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Merge pull request #547 from alrs/util
Move zenhack.net/go/util into go-capnp repository
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,2 @@ | ||
| This directory contains misc. Go utility packages that Ian Denhardt wrote as he | ||
| needed them for other projects. |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,14 @@ | ||
| package util | ||
|
|
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| // Chkfatal panics if err is not nil | ||
| func Chkfatal(err error) { | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| } | ||
|
|
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| // Must panics if err != nil, otherwise returns value. | ||
| func Must[T any](value T, err error) T { | ||
| Chkfatal(err) | ||
| return value | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,18 @@ | ||
| package util | ||
|
|
||
| import ( | ||
| "errors" | ||
| "testing" | ||
|
|
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| "github.com/stretchr/testify/assert" | ||
| ) | ||
|
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| func TestChkfatal(t *testing.T) { | ||
| assert.NotPanics(t, func() { | ||
| Chkfatal(nil) | ||
| }, "Chkfatal does not panic on a nil error.") | ||
|
|
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| assert.Panics(t, func() { | ||
| Chkfatal(errors.New("Some error.")) | ||
| }, "Chkfatal panics on a non-nil error.") | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,13 @@ | ||
| // Package debugging exports various helpers useful when debugging. In general, | ||
| // code from this package should not be included in production builds. | ||
| package debugging | ||
|
|
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| import "runtime" | ||
|
|
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| // Wrapper around runtime.Stack, which allocates a buffer and returns the stack | ||
| // trace as a string. Stack traces over 1MB will be truncated. | ||
| func StackString(all bool) string { | ||
| var buf [1e6]byte | ||
| n := runtime.Stack(buf[:], all) | ||
| return string(buf[:n]) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,41 @@ | ||
| // Package deferred provides tools for deferring actions | ||
| // to be run at a later time. These can be thought of as | ||
| // an extension and generalization of the language's built-in | ||
| // defer statement. | ||
| package deferred | ||
|
|
||
| // A Queue is a queue of actions to run at some later time. | ||
| // The actions will be run in the order they are added with | ||
| // Defer. Note that this is different from the language's | ||
| // built-in defer statement, which runs actions in reverse | ||
| // order (future versions of this package may add a Stack | ||
| // type to support those semantics). | ||
| // | ||
| // The zero value is an empty queue. | ||
| // | ||
| // The advantage of this vs. built-in defer is that it needn't | ||
| // be tied to the scope of a single function; for example, | ||
| // you can write code like: | ||
| // | ||
| // q := &Queue{} | ||
| // defer q.Run() | ||
| // f(q) // pass the queue to a subroutine, which may queue | ||
| // // up actions to be run after *this* function returns. | ||
| type Queue []func() | ||
|
|
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| // Run runs all deferred actions, in the order they were added. | ||
| func (q *Queue) Run() { | ||
| funcs := *q | ||
| for i, f := range funcs { | ||
| if f != nil { | ||
| f() | ||
| funcs[i] = nil | ||
| } | ||
| } | ||
| } | ||
|
|
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| // Defer adds f to the list of functions to call when Run() | ||
| // is invoked. | ||
| func (q *Queue) Defer(f func()) { | ||
| *q = append(*q, f) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,95 @@ | ||
| // Package exn provides an exception-like mechanism. | ||
| // | ||
| // It is a bit easier to reason about than standard exceptions, since | ||
| // not any code can throw, only code given access to a throw callback. | ||
| // See the docs for Try. | ||
| package exn | ||
|
|
||
| // exn is a wrapper type used to distinguish values this package passes | ||
| // to panic() from anything else that might be passed to panic by | ||
| // unrelated code. | ||
| type exn struct { | ||
| err error | ||
| } | ||
|
|
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| // An alias for the type of the callback provided by Try. | ||
| type Thrower = func(error, ...string) | ||
|
|
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| // Try invokes f, which is a callback with type: | ||
| // | ||
| // func(throw Thrower) T | ||
| // | ||
| // Thrower is an alias for func(error, ...string). | ||
| // | ||
| // If f returns normally, Try returns the value f returned and a nil | ||
| // error. | ||
| // | ||
| // If f invokes throw with a non-nil error, f's execution is | ||
| // terminated, and Try returns the zero value for T and the | ||
| // error that was passed to throw. | ||
| // | ||
| // If f invokes throw with a nil argument, throw returns normally | ||
| // without terminating f. This is so that error handling code can | ||
| // pass errors to throw unconditionally, like: | ||
| // | ||
| // v, err := foo() | ||
| // throw(err) | ||
| // | ||
| // f must not store throw or otherwise cause it to be invoked after | ||
| // Try returns. | ||
| // | ||
| // Callers may pass additonal string arguments to throw, which will | ||
| // wrap the error with additional context, i.e. throw(err, "something") | ||
| // is equivalent to throw(Wrap("something", err)) | ||
| func Try[T any](f func(Thrower) T) (result T, err error) { | ||
| throw := func(e error, context ...string) { | ||
| if e == nil { | ||
| return | ||
| } | ||
| for i := len(context) - 1; i >= 0; i-- { | ||
| e = Wrap(context[i], e) | ||
| } | ||
| panic(exn{err: e}) | ||
| } | ||
| finishedCall := false | ||
| defer func() { | ||
| if finishedCall { | ||
| return | ||
| } | ||
|
|
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| panicVal := recover() | ||
| if e, ok := panicVal.(exn); ok { | ||
| err = e.err | ||
| } else { | ||
| panic(panicVal) | ||
| } | ||
| }() | ||
| result = f(throw) | ||
| finishedCall = true | ||
| return | ||
| } | ||
|
|
||
| // Try0 is like Try, but f does not return a value, and Try0 only returns | ||
| // an error. | ||
| func Try0(f func(Thrower)) error { | ||
| _, err := Try(func(throw Thrower) struct{} { | ||
| f(throw) | ||
| return struct{}{} | ||
| }) | ||
| return err | ||
| } | ||
|
|
||
| // Try2 is like Try, but with two values instead of 1. | ||
| func Try2[A, B any](f func(Thrower) (A, B)) (A, B, error) { | ||
| r, err := Try(func(throw Thrower) pair[A, B] { | ||
| a, b := f(throw) | ||
| return pair[A, B]{a: a, b: b} | ||
| }) | ||
| return r.a, r.b, err | ||
| } | ||
|
|
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| // TODO: move into its own package. | ||
| type pair[A, B any] struct { | ||
| a A | ||
| b B | ||
| } |
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