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/cpu"
    11  	"internal/goarch"
    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  // runtime variable to check if the processor we're running on
    58  // actually supports the instructions used by the AES-based
    59  // hash implementation.
    60  var useAeshash bool
    61  
    62  // in asm_*.s
    63  
    64  // memhash should be an internal detail,
    65  // but widely used packages access it using linkname.
    66  // Notable members of the hall of shame include:
    67  //   - github.com/aacfactory/fns
    68  //   - github.com/dgraph-io/ristretto
    69  //   - github.com/minio/simdjson-go
    70  //   - github.com/nbd-wtf/go-nostr
    71  //   - github.com/outcaste-io/ristretto
    72  //   - github.com/puzpuzpuz/xsync/v2
    73  //   - github.com/puzpuzpuz/xsync/v3
    74  //   - github.com/authzed/spicedb
    75  //   - github.com/pingcap/badger
    76  //
    77  // Do not remove or change the type signature.
    78  // See go.dev/issue/67401.
    79  //
    80  //go:linkname memhash
    81  func memhash(p unsafe.Pointer, h, s uintptr) uintptr
    82  
    83  // Accessed in internal/runtime/maps.
    84  //
    85  //go:linknamestd memhash32
    86  func memhash32(p unsafe.Pointer, h uintptr) uintptr
    87  
    88  //go:linknamestd memhash64
    89  func memhash64(p unsafe.Pointer, h uintptr) uintptr
    90  
    91  // strhash should be an internal detail,
    92  // but widely used packages access it using linkname.
    93  // Notable members of the hall of shame include:
    94  //   - github.com/aristanetworks/goarista
    95  //   - github.com/bytedance/sonic
    96  //   - github.com/bytedance/go-tagexpr/v2
    97  //   - github.com/cloudwego/dynamicgo
    98  //   - github.com/v2fly/v2ray-core/v5
    99  //
   100  // Do not remove or change the type signature.
   101  // See go.dev/issue/67401.
   102  //
   103  //go:linkname strhash
   104  func strhash(p unsafe.Pointer, h uintptr) uintptr
   105  
   106  func strhashFallback(a unsafe.Pointer, h uintptr) uintptr {
   107  	x := (*stringStruct)(a)
   108  	return memhashFallback(x.str, h, uintptr(x.len))
   109  }
   110  
   111  // NOTE: Because NaN != NaN, a map can contain any
   112  // number of (mostly useless) entries keyed with NaNs.
   113  // To avoid long hash chains, we assign a random number
   114  // as the hash value for a NaN.
   115  
   116  func f32hash(p unsafe.Pointer, h uintptr) uintptr {
   117  	f := *(*float32)(p)
   118  	switch {
   119  	case f == 0:
   120  		return trimHash(c1 * (c0 ^ h)) // +0, -0
   121  	case f != f:
   122  		return trimHash(c1 * (c0 ^ h ^ uintptr(rand()))) // any kind of NaN
   123  	default:
   124  		return memhash(p, h, 4)
   125  	}
   126  }
   127  
   128  func f64hash(p unsafe.Pointer, h uintptr) uintptr {
   129  	f := *(*float64)(p)
   130  	switch {
   131  	case f == 0:
   132  		return trimHash(c1 * (c0 ^ h)) // +0, -0
   133  	case f != f:
   134  		return trimHash(c1 * (c0 ^ h ^ uintptr(rand()))) // any kind of NaN
   135  	default:
   136  		return memhash(p, h, 8)
   137  	}
   138  }
   139  
   140  func c64hash(p unsafe.Pointer, h uintptr) uintptr {
   141  	x := (*[2]float32)(p)
   142  	return f32hash(unsafe.Pointer(&x[1]), f32hash(unsafe.Pointer(&x[0]), h))
   143  }
   144  
   145  func c128hash(p unsafe.Pointer, h uintptr) uintptr {
   146  	x := (*[2]float64)(p)
   147  	return f64hash(unsafe.Pointer(&x[1]), f64hash(unsafe.Pointer(&x[0]), h))
   148  }
   149  
   150  func interhash(p unsafe.Pointer, h uintptr) uintptr {
   151  	a := (*iface)(p)
   152  	tab := a.tab
   153  	if tab == nil {
   154  		return h
   155  	}
   156  	t := tab.Type
   157  	if t.Equal == nil {
   158  		// Check hashability here. We could do this check inside
   159  		// typehash, but we want to report the topmost type in
   160  		// the error text (e.g. in a struct with a field of slice type
   161  		// we want to report the struct, not the slice).
