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-rw-r--r--src/context/benchmark_test.go140
-rw-r--r--src/context/context.go563
-rw-r--r--src/context/context_test.go788
-rw-r--r--src/context/example_test.go120
-rw-r--r--src/context/net_test.go21
-rw-r--r--src/context/x_test.go31
6 files changed, 1663 insertions, 0 deletions
diff --git a/src/context/benchmark_test.go b/src/context/benchmark_test.go
new file mode 100644
index 0000000..5d56863
--- /dev/null
+++ b/src/context/benchmark_test.go
@@ -0,0 +1,140 @@
+// Copyright 2014 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 context_test
+
+import (
+ . "context"
+ "fmt"
+ "runtime"
+ "sync"
+ "testing"
+ "time"
+)
+
+func BenchmarkCommonParentCancel(b *testing.B) {
+ root := WithValue(Background(), "key", "value")
+ shared, sharedcancel := WithCancel(root)
+ defer sharedcancel()
+
+ b.ResetTimer()
+ b.RunParallel(func(pb *testing.PB) {
+ x := 0
+ for pb.Next() {
+ ctx, cancel := WithCancel(shared)
+ if ctx.Value("key").(string) != "value" {
+ b.Fatal("should not be reached")
+ }
+ for i := 0; i < 100; i++ {
+ x /= x + 1
+ }
+ cancel()
+ for i := 0; i < 100; i++ {
+ x /= x + 1
+ }
+ }
+ })
+}
+
+func BenchmarkWithTimeout(b *testing.B) {
+ for concurrency := 40; concurrency <= 4e5; concurrency *= 100 {
+ name := fmt.Sprintf("concurrency=%d", concurrency)
+ b.Run(name, func(b *testing.B) {
+ benchmarkWithTimeout(b, concurrency)
+ })
+ }
+}
+
+func benchmarkWithTimeout(b *testing.B, concurrentContexts int) {
+ gomaxprocs := runtime.GOMAXPROCS(0)
+ perPContexts := concurrentContexts / gomaxprocs
+ root := Background()
+
+ // Generate concurrent contexts.
+ var wg sync.WaitGroup
+ ccf := make([][]CancelFunc, gomaxprocs)
+ for i := range ccf {
+ wg.Add(1)
+ go func(i int) {
+ defer wg.Done()
+ cf := make([]CancelFunc, perPContexts)
+ for j := range cf {
+ _, cf[j] = WithTimeout(root, time.Hour)
+ }
+ ccf[i] = cf
+ }(i)
+ }
+ wg.Wait()
+
+ b.ResetTimer()
+ b.RunParallel(func(pb *testing.PB) {
+ wcf := make([]CancelFunc, 10)
+ for pb.Next() {
+ for i := range wcf {
+ _, wcf[i] = WithTimeout(root, time.Hour)
+ }
+ for _, f := range wcf {
+ f()
+ }
+ }
+ })
+ b.StopTimer()
+
+ for _, cf := range ccf {
+ for _, f := range cf {
+ f()
+ }
+ }
+}
+
+func BenchmarkCancelTree(b *testing.B) {
+ depths := []int{1, 10, 100, 1000}
+ for _, d := range depths {
+ b.Run(fmt.Sprintf("depth=%d", d), func(b *testing.B) {
+ b.Run("Root=Background", func(b *testing.B) {
+ for i := 0; i < b.N; i++ {
+ buildContextTree(Background(), d)
+ }
+ })
+ b.Run("Root=OpenCanceler", func(b *testing.B) {
+ for i := 0; i < b.N; i++ {
+ ctx, cancel := WithCancel(Background())
+ buildContextTree(ctx, d)
+ cancel()
+ }
+ })
+ b.Run("Root=ClosedCanceler", func(b *testing.B) {
+ for i := 0; i < b.N; i++ {
+ ctx, cancel := WithCancel(Background())
+ cancel()
+ buildContextTree(ctx, d)
+ }
+ })
+ })
+ }
+}
+
+func buildContextTree(root Context, depth int) {
+ for d := 0; d < depth; d++ {
+ root, _ = WithCancel(root)
+ }
+}
+
+func BenchmarkCheckCanceled(b *testing.B) {
+ ctx, cancel := WithCancel(Background())
+ cancel()
+ b.Run("Err", func(b *testing.B) {
+ for i := 0; i < b.N; i++ {
+ ctx.Err()
+ }
+ })
+ b.Run("Done", func(b *testing.B) {
+ for i := 0; i < b.N; i++ {
+ select {
+ case <-ctx.Done():
+ default:
+ }
+ }
+ })
+}
diff --git a/src/context/context.go b/src/context/context.go
new file mode 100644
index 0000000..b3fdb82
--- /dev/null
+++ b/src/context/context.go
@@ -0,0 +1,563 @@
+// Copyright 2014 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 context defines the Context type, which carries deadlines,
+// cancellation signals, and other request-scoped values across API boundaries
+// and between processes.
+//
+// Incoming requests to a server should create a Context, and outgoing
+// calls to servers should accept a Context. The chain of function
+// calls between them must propagate the Context, optionally replacing
+// it with a derived Context created using WithCancel, WithDeadline,
+// WithTimeout, or WithValue. When a Context is canceled, all
+// Contexts derived from it are also canceled.
+//
+// The WithCancel, WithDeadline, and WithTimeout functions take a
+// Context (the parent) and return a derived Context (the child) and a
+// CancelFunc. Calling the CancelFunc cancels the child and its
+// children, removes the parent's reference to the child, and stops
+// any associated timers. Failing to call the CancelFunc leaks the
+// child and its children until the parent is canceled or the timer
+// fires. The go vet tool checks that CancelFuncs are used on all
+// control-flow paths.
+//
+// Programs that use Contexts should follow these rules to keep interfaces
+// consistent across packages and enable static analysis tools to check context
+// propagation:
+//
+// Do not store Contexts inside a struct type; instead, pass a Context
+// explicitly to each function that needs it. The Context should be the first
+// parameter, typically named ctx:
+//
+// func DoSomething(ctx context.Context, arg Arg) error {
+// // ... use ctx ...
+// }
+//
+// Do not pass a nil Context, even if a function permits it. Pass context.TODO
+// if you are unsure about which Context to use.
+//
+// Use context Values only for request-scoped data that transits processes and
+// APIs, not for passing optional parameters to functions.
+//
+// The same Context may be passed to functions running in different goroutines;
+// Contexts are safe for simultaneous use by multiple goroutines.
+//
+// See https://blog.golang.org/context for example code for a server that uses
+// Contexts.
+package context
+
+import (
+ "errors"
+ "internal/reflectlite"
+ "sync"
+ "sync/atomic"
+ "time"
+)
+
+// A Context carries a deadline, a cancellation signal, and other values across
+// API boundaries.
+//
+// Context's methods may be called by multiple goroutines simultaneously.
