tailscale/util/deephash/pointer_norace.go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause

//go:build !race

package deephash

import "reflect"

type pointer = unsafePointer

// pointerOf returns a pointer from v, which must be a reflect.Pointer.
func pointerOf(v reflect.Value) pointer { return unsafePointerOf(v) }
all: update copyright and license headers This updates all source files to use a new standard header for copyright and license declaration. Notably, copyright no longer includes a date, and we now use the standard SPDX-License-Identifier header. This commit was done almost entirely mechanically with perl, and then some minimal manual fixes. Updates #6865 Signed-off-by: Will Norris <will@tailscale.com> 2023-01-27 21:37:20 +00:00			`// Copyright (c) Tailscale Inc & AUTHORS`
			`// SPDX-License-Identifier: BSD-3-Clause`
util/deephash: use unsafe.Pointer instead of reflect.Value (#5459) Use of reflect.Value.SetXXX panics if the provided argument was obtained from an unexported struct field. Instead, pass an unsafe.Pointer around and convert to a reflect.Value when necessary (i.e., for maps and interfaces). Converting from unsafe.Pointer to reflect.Value guarantees that none of the read-only bits will be populated. When running in race mode, we attach type information to the pointer so that we can type check every pointer operation. This also type-checks that direct memory hashing is within the valid range of a struct value. We add test cases that previously caused deephash to panic, but now pass. Performance: name old time/op new time/op delta Hash 14.1µs ± 1% 14.1µs ± 1% ~ (p=0.590 n=10+9) HashPacketFilter 2.53µs ± 2% 2.44µs ± 1% -3.79% (p=0.000 n=9+10) TailcfgNode 1.45µs ± 1% 1.43µs ± 0% -1.36% (p=0.000 n=9+9) HashArray 318ns ± 2% 318ns ± 2% ~ (p=0.541 n=10+10) HashMapAcyclic 32.9µs ± 1% 31.6µs ± 1% -4.16% (p=0.000 n=10+9) There is a slight performance gain due to the use of unsafe.Pointer over reflect.Value methods. Also, passing an unsafe.Pointer (1 word) on the stack is cheaper than passing a reflect.Value (3 words). Performance gains are diminishing since SHA-256 hashing now dominates the runtime. Signed-off-by: Joe Tsai <joetsai@digital-static.net> 2022-08-27 19:30:35 +00:00
			`//go:build !race`

			`package deephash`

			`import "reflect"`

			`type pointer = unsafePointer`

			`// pointerOf returns a pointer from v, which must be a reflect.Pointer.`
			`func pointerOf(v reflect.Value) pointer { return unsafePointerOf(v) }`