alg.go

     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  	"internal/abi"
     9  	"internal/byteorder"
    10  	"internal/goarch"
    11  	"internal/runtime/maps"
    12  	"internal/runtime/sys"
    13  	"unsafe"
    14  )
    15  
    16  const (
    17  	// We use 32-bit hash on Wasm, see hash32.go.
    18  	hashSize = (1-goarch.IsWasm)*goarch.PtrSize + goarch.IsWasm*4
    19  	c0       = uintptr((8-hashSize)/4*2860486313 + (hashSize-4)/4*33054211828000289)
    20  	c1       = uintptr((8-hashSize)/4*3267000013 + (hashSize-4)/4*23344194077549503)
    21  )
    22  
    23  func trimHash(h uintptr) uintptr {
    24  	if goarch.IsWasm != 0 {
    25  		// On Wasm, we use 32-bit hash, despite that uintptr is 64-bit.
    26  		// memhash* always returns a uintptr with high 32-bit being 0
    27  		// (see hash32.go). We trim the hash in other places where we
    28  		// compute the hash manually, e.g. in interhash.
    29  		return uintptr(uint32(h))
    30  	}
    31  	return h
    32  }
    33  
    34  func memhash0(p unsafe.Pointer, h uintptr) uintptr {
    35  	return h
    36  }
    37  
    38  func memhash8(p unsafe.Pointer, h uintptr) uintptr {
    39  	return memhash(p, h, 1)
    40  }
    41  
    42  func memhash16(p unsafe.Pointer, h uintptr) uintptr {
    43  	return memhash(p, h, 2)
    44  }
    45  
    46  func memhash128(p unsafe.Pointer, h uintptr) uintptr {
    47  	return memhash(p, h, 16)
    48  }
    49  
    50  //go:nosplit
    51  func memhash_varlen(p unsafe.Pointer, h uintptr) uintptr {
    52  	ptr := sys.GetClosurePtr()
    53  	size := *(*uintptr)(unsafe.Pointer(ptr + unsafe.Sizeof(h)))
    54  	return memhash(p, h, size)
    55  }
    56  
    57  // This is simple wrappers.
    58  // It's better to use maps.MemHash functions directly,
    59  // but we have reflection code that still calls hashing from runtime via LookupRuntime,
    60  // so we have to try to minimize overhead of an extra call.
    61  // For this add nosplit for performance
    62  
    63  // memhash should be an internal detail,
    64  // but widely used packages access it using linkname.
    65  // Notable members of the hall of shame include:
    66  //   - github.com/aacfactory/fns
    67  //   - github.com/dgraph-io/ristretto
    68  //   - github.com/minio/simdjson-go
    69  //   - github.com/nbd-wtf/go-nostr
    70  //   - github.com/outcaste-io/ristretto
    71  //   - github.com/puzpuzpuz/xsync/v2
    72  //   - github.com/puzpuzpuz/xsync/v3
    73  //   - github.com/authzed/spicedb
    74  //   - github.com/pingcap/badger
    75  //
    76  // Do not remove or change the type signature.
    77  // See go.dev/issue/67401.
    78  //
    79  //go:nosplit
    80  //go:linkname memhash
    81  func memhash(p unsafe.Pointer, h, s uintptr) uintptr {
    82  	return maps.MemHash(p, h, s)
    83  }
    84  
    85  //go:nosplit
    86  func memhash64(p unsafe.Pointer, seed uintptr) uintptr {
    87  	return maps.MemHash64(readUnaligned64(p), seed)
    88  }
    89  
    90  //go:nosplit
    91  func memhash32(p unsafe.Pointer, seed uintptr) uintptr {
    92  	return maps.MemHash32(readUnaligned32(p), seed)
    93  }
    94  
    95  // strhash should be an internal detail,
    96  // but widely used packages access it using linkname.
    97  // Notable members of the hall of shame include:
    98  //   - github.com/aristanetworks/goarista
    99  //   - github.com/bytedance/sonic
   100  //   - github.com/bytedance/go-tagexpr/v2
   101  //   - github.com/cloudwego/dynamicgo
   102  //   - github.com/v2fly/v2ray-core/v5
   103  //
   104  // Do not remove or change the type signature.