+type Context interface {
+ // Deadline returns the time when work done on behalf of this context
+ // should be canceled. Deadline returns ok==false when no deadline is
+ // set. Successive calls to Deadline return the same results.
+ Deadline() (deadline time.Time, ok bool)
+
+ // Done returns a channel that's closed when work done on behalf of this
+ // context should be canceled. Done may return nil if this context can
+ // never be canceled. Successive calls to Done return the same value.
+ // The close of the Done channel may happen asynchronously,
+ // after the cancel function returns.
+ //
+ // WithCancel arranges for Done to be closed when cancel is called;
+ // WithDeadline arranges for Done to be closed when the deadline
+ // expires; WithTimeout arranges for Done to be closed when the timeout
+ // elapses.
+ //
+ // Done is provided for use in select statements:
+ //
+ // // Stream generates values with DoSomething and sends them to out
+ // // until DoSomething returns an error or ctx.Done is closed.
+ // func Stream(ctx context.Context, out chan<- Value) error {
+ // for {
+ // v, err := DoSomething(ctx)
+ // if err != nil {
+ // return err
+ // }
+ // select {
+ // case <-ctx.Done():
+ // return ctx.Err()
+ // case out <- v:
+ // }
+ // }
+ // }
+ //
+ // See https://blog.golang.org/pipelines for more examples of how to use
+ // a Done channel for cancellation.
+ Done() <-chan struct{}
+
+ // If Done is not yet closed, Err returns nil.
+ // If Done is closed, Err returns a non-nil error explaining why:
+ // Canceled if the context was canceled
+ // or DeadlineExceeded if the context's deadline passed.
+ // After Err returns a non-nil error, successive calls to Err return the same error.
+ Err() error
+
+ // Value returns the value associated with this context for key, or nil
+ // if no value is associated with key. Successive calls to Value with
+ // the same key returns the same result.
+ //
+ // Use context values only for request-scoped data that transits
+ // processes and API boundaries, not for passing optional parameters to
+ // functions.
+ //
+ // A key identifies a specific value in a Context. Functions that wish
+ // to store values in Context typically allocate a key in a global
+ // variable then use that key as the argument to context.WithValue and
+ // Context.Value. A key can be any type that supports equality;
+ // packages should define keys as an unexported type to avoid
+ // collisions.
+ //
+ // Packages that define a Context key should provide type-safe accessors
+ // for the values stored using that key:
+ //
+ // // Package user defines a User type that's stored in Contexts.
+ // package user
+ //
+ // import "context"
+ //
+ // // User is the type of value stored in the Contexts.
+ // type User struct {...}
+ //
+ // // key is an unexported type for keys defined in this package.
+ // // This prevents collisions with keys defined in other packages.
+ // type key int
+ //
+ // // userKey is the key for user.User values in Contexts. It is
+ // // unexported; clients use user.NewContext and user.FromContext
+ // // instead of using this key directly.
+ // var userKey key
+ //
+ // // NewContext returns a new Context that carries value u.
+ // func NewContext(ctx context.Context, u *User) context.Context {
+ // return context.WithValue(ctx, userKey, u)
+ // }
+ //
+ // // FromContext returns the User value stored in ctx, if any.
+ // func FromContext(ctx context.Context) (*User, bool) {
+ // u, ok := ctx.Value(userKey).(*User)
+ // return u, ok
+ // }
+ Value(key interface{}) interface{}
+}
+
+// Canceled is the error returned by Context.Err when the context is canceled.
+var Canceled = errors.New("context canceled")
+
+// DeadlineExceeded is the error returned by Context.Err when the context's
+// deadline passes.
+var DeadlineExceeded error = deadlineExceededError{}
+
+type deadlineExceededError struct{}
+
+func (deadlineExceededError) Error() string { return "context deadline exceeded" }
+func (deadlineExceededError) Timeout() bool { return true }
+func (deadlineExceededError) Temporary() bool { return true }
+
+// An emptyCtx is never canceled, has no values, and has no deadline. It is not
+// struct{}, since vars of this type must have distinct addresses.
+type emptyCtx int
+
+func (*emptyCtx) Deadline() (deadline time.Time, ok bool) {
+ return
+}
+
+func (*emptyCtx) Done() <-chan struct{} {
+ return nil
+}
+
+func (*emptyCtx) Err() error {
+ return nil
+}
+
+func (*emptyCtx) Value(key interface{}) interface{} {
+ return nil
+}
+
+func (e *emptyCtx) String() string {
+ switch e {
+ case background:
+ return "context.Background"
+ case todo:
+ return "context.TODO"
+ }
+ return "unknown empty Context"
+}
+
+var (
+ background = new(emptyCtx)
+ todo = new(emptyCtx)
+)
+
+// Background returns a non-nil, empty Context. It is never canceled, has no
+// values, and has no deadline. It is typically used by the main function,
+// initialization, and tests, and as the top-level Context for incoming
+// requests.
+func Background() Context {
+ return background
+}
+
+// TODO returns a non-nil, empty Context. Code should use context.TODO when
+// it's unclear which Context to use or it is not yet available (because the
+// surrounding function has not yet been extended to accept a Context
+// parameter).
+func TODO() Context {
+ return todo
+}
+
+// A CancelFunc tells an operation to abandon its work.
+// A CancelFunc does not wait for the work to stop.
+// A CancelFunc may be called by multiple goroutines simultaneously.
+// After the first call, subsequent calls to a CancelFunc do nothing.
+type CancelFunc func()
+
+// WithCancel returns a copy of parent with a new Done channel. The returned
+// context's Done channel is closed when the returned cancel function is called
+// or when the parent context's Done channel is closed, whichever happens first.
+//
+// Canceling this context releases resources associated with it, so code should
+// call cancel as soon as the operations running in this Context complete.
+func WithCancel(parent Context) (ctx Context, cancel CancelFunc) {
+ if parent == nil {
+ panic("cannot create context from nil parent")
+ }
+ c := newCancelCtx(parent)
+ propagateCancel(parent, &c)
+ return &c, func() { c.cancel(true, Canceled) }
+}
+
+// newCancelCtx returns an initialized cancelCtx.
+func newCancelCtx(parent Context) cancelCtx {
+ return cancelCtx{Context: parent}
+}
+
+// goroutines counts the number of goroutines ever created; for testing.
+var goroutines int32
+
+// propagateCancel arranges for child to be canceled when parent is.
+func propagateCancel(parent Context, child canceler) {
+ done := parent.Done()
+ if done == nil {
+ return // parent is never canceled
+ }
+
+ select {
+ case <-done:
+ // parent is already canceled
+ child.cancel(false, parent.Err())
+ return
+ default:
+ }
+
+ if p, ok := parentCancelCtx(parent); ok {
+ p.mu.Lock()
+ if p.err != nil {
+ // parent has already been canceled
+ child.cancel(false, p.err)
+ } else {
+ if p.children == nil {
+ p.children = make(map[canceler]struct{})
+ }
+ p.children[child] = struct{}{}
+ }
+ p.mu.Unlock()
+ } else {
+ atomic.AddInt32(&goroutines, +1)
+ go func() {
+ select {
+ case <-parent.Done():
+ child.cancel(false, parent.Err())
+ case <-child.Done():
+ }
+ }()
+ }
+}
+
+// &cancelCtxKey is the key that a cancelCtx returns itself for.
