maphash_runtime.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  //go:build !purego
     6  
     7  package maphash
     8  
     9  import (
    10  	"unsafe"
    11  )
    12  
    13  //go:linkname runtime_rand runtime.rand
    14  func runtime_rand() uint64
    15  
    16  //go:linkname runtime_memhash runtime.memhash
    17  //go:noescape
    18  func runtime_memhash(p unsafe.Pointer, seed, s uintptr) uintptr
    19  
    20  func rthash(buf []byte, seed uint64) uint64 {
    21  	if len(buf) == 0 {
    22  		return seed
    23  	}
    24  	len := len(buf)
    25  	// The runtime hasher only works on uintptr. For 64-bit
    26  	// architectures, we use the hasher directly. Otherwise,
    27  	// we use two parallel hashers on the lower and upper 32 bits.
    28  	if unsafe.Sizeof(uintptr(0)) == 8 {
    29  		return uint64(runtime_memhash(unsafe.Pointer(&buf[0]), uintptr(seed), uintptr(len)))
    30  	}
    31  	lo := runtime_memhash(unsafe.Pointer(&buf[0]), uintptr(seed), uintptr(len))
    32  	hi := runtime_memhash(unsafe.Pointer(&buf[0]), uintptr(seed>>32), uintptr(len))
    33  	return uint64(hi)<<32 | uint64(lo)
    34  }
    35  
    36  func rthashString(s string, state uint64) uint64 {
    37  	buf := unsafe.Slice(unsafe.StringData(s), len(s))
    38  	return rthash(buf, state)
    39  }
    40  
    41  func randUint64() uint64 {
    42  	return runtime_rand()
    43  }
    44
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