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// Copyright 2022 Dolthub, 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.
//
// This file incorporates work covered by the following copyright and
// permission notice:
//
// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build go1.18 || go1.19
// +build go1.18 go1.19
package maphash
import (
"math/rand"
"unsafe"
)
type hashfn func(unsafe.Pointer, uintptr) uintptr
func getRuntimeHasher[K comparable]() (h hashfn) {
a := any(make(map[K]struct{}))
i := (*mapiface)(unsafe.Pointer(&a))
h = i.typ.hasher
return
}
func newHashSeed() uintptr {
return uintptr(rand.Int())
}
// noescape hides a pointer from escape analysis. It is the identity function
// but escape analysis doesn't think the output depends on the input.
// noescape is inlined and currently compiles down to zero instructions.
// USE CAREFULLY!
// This was copied from the runtime (via pkg "strings"); see issues 23382 and 7921.
//
//go:nosplit
//go:nocheckptr
func noescape(p unsafe.Pointer) unsafe.Pointer {
x := uintptr(p)
return unsafe.Pointer(x ^ 0)
}
type mapiface struct {
typ *maptype
val *hmap
}
// go/src/runtime/type.go
type maptype struct {
typ _type
key *_type
elem *_type
bucket *_type
// function for hashing keys (ptr to key, seed) -> hash
hasher func(unsafe.Pointer, uintptr) uintptr
keysize uint8
elemsize uint8
bucketsize uint16
flags uint32
}
// go/src/runtime/map.go
type hmap struct {
count int
flags uint8
B uint8
noverflow uint16
// hash seed
hash0 uint32
buckets unsafe.Pointer
oldbuckets unsafe.Pointer
nevacuate uintptr
// true type is *mapextra
// but we don't need this data
extra unsafe.Pointer
}
// go/src/runtime/type.go
type tflag uint8
type nameOff int32
type typeOff int32
// go/src/runtime/type.go
type _type struct {
size uintptr
ptrdata uintptr
hash uint32
tflag tflag
align uint8
fieldAlign uint8
kind uint8
equal func(unsafe.Pointer, unsafe.Pointer) bool
gcdata *byte
str nameOff
ptrToThis typeOff
}
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