feat: add vendor

vendor/go4.org/intern/LICENSE

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+BSD 3-Clause License
+
+Copyright (c) 2020, Brad Fitzpatrick
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its
+   contributors may be used to endorse or promote products derived from
+   this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/go4.org/intern/README.md

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+# go4.org/intern
+
+See https://godoc.org/go4.org/intern
+

vendor/go4.org/intern/intern.go

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+// Copyright 2020 Brad Fitzpatrick. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package intern lets you make smaller comparable values by boxing
+// a larger comparable value (such as a 16 byte string header) down
+// into a globally unique 8 byte pointer.
+//
+// The globally unique pointers are garbage collected with weak
+// references and finalizers. This package hides that.
+//
+// The GitHub repo is https://github.com/go4org/intern
+package intern // import "go4.org/intern"
+
+import (
+	"os"
+	"runtime"
+	"strconv"
+	"sync"
+	"unsafe"
+
+	_ "go4.org/unsafe/assume-no-moving-gc"
+)
+
+// A Value pointer is the handle to an underlying comparable value.
+// See func Get for how Value pointers may be used.
+type Value struct {
+	_      [0]func() // prevent people from accidentally using value type as comparable
+	cmpVal interface{}
+	// resurrected is guarded by mu (for all instances of Value).
+	// It is set true whenever v is synthesized from a uintptr.
+	resurrected bool
+}
+
+// Get returns the comparable value passed to the Get func
+// that returned v.
+func (v *Value) Get() interface{} { return v.cmpVal }
+
+// key is a key in our global value map.
+// It contains type-specialized fields to avoid allocations
+// when converting common types to empty interfaces.
+type key struct {
+	s      string
+	cmpVal interface{}
+	// isString reports whether key contains a string.
+	// Without it, the zero value of key is ambiguous.
+	isString bool
+}
+
+// keyFor returns a key to use with cmpVal.
+func keyFor(cmpVal interface{}) key {
+	if s, ok := cmpVal.(string); ok {
+		return key{s: s, isString: true}
+	}
+	return key{cmpVal: cmpVal}
+}
+
+// Value returns a *Value built from k.
+func (k key) Value() *Value {
+	if k.isString {
+		return &Value{cmpVal: k.s}
+	}
+	return &Value{cmpVal: k.cmpVal}
+}
+
+var (
+	// mu guards valMap, a weakref map of *Value by underlying value.
+	// It also guards the resurrected field of all *Values.
+	mu      sync.Mutex
+	valMap  = map[key]uintptr{} // to uintptr(*Value)
+	valSafe = safeMap()         // non-nil in safe+leaky mode
+)
+
+// safeMap returns a non-nil map if we're in safe-but-leaky mode,
+// as controlled by GO4_INTERN_SAFE_BUT_LEAKY.
+func safeMap() map[key]*Value {
+	if v, _ := strconv.ParseBool(os.Getenv("GO4_INTERN_SAFE_BUT_LEAKY")); v {
+		return map[key]*Value{}
+	}
+	return nil
+}
+
+// Get returns a pointer representing the comparable value cmpVal.
+//
+// The returned pointer will be the same for Get(v) and Get(v2)
+// if and only if v == v2, and can be used as a map key.
+func Get(cmpVal interface{}) *Value {
+	return get(keyFor(cmpVal))
+}
+
+// GetByString is identical to Get, except that it is specialized for strings.
+// This avoids an allocation from putting a string into an interface{}
+// to pass as an argument to Get.
+func GetByString(s string) *Value {
+	return get(key{s: s, isString: true})
+}
+
+// We play unsafe games that violate Go's rules (and assume a non-moving
+// collector). So we quiet Go here.
+// See the comment below Get for more implementation details.
+//go:nocheckptr
+func get(k key) *Value {
+	mu.Lock()
+	defer mu.Unlock()
+
+	var v *Value
+	if valSafe != nil {
+		v = valSafe[k]
+	} else if addr, ok := valMap[k]; ok {
+		v = (*Value)((unsafe.Pointer)(addr))
+		v.resurrected = true
+	}
+	if v != nil {
+		return v
+	}
+	v = k.Value()
+	if valSafe != nil {
+		valSafe[k] = v
+	} else {
+		// SetFinalizer before uintptr conversion (theoretical concern;
+		// see https://github.com/go4org/intern/issues/13)
+		runtime.SetFinalizer(v, finalize)
+		valMap[k] = uintptr(unsafe.Pointer(v))
+	}
+	return v
+}
+
+func finalize(v *Value) {
+	mu.Lock()
+	defer mu.Unlock()
+	if v.resurrected {
+		// We lost the race. Somebody resurrected it while we
+		// were about to finalize it. Try again next round.
+		v.resurrected = false
+		runtime.SetFinalizer(v, finalize)
+		return
+	}
+	delete(valMap, keyFor(v.cmpVal))
+}
+
+// Interning is simple if you don't require that unused values be
+// garbage collectable. But we do require that; we don't want to be
+// DOS vector. We do this by using a uintptr to hide the pointer from
+// the garbage collector, and using a finalizer to eliminate the
+// pointer when no other code is using it.
+//
+// The obvious implementation of this is to use a
+// map[interface{}]uintptr-of-*interface{}, and set up a finalizer to
+// delete from the map. Unfortunately, this is racy. Because pointers
+// are being created in violation of Go's unsafety rules, it's
+// possible to create a pointer to a value concurrently with the GC
+// concluding that the value can be collected. There are other races
+// that break the equality invariant as well, but the use-after-free
+// will cause a runtime crash.
+//
+// To make this work, the finalizer needs to know that no references
+// have been unsafely created since the finalizer was set up. To do
+// this, values carry a "resurrected" sentinel, which gets set
+// whenever a pointer is unsafely created. If the finalizer encounters
+// the sentinel, it clears the sentinel and delays collection for one
+// additional GC cycle, by re-installing itself as finalizer. This
+// ensures that the unsafely created pointer is visible to the GC, and
+// will correctly prevent collection.
+//
+// This technique does mean that interned values that get reused take
+// at least 3 GC cycles to fully collect (1 to clear the sentinel, 1
+// to clean up the unsafe map, 1 to be actually deleted).
+//
+// @ianlancetaylor commented in
+// https://github.com/golang/go/issues/41303#issuecomment-717401656
+// that it is possible to implement weak references in terms of
+// finalizers without unsafe. Unfortunately, the approach he outlined
+// does not work here, for two reasons. First, there is no way to
+// construct a strong pointer out of a weak pointer; our map stores
+// weak pointers, but we must return strong pointers to callers.
+// Second, and more fundamentally, we must return not just _a_ strong
+// pointer to callers, but _the same_ strong pointer to callers. In
+// order to return _the same_ strong pointer to callers, we must track
+// it, which is exactly what we cannot do with strong pointers.
+//
+// See https://github.com/inetaf/netaddr/issues/53 for more
+// discussion, and https://github.com/go4org/intern/issues/2 for an
+// illustration of the subtleties at play.

