alg.go

Documentation: runtime

     1  // Copyright 2014 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 runtime
     6  
     7  import (
     8  	"runtime/internal/sys"
     9  	"unsafe"
    10  )
    11  
    12  const (
    13  	c0 = uintptr((8-sys.PtrSize)/4*2860486313 + (sys.PtrSize-4)/4*33054211828000289)
    14  	c1 = uintptr((8-sys.PtrSize)/4*3267000013 + (sys.PtrSize-4)/4*23344194077549503)
    15  )
    16  
    17  // type algorithms - known to compiler
    18  const (
    19  	alg_NOEQ = iota
    20  	alg_MEM0
    21  	alg_MEM8
    22  	alg_MEM16
    23  	alg_MEM32
    24  	alg_MEM64
    25  	alg_MEM128
    26  	alg_STRING
    27  	alg_INTER
    28  	alg_NILINTER
    29  	alg_FLOAT32
    30  	alg_FLOAT64
    31  	alg_CPLX64
    32  	alg_CPLX128
    33  	alg_max
    34  )
    35  
    36  // typeAlg is also copied/used in reflect/type.go.
    37  // keep them in sync.
    38  type typeAlg struct {
    39  	// function for hashing objects of this type
    40  	// (ptr to object, seed) -> hash
    41  	hash func(unsafe.Pointer, uintptr) uintptr
    42  	// function for comparing objects of this type
    43  	// (ptr to object A, ptr to object B) -> ==?
    44  	equal func(unsafe.Pointer, unsafe.Pointer) bool
    45  }
    46  
    47  func memhash0(p unsafe.Pointer, h uintptr) uintptr {
    48  	return h
    49  }
    50  
    51  func memhash8(p unsafe.Pointer, h uintptr) uintptr {
    52  	return memhash(p, h, 1)
    53  }
    54  
    55  func memhash16(p unsafe.Pointer, h uintptr) uintptr {
    56  	return memhash(p, h, 2)
    57  }
    58  
    59  func memhash128(p unsafe.Pointer, h uintptr) uintptr {
    60  	return memhash(p, h, 16)
    61  }
    62  
    63  //go:nosplit
    64  func memhash_varlen(p unsafe.Pointer, h uintptr) uintptr {
    65  	ptr := getclosureptr()
    66  	size := *(*uintptr)(unsafe.Pointer(ptr + unsafe.Sizeof(h)))
    67  	return memhash(p, h, size)
    68  }
    69  
    70  var algarray = [alg_max]typeAlg{
    71  	alg_NOEQ:     {nil, nil},
    72  	alg_MEM0:     {memhash0, memequal0},
    73  	alg_MEM8:     {memhash8, memequal8},
    74  	alg_MEM16:    {memhash16, memequal16},
    75  	alg_MEM32:    {memhash32, memequal32},
    76  	alg_MEM64:    {memhash64, memequal64},
    77  	alg_MEM128:   {memhash128, memequal128},
    78  	alg_STRING:   {strhash, strequal},
    79  	alg_INTER:    {interhash, interequal},
    80  	alg_NILINTER: {nilinterhash, nilinterequal},
    81  	alg_FLOAT32:  {f32hash, f32equal},
    82  	alg_FLOAT64:  {f64hash, f64equal},
    83  	alg_CPLX64:   {c64hash, c64equal},
    84  	alg_CPLX128:  {c128hash, c128equal},
    85  }
    86  
    87  var useAeshash bool
    88  
    89  // in asm_*.s
    90  func aeshash(p unsafe.Pointer, h, s uintptr) uintptr
    91  func aeshash32(p unsafe.Pointer, h uintptr) uintptr
    92  func aeshash64(p unsafe.Pointer, h uintptr) uintptr
    93  func aeshashstr(p unsafe.Pointer, h uintptr) uintptr
    94  
    95  func strhash(a unsafe.Pointer, h uintptr) uintptr {
    96  	x := (*stringStruct)(a)
    97  	return memhash(x.str, h, uintptr(x.len))
    98  }
    99  
   100  // NOTE: Because NaN != NaN, a map can contain any
   101  // number of (mostly useless) entries keyed with NaNs.
   102  // To avoid long hash chains, we assign a random number
   103  // as the hash value for a NaN.
