1 files changed, 140 insertions, 0 deletions
diff --git a/xpcom/glue/FileUtils.h b/xpcom/glue/FileUtils.h
new file mode 100644
index 0000000000..8e66ee5860
--- /dev/null
+++ b/xpcom/glue/FileUtils.h
@@ -0,0 +1,140 @@
+/* -*- 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_FileUtils_h
+#define mozilla_FileUtils_h
+
+#include "nscore.h"  // nullptr
+
+#if defined(XP_UNIX)
+#  include <unistd.h>
+#elif defined(XP_WIN)
+#  include <io.h>
+#endif
+#include "prio.h"
+#include "prlink.h"
+
+#include <memory>  // unique_ptr
+#include "nsIFile.h"
+#include <errno.h>
+#include <limits.h>
+
+namespace mozilla {
+
+#if defined(XP_WIN)
+typedef void* filedesc_t;
+typedef const wchar_t* pathstr_t;
+#else
+typedef int filedesc_t;
+typedef const char* pathstr_t;
+#endif
+
+#if defined(MOZILLA_INTERNAL_API)
+
+struct PRCloseDeleter {
+  void operator()(PRFileDesc* aFd) {
+    if (aFd) {
+      PR_Close(aFd);
+    }
+  }
+};
+using AutoFDClose = UniquePtr<PRFileDesc, PRCloseDeleter>;
+
+/* RAII wrapper for FILE descriptors */
+struct FCloseDeleter {
+  void operator()(FILE* p) {
+    if (p) {
+      fclose(p);
+    }
+  }
+};
+using ScopedCloseFile = UniquePtr<FILE, FCloseDeleter>;
+
+/**
+ * Fallocate efficiently and continuously allocates files via fallocate-type
+ * APIs. This is useful for avoiding fragmentation. On sucess the file be padded
+ * with zeros to grow to aLength.
+ *
+ * @param aFD file descriptor.
+ * @param aLength length of file to grow to.
+ * @return true on success.
+ */
+bool fallocate(PRFileDesc* aFD, int64_t aLength);
+
+/**
+ * Use readahead to preload shared libraries into the file cache before loading.
+ * WARNING: This function should not be used without a telemetry field trial
+ *          demonstrating a clear performance improvement!
+ *
+ * @param aFile nsIFile representing path to shared library
+ */
+void ReadAheadLib(nsIFile* aFile);
+
+/**
+ * Use readahead to preload a file into the file cache before reading.
+ * WARNING: This function should not be used without a telemetry field trial
+ *          demonstrating a clear performance improvement!
+ *
+ * @param aFile nsIFile representing path to shared library
+ * @param aOffset Offset into the file to begin preloading
+ * @param aCount Number of bytes to preload (SIZE_MAX implies file size)
+ * @param aOutFd Pointer to file descriptor. If specified, ReadAheadFile will
+ *        return its internal, opened file descriptor instead of closing it.
+ */
+void ReadAheadFile(nsIFile* aFile, const size_t aOffset = 0,
+                   const size_t aCount = SIZE_MAX,
+                   filedesc_t* aOutFd = nullptr);
+
+/*
+ * Wrappers for PR_GetLibraryName and PR_GetLibraryFilePathname.
+ */
+PathString GetLibraryName(pathstr_t aDirectory, const char* aLib);
+PathString GetLibraryFilePathname(pathstr_t aName, PRFuncPtr aAddr);
+
+#endif  // MOZILLA_INTERNAL_API
+
+/**
+ * Use readahead to preload shared libraries into the file cache before loading.
+ * WARNING: This function should not be used without a telemetry field trial
+ *          demonstrating a clear performance improvement!
+ *
+ * @param aFilePath path to shared library
+ */
+void ReadAheadLib(pathstr_t aFilePath);
+
+/**
+ * Use readahead to preload a file into the file cache before loading.
+ * WARNING: This function should not be used without a telemetry field trial
+ *          demonstrating a clear performance improvement!
+ *
+ * @param aFilePath path to shared library
+ * @param aOffset Offset into the file to begin preloading
+ * @param aCount Number of bytes to preload (SIZE_MAX implies file size)
+ * @param aOutFd Pointer to file descriptor. If specified, ReadAheadFile will
+ *        return its internal, opened file descriptor instead of closing it.
+ */
+void ReadAheadFile(pathstr_t aFilePath, const size_t aOffset = 0,
+                   const size_t aCount = SIZE_MAX,
+                   filedesc_t* aOutFd = nullptr);
+
+/**
+ * Use readahead to preload a file into the file cache before reading.
+ * When this function exits, the file pointer is guaranteed to be in the same
+ * position it was in before this function was called.
+ * WARNING: This function should not be used without a telemetry field trial
+ *          demonstrating a clear performance improvement!
+ *
+ * @param aFd file descriptor opened for read access
+ * (on Windows, file must be opened with FILE_FLAG_SEQUENTIAL_SCAN)
+ * @param aOffset Offset into the file to begin preloading
+ * @param aCount Number of bytes to preload (SIZE_MAX implies file size)
+ */
+void ReadAhead(filedesc_t aFd, const size_t aOffset = 0,
+               const size_t aCount = SIZE_MAX);
+
+}  // namespace mozilla
+
+#endif