1 files changed, 79 insertions, 0 deletions
diff --git a/xpcom/base/nsGZFileWriter.h b/xpcom/base/nsGZFileWriter.h
new file mode 100644
index 0000000000..dc33b4a2de
--- /dev/null
+++ b/xpcom/base/nsGZFileWriter.h
@@ -0,0 +1,79 @@
+/* -*- 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 nsGZFileWriter_h
+#define nsGZFileWriter_h
+
+#include "nsISupportsImpl.h"
+#include "zlib.h"
+#include "nsDependentString.h"
+#include <stdio.h>
+
+/**
+ * A simple class for writing to a .gz file.
+ *
+ * Note that the file that this interface produces has a different format than
+ * what you'd get if you compressed your data as a gzip stream and dumped the
+ * result to a file.
+ *
+ * The standard gunzip tool cannot decompress a raw gzip stream, but can handle
+ * the files produced by this interface.
+ */
+class nsGZFileWriter final {
+  virtual ~nsGZFileWriter();
+
+ public:
+  enum Operation { Append, Create };
+
+  explicit nsGZFileWriter(Operation aMode = Create);
+
+  NS_INLINE_DECL_REFCOUNTING(nsGZFileWriter)
+
+  /**
+   * Initialize this object.  We'll write our gzip'ed data to the given file,
+   * overwriting its contents if the file exists.
+   *
+   * Init() will return an error if called twice.  It's an error to call any
+   * other method on this interface without first calling Init().
+   */
+  [[nodiscard]] nsresult Init(nsIFile* aFile);
+
+  /**
+   * Alternate version of Init() for use when the file is already opened;
+   * e.g., with a FileDescriptor passed over IPC.
+   */
+  [[nodiscard]] nsresult InitANSIFileDesc(FILE* aFile);
+
+  /**
+   * Write the given string to the file.
+   */
+  [[nodiscard]] nsresult Write(const nsACString& aStr);
+
+  /**
+   * Write |length| bytes of |str| to the file.
+   */
+  [[nodiscard]] nsresult Write(const char* aStr, uint32_t aLen) {
+    return Write(nsDependentCSubstring(aStr, aLen));
+  }
+
+  /**
+   * Close this nsGZFileWriter. This method will be run when the underlying
+   * object is destroyed, so it's not strictly necessary to explicitly call it
+   * from your code.
+   *
+   * It's an error to call this method twice, and it's an error to call Write()
+   * after Finish() has been called.
+   */
+  nsresult Finish();
+
+ private:
+  Operation mMode;
+  bool mInitialized;
+  bool mFinished;
+  gzFile mGZFile;
+};
+
+#endif