   162  		panic(errorString("hash of unhashable type " + toRType(t).string()))
   163  	}
   164  	if t.IsDirectIface() {
   165  		return trimHash(c1 * typehash(t, unsafe.Pointer(&a.data), h^c0))
   166  	} else {
   167  		return trimHash(c1 * typehash(t, a.data, h^c0))
   168  	}
   169  }
   170  
   171  // nilinterhash should be an internal detail,
   172  // but widely used packages access it using linkname.
   173  // Notable members of the hall of shame include:
   174  //   - github.com/anacrolix/stm
   175  //   - github.com/aristanetworks/goarista
   176  //
   177  // Do not remove or change the type signature.
   178  // See go.dev/issue/67401.
   179  //
   180  //go:linkname nilinterhash
   181  func nilinterhash(p unsafe.Pointer, h uintptr) uintptr {
   182  	a := (*eface)(p)
   183  	t := a._type
   184  	if t == nil {
   185  		return h
   186  	}
   187  	if t.Equal == nil {
   188  		// See comment in interhash above.
   189  		panic(errorString("hash of unhashable type " + toRType(t).string()))
   190  	}
   191  	if t.IsDirectIface() {
   192  		return trimHash(c1 * typehash(t, unsafe.Pointer(&a.data), h^c0))
   193  	} else {
   194  		return trimHash(c1 * typehash(t, a.data, h^c0))
   195  	}
   196  }
   197  
   198  // typehash computes the hash of the object of type t at address p.
   199  // h is the seed.
   200  // This function is seldom used. Most maps use for hashing either
   201  // fixed functions (e.g. f32hash) or compiler-generated functions
   202  // (e.g. for a type like struct { x, y string }). This implementation
   203  // is slower but more general and is used for hashing interface types
   204  // (called from interhash or nilinterhash, above) or for hashing in
   205  // maps generated by reflect.MapOf (reflect_typehash, below).
   206  //
   207  // typehash should be an internal detail,
   208  // but widely used packages access it using linkname.
   209  // Notable members of the hall of shame include:
   210  //   - github.com/puzpuzpuz/xsync/v2
   211  //   - github.com/puzpuzpuz/xsync/v3
   212  //
   213  // Do not remove or change the type signature.
   214  // See go.dev/issue/67401.
   215  //
   216  //go:linkname typehash
   217  func typehash(t *_type, p unsafe.Pointer, h uintptr) uintptr {
   218  	if t.TFlag&abi.TFlagRegularMemory != 0 {
   219  		// Handle ptr sizes specially, see issue 37086.
   220  		switch t.Size_ {
   221  		case 4:
   222  			return memhash32(p, h)
   223  		case 8:
   224  			return memhash64(p, h)
   225  		default:
   226  			return memhash(p, h, t.Size_)
   227  		}
   228  	}
   229  	switch t.Kind() {
   230  	case abi.Float32:
   231  		return f32hash(p, h)
   232  	case abi.Float64:
   233  		return f64hash(p, h)
   234  	case abi.Complex64:
   235  		return c64hash(p, h)
   236  	case abi.Complex128:
   237  		return c128hash(p, h)
   238  	case abi.String:
   239  		return strhash(p, h)
   240  	case abi.Interface:
   241  		i := (*interfacetype)(unsafe.Pointer(t))
   242  		if len(i.Methods) == 0 {
   243  			return nilinterhash(p, h)
   244  		}
   245  		return interhash(p, h)
   246  	case abi.Array:
   247  		a := (*arraytype)(unsafe.Pointer(t))
   248  		for i := uintptr(0); i < a.Len; i++ {
   249  			h = typehash(a.Elem, add(p, i*a.Elem.Size_), h)
   250  		}
   251  		return h
   252  	case abi.Struct:
   253  		s := (*structtype)(unsafe.Pointer(t))
   254  		for _, f := range s.Fields {
   255  			if f.Name.IsBlank() {
   256  				continue
   257  			}
   258  			h = typehash(f.Typ, add(p, f.Offset), h)
   259  		}
   260  		return h
   261  	default:
   262  		// Should never happen, as typehash should only be called
   263  		// with comparable types.