+var cancelCtxKey int
+
+// parentCancelCtx returns the underlying *cancelCtx for parent.
+// It does this by looking up parent.Value(&cancelCtxKey) to find
+// the innermost enclosing *cancelCtx and then checking whether
+// parent.Done() matches that *cancelCtx. (If not, the *cancelCtx
+// has been wrapped in a custom implementation providing a
+// different done channel, in which case we should not bypass it.)
+func parentCancelCtx(parent Context) (*cancelCtx, bool) {
+ done := parent.Done()
+ if done == closedchan || done == nil {
+ return nil, false
+ }
+ p, ok := parent.Value(&cancelCtxKey).(*cancelCtx)
+ if !ok {
+ return nil, false
+ }
+ p.mu.Lock()
+ ok = p.done == done
+ p.mu.Unlock()
+ if !ok {
+ return nil, false
+ }
+ return p, true
+}
+
+// removeChild removes a context from its parent.
+func removeChild(parent Context, child canceler) {
+ p, ok := parentCancelCtx(parent)
+ if !ok {
+ return
+ }
+ p.mu.Lock()
+ if p.children != nil {
+ delete(p.children, child)
+ }
+ p.mu.Unlock()
+}
+
+// A canceler is a context type that can be canceled directly. The
+// implementations are *cancelCtx and *timerCtx.
+type canceler interface {
+ cancel(removeFromParent bool, err error)
+ Done() <-chan struct{}
+}
+
+// closedchan is a reusable closed channel.
+var closedchan = make(chan struct{})
+
+func init() {
+ close(closedchan)
+}
+
+// A cancelCtx can be canceled. When canceled, it also cancels any children
+// that implement canceler.
+type cancelCtx struct {
+ Context
+
+ mu sync.Mutex // protects following fields
+ done chan struct{} // created lazily, closed by first cancel call
+ children map[canceler]struct{} // set to nil by the first cancel call
+ err error // set to non-nil by the first cancel call
+}
+
+func (c *cancelCtx) Value(key interface{}) interface{} {
+ if key == &cancelCtxKey {
+ return c
+ }
+ return c.Context.Value(key)
+}
+
+func (c *cancelCtx) Done() <-chan struct{} {
+ c.mu.Lock()
+ if c.done == nil {
+ c.done = make(chan struct{})
+ }
+ d := c.done
+ c.mu.Unlock()
+ return d
+}
+
+func (c *cancelCtx) Err() error {
+ c.mu.Lock()
+ err := c.err
+ c.mu.Unlock()
+ return err
+}
+
+type stringer interface {
+ String() string
+}
+
+func contextName(c Context) string {
+ if s, ok := c.(stringer); ok {
+ return s.String()
+ }
+ return reflectlite.TypeOf(c).String()
+}
+
+func (c *cancelCtx) String() string {
+ return contextName(c.Context) + ".WithCancel"
+}
+
+// cancel closes c.done, cancels each of c's children, and, if
+// removeFromParent is true, removes c from its parent's children.
+func (c *cancelCtx) cancel(removeFromParent bool, err error) {
+ if err == nil {
+ panic("context: internal error: missing cancel error")
+ }
+ c.mu.Lock()
+ if c.err != nil {
+ c.mu.Unlock()
+ return // already canceled
+ }
+ c.err = err
+ if c.done == nil {
+ c.done = closedchan
+ } else {
+ close(c.done)
+ }
+ for child := range c.children {
+ // NOTE: acquiring the child's lock while holding parent's lock.
+ child.cancel(false, err)
+ }
+ c.children = nil
+ c.mu.Unlock()
+
+ if removeFromParent {
+ removeChild(c.Context, c)
+ }
+}
+
+// WithDeadline returns a copy of the parent context with the deadline adjusted
+// to be no later than d. If the parent's deadline is already earlier than d,
+// WithDeadline(parent, d) is semantically equivalent to parent. The returned
+// context's Done channel is closed when the deadline expires, when the returned
+// cancel function is called, or when the parent context's Done channel is
+// closed, whichever happens first.
+//
+// Canceling this context releases resources associated with it, so code should
+// call cancel as soon as the operations running in this Context complete.
+func WithDeadline(parent Context, d time.Time) (Context, CancelFunc) {
+ if parent == nil {
+ panic("cannot create context from nil parent")
+ }
+ if cur, ok := parent.Deadline(); ok && cur.Before(d) {
+ // The current deadline is already sooner than the new one.
+ return WithCancel(parent)
+ }
+ c := &timerCtx{
+ cancelCtx: newCancelCtx(parent),
+ deadline: d,
+ }
+ propagateCancel(parent, c)
+ dur := time.Until(d)
+ if dur <= 0 {
+ c.cancel(true, DeadlineExceeded) // deadline has already passed
+ return c, func() { c.cancel(false, Canceled) }
+ }
+ c.mu.Lock()
+ defer c.mu.Unlock()
+ if c.err == nil {
+ c.timer = time.AfterFunc(dur, func() {
+ c.cancel(true, DeadlineExceeded)
+ })
+ }
+ return c, func() { c.cancel(true, Canceled) }
+}
+
+// A timerCtx carries a timer and a deadline. It embeds a cancelCtx to
+// implement Done and Err. It implements cancel by stopping its timer then
+// delegating to cancelCtx.cancel.
+type timerCtx struct {
+ cancelCtx
+ timer *time.Timer // Under cancelCtx.mu.
+
+ deadline time.Time
+}
+
+func (c *timerCtx) Deadline() (deadline time.Time, ok bool) {
+ return c.deadline, true
+}
+
+func (c *timerCtx) String() string {
+ return contextName(c.cancelCtx.Context) + ".WithDeadline(" +
+ c.deadline.String() + " [" +
+ time.Until(c.deadline).String() + "])"
+}
+
+func (c *timerCtx) cancel(removeFromParent bool, err error) {
+ c.cancelCtx.cancel(false, err)
+ if removeFromParent {
+ // Remove this timerCtx from its parent cancelCtx's children.
+ removeChild(c.cancelCtx.Context, c)
+ }
+ c.mu.Lock()
+ if c.timer != nil {
+ c.timer.Stop()
+ c.timer = nil
+ }
+ c.mu.Unlock()
+}
+
+// WithTimeout returns WithDeadline(parent, time.Now().Add(timeout)).
+//
+// Canceling this context releases resources associated with it, so code should
+// call cancel as soon as the operations running in this Context complete:
+//
+// func slowOperationWithTimeout(ctx context.Context) (Result, error) {
+// ctx, cancel := context.WithTimeout(ctx, 100*time.Millisecond)
+// defer cancel() // releases resources if slowOperation completes before timeout elapses
+// return slowOperation(ctx)
+// }
+func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc) {
+ return WithDeadline(parent, time.Now().Add(timeout))
+}
+
+// WithValue returns a copy of parent in which the value associated with key is
+// val.
