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async_hooks: clean up comments
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With some of the recent work, some of the comments were no longer
representative of the code, or were otherwise unclear. This commit
fixes some obvious issues I found.

Ref: 83e5215
Ref: 0784b04
PR-URL: #18467
Reviewed-By: Andreas Madsen <amwebdk@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
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ofrobots authored and MylesBorins committed Feb 21, 2018
1 parent da0d776 commit 0865d11
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Showing 2 changed files with 14 additions and 13 deletions.
23 changes: 12 additions & 11 deletions lib/internal/async_hooks.js
Original file line number Diff line number Diff line change
Expand Up @@ -11,27 +11,28 @@ const async_wrap = process.binding('async_wrap');
* the various asynchronous states of the application. These are:
* kExecutionAsyncId: The async_id assigned to the resource responsible for the
* current execution stack.
* kTriggerAsyncId: The trigger_async_id of the resource responsible for
* the current execution stack.
* kTriggerAsyncId: The async_id of the resource that caused (or 'triggered')
* the resource corresponding to the current execution stack.
* kAsyncIdCounter: Incremental counter tracking the next assigned async_id.
* kDefaultTriggerAsyncId: Written immediately before a resource's constructor
* that sets the value of the init()'s triggerAsyncId. The order of
* retrieving the triggerAsyncId value is passing directly to the
* constructor -> value set in kDefaultTriggerAsyncId -> executionAsyncId of
* the current resource.
* that sets the value of the init()'s triggerAsyncId. The precedence order
* of retrieving the triggerAsyncId value is:
* 1. the value passed directly to the constructor
* 2. value set in kDefaultTriggerAsyncId
* 3. executionAsyncId of the current resource.
*
* async_ids_fast_stack is a Float64Array that contains part of the async ID
* async_ids_stack is a Float64Array that contains part of the async ID
* stack. Each pushAsyncIds() call adds two doubles to it, and each
* popAsyncIds() call removes two doubles from it.
* It has a fixed size, so if that is exceeded, calls to the native
* side are used instead in pushAsyncIds() and popAsyncIds().
*/
const { async_id_symbol, async_hook_fields, async_id_fields } = async_wrap;
// Store the pair executionAsyncId and triggerAsyncId in a std::stack on
// Environment::AsyncHooks::ids_stack_ tracks the resource responsible for the
// current execution stack. This is unwound as each resource exits. In the case
// of a fatal exception this stack is emptied after calling each hook's after()
// callback.
// Environment::AsyncHooks::async_ids_stack_ tracks the resource responsible for
// the current execution stack. This is unwound as each resource exits. In the
// case of a fatal exception this stack is emptied after calling each hook's
// after() callback.
const { pushAsyncIds: pushAsyncIds_, popAsyncIds: popAsyncIds_ } = async_wrap;
// For performance reasons, only track Promises when a hook is enabled.
const { enablePromiseHook, disablePromiseHook } = async_wrap;
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4 changes: 2 additions & 2 deletions src/async_wrap.cc
Original file line number Diff line number Diff line change
Expand Up @@ -532,12 +532,12 @@ void AsyncWrap::Initialize(Local<Object> target,
// this way to allow JS and C++ to read/write each value as quickly as
// possible. The fields are represented as follows:
//
// kAsyncUid: Maintains the state of the next unique id to be assigned.
// kAsyncIdCounter: Maintains the state of the next unique id to be assigned.
//
// kDefaultTriggerAsyncId: Write the id of the resource responsible for a
// handle's creation just before calling the new handle's constructor.
// After the new handle is constructed kDefaultTriggerAsyncId is set back
// to 0.
// to -1.
FORCE_SET_TARGET_FIELD(target,
"async_id_fields",
env->async_hooks()->async_id_fields().GetJSArray());
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