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author | Indrajith K L | 2022-12-03 17:00:20 +0530 |
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committer | Indrajith K L | 2022-12-03 17:00:20 +0530 |
commit | f5c4671bfbad96bf346bd7e9a21fc4317b4959df (patch) | |
tree | 2764fc62da58f2ba8da7ed341643fc359873142f /v_windows/v/old/vlib/context/cancel.v | |
download | cli-tools-windows-master.tar.gz cli-tools-windows-master.tar.bz2 cli-tools-windows-master.zip |
Diffstat (limited to 'v_windows/v/old/vlib/context/cancel.v')
-rw-r--r-- | v_windows/v/old/vlib/context/cancel.v | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/v_windows/v/old/vlib/context/cancel.v b/v_windows/v/old/vlib/context/cancel.v new file mode 100644 index 0000000..2972b17 --- /dev/null +++ b/v_windows/v/old/vlib/context/cancel.v @@ -0,0 +1,181 @@ +// This module defines the Context type, which carries deadlines, cancellation signals, +// and other request-scoped values across API boundaries and between processes. +// Based off: https://github.com/golang/go/tree/master/src/context +// Last commit: https://github.com/golang/go/commit/52bf14e0e8bdcd73f1ddfb0c4a1d0200097d3ba2 +module context + +import rand +import sync +import time + +pub interface Canceler { + id string + cancel(remove_from_parent bool, err IError) + done() chan int +} + +pub fn cancel(ctx Context) { + match mut ctx { + CancelContext { + ctx.cancel(true, canceled) + } + TimerContext { + ctx.cancel(true, canceled) + } + else {} + } +} + +// A CancelContext can be canceled. When canceled, it also cancels any children +// that implement Canceler. +pub struct CancelContext { + id string +mut: + context Context + mutex &sync.Mutex + done chan int + children map[string]Canceler + err IError +} + +// with_cancel 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. +pub fn with_cancel(parent Context) Context { + mut c := new_cancel_context(parent) + propagate_cancel(parent, mut c) + return Context(c) +} + +// new_cancel_context returns an initialized CancelContext. +fn new_cancel_context(parent Context) &CancelContext { + return &CancelContext{ + id: rand.uuid_v4() + context: parent + mutex: sync.new_mutex() + done: chan int{cap: 2} + err: none + } +} + +pub fn (ctx CancelContext) deadline() ?time.Time { + return none +} + +pub fn (mut ctx CancelContext) done() chan int { + ctx.mutex.@lock() + done := ctx.done + ctx.mutex.unlock() + return done +} + +pub fn (mut ctx CancelContext) err() IError { + ctx.mutex.@lock() + err := ctx.err + ctx.mutex.unlock() + return err +} + +pub fn (ctx CancelContext) value(key string) ?voidptr { + if key == cancel_context_key { + return voidptr(unsafe { &ctx }) + } + return ctx.context.value(key) +} + +pub fn (ctx CancelContext) str() string { + return context_name(ctx.context) + '.with_cancel' +} + +fn (mut ctx CancelContext) cancel(remove_from_parent bool, err IError) { + if err is none { + panic('context: internal error: missing cancel error') + } + + ctx.mutex.@lock() + if !(ctx.err is none) { + ctx.mutex.unlock() + // already canceled + return + } + + ctx.err = err + + if !ctx.done.closed { + ctx.done <- 0 + ctx.done.close() + } + + for _, child in ctx.children { + // NOTE: acquiring the child's lock while holding parent's lock. + child.cancel(false, err) + } + + ctx.children = map[string]Canceler{} + ctx.mutex.unlock() + + if remove_from_parent { + remove_child(ctx.context, ctx) + } +} + +fn propagate_cancel(parent Context, mut child Canceler) { + done := parent.done() + select { + _ := <-done { + // parent is already canceled + child.cancel(false, parent.err()) + return + } + } + mut p := parent_cancel_context(parent) or { + go fn (parent Context, mut child Canceler) { + pdone := parent.done() + select { + _ := <-pdone { + child.cancel(false, parent.err()) + } + } + }(parent, mut child) + return + } + + if p.err is none { + p.children[child.id] = *child + } else { + // parent has already been canceled + child.cancel(false, p.err) + } +} + +// parent_cancel_context returns the underlying CancelContext for parent. +// It does this by looking up parent.value(&cancel_context_key) to find +// the innermost enclosing CancelContext and then checking whether +// parent.done() matches that CancelContext. (If not, the CancelContext +// has been wrapped in a custom implementation providing a +// different done channel, in which case we should not bypass it.) +fn parent_cancel_context(parent Context) ?CancelContext { + done := parent.done() + if done.closed { + return none + } + if p_ptr := parent.value(cancel_context_key) { + if !isnil(p_ptr) { + mut p := &CancelContext(p_ptr) + pdone := p.done() + if done == pdone { + return *p + } + } + } + return none +} + +// remove_child removes a context from its parent. +fn remove_child(parent Context, child Canceler) { + mut p := parent_cancel_context(parent) or { return } + p.children.delete(child.id) +} |