+//
+// Use context Values only for request-scoped data that transits processes and
+// APIs, not for passing optional parameters to functions.
+//
+// The provided key must be comparable and should not be of type
+// string or any other built-in type to avoid collisions between
+// packages using context. Users of WithValue should define their own
+// types for keys. To avoid allocating when assigning to an
+// interface{}, context keys often have concrete type
+// struct{}. Alternatively, exported context key variables' static
+// type should be a pointer or interface.
+func WithValue(parent Context, key, val interface{}) Context {
+ if parent == nil {
+ panic("cannot create context from nil parent")
+ }
+ if key == nil {
+ panic("nil key")
+ }
+ if !reflectlite.TypeOf(key).Comparable() {
+ panic("key is not comparable")
+ }
+ return &valueCtx{parent, key, val}
+}
+
+// A valueCtx carries a key-value pair. It implements Value for that key and
+// delegates all other calls to the embedded Context.
+type valueCtx struct {
+ Context
+ key, val interface{}
+}
+
+// stringify tries a bit to stringify v, without using fmt, since we don't
+// want context depending on the unicode tables. This is only used by
+// *valueCtx.String().
+func stringify(v interface{}) string {
+ switch s := v.(type) {
+ case stringer:
+ return s.String()
+ case string:
+ return s
+ }
+ return "<not Stringer>"
+}
+
+func (c *valueCtx) String() string {
+ return contextName(c.Context) + ".WithValue(type " +
+ reflectlite.TypeOf(c.key).String() +
+ ", val " + stringify(c.val) + ")"
+}
+
+func (c *valueCtx) Value(key interface{}) interface{} {
+ if c.key == key {
+ return c.val
+ }
+ return c.Context.Value(key)
+}
diff --git a/src/context/context_test.go b/src/context/context_test.go
new file mode 100644
index 0000000..6b392a2
--- /dev/null
+++ b/src/context/context_test.go
@@ -0,0 +1,788 @@
+// Copyright 2014 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 context
+
+import (
+ "fmt"
+ "math/rand"
+ "runtime"
+ "strings"
+ "sync"
+ "sync/atomic"
+ "time"
+)
+
+type testingT interface {
+ Deadline() (time.Time, bool)
+ Error(args ...interface{})
+ Errorf(format string, args ...interface{})
+ Fail()
+ FailNow()
+ Failed() bool
+ Fatal(args ...interface{})
+ Fatalf(format string, args ...interface{})
+ Helper()
+ Log(args ...interface{})
+ Logf(format string, args ...interface{})
+ Name() string
+ Parallel()
+ Skip(args ...interface{})
+ SkipNow()
+ Skipf(format string, args ...interface{})
+ Skipped() bool
+}
+
+// otherContext is a Context that's not one of the types defined in context.go.
+// This lets us test code paths that differ based on the underlying type of the
+// Context.
+type otherContext struct {
+ Context
+}
+
+const (
+ shortDuration = 1 * time.Millisecond // a reasonable duration to block in a test
+ veryLongDuration = 1000 * time.Hour // an arbitrary upper bound on the test's running time
+)
+
+// quiescent returns an arbitrary duration by which the program should have
+// completed any remaining work and reached a steady (idle) state.
+func quiescent(t testingT) time.Duration {
+ deadline, ok := t.Deadline()
+ if !ok {
+ return 5 * time.Second
+ }
+
+ const arbitraryCleanupMargin = 1 * time.Second
+ return time.Until(deadline) - arbitraryCleanupMargin
+}
+
+func XTestBackground(t testingT) {
+ c := Background()
+ if c == nil {
+ t.Fatalf("Background returned nil")
+ }
+ select {
+ case x := <-c.Done():
+ t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+ if got, want := fmt.Sprint(c), "context.Background"; got != want {
+ t.Errorf("Background().String() = %q want %q", got, want)
+ }
+}
+
+func XTestTODO(t testingT) {
+ c := TODO()
+ if c == nil {
+ t.Fatalf("TODO returned nil")
+ }
+ select {
+ case x := <-c.Done():
+ t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+ if got, want := fmt.Sprint(c), "context.TODO"; got != want {
+ t.Errorf("TODO().String() = %q want %q", got, want)
+ }
+}
+
+func XTestWithCancel(t testingT) {
+ c1, cancel := WithCancel(Background())
+
+ if got, want := fmt.Sprint(c1), "context.Background.WithCancel"; got != want {
+ t.Errorf("c1.String() = %q want %q", got, want)
+ }
+
+ o := otherContext{c1}
+ c2, _ := WithCancel(o)
+ contexts := []Context{c1, o, c2}
+
+ for i, c := range contexts {
+ if d := c.Done(); d == nil {
+ t.Errorf("c[%d].Done() == %v want non-nil", i, d)
+ }
+ if e := c.Err(); e != nil {
+ t.Errorf("c[%d].Err() == %v want nil", i, e)
+ }
+
+ select {
+ case x := <-c.Done():
+ t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+ }
+
+ cancel() // Should propagate synchronously.
+ for i, c := range contexts {
+ select {
+ case <-c.Done():
+ default:
+ t.Errorf("<-c[%d].Done() blocked, but shouldn't have", i)
+ }
+ if e := c.Err(); e != Canceled {
+ t.Errorf("c[%d].Err() == %v want %v", i, e, Canceled)
+ }
+ }
+}
+
+func contains(m map[canceler]struct{}, key canceler) bool {
+ _, ret := m[key]
+ return ret
+}
+
+func XTestParentFinishesChild(t testingT) {
+ // Context tree:
+ // parent -> cancelChild
+ // parent -> valueChild -> timerChild
+ parent, cancel := WithCancel(Background())
+ cancelChild, stop := WithCancel(parent)
+ defer stop()
+ valueChild := WithValue(parent, "key", "value")
+ timerChild, stop := WithTimeout(valueChild, veryLongDuration)
+ defer stop()
+
+ select {
+ case x := <-parent.Done():
+ t.Errorf("<-parent.Done() == %v want nothing (it should block)", x)
+ case x := <-cancelChild.Done():
+ t.Errorf("<-cancelChild.Done() == %v want nothing (it should block)", x)
+ case x := <-timerChild.Done():
+ t.Errorf("<-timerChild.Done() == %v want nothing (it should block)", x)
+ case x := <-valueChild.Done():
+ t.Errorf("<-valueChild.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+
+ // The parent's children should contain the two cancelable children.
