Bug 1364768: Part 1 - Add NetUtil.readInputStream helper. r=aswan

MozReview-Commit-ID: IZRvdcIiV4z

--HG--
extra : rebase_source : e209f70d27f32ed0a073b7dc6c07bdcd1cfffdb7

netwerk/base/NetUtil.jsm

@@ -25,6 +25,9 @@ const PR_UINT32_MAX = 0xffffffff;
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 Components.utils.import("resource://gre/modules/Services.jsm");
 
+const BinaryInputStream = Components.Constructor("@mozilla.org/binaryinputstream;1",
+                                                 "nsIBinaryInputStream", "setInputStream");
+
 ////////////////////////////////////////////////////////////////////////////////
 //// NetUtil Object
 
@@ -447,6 +450,43 @@ this.NetUtil = {
         }
     },
 
+    /**
+     * Reads aCount bytes from aInputStream into a string.
+     *
+     * @param {nsIInputStream} aInputStream
+     *        The input stream to read from.
+     * @param {integer} [aCount = aInputStream.available()]
+     *        The number of bytes to read from the stream.
+     *
+     * @return the bytes from the input stream in string form.
+     *
+     * @throws NS_ERROR_INVALID_ARG if aInputStream is not an nsIInputStream.
+     * @throws NS_BASE_STREAM_WOULD_BLOCK if reading from aInputStream would
+     *         block the calling thread (non-blocking mode only).
+     * @throws NS_ERROR_FAILURE if there are not enough bytes available to read
+     *         aCount amount of data.
+     */
+    readInputStream(aInputStream, aCount)
+    {
+        if (!(aInputStream instanceof Ci.nsIInputStream)) {
+            let exception = new Components.Exception(
+                "First argument should be an nsIInputStream",
+                Cr.NS_ERROR_INVALID_ARG,
+                Components.stack.caller
+            );
+            throw exception;
+        }
+
+        if (!aCount) {
+            aCount = aInputStream.available();
+        }
+
+        let stream = new BinaryInputStream(aInputStream);
+        let result = new ArrayBuffer(aCount);
+        stream.readArrayBuffer(result.byteLength, result);
+        return result;
+    },
+
     /**
      * Returns a reference to nsIIOService.
      *