Add async queueing methods

README.md

@@ -50,6 +50,16 @@ synonymous.
 If more than one value is supplied, then they will all be added to the queue
 in the order that they are supplied.
 
+### .pushAsync(), .enqueueAsync()
+```javascript
+  for (let item of items) {
+    await s.pushAsync(item);
+  }
+```
+Asynchronous version of `push()` / `enqueue()`, returning a `Promise`. Allows
+for backpressure and feeding the queue at the same rate items are removed from
+it.
+
 ### .shift(), .dequeue()
 ```javascript
 var myValue = s.shift();
@@ -69,6 +79,16 @@ the queue is full, then this method will return an error.
 If more than one value is supplied, then they will all be added to the queue
 in the order that they are supplied.
 
+### .unshiftAsync()
+```javascript
+  for (let item of items) {
+    await s.unshiftAsync(item);
+  }
+```
+Asynchronous version of `unshift()`, returning a `Promise`. Allows
+for backpressure and feeding the queue at the same rate items are removed from
+it.
+
 ### .pop()
 ```javascript
 var myValue = s.pop();

package.json

@@ -1,6 +1,6 @@
 {
   "name": "spique",
-  "version": "2.2.0",
+  "version": "2.3.0",
   "description": "A spiral deque - high performance and dynamic queue size",
   "main": "spique.js",
   "scripts": {

spique.js

@@ -31,6 +31,7 @@ module.exports = class Spique extends events.EventEmitter {
     var spareRing = undefined;
     var rings = 1;
     var items = 0;
+    var pending = new Spique();
 
     // allocate a new ring, or return the spare if available
     function allocateRing() {
@@ -80,6 +81,17 @@ module.exports = class Spique extends events.EventEmitter {
       }
     }
 
+    // push item(s) onto the end of the buffer when there is space available
+    this.enqueueAsync = this.pushAsync = function pushAsync(value) {
+      if (!this.isFull()) {
+        return Promise.resolve(this.push(value));
+      } else {
+        pending.push(() => {
+          return Promise.resolve(this.push(value));
+        });
+      }
+    }
+
     // push item(s) onto the start of the buffer
     this.unshift = function unshift(value) {
       if(items >= maxItems)
@@ -108,6 +120,17 @@ module.exports = class Spique extends events.EventEmitter {
       }
     }
 
+    // push item(s) onto the start of the buffer when there is space available
+    this.unshiftAsync = function unshiftAsync(value) {
+      if (!this.isFull()) {
+        return Promise.resolve(this.unshift(value));
+      } else {
+        pending.push(() => {
+          return Promise.resolve(this.unshift(value));
+        });
+      }
+    }
+
     // pop an item off the end of the buffer
     this.pop = function() {
       var value = lastRing.pop();
@@ -121,8 +144,12 @@ module.exports = class Spique extends events.EventEmitter {
       items--;
       if (items === 0)
         this.emit("empty", this);
-      if (items < maxItems)
-        this.emit("space", this);
+      if (items < maxItems) {
+        while (!this.isFull() && !pending.isEmpty())
+          this.pending.shift()();
+        if (items < maxItems)
+          this.emit("space", this);
+      }
       return value;
     };
 
@@ -139,8 +166,12 @@ module.exports = class Spique extends events.EventEmitter {
       items--;
       if (items === 0)
         this.emit("empty", this);
-      if (items < maxItems)
-        this.emit("space", this);
+      if (items < maxItems) {
+        while (!this.isFull() && !pending.isEmpty())
+          this.pending.shift()();
+        if (items < maxItems)
+          this.emit("space", this);
+      }
       return value;
     };