From 21cc17196d4c5b38a507570be2e54a7367800686 Mon Sep 17 00:00:00 2001
From: Nathan Froyd <froydnj@mozilla.com>
Date: Thu, 2 Apr 2015 14:22:14 -0400
Subject: [PATCH] Bug 1153259 - use NS_NewByteInputStream in zipwriter to
 reduce do_CreateInstance overhead; r=aklotz

Profiling startup shows that we have several thousand calls to:

  do_CreateInstance("@mozilla.org/io/string-input-stream;1")

and virtually all of them are located in the zipwriter code.  We can
create string input streams much more directly with
NS_NewByteInputStream, which avoids a lot of overhead associated with
do_CreateInstance.
---
 modules/libjar/zipwriter/nsDeflateConverter.cpp | 10 +++++-----
 modules/libjar/zipwriter/nsZipDataStream.cpp    | 10 +++++-----
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/modules/libjar/zipwriter/nsDeflateConverter.cpp b/modules/libjar/zipwriter/nsDeflateConverter.cpp
index 77eb825db2dd..0583b68cef62 100644
--- a/modules/libjar/zipwriter/nsDeflateConverter.cpp
+++ b/modules/libjar/zipwriter/nsDeflateConverter.cpp
@@ -5,7 +5,7 @@
 
 #include "StreamFunctions.h"
 #include "nsDeflateConverter.h"
-#include "nsIStringStream.h"
+#include "nsStringStream.h"
 #include "nsIInputStreamPump.h"
 #include "nsComponentManagerUtils.h"
 #include "nsMemory.h"
@@ -180,12 +180,12 @@ nsresult nsDeflateConverter::PushAvailableData(nsIRequest *aRequest,
     if (bytesToWrite == 0)
         return NS_OK;
 
-    nsresult rv;
-    nsCOMPtr<nsIStringInputStream> stream =
-             do_CreateInstance("@mozilla.org/io/string-input-stream;1", &rv);
+    MOZ_ASSERT(bytesToWrite <= INT32_MAX);
+    nsCOMPtr<nsIInputStream> stream;
+    nsresult rv = NS_NewByteInputStream(getter_AddRefs(stream),
+					(char*)mWriteBuffer, bytesToWrite);
     NS_ENSURE_SUCCESS(rv, rv);
 
-    stream->ShareData((char*)mWriteBuffer, bytesToWrite);
     rv = mListener->OnDataAvailable(aRequest, mContext, stream, mOffset,
                                     bytesToWrite);
 
diff --git a/modules/libjar/zipwriter/nsZipDataStream.cpp b/modules/libjar/zipwriter/nsZipDataStream.cpp
index f7fcb622a58f..d885c7197b2a 100644
--- a/modules/libjar/zipwriter/nsZipDataStream.cpp
+++ b/modules/libjar/zipwriter/nsZipDataStream.cpp
@@ -5,7 +5,7 @@
 
 #include "StreamFunctions.h"
 #include "nsZipDataStream.h"
-#include "nsIStringStream.h"
+#include "nsStringStream.h"
 #include "nsISeekableStream.h"
 #include "nsDeflateConverter.h"
 #include "nsNetUtil.h"
@@ -138,12 +138,12 @@ nsresult nsZipDataStream::ProcessData(nsIRequest *aRequest,
                           reinterpret_cast<const unsigned char*>(aBuffer),
                           aCount);
 
-    nsresult rv;
-    nsCOMPtr<nsIStringInputStream> stream =
-             do_CreateInstance("@mozilla.org/io/string-input-stream;1", &rv);
+    MOZ_ASSERT(aCount <= INT32_MAX);
+    nsCOMPtr<nsIInputStream> stream;
+    nsresult rv = NS_NewByteInputStream(getter_AddRefs(stream),
+					aBuffer, aCount);
     NS_ENSURE_SUCCESS(rv, rv);
 
-    stream->ShareData(aBuffer, aCount);
     rv = mOutput->OnDataAvailable(aRequest, aContext, stream, aOffset, aCount);
     mHeader->mUSize += aCount;