Bug 1538279 - Extract nsZipArchive's madvise and similar to a helper r=glandium,froydnj

This is just to make it simpler to use PrefetchVirtualMemory in subsequent patches.

Differential Revision: https://phabricator.services.mozilla.com/D26016

--HG--
extra : moz-landing-system : lando

modules/libjar/nsZipArchive.cpp

@@ -20,6 +20,7 @@
 #include "plstr.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/Logging.h"
+#include "mozilla/MemUtils.h"
 #include "mozilla/UniquePtrExtensions.h"
 #include "stdlib.h"
 #include "nsDirectoryService.h"
@@ -650,32 +651,8 @@ nsresult nsZipArchive::BuildFileList(PRFileDesc *aFd) {
       xtolong(startp + centralOffset) == CENTRALSIG) {
     // Success means optimized jar layout from bug 559961 is in effect
     uint32_t readaheadLength = xtolong(startp);
-    if (readaheadLength) {
-#if defined(XP_SOLARIS)
-      posix_madvise(const_cast<uint8_t *>(startp), readaheadLength,
-                    POSIX_MADV_WILLNEED);
-#elif defined(XP_UNIX)
-      madvise(const_cast<uint8_t *>(startp), readaheadLength, MADV_WILLNEED);
-#elif defined(XP_WIN)
-      static auto prefetchVirtualMemory =
-          reinterpret_cast<BOOL(WINAPI *)(HANDLE, ULONG_PTR, PVOID, ULONG)>(
-              GetProcAddress(GetModuleHandle(L"kernel32.dll"),
-                             "PrefetchVirtualMemory"));
-      if (prefetchVirtualMemory) {
-        // Normally, we'd use WIN32_MEMORY_RANGE_ENTRY, but that requires
-        // a different _WIN32_WINNT value before including windows.h, but
-        // that causes complications with unified sources. It's a simple
-        // enough struct anyways.
-        struct {
-          PVOID VirtualAddress;
-          SIZE_T NumberOfBytes;
-        } entry;
-        entry.VirtualAddress = const_cast<uint8_t *>(startp);
-        entry.NumberOfBytes = readaheadLength;
-        prefetchVirtualMemory(GetCurrentProcess(), 1, &entry, 0);
-      }
-#endif
-    }
+    mozilla::MaybePrefetchMemory(const_cast<uint8_t *>(startp),
+                                 readaheadLength);
   } else {
     for (buf = endp - ZIPEND_SIZE; buf > startp; buf--) {
       if (xtolong(buf) == ENDSIG) {

xpcom/glue/MemUtils.cpp

@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/MemUtils.h"
+
+#if defined(XP_WIN)
+#  include <windows.h>
+#else
+#  include <sys/mman.h>
+#endif
+
+bool mozilla::MaybePrefetchMemory(uint8_t* aStart, size_t aNumBytes) {
+  if (aNumBytes == 0) {
+    return true;
+  }
+
+#if defined(XP_SOLARIS)
+  posix_madvise(aStart, aNumBytes, POSIX_MADV_WILLNEED);
+  return true;
+#elif defined(XP_UNIX)
+  madvise(aStart, aNumBytes, MADV_WILLNEED);
+  return true;
+#elif defined(XP_WIN)
+  static auto prefetchVirtualMemory =
+      reinterpret_cast<BOOL(WINAPI*)(HANDLE, ULONG_PTR, PVOID, ULONG)>(
+          GetProcAddress(GetModuleHandleW(L"kernel32.dll"),
+                         "PrefetchVirtualMemory"));
+
+  if (prefetchVirtualMemory) {
+    // Normally, we'd use WIN32_MEMORY_RANGE_ENTRY, but that requires
+    // a different _WIN32_WINNT value before including windows.h, but
+    // that causes complications with unified sources. It's a simple
+    // enough struct anyways.
+    struct {
+      PVOID VirtualAddress;
+      SIZE_T NumberOfBytes;
+    } entry;
+    entry.VirtualAddress = aStart;
+    entry.NumberOfBytes = aNumBytes;
+    prefetchVirtualMemory(GetCurrentProcess(), 1, &entry, 0);
+    return true;
+  }
+  return false;
+#else
+  return false;
+#endif
+}

xpcom/glue/MemUtils.h

@@ -0,0 +1,19 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_MemUtils_h
+#define mozilla_MemUtils_h
+
+#include <stddef.h>
+#include <stdint.h>
+
+namespace mozilla {
+
+bool MaybePrefetchMemory(uint8_t* aStart, size_t aNumBytes);
+
+}  // namespace mozilla
+
+#endif

xpcom/glue/moz.build

@@ -8,4 +8,5 @@ DIRS += ['standalone']
 
 EXPORTS.mozilla += [
     'FileUtils.h',
+    'MemUtils.h',
 ]

xpcom/glue/objs.mozbuild

@@ -6,6 +6,7 @@
 
 xpcom_glue_src_lcppsrcs = [
     'FileUtils.cpp',
+    'MemUtils.cpp',
     'XREAppData.cpp',
 ]