+ pc := parent.(*cancelCtx)
+ cc := cancelChild.(*cancelCtx)
+ tc := timerChild.(*timerCtx)
+ pc.mu.Lock()
+ if len(pc.children) != 2 || !contains(pc.children, cc) || !contains(pc.children, tc) {
+ t.Errorf("bad linkage: pc.children = %v, want %v and %v",
+ pc.children, cc, tc)
+ }
+ pc.mu.Unlock()
+
+ if p, ok := parentCancelCtx(cc.Context); !ok || p != pc {
+ t.Errorf("bad linkage: parentCancelCtx(cancelChild.Context) = %v, %v want %v, true", p, ok, pc)
+ }
+ if p, ok := parentCancelCtx(tc.Context); !ok || p != pc {
+ t.Errorf("bad linkage: parentCancelCtx(timerChild.Context) = %v, %v want %v, true", p, ok, pc)
+ }
+
+ cancel()
+
+ pc.mu.Lock()
+ if len(pc.children) != 0 {
+ t.Errorf("pc.cancel didn't clear pc.children = %v", pc.children)
+ }
+ pc.mu.Unlock()
+
+ // parent and children should all be finished.
+ check := func(ctx Context, name string) {
+ select {
+ case <-ctx.Done():
+ default:
+ t.Errorf("<-%s.Done() blocked, but shouldn't have", name)
+ }
+ if e := ctx.Err(); e != Canceled {
+ t.Errorf("%s.Err() == %v want %v", name, e, Canceled)
+ }
+ }
+ check(parent, "parent")
+ check(cancelChild, "cancelChild")
+ check(valueChild, "valueChild")
+ check(timerChild, "timerChild")
+
+ // WithCancel should return a canceled context on a canceled parent.
+ precanceledChild := WithValue(parent, "key", "value")
+ select {
+ case <-precanceledChild.Done():
+ default:
+ t.Errorf("<-precanceledChild.Done() blocked, but shouldn't have")
+ }
+ if e := precanceledChild.Err(); e != Canceled {
+ t.Errorf("precanceledChild.Err() == %v want %v", e, Canceled)
+ }
+}
+
+func XTestChildFinishesFirst(t testingT) {
+ cancelable, stop := WithCancel(Background())
+ defer stop()
+ for _, parent := range []Context{Background(), cancelable} {
+ child, cancel := WithCancel(parent)
+
+ select {
+ case x := <-parent.Done():
+ t.Errorf("<-parent.Done() == %v want nothing (it should block)", x)
+ case x := <-child.Done():
+ t.Errorf("<-child.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+
+ cc := child.(*cancelCtx)
+ pc, pcok := parent.(*cancelCtx) // pcok == false when parent == Background()
+ if p, ok := parentCancelCtx(cc.Context); ok != pcok || (ok && pc != p) {
+ t.Errorf("bad linkage: parentCancelCtx(cc.Context) = %v, %v want %v, %v", p, ok, pc, pcok)
+ }
+
+ if pcok {
+ pc.mu.Lock()
+ if len(pc.children) != 1 || !contains(pc.children, cc) {
+ t.Errorf("bad linkage: pc.children = %v, cc = %v", pc.children, cc)
+ }
+ pc.mu.Unlock()
+ }
+
+ cancel()
+
+ if pcok {
+ pc.mu.Lock()
+ if len(pc.children) != 0 {
+ t.Errorf("child's cancel didn't remove self from pc.children = %v", pc.children)
+ }
+ pc.mu.Unlock()
+ }
+
+ // child should be finished.
+ select {
+ case <-child.Done():
+ default:
+ t.Errorf("<-child.Done() blocked, but shouldn't have")
+ }
+ if e := child.Err(); e != Canceled {
+ t.Errorf("child.Err() == %v want %v", e, Canceled)
+ }
+
+ // parent should not be finished.
+ select {
+ case x := <-parent.Done():
+ t.Errorf("<-parent.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+ if e := parent.Err(); e != nil {
+ t.Errorf("parent.Err() == %v want nil", e)
+ }
+ }
+}
+
+func testDeadline(c Context, name string, t testingT) {
+ t.Helper()
+ d := quiescent(t)
+ timer := time.NewTimer(d)
+ defer timer.Stop()
+ select {
+ case <-timer.C:
+ t.Fatalf("%s: context not timed out after %v", name, d)
+ case <-c.Done():
+ }
+ if e := c.Err(); e != DeadlineExceeded {
+ t.Errorf("%s: c.Err() == %v; want %v", name, e, DeadlineExceeded)
+ }
+}
+
+func XTestDeadline(t testingT) {
+ t.Parallel()
+
+ c, _ := WithDeadline(Background(), time.Now().Add(shortDuration))
+ if got, prefix := fmt.Sprint(c), "context.Background.WithDeadline("; !strings.HasPrefix(got, prefix) {
+ t.Errorf("c.String() = %q want prefix %q", got, prefix)
+ }
+ testDeadline(c, "WithDeadline", t)
+
+ c, _ = WithDeadline(Background(), time.Now().Add(shortDuration))
+ o := otherContext{c}
+ testDeadline(o, "WithDeadline+otherContext", t)
+
+ c, _ = WithDeadline(Background(), time.Now().Add(shortDuration))
+ o = otherContext{c}
+ c, _ = WithDeadline(o, time.Now().Add(veryLongDuration))
+ testDeadline(c, "WithDeadline+otherContext+WithDeadline", t)
+
+ c, _ = WithDeadline(Background(), time.Now().Add(-shortDuration))
+ testDeadline(c, "WithDeadline+inthepast", t)
+
+ c, _ = WithDeadline(Background(), time.Now())
+ testDeadline(c, "WithDeadline+now", t)
+}
+
+func XTestTimeout(t testingT) {
+ t.Parallel()
+
+ c, _ := WithTimeout(Background(), shortDuration)
+ if got, prefix := fmt.Sprint(c), "context.Background.WithDeadline("; !strings.HasPrefix(got, prefix) {
+ t.Errorf("c.String() = %q want prefix %q", got, prefix)
+ }
+ testDeadline(c, "WithTimeout", t)
+
+ c, _ = WithTimeout(Background(), shortDuration)
+ o := otherContext{c}
+ testDeadline(o, "WithTimeout+otherContext", t)
+
+ c, _ = WithTimeout(Background(), shortDuration)
+ o = otherContext{c}
+ c, _ = WithTimeout(o, veryLongDuration)
+ testDeadline(c, "WithTimeout+otherContext+WithTimeout", t)
+}
+
+func XTestCanceledTimeout(t testingT) {
+ c, _ := WithTimeout(Background(), time.Second)
+ o := otherContext{c}
+ c, cancel := WithTimeout(o, veryLongDuration)
+ cancel() // Should propagate synchronously.