   105  // See go.dev/issue/67401.
   106  //
   107  //go:nosplit
   108  //go:linkname strhash
   109  func strhash(p unsafe.Pointer, h uintptr) uintptr {
   110  	return maps.StrHash(*(*string)(p), h)
   111  }
   112  
   113  // NOTE: Because NaN != NaN, a map can contain any
   114  // number of (mostly useless) entries keyed with NaNs.
   115  // To avoid long hash chains, we assign a random number
   116  // as the hash value for a NaN.
   117  
   118  func f32hash(p unsafe.Pointer, h uintptr) uintptr {
   119  	f := *(*float32)(p)
   120  	switch {
   121  	case f == 0:
   122  		return trimHash(c1 * (c0 ^ h)) // +0, -0
   123  	case f != f:
   124  		return trimHash(c1 * (c0 ^ h ^ uintptr(rand()))) // any kind of NaN
   125  	default:
   126  		return memhash(p, h, 4)
   127  	}
   128  }
   129  
   130  func f64hash(p unsafe.Pointer, h uintptr) uintptr {
   131  	f := *(*float64)(p)
   132  	switch {
   133  	case f == 0:
   134  		return trimHash(c1 * (c0 ^ h)) // +0, -0
   135  	case f != f:
   136  		return trimHash(c1 * (c0 ^ h ^ uintptr(rand()))) // any kind of NaN
   137  	default:
   138  		return memhash(p, h, 8)
   139  	}
   140  }
   141  
   142  func c64hash(p unsafe.Pointer, h uintptr) uintptr {
   143  	x := (*[2]float32)(p)
   144  	return f32hash(unsafe.Pointer(&x[1]), f32hash(unsafe.Pointer(&x[0]), h))
   145  }
   146  
   147  func c128hash(p unsafe.Pointer, h uintptr) uintptr {
   148  	x := (*[2]float64)(p)
   149  	return f64hash(unsafe.Pointer(&x[1]), f64hash(unsafe.Pointer(&x[0]), h))
   150  }
   151  
   152  func interhash(p unsafe.Pointer, h uintptr) uintptr {
   153  	a := (*iface)(p)
   154  	tab := a.tab
   155  	if tab == nil {
   156  		return h
   157  	}
   158  	t := tab.Type
   159  	if t.Equal == nil {
   160  		// Check hashability here. We could do this check inside
   161  		// typehash, but we want to report the topmost type in
   162  		// the error text (e.g. in a struct with a field of slice type
   163  		// we want to report the struct, not the slice).
   164  		panic(errorString("hash of unhashable type " + toRType(t).string()))
   165  	}
   166  	if t.IsDirectIface() {
   167  		return trimHash(c1 * typehash(t, unsafe.Pointer(&a.data), h^c0))
   168  	} else {
   169  		return trimHash(c1 * typehash(t, a.data, h^c0))
   170  	}
   171  }
   172  
   173  // nilinterhash should be an internal detail,
   174  // but widely used packages access it using linkname.
   175  // Notable members of the hall of shame include:
   176  //   - github.com/anacrolix/stm
   177  //   - github.com/aristanetworks/goarista
   178  //
   179  // Do not remove or change the type signature.
   180  // See go.dev/issue/67401.
   181  //
   182  //go:linkname nilinterhash
   183  func nilinterhash(p unsafe.Pointer, h uintptr) uintptr {
   184  	a := (*eface)(p)
   185  	t := a._type
   186  	if t == nil {
   187  		return h
   188  	}
   189  	if t.Equal == nil {
   190  		// See comment in interhash above.
   191  		panic(errorString("hash of unhashable type " + toRType(t).string()))
   192  	}
   193  	if t.IsDirectIface() {
   194  		return trimHash(c1 * typehash(t, unsafe.Pointer(&a.data), h^c0))
   195  	} else {
   196  		return trimHash(c1 * typehash(t, a.data, h^c0))
   197  	}
   198  }
   199  
   200  // typehash computes the hash of the object of type t at address p.
   201  // h is the seed.
