Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 205 insertions, 0 deletions

diff --git a/src/unsafe/unsafe.go b/src/unsafe/unsafe.go
new file mode 100644
index 0000000..272761d
--- /dev/null
+++ b/src/unsafe/unsafe.go
@@ -0,0 +1,205 @@
+// Copyright 2009 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 unsafe contains operations that step around the type safety of Go programs.
+
+	Packages that import unsafe may be non-portable and are not protected by the
+	Go 1 compatibility guidelines.
+*/
+package unsafe
+
+// ArbitraryType is here for the purposes of documentation only and is not actually
+// part of the unsafe package. It represents the type of an arbitrary Go expression.
+type ArbitraryType int
+
+// Pointer represents a pointer to an arbitrary type. There are four special operations
+// available for type Pointer that are not available for other types:
+//	- A pointer value of any type can be converted to a Pointer.
+//	- A Pointer can be converted to a pointer value of any type.
+//	- A uintptr can be converted to a Pointer.
+//	- A Pointer can be converted to a uintptr.
+// Pointer therefore allows a program to defeat the type system and read and write
+// arbitrary memory. It should be used with extreme care.
+//
+// The following patterns involving Pointer are valid.
+// Code not using these patterns is likely to be invalid today
+// or to become invalid in the future.
+// Even the valid patterns below come with important caveats.
+//
+// Running "go vet" can help find uses of Pointer that do not conform to these patterns,
+// but silence from "go vet" is not a guarantee that the code is valid.
+//
+// (1) Conversion of a *T1 to Pointer to *T2.
+//
+// Provided that T2 is no larger than T1 and that the two share an equivalent
+// memory layout, this conversion allows reinterpreting data of one type as
+// data of another type. An example is the implementation of
+// math.Float64bits:
+//
+//	func Float64bits(f float64) uint64 {
+//		return *(*uint64)(unsafe.Pointer(&f))
+//	}
+//
+// (2) Conversion of a Pointer to a uintptr (but not back to Pointer).
+//
+// Converting a Pointer to a uintptr produces the memory address of the value
+// pointed at, as an integer. The usual use for such a uintptr is to print it.
+//
+// Conversion of a uintptr back to Pointer is not valid in general.
+//
+// A uintptr is an integer, not a reference.
+// Converting a Pointer to a uintptr creates an integer value
+// with no pointer semantics.
+// Even if a uintptr holds the address of some object,
+// the garbage collector will not update that uintptr's value
+// if the object moves, nor will that uintptr keep the object
+// from being reclaimed.
+//
+// The remaining patterns enumerate the only valid conversions
+// from uintptr to Pointer.
+//
+// (3) Conversion of a Pointer to a uintptr and back, with arithmetic.
+//
+// If p points into an allocated object, it can be advanced through the object
+// by conversion to uintptr, addition of an offset, and conversion back to Pointer.
+//
+//	p = unsafe.Pointer(uintptr(p) + offset)
+//
+// The most common use of this pattern is to access fields in a struct
+// or elements of an array:
+//
+//	// equivalent to f := unsafe.Pointer(&s.f)
+//	f := unsafe.Pointer(uintptr(unsafe.Pointer(&s)) + unsafe.Offsetof(s.f))
+//
+//	// equivalent to e := unsafe.Pointer(&x[i])
+//	e := unsafe.Pointer(uintptr(unsafe.Pointer(&x[0])) + i*unsafe.Sizeof(x[0]))
+//
+// It is valid both to add and to subtract offsets from a pointer in this way.
+// It is also valid to use &^ to round pointers, usually for alignment.
+// In all cases, the result must continue to point into the original allocated object.
+//
+// Unlike in C, it is not valid to advance a pointer just beyond the end of
+// its original allocation:
+//
+//	// INVALID: end points outside allocated space.
+//	var s thing
+//	end = unsafe.Pointer(uintptr(unsafe.Pointer(&s)) + unsafe.Sizeof(s))
+//
+//	// INVALID: end points outside allocated space.
+//	b := make([]byte, n)
+//	end = unsafe.Pointer(uintptr(unsafe.Pointer(&b[0])) + uintptr(n))
+//
+// Note that both conversions must appear in the same expression, with only
+// the intervening arithmetic between them:
+//
+//	// INVALID: uintptr cannot be stored in variable
+//	// before conversion back to Pointer.
+//	u := uintptr(p)
+//	p = unsafe.Pointer(u + offset)
+//
+// Note that the pointer must point into an allocated object, so it may not be nil.
+//
+//	// INVALID: conversion of nil pointer
+//	u := unsafe.Pointer(nil)
+//	p := unsafe.Pointer(uintptr(u) + offset)
+//
+// (4) Conversion of a Pointer to a uintptr when calling syscall.Syscall.