+ select {
+ case <-c.Done():
+ default:
+ t.Errorf("<-c.Done() blocked, but shouldn't have")
+ }
+ if e := c.Err(); e != Canceled {
+ t.Errorf("c.Err() == %v want %v", e, Canceled)
+ }
+}
+
+type key1 int
+type key2 int
+
+var k1 = key1(1)
+var k2 = key2(1) // same int as k1, different type
+var k3 = key2(3) // same type as k2, different int
+
+func XTestValues(t testingT) {
+ check := func(c Context, nm, v1, v2, v3 string) {
+ if v, ok := c.Value(k1).(string); ok == (len(v1) == 0) || v != v1 {
+ t.Errorf(`%s.Value(k1).(string) = %q, %t want %q, %t`, nm, v, ok, v1, len(v1) != 0)
+ }
+ if v, ok := c.Value(k2).(string); ok == (len(v2) == 0) || v != v2 {
+ t.Errorf(`%s.Value(k2).(string) = %q, %t want %q, %t`, nm, v, ok, v2, len(v2) != 0)
+ }
+ if v, ok := c.Value(k3).(string); ok == (len(v3) == 0) || v != v3 {
+ t.Errorf(`%s.Value(k3).(string) = %q, %t want %q, %t`, nm, v, ok, v3, len(v3) != 0)
+ }
+ }
+
+ c0 := Background()
+ check(c0, "c0", "", "", "")
+
+ c1 := WithValue(Background(), k1, "c1k1")
+ check(c1, "c1", "c1k1", "", "")
+
+ if got, want := fmt.Sprint(c1), `context.Background.WithValue(type context.key1, val c1k1)`; got != want {
+ t.Errorf("c.String() = %q want %q", got, want)
+ }
+
+ c2 := WithValue(c1, k2, "c2k2")
+ check(c2, "c2", "c1k1", "c2k2", "")
+
+ c3 := WithValue(c2, k3, "c3k3")
+ check(c3, "c2", "c1k1", "c2k2", "c3k3")
+
+ c4 := WithValue(c3, k1, nil)
+ check(c4, "c4", "", "c2k2", "c3k3")
+
+ o0 := otherContext{Background()}
+ check(o0, "o0", "", "", "")
+
+ o1 := otherContext{WithValue(Background(), k1, "c1k1")}
+ check(o1, "o1", "c1k1", "", "")
+
+ o2 := WithValue(o1, k2, "o2k2")
+ check(o2, "o2", "c1k1", "o2k2", "")
+
+ o3 := otherContext{c4}
+ check(o3, "o3", "", "c2k2", "c3k3")
+
+ o4 := WithValue(o3, k3, nil)
+ check(o4, "o4", "", "c2k2", "")
+}
+
+func XTestAllocs(t testingT, testingShort func() bool, testingAllocsPerRun func(int, func()) float64) {
+ bg := Background()
+ for _, test := range []struct {
+ desc string
+ f func()
+ limit float64
+ gccgoLimit float64
+ }{
+ {
+ desc: "Background()",
+ f: func() { Background() },
+ limit: 0,
+ gccgoLimit: 0,
+ },
+ {
+ desc: fmt.Sprintf("WithValue(bg, %v, nil)", k1),
+ f: func() {
+ c := WithValue(bg, k1, nil)
+ c.Value(k1)
+ },
+ limit: 3,
+ gccgoLimit: 3,
+ },
+ {
+ desc: "WithTimeout(bg, 1*time.Nanosecond)",
+ f: func() {
+ c, _ := WithTimeout(bg, 1*time.Nanosecond)
+ <-c.Done()
+ },
+ limit: 12,
+ gccgoLimit: 15,
+ },
+ {
+ desc: "WithCancel(bg)",
+ f: func() {
+ c, cancel := WithCancel(bg)
+ cancel()
+ <-c.Done()
+ },
+ limit: 5,
+ gccgoLimit: 8,
+ },
+ {
+ desc: "WithTimeout(bg, 5*time.Millisecond)",
+ f: func() {
+ c, cancel := WithTimeout(bg, 5*time.Millisecond)
+ cancel()
+ <-c.Done()
+ },
+ limit: 8,
+ gccgoLimit: 25,
+ },
+ } {
+ limit := test.limit
+ if runtime.Compiler == "gccgo" {
+ // gccgo does not yet do escape analysis.
+ // TODO(iant): Remove this when gccgo does do escape analysis.
+ limit = test.gccgoLimit
+ }
+ numRuns := 100
+ if testingShort() {
+ numRuns = 10
+ }
+ if n := testingAllocsPerRun(numRuns, test.f); n > limit {
+ t.Errorf("%s allocs = %f want %d", test.desc, n, int(limit))
+ }
+ }
+}
+
+func XTestSimultaneousCancels(t testingT) {
+ root, cancel := WithCancel(Background())
+ m := map[Context]CancelFunc{root: cancel}
+ q := []Context{root}
+ // Create a tree of contexts.
+ for len(q) != 0 && len(m) < 100 {
+ parent := q[0]
+ q = q[1:]
+ for i := 0; i < 4; i++ {
+ ctx, cancel := WithCancel(parent)
+ m[ctx] = cancel
+ q = append(q, ctx)
+ }
+ }
+ // Start all the cancels in a random order.
+ var wg sync.WaitGroup
+ wg.Add(len(m))
+ for _, cancel := range m {
+ go func(cancel CancelFunc) {
+ cancel()
+ wg.Done()
+ }(cancel)
+ }
+
+ d := quiescent(t)
+ stuck := make(chan struct{})
+ timer := time.AfterFunc(d, func() { close(stuck) })
+ defer timer.Stop()
+
+ // Wait on all the contexts in a random order.
+ for ctx := range m {
+ select {
+ case <-ctx.Done():
+ case <-stuck:
+ buf := make([]byte, 10<<10)
+ n := runtime.Stack(buf, true)
+ t.Fatalf("timed out after %v waiting for <-ctx.Done(); stacks:\n%s", d, buf[:n])
+ }
+ }
+ // Wait for all the cancel functions to return.
+ done := make(chan struct{})
+ go func() {
+ wg.Wait()
+ close(done)
+ }()
+ select {
+ case <-done:
+ case <-stuck:
+ buf := make([]byte, 10<<10)
+ n := runtime.Stack(buf, true)
+ t.Fatalf("timed out after %v waiting for cancel functions; stacks:\n%s", d, buf[:n])
+ }
+}
+
+func XTestInterlockedCancels(t testingT) {
+ parent, cancelParent := WithCancel(Background())
+ child, cancelChild := WithCancel(parent)
+ go func() {
+ parent.Done()
+ cancelChild()
+ }()
+ cancelParent()
+ d := quiescent(t)
+ timer := time.NewTimer(d)
+ defer timer.Stop()
+ select {
+ case <-child.Done():
+ case <-timer.C:
+ buf := make([]byte, 10<<10)
+ n := runtime.Stack(buf, true)
+ t.Fatalf("timed out after %v waiting for child.Done(); stacks:\n%s", d, buf[:n])
+ }
+}
+
+func XTestLayersCancel(t testingT) {
+ testLayers(t, time.Now().UnixNano(), false)
+}
+
+func XTestLayersTimeout(t testingT) {
+ testLayers(t, time.Now().UnixNano(), true)
+}
+
+func testLayers(t testingT, seed int64, testTimeout bool) {
+ t.Parallel()
+
+ r := rand.New(rand.NewSource(seed))
+ errorf := func(format string, a ...interface{}) {
+ t.Errorf(fmt.Sprintf("seed=%d: %s", seed, format), a...)
