scratch-vm/src/engine/thread.js

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/**
* A thread is a running stack context and all the metadata needed.
* @param {?string} firstBlock First block to execute in the thread.
* @constructor
*/
function Thread (firstBlock) {
/**
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* ID of top block of the thread
* @type {!string}
*/
this.topBlock = firstBlock;
/**
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* ID of next block that the thread will execute, or null if none.
* @type {?string}
*/
this.nextBlock = firstBlock;
/**
* Stack for the thread. When the sequencer enters a control structure,
* the block is pushed onto the stack so we know where to exit.
* @type {Array.<string>}
*/
this.stack = [];
/**
* Status of the thread, one of three states (below)
* @type {number}
*/
this.status = 0; /* Thread.STATUS_RUNNING */
/**
* Yield timer ID (for checking when the thread should unyield).
* @type {number}
*/
this.yieldTimerId = -1;
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}
/**
* Thread status for initialized or running thread.
* Threads are in this state when the primitive is called for the first time.
* @const
*/
Thread.STATUS_RUNNING = 0;
/**
* Thread status for a yielded thread.
* Threads are in this state when a primitive has yielded.
* @const
*/
Thread.STATUS_YIELD = 1;
/**
* Thread status for a finished/done thread.
* Thread is moved to this state when the interpreter
* can proceed with execution.
* @const
*/
Thread.STATUS_DONE = 2;
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module.exports = Thread;