   202  // This function is seldom used. Most maps use for hashing either
   203  // fixed functions (e.g. f32hash) or compiler-generated functions
   204  // (e.g. for a type like struct { x, y string }). This implementation
   205  // is slower but more general and is used for hashing interface types
   206  // (called from interhash or nilinterhash, above) or for hashing in
   207  // maps generated by reflect.MapOf (reflect_typehash, below).
   208  //
   209  // typehash should be an internal detail,
   210  // but widely used packages access it using linkname.
   211  // Notable members of the hall of shame include:
   212  //   - github.com/puzpuzpuz/xsync/v2
   213  //   - github.com/puzpuzpuz/xsync/v3
   214  //
   215  // Do not remove or change the type signature.
   216  // See go.dev/issue/67401.
   217  //
   218  //go:linkname typehash
   219  func typehash(t *_type, p unsafe.Pointer, h uintptr) uintptr {
   220  	if t.TFlag&abi.TFlagRegularMemory != 0 {
   221  		// Handle ptr sizes specially, see issue 37086.
   222  		switch t.Size_ {
   223  		case 4:
   224  			return memhash32(p, h)
   225  		case 8:
   226  			return memhash64(p, h)
   227  		default:
   228  			return memhash(p, h, t.Size_)
   229  		}
   230  	}
   231  	switch t.Kind() {
   232  	case abi.Float32:
   233  		return f32hash(p, h)
   234  	case abi.Float64:
   235  		return f64hash(p, h)
   236  	case abi.Complex64:
   237  		return c64hash(p, h)
   238  	case abi.Complex128:
   239  		return c128hash(p, h)
   240  	case abi.String:
   241  		return strhash(p, h)
   242  	case abi.Interface:
   243  		i := (*interfacetype)(unsafe.Pointer(t))
   244  		if len(i.Methods) == 0 {
   245  			return nilinterhash(p, h)
   246  		}
   247  		return interhash(p, h)
   248  	case abi.Array:
   249  		a := (*arraytype)(unsafe.Pointer(t))
   250  		for i := uintptr(0); i < a.Len; i++ {
   251  			h = typehash(a.Elem, add(p, i*a.Elem.Size_), h)
   252  		}
   253  		return h
   254  	case abi.Struct:
   255  		s := (*structtype)(unsafe.Pointer(t))
   256  		for _, f := range s.Fields {
   257  			if f.Name.IsBlank() {
   258  				continue
   259  			}
   260  			h = typehash(f.Typ, add(p, f.Offset), h)
   261  		}
   262  		return h
   263  	default:
   264  		// Should never happen, as typehash should only be called
   265  		// with comparable types.
   266  		panic(errorString("hash of unhashable type " + toRType(t).string()))
   267  	}
   268  }
   269  
   270  //go:linkname reflect_typehash reflect.typehash
   271  func reflect_typehash(t *_type, p unsafe.Pointer, h uintptr) uintptr {
   272  	return typehash(t, p, h)
   273  }
   274  
   275  func memequal0(p, q unsafe.Pointer) bool {
   276  	return true
   277  }
   278  func memequal8(p, q unsafe.Pointer) bool {
   279  	return *(*int8)(p) == *(*int8)(q)
   280  }
   281  func memequal16(p, q unsafe.Pointer) bool {
   282  	return *(*int16)(p) == *(*int16)(q)
   283  }
   284  func memequal32(p, q unsafe.Pointer) bool {
   285  	return *(*int32)(p) == *(*int32)(q)
   286  }
   287  func memequal64(p, q unsafe.Pointer) bool {
   288  	return *(*int64)(p) == *(*int64)(q)
   289  }
   290  func memequal128(p, q unsafe.Pointer) bool {
   291  	return *(*[2]int64)(p) == *(*[2]int64)(q)
   292  }
   293  func f32equal(p, q unsafe.Pointer) bool {
   294  	return *(*float32)(p) == *(*float32)(q)
   295  }
   296  func f64equal(p, q unsafe.Pointer) bool {
   297  	return *(*float64)(p) == *(*float64)(q)
   298  }
   299  func c64equal(p, q unsafe.Pointer) bool {