   104  
   105  func f32hash(p unsafe.Pointer, h uintptr) uintptr {
   106  	f := *(*float32)(p)
   107  	switch {
   108  	case f == 0:
   109  		return c1 * (c0 ^ h) // +0, -0
   110  	case f != f:
   111  		return c1 * (c0 ^ h ^ uintptr(fastrand())) // any kind of NaN
   112  	default:
   113  		return memhash(p, h, 4)
   114  	}
   115  }
   116  
   117  func f64hash(p unsafe.Pointer, h uintptr) uintptr {
   118  	f := *(*float64)(p)
   119  	switch {
   120  	case f == 0:
   121  		return c1 * (c0 ^ h) // +0, -0
   122  	case f != f:
   123  		return c1 * (c0 ^ h ^ uintptr(fastrand())) // any kind of NaN
   124  	default:
   125  		return memhash(p, h, 8)
   126  	}
   127  }
   128  
   129  func c64hash(p unsafe.Pointer, h uintptr) uintptr {
   130  	x := (*[2]float32)(p)
   131  	return f32hash(unsafe.Pointer(&x[1]), f32hash(unsafe.Pointer(&x[0]), h))
   132  }
   133  
   134  func c128hash(p unsafe.Pointer, h uintptr) uintptr {
   135  	x := (*[2]float64)(p)
   136  	return f64hash(unsafe.Pointer(&x[1]), f64hash(unsafe.Pointer(&x[0]), h))
   137  }
   138  
   139  func interhash(p unsafe.Pointer, h uintptr) uintptr {
   140  	a := (*iface)(p)
   141  	tab := a.tab
   142  	if tab == nil {
   143  		return h
   144  	}
   145  	t := tab._type
   146  	fn := t.alg.hash
   147  	if fn == nil {
   148  		panic(errorString("hash of unhashable type " + t.string()))
   149  	}
   150  	if isDirectIface(t) {
   151  		return c1 * fn(unsafe.Pointer(&a.data), h^c0)
   152  	} else {
   153  		return c1 * fn(a.data, h^c0)
   154  	}
   155  }
   156  
   157  func nilinterhash(p unsafe.Pointer, h uintptr) uintptr {
   158  	a := (*eface)(p)
   159  	t := a._type
   160  	if t == nil {
   161  		return h
   162  	}
   163  	fn := t.alg.hash
   164  	if fn == nil {
   165  		panic(errorString("hash of unhashable type " + t.string()))
   166  	}
   167  	if isDirectIface(t) {
   168  		return c1 * fn(unsafe.Pointer(&a.data), h^c0)
   169  	} else {
   170  		return c1 * fn(a.data, h^c0)
   171  	}
   172  }
   173  
   174  func memequal0(p, q unsafe.Pointer) bool {
   175  	return true
   176  }
   177  func memequal8(p, q unsafe.Pointer) bool {
   178  	return *(*int8)(p) == *(*int8)(q)
   179  }
   180  func memequal16(p, q unsafe.Pointer) bool {
   181  	return *(*int16)(p) == *(*int16)(q)
   182  }
   183  func memequal32(p, q unsafe.Pointer) bool {
   184  	return *(*int32)(p) == *(*int32)(q)
   185  }
   186  func memequal64(p, q unsafe.Pointer) bool {
   187  	return *(*int64)(p) == *(*int64)(q)
   188  }
   189  func memequal128(p, q unsafe.Pointer) bool {
   190  	return *(*[2]int64)(p) == *(*[2]int64)(q)
   191  }
   192  func f32equal(p, q unsafe.Pointer) bool {
   193  	return *(*float32)(p) == *(*float32)(q)
   194  }
   195  func f64equal(p, q unsafe.Pointer) bool {
   196  	return *(*float64)(p) == *(*float64)(q)
   197  }
   198  func c64equal(p, q unsafe.Pointer) bool {
   199  	return *(*complex64)(p) == *(*complex64)(q)
   200  }
   201  func c128equal(p, q unsafe.Pointer) bool {
   202  	return *(*complex128)(p) == *(*complex128)(q)
   203  }
   204  func strequal(p, q unsafe.Pointer) bool {
   205  	return *(*string)(p) == *(*string)(q)
   206  }
   207  func interequal(p, q unsafe.Pointer) bool {
   208  	x := *(*iface)(p)
   209  	y := *(*iface)(q)