+ }
+ const (
+ minLayers = 30
+ )
+ type value int
+ var (
+ vals []*value
+ cancels []CancelFunc
+ numTimers int
+ ctx = Background()
+ )
+ for i := 0; i < minLayers || numTimers == 0 || len(cancels) == 0 || len(vals) == 0; i++ {
+ switch r.Intn(3) {
+ case 0:
+ v := new(value)
+ ctx = WithValue(ctx, v, v)
+ vals = append(vals, v)
+ case 1:
+ var cancel CancelFunc
+ ctx, cancel = WithCancel(ctx)
+ cancels = append(cancels, cancel)
+ case 2:
+ var cancel CancelFunc
+ d := veryLongDuration
+ if testTimeout {
+ d = shortDuration
+ }
+ ctx, cancel = WithTimeout(ctx, d)
+ cancels = append(cancels, cancel)
+ numTimers++
+ }
+ }
+ checkValues := func(when string) {
+ for _, key := range vals {
+ if val := ctx.Value(key).(*value); key != val {
+ errorf("%s: ctx.Value(%p) = %p want %p", when, key, val, key)
+ }
+ }
+ }
+ if !testTimeout {
+ select {
+ case <-ctx.Done():
+ errorf("ctx should not be canceled yet")
+ default:
+ }
+ }
+ if s, prefix := fmt.Sprint(ctx), "context.Background."; !strings.HasPrefix(s, prefix) {
+ t.Errorf("ctx.String() = %q want prefix %q", s, prefix)
+ }
+ t.Log(ctx)
+ checkValues("before cancel")
+ if testTimeout {
+ d := quiescent(t)
+ timer := time.NewTimer(d)
+ defer timer.Stop()
+ select {
+ case <-ctx.Done():
+ case <-timer.C:
+ errorf("ctx should have timed out after %v", d)
+ }
+ checkValues("after timeout")
+ } else {
+ cancel := cancels[r.Intn(len(cancels))]
+ cancel()
+ select {
+ case <-ctx.Done():
+ default:
+ errorf("ctx should be canceled")
+ }
+ checkValues("after cancel")
+ }
+}
+
+func XTestCancelRemoves(t testingT) {
+ checkChildren := func(when string, ctx Context, want int) {
+ if got := len(ctx.(*cancelCtx).children); got != want {
+ t.Errorf("%s: context has %d children, want %d", when, got, want)
+ }
+ }
+
+ ctx, _ := WithCancel(Background())
+ checkChildren("after creation", ctx, 0)
+ _, cancel := WithCancel(ctx)
+ checkChildren("with WithCancel child ", ctx, 1)
+ cancel()
+ checkChildren("after canceling WithCancel child", ctx, 0)
+
+ ctx, _ = WithCancel(Background())
+ checkChildren("after creation", ctx, 0)
+ _, cancel = WithTimeout(ctx, 60*time.Minute)
+ checkChildren("with WithTimeout child ", ctx, 1)
+ cancel()
+ checkChildren("after canceling WithTimeout child", ctx, 0)
+}
+
+func XTestWithCancelCanceledParent(t testingT) {
+ parent, pcancel := WithCancel(Background())
+ pcancel()
+
+ c, _ := WithCancel(parent)
+ select {
+ case <-c.Done():
+ default:
+ t.Errorf("child not done immediately upon construction")
+ }
+ if got, want := c.Err(), Canceled; got != want {
+ t.Errorf("child not cancelled; got = %v, want = %v", got, want)
+ }
+}
+
+func XTestWithValueChecksKey(t testingT) {
+ panicVal := recoveredValue(func() { WithValue(Background(), []byte("foo"), "bar") })
+ if panicVal == nil {
+ t.Error("expected panic")
+ }
+ panicVal = recoveredValue(func() { WithValue(Background(), nil, "bar") })
+ if got, want := fmt.Sprint(panicVal), "nil key"; got != want {
+ t.Errorf("panic = %q; want %q", got, want)
+ }
+}
+
+func XTestInvalidDerivedFail(t testingT) {
+ panicVal := recoveredValue(func() { WithCancel(nil) })
+ if panicVal == nil {
+ t.Error("expected panic")
+ }
+ panicVal = recoveredValue(func() { WithDeadline(nil, time.Now().Add(shortDuration)) })
+ if panicVal == nil {
+ t.Error("expected panic")
+ }
+ panicVal = recoveredValue(func() { WithValue(nil, "foo", "bar") })
+ if panicVal == nil {
+ t.Error("expected panic")
+ }
+}
+
+func recoveredValue(fn func()) (v interface{}) {
+ defer func() { v = recover() }()
+ fn()
+ return
+}
+
+func XTestDeadlineExceededSupportsTimeout(t testingT) {
+ i, ok := DeadlineExceeded.(interface {
+ Timeout() bool
+ })
+ if !ok {
+ t.Fatal("DeadlineExceeded does not support Timeout interface")
+ }
+ if !i.Timeout() {
+ t.Fatal("wrong value for timeout")
+ }
+}
+
+type myCtx struct {
+ Context
+}
+
+type myDoneCtx struct {
+ Context
+}
+
+func (d *myDoneCtx) Done() <-chan struct{} {
+ c := make(chan struct{})
+ return c
+}
+
+func XTestCustomContextGoroutines(t testingT) {
+ g := atomic.LoadInt32(&goroutines)
+ checkNoGoroutine := func() {
+ t.Helper()
+ now := atomic.LoadInt32(&goroutines)
+ if now != g {
+ t.Fatalf("%d goroutines created", now-g)
+ }
+ }
+ checkCreatedGoroutine := func() {
+ t.Helper()
+ now := atomic.LoadInt32(&goroutines)
+ if now != g+1 {
+ t.Fatalf("%d goroutines created, want 1", now-g)
+ }
+ g = now
+ }
+
+ _, cancel0 := WithCancel(&myDoneCtx{Background()})
+ cancel0()
+ checkCreatedGoroutine()
+
+ _, cancel0 = WithTimeout(&myDoneCtx{Background()}, veryLongDuration)
+ cancel0()
+ checkCreatedGoroutine()
+
+ checkNoGoroutine()
+ defer checkNoGoroutine()
+
+ ctx1, cancel1 := WithCancel(Background())
+ defer cancel1()
+ checkNoGoroutine()
+
+ ctx2 := &myCtx{ctx1}
+ ctx3, cancel3 := WithCancel(ctx2)
+ defer cancel3()
+ checkNoGoroutine()
+
+ _, cancel3b := WithCancel(&myDoneCtx{ctx2})
+ defer cancel3b()
+ checkCreatedGoroutine() // ctx1 is not providing Done, must not be used
+
+ ctx4, cancel4 := WithTimeout(ctx3, veryLongDuration)
+ defer cancel4()
+ checkNoGoroutine()
+
+ ctx5, cancel5 := WithCancel(ctx4)
+ defer cancel5()
+ checkNoGoroutine()
+
+ cancel5()
+ checkNoGoroutine()
+
+ _, cancel6 := WithTimeout(ctx5, veryLongDuration)
+ defer cancel6()
+ checkNoGoroutine()
+
+ // Check applied to cancelled context.
