94c6/internal/caching/fcache.go (about)

     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/goshafaq/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  }