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This article covers features introduced in SpiderMonkey 31
Set a callback function that is automatically called periodically while JavaScript code runs.
Syntax
JSInterruptCallback JS_SetInterruptCallback(JSRuntime *rt, JSInterruptCallback callback); JSInterruptCallback JS_GetInterruptCallback(JSRuntime *rt); void JS_RequestInterruptCallback(JSRuntime *rt);
Name | Type | Description |
---|---|---|
rt |
* |
The runtime. |
callback |
JSInterruptCallback |
The callback function to install. |
Callback syntax
bool (* JSInterruptCallback)(JSContext *cx);
Name | Type | Description |
---|---|---|
cx |
|
Pointer to a Provides request. In |
Description
These functions allow setting an interrupt callback that will be called from the JS thread some time after any thread triggered the callback using JS_RequestInterruptCallback
.
To schedule the GC and for other activities the engine internally triggers interrupt callbacks. The embedding should thus not rely on callbacks being triggered through the external API only.
Important note: Additional callbacks can occur inside the callback handler if it re-enters the JS engine. The embedding must ensure that the callback is disconnected before attempting such re-entry.
JS_SetInterruptCallback
sets a callback that can be called asynchronously. Some common uses for an interrupt callback are:
- To run garbage collection periodically, by calling
;JS_MaybeGC
- To periodically take a break from script execution to update the UI (though note that Mozilla does not do this, by design);
- To enforce application limits on the amount of time a script may run. (In this case, the callback may terminate the script by returning
false
.)
JS_GetInterruptCallback
returns the currently installed interrupt callback, or NULL
if none is currently installed.
JS_RequestInterruptCallback
requests a callback set using JS_SetInterruptCallback
.