   210  	return x.tab == y.tab && ifaceeq(x.tab, x.data, y.data)
   211  }
   212  func nilinterequal(p, q unsafe.Pointer) bool {
   213  	x := *(*eface)(p)
   214  	y := *(*eface)(q)
   215  	return x._type == y._type && efaceeq(x._type, x.data, y.data)
   216  }
   217  func efaceeq(t *_type, x, y unsafe.Pointer) bool {
   218  	if t == nil {
   219  		return true
   220  	}
   221  	eq := t.alg.equal
   222  	if eq == nil {
   223  		panic(errorString("comparing uncomparable type " + t.string()))
   224  	}
   225  	if isDirectIface(t) {
   226  		return eq(noescape(unsafe.Pointer(&x)), noescape(unsafe.Pointer(&y)))
   227  	}
   228  	return eq(x, y)
   229  }
   230  func ifaceeq(tab *itab, x, y unsafe.Pointer) bool {
   231  	if tab == nil {
   232  		return true
   233  	}
   234  	t := tab._type
   235  	eq := t.alg.equal
   236  	if eq == nil {
   237  		panic(errorString("comparing uncomparable type " + t.string()))
   238  	}
   239  	if isDirectIface(t) {
   240  		return eq(noescape(unsafe.Pointer(&x)), noescape(unsafe.Pointer(&y)))
   241  	}
   242  	return eq(x, y)
   243  }
   244  
   245  // Testing adapters for hash quality tests (see hash_test.go)
   246  func stringHash(s string, seed uintptr) uintptr {
   247  	return algarray[alg_STRING].hash(noescape(unsafe.Pointer(&s)), seed)
   248  }
   249  
   250  func bytesHash(b []byte, seed uintptr) uintptr {
   251  	s := (*slice)(unsafe.Pointer(&b))
   252  	return memhash(s.array, seed, uintptr(s.len))
   253  }
   254  
   255  func int32Hash(i uint32, seed uintptr) uintptr {
   256  	return algarray[alg_MEM32].hash(noescape(unsafe.Pointer(&i)), seed)
   257  }
   258  
   259  func int64Hash(i uint64, seed uintptr) uintptr {
   260  	return algarray[alg_MEM64].hash(noescape(unsafe.Pointer(&i)), seed)
   261  }
   262  
   263  func efaceHash(i interface{}, seed uintptr) uintptr {
   264  	return algarray[alg_NILINTER].hash(noescape(unsafe.Pointer(&i)), seed)
   265  }
   266  
   267  func ifaceHash(i interface {
   268  	F()
   269  }, seed uintptr) uintptr {
   270  	return algarray[alg_INTER].hash(noescape(unsafe.Pointer(&i)), seed)
   271  }
   272  
   273  const hashRandomBytes = sys.PtrSize / 4 * 64
   274  
   275  // used in asm_{386,amd64}.s to seed the hash function
   276  var aeskeysched [hashRandomBytes]byte
   277  
   278  // used in hash{32,64}.go to seed the hash function
   279  var hashkey [4]uintptr
   280  
   281  func alginit() {
   282  	// Install aes hash algorithm if we have the instructions we need
   283  	if (GOARCH == "386" || GOARCH == "amd64") &&
   284  		GOOS != "nacl" &&
   285  		support_aes && // AESENC
   286  		support_ssse3 && // PSHUFB
   287  		support_sse41 { // PINSR{D,Q}
   288  		useAeshash = true
   289  		algarray[alg_MEM32].hash = aeshash32
   290  		algarray[alg_MEM64].hash = aeshash64
   291  		algarray[alg_STRING].hash = aeshashstr
   292  		// Initialize with random data so hash collisions will be hard to engineer.
   293  		getRandomData(aeskeysched[:])
   294  		return
   295  	}
   296  	getRandomData((*[len(hashkey) * sys.PtrSize]byte)(unsafe.Pointer(&hashkey))[:])
   297  	hashkey[0] |= 1 // make sure these numbers are odd
   298  	hashkey[1] |= 1
   299  	hashkey[2] |= 1
   300  	hashkey[3] |= 1
   301  }
   302
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