1 files changed, 142 insertions, 0 deletions
diff --git a/vendor/google.golang.org/protobuf/internal/impl/presence.go b/vendor/google.golang.org/protobuf/internal/impl/presence.go
new file mode 100644
index 000000000..914cb1ded
--- /dev/null
+++ b/vendor/google.golang.org/protobuf/internal/impl/presence.go
@@ -0,0 +1,142 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package impl
+
+import (
+	"sync/atomic"
+	"unsafe"
+)
+
+// presenceSize represents the size of a presence set, which should be the largest index of the set+1
+type presenceSize uint32
+
+// presence is the internal representation of the bitmap array in a generated protobuf
+type presence struct {
+	// This is a pointer to the beginning of an array of uint32
+	P unsafe.Pointer
+}
+
+func (p presence) toElem(num uint32) (ret *uint32) {
+	const (
+		bitsPerByte = 8
+		siz         = unsafe.Sizeof(*ret)
+	)
+	// p.P points to an array of uint32, num is the bit in this array that the
+	// caller wants to check/manipulate. Calculate the index in the array that
+	// contains this specific bit. E.g.: 76 / 32 = 2 (integer division).
+	offset := uintptr(num) / (siz * bitsPerByte) * siz
+	return (*uint32)(unsafe.Pointer(uintptr(p.P) + offset))
+}
+
+// Present checks for the presence of a specific field number in a presence set.
+func (p presence) Present(num uint32) bool {
+	if p.P == nil {
+		return false
+	}
+	return Export{}.Present(p.toElem(num), num)
+}
+
+// SetPresent adds presence for a specific field number in a presence set.
+func (p presence) SetPresent(num uint32, size presenceSize) {
+	Export{}.SetPresent(p.toElem(num), num, uint32(size))
+}
+
+// SetPresentUnatomic adds presence for a specific field number in a presence set without using
+// atomic operations. Only to be called during unmarshaling.
+func (p presence) SetPresentUnatomic(num uint32, size presenceSize) {
+	Export{}.SetPresentNonAtomic(p.toElem(num), num, uint32(size))
+}
+
+// ClearPresent removes presence for a specific field number in a presence set.
+func (p presence) ClearPresent(num uint32) {
+	Export{}.ClearPresent(p.toElem(num), num)
+}
+
+// LoadPresenceCache (together with PresentInCache) allows for a
+// cached version of checking for presence without re-reading the word
+// for every field. It is optimized for efficiency and assumes no
+// simltaneous mutation of the presence set (or at least does not have
+// a problem with simultaneous mutation giving inconsistent results).
+func (p presence) LoadPresenceCache() (current uint32) {
+	if p.P == nil {
+		return 0
+	}
+	return atomic.LoadUint32((*uint32)(p.P))
+}
+
+// PresentInCache reads presence from a cached word in the presence
+// bitmap. It caches up a new word if the bit is outside the
+// word. This is for really fast iteration through bitmaps in cases
+// where we either know that the bitmap will not be altered, or we
+// don't care about inconsistencies caused by simultaneous writes.
+func (p presence) PresentInCache(num uint32, cachedElement *uint32, current *uint32) bool {
+	if num/32 != *cachedElement {
+		o := uintptr(num/32) * unsafe.Sizeof(uint32(0))
+		q := (*uint32)(unsafe.Pointer(uintptr(p.P) + o))
+		*current = atomic.LoadUint32(q)
+		*cachedElement = num / 32
+	}
+	return (*current & (1 << (num % 32))) > 0
+}
+
+// AnyPresent checks if any field is marked as present in the bitmap.
+func (p presence) AnyPresent(size presenceSize) bool {
+	n := uintptr((size + 31) / 32)
+	for j := uintptr(0); j < n; j++ {
+		o := j * unsafe.Sizeof(uint32(0))
+		q := (*uint32)(unsafe.Pointer(uintptr(p.P) + o))
+		b := atomic.LoadUint32(q)
+		if b > 0 {
+			return true
+		}
+	}
+	return false
+}
+
+// toRaceDetectData finds the preceding RaceDetectHookData in a
+// message by using pointer arithmetic. As the type of the presence
+// set (bitmap) varies with the number of fields in the protobuf, we
+// can not have a struct type containing the array and the
+// RaceDetectHookData.  instead the RaceDetectHookData is placed
+// immediately before the bitmap array, and we find it by walking
+// backwards in the struct.
+//
+// This method is only called from the race-detect version of the code,
+// so RaceDetectHookData is never an empty struct.
+func (p presence) toRaceDetectData() *RaceDetectHookData {
+	var template struct {
+		d RaceDetectHookData
+		a [1]uint32
+	}
+	o := (uintptr(unsafe.Pointer(&template.a)) - uintptr(unsafe.Pointer(&template.d)))
+	return (*RaceDetectHookData)(unsafe.Pointer(uintptr(p.P) - o))
+}
+
+func atomicLoadShadowPresence(p **[]byte) *[]byte {
+	return (*[]byte)(atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(p))))
+}
+func atomicStoreShadowPresence(p **[]byte, v *[]byte) {
+	atomic.CompareAndSwapPointer((*unsafe.Pointer)(unsafe.Pointer(p)), nil, unsafe.Pointer(v))
+}
+
+// findPointerToRaceDetectData finds the preceding RaceDetectHookData
+// in a message by using pointer arithmetic. For the methods called
+// directy from generated code, we don't have a pointer to the
+// beginning of the presence set, but a pointer inside the array. As
+// we know the index of the bit we're manipulating (num), we can
+// calculate which element of the array ptr is pointing to. With that
+// information we find the preceding RaceDetectHookData and can
+// manipulate the shadow bitmap.
+//
+// This method is only called from the race-detect version of the
+// code, so RaceDetectHookData is never an empty struct.
+func findPointerToRaceDetectData(ptr *uint32, num uint32) *RaceDetectHookData {
+	var template struct {
+		d RaceDetectHookData
+		a [1]uint32
+	}
+	o := (uintptr(unsafe.Pointer(&template.a)) - uintptr(unsafe.Pointer(&template.d))) + uintptr(num/32)*unsafe.Sizeof(uint32(0))
+	return (*RaceDetectHookData)(unsafe.Pointer(uintptr(unsafe.Pointer(ptr)) - o))
+}