   300  	return *(*complex64)(p) == *(*complex64)(q)
   301  }
   302  func c128equal(p, q unsafe.Pointer) bool {
   303  	return *(*complex128)(p) == *(*complex128)(q)
   304  }
   305  func strequal(p, q unsafe.Pointer) bool {
   306  	return *(*string)(p) == *(*string)(q)
   307  }
   308  func interequal(p, q unsafe.Pointer) bool {
   309  	x := *(*iface)(p)
   310  	y := *(*iface)(q)
   311  	return x.tab == y.tab && ifaceeq(x.tab, x.data, y.data)
   312  }
   313  func nilinterequal(p, q unsafe.Pointer) bool {
   314  	x := *(*eface)(p)
   315  	y := *(*eface)(q)
   316  	return x._type == y._type && efaceeq(x._type, x.data, y.data)
   317  }
   318  func efaceeq(t *_type, x, y unsafe.Pointer) bool {
   319  	if t == nil {
   320  		return true
   321  	}
   322  	eq := t.Equal
   323  	if eq == nil {
   324  		panic(errorString("comparing uncomparable type " + toRType(t).string()))
   325  	}
   326  	if t.IsDirectIface() {
   327  		// Direct interface types are ptr, chan, map, func, and single-element structs/arrays thereof.
   328  		// Maps and funcs are not comparable, so they can't reach here.
   329  		// Ptrs, chans, and single-element items can be compared directly using ==.
   330  		return x == y
   331  	}
   332  	return eq(x, y)
   333  }
   334  func ifaceeq(tab *itab, x, y unsafe.Pointer) bool {
   335  	if tab == nil {
   336  		return true
   337  	}
   338  	t := tab.Type
   339  	eq := t.Equal
   340  	if eq == nil {
   341  		panic(errorString("comparing uncomparable type " + toRType(t).string()))
   342  	}
   343  	if t.IsDirectIface() {
   344  		// See comment in efaceeq.
   345  		return x == y
   346  	}
   347  	return eq(x, y)
   348  }
   349  
   350  // Testing adapters for hash quality tests (see hash_test.go)
   351  //
   352  // stringHash should be an internal detail,
   353  // but widely used packages access it using linkname.
   354  // Notable members of the hall of shame include:
   355  //   - github.com/k14s/starlark-go
   356  //
   357  // Do not remove or change the type signature.
   358  // See go.dev/issue/67401.
   359  //
   360  //go:linkname stringHash
   361  func stringHash(s string, seed uintptr) uintptr {
   362  	return strhash(noescape(unsafe.Pointer(&s)), seed)
   363  }
   364  
   365  func bytesHash(b []byte, seed uintptr) uintptr {
   366  	s := (*slice)(unsafe.Pointer(&b))
   367  	return memhash(s.array, seed, uintptr(s.len))
   368  }
   369  
   370  func int32Hash(i uint32, seed uintptr) uintptr {
   371  	return memhash32(noescape(unsafe.Pointer(&i)), seed)
   372  }
   373  
   374  func int64Hash(i uint64, seed uintptr) uintptr {
   375  	return memhash64(noescape(unsafe.Pointer(&i)), seed)
   376  }
   377  
   378  func efaceHash(i any, seed uintptr) uintptr {
   379  	return nilinterhash(noescape(unsafe.Pointer(&i)), seed)
   380  }
   381  
   382  func ifaceHash(i interface {
   383  	F()
   384  }, seed uintptr) uintptr {
   385  	return interhash(noescape(unsafe.Pointer(&i)), seed)
   386  }
   387  
   388  func readUnaligned32(p unsafe.Pointer) uint32 {
   389  	q := (*[4]byte)(p)
   390  	if goarch.BigEndian {
   391  		return byteorder.BEUint32(q[:])
   392  	}
   393  	return byteorder.LEUint32(q[:])
   394  }
   395  
   396  func readUnaligned64(p unsafe.Pointer) uint64 {
   397  	q := (*[8]byte)(p)
   398  	if goarch.BigEndian {
   399  		return byteorder.BEUint64(q[:])
   400  	}
   401  	return byteorder.LEUint64(q[:])
   402  }
   403
View as plain text