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src/runtime: add per-map hash seeds

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This commit is contained in:
Damian Gryski
2022-03-09 13:47:27 -08:00
committed by Ron Evans
parent 39805bca45
commit e45ff9c0e8
2 changed files with 61 additions and 44 deletions
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src/runtime/algorithm.go
+6 -6
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@@ -26,16 +26,16 @@ func xorshift32(x uint32) uint32 {
// This function is used by hash/maphash.
func memhash(p unsafe.Pointer, seed, s uintptr) uintptr {
if unsafe.Sizeof(uintptr(0)) > 4 {
return seed ^ uintptr(hash64(p, s))
return uintptr(hash64(p, s, seed))
}
return seed ^ uintptr(hash32(p, s))
return uintptr(hash32(p, s, seed))
}
// Get FNV-1a hash of the given memory buffer.
//
// https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function#FNV-1a_hash
func hash32(ptr unsafe.Pointer, n uintptr) uint32 {
var result uint32 = 2166136261 // FNV offset basis
func hash32(ptr unsafe.Pointer, n uintptr, seed uintptr) uint32 {
var result uint32 = 2166136261 ^ uint32(seed) // FNV offset basis
for i := uintptr(0); i < n; i++ {
c := *(*uint8)(unsafe.Pointer(uintptr(ptr) + i))
result ^= uint32(c) // XOR with byte
@@ -45,8 +45,8 @@ func hash32(ptr unsafe.Pointer, n uintptr) uint32 {
}
// Also a FNV-1a hash.
func hash64(ptr unsafe.Pointer, n uintptr) uint64 {
var result uint64 = 14695981039346656037 // FNV offset basis
func hash64(ptr unsafe.Pointer, n uintptr, seed uintptr) uint64 {
var result uint64 = 14695981039346656037 ^ uint64(seed) // FNV offset basis
for i := uintptr(0); i < n; i++ {
c := *(*uint8)(unsafe.Pointer(uintptr(ptr) + i))
result ^= uint64(c) // XOR with byte