+//
+// The Syscall functions in package syscall pass their uintptr arguments directly
+// to the operating system, which then may, depending on the details of the call,
+// reinterpret some of them as pointers.
+// That is, the system call implementation is implicitly converting certain arguments
+// back from uintptr to pointer.
+//
+// If a pointer argument must be converted to uintptr for use as an argument,
+// that conversion must appear in the call expression itself:
+//
+//	syscall.Syscall(SYS_READ, uintptr(fd), uintptr(unsafe.Pointer(p)), uintptr(n))
+//
+// The compiler handles a Pointer converted to a uintptr in the argument list of
+// a call to a function implemented in assembly by arranging that the referenced
+// allocated object, if any, is retained and not moved until the call completes,
+// even though from the types alone it would appear that the object is no longer
+// needed during the call.
+//
+// For the compiler to recognize this pattern,
+// the conversion must appear in the argument list:
+//
+//	// INVALID: uintptr cannot be stored in variable
+//	// before implicit conversion back to Pointer during system call.
+//	u := uintptr(unsafe.Pointer(p))
+//	syscall.Syscall(SYS_READ, uintptr(fd), u, uintptr(n))
+//
+// (5) Conversion of the result of reflect.Value.Pointer or reflect.Value.UnsafeAddr
+// from uintptr to Pointer.
+//
+// Package reflect's Value methods named Pointer and UnsafeAddr return type uintptr
+// instead of unsafe.Pointer to keep callers from changing the result to an arbitrary
+// type without first importing "unsafe". However, this means that the result is
+// fragile and must be converted to Pointer immediately after making the call,
+// in the same expression:
+//
+//	p := (*int)(unsafe.Pointer(reflect.ValueOf(new(int)).Pointer()))
+//
+// As in the cases above, it is invalid to store the result before the conversion:
+//
+//	// INVALID: uintptr cannot be stored in variable
+//	// before conversion back to Pointer.
+//	u := reflect.ValueOf(new(int)).Pointer()
+//	p := (*int)(unsafe.Pointer(u))
+//
+// (6) Conversion of a reflect.SliceHeader or reflect.StringHeader Data field to or from Pointer.
+//
+// As in the previous case, the reflect data structures SliceHeader and StringHeader
+// declare the field Data as a uintptr to keep callers from changing the result to
+// an arbitrary type without first importing "unsafe". However, this means that
+// SliceHeader and StringHeader are only valid when interpreting the content
+// of an actual slice or string value.
+//
+//	var s string
+//	hdr := (*reflect.StringHeader)(unsafe.Pointer(&s)) // case 1
+//	hdr.Data = uintptr(unsafe.Pointer(p))              // case 6 (this case)
+//	hdr.Len = n
+//
+// In this usage hdr.Data is really an alternate way to refer to the underlying
+// pointer in the string header, not a uintptr variable itself.
+//
+// In general, reflect.SliceHeader and reflect.StringHeader should be used
+// only as *reflect.SliceHeader and *reflect.StringHeader pointing at actual
+// slices or strings, never as plain structs.
+// A program should not declare or allocate variables of these struct types.
+//
+//	// INVALID: a directly-declared header will not hold Data as a reference.
+//	var hdr reflect.StringHeader
+//	hdr.Data = uintptr(unsafe.Pointer(p))
+//	hdr.Len = n
+//	s := *(*string)(unsafe.Pointer(&hdr)) // p possibly already lost
+//
+type Pointer *ArbitraryType
+
+// Sizeof takes an expression x of any type and returns the size in bytes
+// of a hypothetical variable v as if v was declared via var v = x.
+// The size does not include any memory possibly referenced by x.
+// For instance, if x is a slice, Sizeof returns the size of the slice
+// descriptor, not the size of the memory referenced by the slice.
+// The return value of Sizeof is a Go constant.
+func Sizeof(x ArbitraryType) uintptr
+
+// Offsetof returns the offset within the struct of the field represented by x,
+// which must be of the form structValue.field. In other words, it returns the
+// number of bytes between the start of the struct and the start of the field.
+// The return value of Offsetof is a Go constant.
+func Offsetof(x ArbitraryType) uintptr
+
+// Alignof takes an expression x of any type and returns the required alignment
+// of a hypothetical variable v as if v was declared via var v = x.
+// It is the largest value m such that the address of v is always zero mod m.
+// It is the same as the value returned by reflect.TypeOf(x).Align().
+// As a special case, if a variable s is of struct type and f is a field
+// within that struct, then Alignof(s.f) will return the required alignment
+// of a field of that type within a struct. This case is the same as the
+// value returned by reflect.TypeOf(s.f).FieldAlign().
+// The return value of Alignof is a Go constant.
+func Alignof(x ArbitraryType) uintptr