   264  		panic(errorString("hash of unhashable type " + toRType(t).string()))
   265  	}
   266  }
   267  
   268  //go:linkname reflect_typehash reflect.typehash
   269  func reflect_typehash(t *_type, p unsafe.Pointer, h uintptr) uintptr {
   270  	return typehash(t, p, h)
   271  }
   272  
   273  func memequal0(p, q unsafe.Pointer) bool {
   274  	return true
   275  }
   276  func memequal8(p, q unsafe.Pointer) bool {
   277  	return *(*int8)(p) == *(*int8)(q)
   278  }
   279  func memequal16(p, q unsafe.Pointer) bool {
   280  	return *(*int16)(p) == *(*int16)(q)
   281  }
   282  func memequal32(p, q unsafe.Pointer) bool {
   283  	return *(*int32)(p) == *(*int32)(q)
   284  }
   285  func memequal64(p, q unsafe.Pointer) bool {
   286  	return *(*int64)(p) == *(*int64)(q)
   287  }
   288  func memequal128(p, q unsafe.Pointer) bool {
   289  	return *(*[2]int64)(p) == *(*[2]int64)(q)
   290  }
   291  func f32equal(p, q unsafe.Pointer) bool {
   292  	return *(*float32)(p) == *(*float32)(q)
   293  }
   294  func f64equal(p, q unsafe.Pointer) bool {
   295  	return *(*float64)(p) == *(*float64)(q)
   296  }
   297  func c64equal(p, q unsafe.Pointer) bool {
   298  	return *(*complex64)(p) == *(*complex64)(q)
   299  }
   300  func c128equal(p, q unsafe.Pointer) bool {
   301  	return *(*complex128)(p) == *(*complex128)(q)
   302  }
   303  func strequal(p, q unsafe.Pointer) bool {
   304  	return *(*string)(p) == *(*string)(q)
   305  }
   306  func interequal(p, q unsafe.Pointer) bool {
   307  	x := *(*iface)(p)
   308  	y := *(*iface)(q)
   309  	return x.tab == y.tab && ifaceeq(x.tab, x.data, y.data)
   310  }
   311  func nilinterequal(p, q unsafe.Pointer) bool {
   312  	x := *(*eface)(p)
   313  	y := *(*eface)(q)
   314  	return x._type == y._type && efaceeq(x._type, x.data, y.data)
   315  }
   316  func efaceeq(t *_type, x, y unsafe.Pointer) bool {
   317  	if t == nil {
   318  		return true
   319  	}
   320  	eq := t.Equal
   321  	if eq == nil {
   322  		panic(errorString("comparing uncomparable type " + toRType(t).string()))
   323  	}
   324  	if t.IsDirectIface() {
   325  		// Direct interface types are ptr, chan, map, func, and single-element structs/arrays thereof.
   326  		// Maps and funcs are not comparable, so they can't reach here.
   327  		// Ptrs, chans, and single-element items can be compared directly using ==.
