From 17561de5b9402e69dd9cc371a50c655bd2be1fe5 Mon Sep 17 00:00:00 2001
From: Boris Zbarsky <bzbarsky@mit.edu>
Date: Wed, 15 May 2019 18:28:00 +0000
Subject: [PATCH] Bug 1551962.  Add a way to create an input stream from a
 moved nsTArray<uint8_t>.  r=froydnj

Differential Revision: https://phabricator.services.mozilla.com/D31296

--HG--
extra : moz-landing-system : lando
---
 xpcom/io/nsStringStream.cpp | 44 +++++++++++++++++++++++++++++++++++++
 xpcom/io/nsStringStream.h   | 14 +++++++++---
 2 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/xpcom/io/nsStringStream.cpp b/xpcom/io/nsStringStream.cpp
index de9f9212a6c4..eae8d901e875 100644
--- a/xpcom/io/nsStringStream.cpp
+++ b/xpcom/io/nsStringStream.cpp
@@ -22,6 +22,7 @@
 #include "nsIClassInfoImpl.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/ipc/InputStreamUtils.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/ReentrantMonitor.h"
 #include "nsIIPCSerializableInputStream.h"
 #include "XPCOMModule.h"
@@ -54,6 +55,8 @@ class nsStringInputStream final : public nsIStringInputStream,
 
   nsresult Init(nsCString&& aString);
 
+  nsresult Init(nsTArray<uint8_t>&& aArray);
+
  private:
   ~nsStringInputStream() {}
 
@@ -72,12 +75,16 @@ class nsStringInputStream final : public nsIStringInputStream,
   nsDependentCSubstring mData;
   uint32_t mOffset;
 
+  // If we were initialized from an nsTArray, we store its data here.
+  Maybe<nsTArray<uint8_t>> mArray;
+
   mozilla::ReentrantMonitor mMon;
 };
 
 nsresult nsStringInputStream::Init(nsCString&& aString) {
   ReentrantMonitorAutoEnter lock(mMon);
 
+  mArray.reset();
   if (!mData.Assign(std::move(aString), fallible)) {
     return NS_ERROR_OUT_OF_MEMORY;
   }
@@ -86,6 +93,24 @@ nsresult nsStringInputStream::Init(nsCString&& aString) {
   return NS_OK;
 }
 
+nsresult nsStringInputStream::Init(nsTArray<uint8_t>&& aArray) {
+  ReentrantMonitorAutoEnter lock(mMon);
+
+  mArray.reset();
+  mArray.emplace(std::move(aArray));
+  mOffset = 0;
+
+  if (mArray->IsEmpty()) {
+    // Not sure it's safe to Rebind() with a null pointer.  Pretty
+    // sure it's not, in fact.
+    mData.Truncate();
+  } else {
+    mData.Rebind(reinterpret_cast<const char*>(mArray->Elements()),
+                 mArray->Length());
+  }
+  return NS_OK;
+}
+
 // This class needs to support threadsafe refcounting since people often
 // allocate a string stream, and then read it from a background thread.
 NS_IMPL_ADDREF(nsStringInputStream)
@@ -132,6 +157,7 @@ NS_IMETHODIMP
 nsStringInputStream::SetData(const nsACString& aData) {
   ReentrantMonitorAutoEnter lock(mMon);
 
+  mArray.reset();
   if (NS_WARN_IF(!mData.Assign(aData, fallible))) {
     return NS_ERROR_OUT_OF_MEMORY;
   }
@@ -158,6 +184,7 @@ nsStringInputStream::SetData(const char* aData, int32_t aDataLen) {
     return NS_ERROR_INVALID_ARG;
   }
 
+  mArray.reset();
   if (NS_WARN_IF(!mData.Assign(aData, aDataLen, fallible))) {
     return NS_ERROR_OUT_OF_MEMORY;
   }
@@ -173,6 +200,7 @@ nsStringInputStream::AdoptData(char* aData, int32_t aDataLen) {
   if (NS_WARN_IF(!aData)) {
     return NS_ERROR_INVALID_ARG;
   }
+  mArray.reset();
   mData.Adopt(aData, aDataLen);
   mOffset = 0;
   return NS_OK;
@@ -186,6 +214,7 @@ nsStringInputStream::ShareData(const char* aData, int32_t aDataLen) {
     return NS_ERROR_INVALID_ARG;
   }
 
+  mArray.reset();
   if (aDataLen < 0) {
     aDataLen = strlen(aData);
   }
@@ -486,6 +515,21 @@ nsresult NS_NewByteInputStream(nsIInputStream** aStreamResult,
   return NS_OK;
 }
 
+nsresult NS_NewByteInputStream(nsIInputStream** aStreamResult,
+                               nsTArray<uint8_t>&& aArray) {
+  MOZ_ASSERT(aStreamResult, "null out ptr");
+
+  RefPtr<nsStringInputStream> stream = new nsStringInputStream();
+
+  nsresult rv = stream->Init(std::move(aArray));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  stream.forget(aStreamResult);
+  return NS_OK;
+}
+
 nsresult NS_NewCStringInputStream(nsIInputStream** aStreamResult,
                                   const nsACString& aStringToRead) {
   MOZ_ASSERT(aStreamResult, "null out ptr");
diff --git a/xpcom/io/nsStringStream.h b/xpcom/io/nsStringStream.h
index 1fdb35d20a29..b2101b14abac 100644
--- a/xpcom/io/nsStringStream.h
+++ b/xpcom/io/nsStringStream.h
@@ -10,6 +10,7 @@
 #include "nsIStringStream.h"
 #include "nsString.h"
 #include "nsMemory.h"
+#include "nsTArray.h"
 
 /**
  * Implements:
@@ -43,14 +44,21 @@
  * If aAssignment is NS_ASSIGNMENT_ADOPT, then the resulting stream refers
  * directly to the given buffer (aStringToRead) and will free aStringToRead
  * once the stream is closed.
- *
- * If aLength is less than zero, then the length of aStringToRead will be
- * determined by scanning the buffer for the first null byte.
  */
 extern nsresult NS_NewByteInputStream(nsIInputStream** aStreamResult,
                                       mozilla::Span<const char> aStringToRead,
                                       nsAssignmentType aAssignment);
 
+/**
+ * Factory method to get an nsIInputStream from an nsTArray representing a byte
+ * buffer.  This will take ownership of the data and empty out the nsTArray.
+ *
+ * Result will implement nsIStringInputStream, nsITellableStream and
+ * nsISeekableStream.
+ */
+extern nsresult NS_NewByteInputStream(nsIInputStream** aStreamResult,
+                                      nsTArray<uint8_t>&& aArray);
+
 /**
  * Factory method to get an nsInputStream from an nsACString.  Result will
  * implement nsIStringInputStream, nsTellableStream and nsISeekableStream.