vendor/go4.org/unsafe/assume-no-moving-gc/LICENSE

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+BSD 3-Clause License
+
+Copyright (c) 2020, Brad Fitzpatrick
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its
+   contributors may be used to endorse or promote products derived from
+   this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/go4.org/unsafe/assume-no-moving-gc/README.md

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+# go4.org/unsafe/assume-no-moving-gc
+
+If your Go package wants to declare that it plays `unsafe` games that only
+work if the Go runtime's garbage collector is not a moving collector, then add:
+
+```go
+import _ "go4.org/unsafe/assume-no-moving-gc"
+```
+
+Then your program will explode if that's no longer the case. (Users can override
+the explosion with a scary sounding environment variable.)
+
+This also gives us a way to find all the really gross unsafe packages.

vendor/go4.org/unsafe/assume-no-moving-gc/assume-no-moving-gc.go

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+// Copyright 2020 Brad Fitzpatrick. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package go4.org/unsafe/assume-no-moving-gc exists so you can depend
+// on it from unsafe code that wants to declare that it assumes that
+// the Go runtime does not using a moving garbage colllector.
+//
+// This package is then updated for new Go versions when that
+// is still the case and explodes at runtime with a failure
+// otherwise, unless an environment variable overrides it.
+//
+// To use:
+//
+//     import _ "go4.org/unsafe/assume-no-moving-gc"
+//
+// There is no API.
+//
+// The GitHub repo is at https://github.com/go4org/unsafe-assume-no-moving-gc
+package assume_no_moving_gc
+
+const env = "ASSUME_NO_MOVING_GC_UNSAFE_RISK_IT_WITH"

vendor/go4.org/unsafe/assume-no-moving-gc/untested.go

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+// Copyright 2020 Brad Fitzpatrick. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.20
+// +build go1.20
+
+package assume_no_moving_gc
+
+import (
+	"os"
+	"runtime"
+	"strings"
+)
+
+func init() {
+	dots := strings.SplitN(runtime.Version(), ".", 3)
+	v := runtime.Version()
+	if len(dots) >= 2 {
+		v = dots[0] + "." + dots[1]
+	}
+	if os.Getenv(env) == v {
+		return
+	}
+	panic("Something in this program imports go4.org/unsafe/assume-no-moving-gc to declare that it assumes a non-moving garbage collector, but your version of go4.org/unsafe/assume-no-moving-gc hasn't been updated to assert that it's safe against the " + v + " runtime. If you want to risk it, run with environment variable " + env + "=" + v + " set. Notably, if " + v + " adds a moving garbage collector, this program is unsafe to use.")
+}