   328  		return x == y
   329  	}
   330  	return eq(x, y)
   331  }
   332  func ifaceeq(tab *itab, x, y unsafe.Pointer) bool {
   333  	if tab == nil {
   334  		return true
   335  	}
   336  	t := tab.Type
   337  	eq := t.Equal
   338  	if eq == nil {
   339  		panic(errorString("comparing uncomparable type " + toRType(t).string()))
   340  	}
   341  	if t.IsDirectIface() {
   342  		// See comment in efaceeq.
   343  		return x == y
   344  	}
   345  	return eq(x, y)
   346  }
   347  
   348  // Testing adapters for hash quality tests (see hash_test.go)
   349  //
   350  // stringHash should be an internal detail,
   351  // but widely used packages access it using linkname.
   352  // Notable members of the hall of shame include:
   353  //   - github.com/k14s/starlark-go
   354  //
   355  // Do not remove or change the type signature.
   356  // See go.dev/issue/67401.
   357  //
   358  //go:linkname stringHash
   359  func stringHash(s string, seed uintptr) uintptr {
   360  	return strhash(noescape(unsafe.Pointer(&s)), seed)
   361  }
   362  
   363  func bytesHash(b []byte, seed uintptr) uintptr {
   364  	s := (*slice)(unsafe.Pointer(&b))
   365  	return memhash(s.array, seed, uintptr(s.len))
   366  }
   367  
   368  func int32Hash(i uint32, seed uintptr) uintptr {
   369  	return memhash32(noescape(unsafe.Pointer(&i)), seed)
   370  }
   371  
   372  func int64Hash(i uint64, seed uintptr) uintptr {
   373  	return memhash64(noescape(unsafe.Pointer(&i)), seed)
   374  }
   375  
   376  func efaceHash(i any, seed uintptr) uintptr {
   377  	return nilinterhash(noescape(unsafe.Pointer(&i)), seed)
   378  }
   379  
   380  func ifaceHash(i interface {
   381  	F()
   382  }, seed uintptr) uintptr {
   383  	return interhash(noescape(unsafe.Pointer(&i)), seed)
   384  }
   385  
   386  const hashRandomBytes = goarch.PtrSize / 4 * 64
   387  
   388  // used in asm_{386,amd64,arm64}.s to seed the hash function
   389  var aeskeysched [hashRandomBytes]byte
   390  
   391  // used in hash{32,64}.go to seed the hash function
   392  var hashkey [4]uintptr
   393  
   394  func alginit() {
   395  	// Install AES hash algorithms if the instructions needed are present.
   396  	if (GOARCH == "386" || GOARCH == "amd64") &&
   397  		cpu.X86.HasAES && // AESENC
   398  		cpu.X86.HasSSSE3 && // PSHUFB
   399  		cpu.X86.HasSSE41 { // PINSR{D,Q}
   400  		initAlgAES()
   401  		return
   402  	}
   403  	if GOARCH == "arm64" && cpu.ARM64.HasAES {
   404  		initAlgAES()
   405  		return
   406  	}
   407  	for i := range hashkey {
   408  		hashkey[i] = uintptr(bootstrapRand())
   409  	}
   410  }
   411  
   412  func initAlgAES() {
   413  	useAeshash = true
   414  	// Initialize with random data so hash collisions will be hard to engineer.
   415  	key := (*[hashRandomBytes / 8]uint64)(unsafe.Pointer(&aeskeysched))
   416  	for i := range key {
   417  		key[i] = bootstrapRand()
   418  	}
   419  }
   420  
   421  // Note: These routines perform the read with a native endianness.
   422  func readUnaligned32(p unsafe.Pointer) uint32 {
   423  	q := (*[4]byte)(p)
   424  	if goarch.BigEndian {
   425  		return byteorder.BEUint32(q[:])
   426  	}
   427  	return byteorder.LEUint32(q[:])
   428  }
   429  
   430  func readUnaligned64(p unsafe.Pointer) uint64 {
   431  	q := (*[8]byte)(p)
   432  	if goarch.BigEndian {
   433  		return byteorder.BEUint64(q[:])
   434  	}
   435  	return byteorder.LEUint64(q[:])
   436  }
   437
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