map_swiss.go

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package abi
     6  
     7  import (
     8  	"unsafe"
     9  )
    10  
    11  // Map constants common to several packages
    12  // runtime/runtime-gdb.py:MapTypePrinter contains its own copy
    13  const (
    14  	// Number of bits in the group.slot count.
    15  	SwissMapGroupSlotsBits = 3
    16  
    17  	// Number of slots in a group.
    18  	SwissMapGroupSlots = 1 << SwissMapGroupSlotsBits // 8
    19  
    20  	// Maximum key or elem size to keep inline (instead of mallocing per element).
    21  	// Must fit in a uint8.
    22  	SwissMapMaxKeyBytes  = 128
    23  	SwissMapMaxElemBytes = 128
    24  
    25  	ctrlEmpty   = 0b10000000
    26  	bitsetLSB   = 0x0101010101010101
    27  
    28  	// Value of control word with all empty slots.
    29  	SwissMapCtrlEmpty = bitsetLSB * uint64(ctrlEmpty)
    30  )
    31  
    32  type SwissMapType struct {
    33  	Type
    34  	Key   *Type
    35  	Elem  *Type
    36  	Group *Type // internal type representing a slot group
    37  	// function for hashing keys (ptr to key, seed) -> hash
    38  	Hasher   func(unsafe.Pointer, uintptr) uintptr
    39  	SlotSize uintptr // size of key/elem slot
    40  	ElemOff  uintptr // offset of elem in key/elem slot
    41  	Flags    uint32
    42  }
    43  
    44  // Flag values
    45  const (
    46  	SwissMapNeedKeyUpdate = 1 << iota
    47  	SwissMapHashMightPanic
    48  	SwissMapIndirectKey
    49  	SwissMapIndirectElem
    50  )
    51  
    52  func (mt *SwissMapType) NeedKeyUpdate() bool { // true if we need to update key on an overwrite
    53  	return mt.Flags&SwissMapNeedKeyUpdate != 0
    54  }
    55  func (mt *SwissMapType) HashMightPanic() bool { // true if hash function might panic
    56  	return mt.Flags&SwissMapHashMightPanic != 0
    57  }
    58  func (mt *SwissMapType) IndirectKey() bool { // store ptr to key instead of key itself
    59  	return mt.Flags&SwissMapIndirectKey != 0
    60  }
    61  func (mt *SwissMapType) IndirectElem() bool { // store ptr to elem instead of elem itself
    62  	return mt.Flags&SwissMapIndirectElem != 0
    63  }
    64
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