[chore] Update gin to v1.9.0 (#1553)

vendor/github.com/bytedance/sonic/internal/caching/pcache.go

@@ -0,0 +1,173 @@
+/*
+ * Copyright 2021 ByteDance Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package caching
+
+import (
+    `sync`
+    `sync/atomic`
+    `unsafe`
+
+    `github.com/bytedance/sonic/internal/rt`
+)
+
+/** Program Map **/
+
+const (
+    _LoadFactor   = 0.5
+    _InitCapacity = 4096    // must be a power of 2
+)
+
+type _ProgramMap struct {
+    n uint64
+    m uint32
+    b []_ProgramEntry
+}
+
+type _ProgramEntry struct {
+    vt *rt.GoType
+    fn interface{}
+}
+
+func newProgramMap() *_ProgramMap {
+    return &_ProgramMap {
+        n: 0,
+        m: _InitCapacity - 1,
+        b: make([]_ProgramEntry, _InitCapacity),
+    }
+}
+
+func (self *_ProgramMap) copy() *_ProgramMap {
+    fork := &_ProgramMap{
+        n: self.n,
+        m: self.m,
+        b: make([]_ProgramEntry, len(self.b)),
+    }
+    for i, f := range self.b {
+        fork.b[i] = f
+    }
+    return fork
+}
+
+func (self *_ProgramMap) get(vt *rt.GoType) interface{} {
+    i := self.m + 1
+    p := vt.Hash & self.m
+
+    /* linear probing */
+    for ; i > 0; i-- {
+        if b := self.b[p]; b.vt == vt {
+            return b.fn
+        } else if b.vt == nil {
+            break
+        } else {
+            p = (p + 1) & self.m
+        }
+    }
+
+    /* not found */
+    return nil
+}
+
+func (self *_ProgramMap) add(vt *rt.GoType, fn interface{}) *_ProgramMap {
+    p := self.copy()
+    f := float64(atomic.LoadUint64(&p.n) + 1) / float64(p.m + 1)
+
+    /* check for load factor */
+    if f > _LoadFactor {
+        p = p.rehash()
+    }
+
+    /* insert the value */
+    p.insert(vt, fn)
+    return p
+}
+
+func (self *_ProgramMap) rehash() *_ProgramMap {
+    c := (self.m + 1) << 1
+    r := &_ProgramMap{m: c - 1, b: make([]_ProgramEntry, int(c))}
+
+    /* rehash every entry */
+    for i := uint32(0); i <= self.m; i++ {
+        if b := self.b[i]; b.vt != nil {
+            r.insert(b.vt, b.fn)
+        }
+    }
+
+    /* rebuild successful */
+    return r
+}
+
+func (self *_ProgramMap) insert(vt *rt.GoType, fn interface{}) {
+    h := vt.Hash
+    p := h & self.m
+
+    /* linear probing */
+    for i := uint32(0); i <= self.m; i++ {
+        if b := &self.b[p]; b.vt != nil {
+            p += 1
+            p &= self.m
+        } else {
+            b.vt = vt
+            b.fn = fn
+            atomic.AddUint64(&self.n, 1)
+            return
+        }
+    }
+
+    /* should never happens */
+    panic("no available slots")
+}
+
+/** RCU Program Cache **/
+
+type ProgramCache struct {
+    m sync.Mutex
+    p unsafe.Pointer
+}
+
+func CreateProgramCache() *ProgramCache {
+    return &ProgramCache {
+        m: sync.Mutex{},
+        p: unsafe.Pointer(newProgramMap()),
+    }
+}
+
+func (self *ProgramCache) Get(vt *rt.GoType) interface{} {
+    return (*_ProgramMap)(atomic.LoadPointer(&self.p)).get(vt)
+}
+
+func (self *ProgramCache) Compute(vt *rt.GoType, compute func(*rt.GoType, ... interface{}) (interface{}, error), ex ...interface{}) (interface{}, error) {
+    var err error
+    var val interface{}
+
+    /* use defer to prevent inlining of this function */
+    self.m.Lock()
+    defer self.m.Unlock()
+
+    /* double check with write lock held */
+    if val = self.Get(vt); val != nil {
+        return val, nil
+    }
+
+    /* compute the value */
+    if val, err = compute(vt, ex...); err != nil {
+        return nil, err
+    }
+
+    /* update the RCU cache */
+    atomic.StorePointer(&self.p, unsafe.Pointer((*_ProgramMap)(atomic.LoadPointer(&self.p)).add(vt, val)))
+    return val, nil
+}