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Saves 139 KB. Also Synology support, which I saw had its own large-ish proxy parsing support on Linux, but support for proxies without Synology proxy support is reasonable, so I pulled that out as its own thing. Updates #12614 Change-Id: I22de285a3def7be77fdcf23e2bec7c83c9655593 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
90 lines
2.1 KiB
Go
90 lines
2.1 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package feature tracks which features are linked into the binary.
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package feature
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import (
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"errors"
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"reflect"
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)
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var ErrUnavailable = errors.New("feature not included in this build")
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var in = map[string]bool{}
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// Register notes that the named feature is linked into the binary.
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func Register(name string) {
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if _, ok := in[name]; ok {
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panic("duplicate feature registration for " + name)
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}
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in[name] = true
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}
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// Hook is a func that can only be set once.
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//
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// It is not safe for concurrent use.
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type Hook[Func any] struct {
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f Func
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ok bool
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}
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// IsSet reports whether the hook has been set.
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func (h *Hook[Func]) IsSet() bool {
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return h.ok
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}
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// Set sets the hook function, panicking if it's already been set
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// or f is the zero value.
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//
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// It's meant to be called in init.
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func (h *Hook[Func]) Set(f Func) {
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if h.ok {
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panic("Set on already-set feature hook")
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}
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if reflect.ValueOf(f).IsZero() {
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panic("Set with zero value")
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}
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h.f = f
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h.ok = true
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}
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// Get returns the hook function, or panics if it hasn't been set.
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// Use IsSet to check if it's been set, or use GetOrNil if you're
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// okay with a nil return value.
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func (h *Hook[Func]) Get() Func {
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if !h.ok {
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panic("Get on unset feature hook, without IsSet")
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}
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return h.f
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}
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// GetOk returns the hook function and true if it has been set,
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// otherwise its zero value and false.
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func (h *Hook[Func]) GetOk() (f Func, ok bool) {
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return h.f, h.ok
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}
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// GetOrNil returns the hook function or nil if it hasn't been set.
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func (h *Hook[Func]) GetOrNil() Func {
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return h.f
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}
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// Hooks is a slice of funcs.
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//
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// As opposed to a single Hook, this is meant to be used when
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// multiple parties are able to install the same hook.
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type Hooks[Func any] []Func
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// Add adds a hook to the list of hooks.
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//
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// Add should only be called during early program
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// startup before Tailscale has started.
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// It is not safe for concurrent use.
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func (h *Hooks[Func]) Add(f Func) {
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if reflect.ValueOf(f).IsZero() {
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panic("Add with zero value")
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}
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*h = append(*h, f)
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}
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