+ cancel6()
+ cancel1()
+ _, cancel7 := WithCancel(ctx5)
+ defer cancel7()
+ checkNoGoroutine()
+}
diff --git a/src/context/example_test.go b/src/context/example_test.go
new file mode 100644
index 0000000..72ac5d2
--- /dev/null
+++ b/src/context/example_test.go
@@ -0,0 +1,120 @@
+// Copyright 2016 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 context_test
+
+import (
+ "context"
+ "fmt"
+ "time"
+)
+
+const shortDuration = 1 * time.Millisecond // a reasonable duration to block in an example
+
+// This example demonstrates the use of a cancelable context to prevent a
+// goroutine leak. By the end of the example function, the goroutine started
+// by gen will return without leaking.
+func ExampleWithCancel() {
+ // gen generates integers in a separate goroutine and
+ // sends them to the returned channel.
+ // The callers of gen need to cancel the context once
+ // they are done consuming generated integers not to leak
+ // the internal goroutine started by gen.
+ gen := func(ctx context.Context) <-chan int {
+ dst := make(chan int)
+ n := 1
+ go func() {
+ for {
+ select {
+ case <-ctx.Done():
+ return // returning not to leak the goroutine
+ case dst <- n:
+ n++
+ }
+ }
+ }()
+ return dst
+ }
+
+ ctx, cancel := context.WithCancel(context.Background())
+ defer cancel() // cancel when we are finished consuming integers
+
+ for n := range gen(ctx) {
+ fmt.Println(n)
+ if n == 5 {
+ break
+ }
+ }
+ // Output:
+ // 1
+ // 2
+ // 3
+ // 4
+ // 5
+}
+
+// This example passes a context with an arbitrary deadline to tell a blocking
+// function that it should abandon its work as soon as it gets to it.
+func ExampleWithDeadline() {
+ d := time.Now().Add(shortDuration)
+ ctx, cancel := context.WithDeadline(context.Background(), d)
+
+ // Even though ctx will be expired, it is good practice to call its
+ // cancellation function in any case. Failure to do so may keep the
+ // context and its parent alive longer than necessary.
+ defer cancel()
+
+ select {
+ case <-time.After(1 * time.Second):
+ fmt.Println("overslept")
+ case <-ctx.Done():
+ fmt.Println(ctx.Err())
+ }
+
+ // Output:
+ // context deadline exceeded
+}
+
+// This example passes a context with a timeout to tell a blocking function that
+// it should abandon its work after the timeout elapses.
+func ExampleWithTimeout() {
+ // Pass a context with a timeout to tell a blocking function that it
+ // should abandon its work after the timeout elapses.
+ ctx, cancel := context.WithTimeout(context.Background(), shortDuration)
+ defer cancel()
+
+ select {
+ case <-time.After(1 * time.Second):
+ fmt.Println("overslept")
+ case <-ctx.Done():
+ fmt.Println(ctx.Err()) // prints "context deadline exceeded"
+ }
+
+ // Output:
+ // context deadline exceeded
+}
+
+// This example demonstrates how a value can be passed to the context
+// and also how to retrieve it if it exists.
+func ExampleWithValue() {
+ type favContextKey string
+
+ f := func(ctx context.Context, k favContextKey) {
+ if v := ctx.Value(k); v != nil {
+ fmt.Println("found value:", v)
+ return
+ }
+ fmt.Println("key not found:", k)
+ }
+
+ k := favContextKey("language")
+ ctx := context.WithValue(context.Background(), k, "Go")
+
+ f(ctx, k)
+ f(ctx, favContextKey("color"))
+
+ // Output:
+ // found value: Go
+ // key not found: color
+}
diff --git a/src/context/net_test.go b/src/context/net_test.go
new file mode 100644
index 0000000..a007689
--- /dev/null
+++ b/src/context/net_test.go
@@ -0,0 +1,21 @@
+// Copyright 2016 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 context_test
+
+import (
+ "context"
+ "net"
+ "testing"
+)
+
+func TestDeadlineExceededIsNetError(t *testing.T) {
+ err, ok := context.DeadlineExceeded.(net.Error)
+ if !ok {
+ t.Fatal("DeadlineExceeded does not implement net.Error")
+ }
+ if !err.Timeout() || !err.Temporary() {
+ t.Fatalf("Timeout() = %v, Temporary() = %v, want true, true", err.Timeout(), err.Temporary())
+ }
+}
diff --git a/src/context/x_test.go b/src/context/x_test.go
new file mode 100644
index 0000000..00eca72
--- /dev/null
+++ b/src/context/x_test.go
@@ -0,0 +1,31 @@
+// Copyright 2016 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 context_test
+
+import (
+ . "context"
+ "testing"
+)
+
+func TestBackground(t *testing.T) { XTestBackground(t) }
+func TestTODO(t *testing.T) { XTestTODO(t) }
+func TestWithCancel(t *testing.T) { XTestWithCancel(t) }
+func TestParentFinishesChild(t *testing.T) { XTestParentFinishesChild(t) }
+func TestChildFinishesFirst(t *testing.T) { XTestChildFinishesFirst(t) }
+func TestDeadline(t *testing.T) { XTestDeadline(t) }
+func TestTimeout(t *testing.T) { XTestTimeout(t) }
+func TestCanceledTimeout(t *testing.T) { XTestCanceledTimeout(t) }
+func TestValues(t *testing.T) { XTestValues(t) }
+func TestAllocs(t *testing.T) { XTestAllocs(t, testing.Short, testing.AllocsPerRun) }
+func TestSimultaneousCancels(t *testing.T) { XTestSimultaneousCancels(t) }
+func TestInterlockedCancels(t *testing.T) { XTestInterlockedCancels(t) }
+func TestLayersCancel(t *testing.T) { XTestLayersCancel(t) }
+func TestLayersTimeout(t *testing.T) { XTestLayersTimeout(t) }
+func TestCancelRemoves(t *testing.T) { XTestCancelRemoves(t) }
+func TestWithCancelCanceledParent(t *testing.T) { XTestWithCancelCanceledParent(t) }
+func TestWithValueChecksKey(t *testing.T) { XTestWithValueChecksKey(t) }
+func TestInvalidDerivedFail(t *testing.T) { XTestInvalidDerivedFail(t) }
+func TestDeadlineExceededSupportsTimeout(t *testing.T) { XTestDeadlineExceededSupportsTimeout(t) }
+func TestCustomContextGoroutines(t *testing.T) { XTestCustomContextGoroutines(t) }
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-16 04:40:31 +0000