xpcom/base/nsGZFileWriter.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef nsGZFileWriter_h
   8 #define nsGZFileWriter_h
   9
  10 #include "nsISupportsImpl.h"
  11 #include "zlib.h"
  12 #include "nsDependentString.h"
  13 #include <stdio.h>
  14
  15 /**
  16  * A simple class for writing to a .gz file.
  17  *
  18  * Note that the file that this interface produces has a different format than
  19  * what you'd get if you compressed your data as a gzip stream and dumped the
  20  * result to a file.
  21  *
  22  * The standard gunzip tool cannot decompress a raw gzip stream, but can handle
  23  * the files produced by this interface.
  24  */
  25 class nsGZFileWriter final {
  26   virtual ~nsGZFileWriter();
  27
  28  public:
  29   explicit nsGZFileWriter();
  30
  31   NS_INLINE_DECL_REFCOUNTING(nsGZFileWriter)
  32
  33   /**
  34    * Initialize this object.  We'll write our gzip'ed data to the given file,
  35    * overwriting its contents if the file exists.
  36    *
  37    * Init() will return an error if called twice.  It's an error to call any
  38    * other method on this interface without first calling Init().
  39    */
  40   [[nodiscard]] nsresult Init(nsIFile* aFile);
  41
  42   /**
  43    * Alternate version of Init() for use when the file is already opened;
  44    * e.g., with a FileDescriptor passed over IPC.
  45    */
  46   [[nodiscard]] nsresult InitANSIFileDesc(FILE* aFile);
  47
  48   /**
  49    * Write the given string to the file.
  50    */
  51   [[nodiscard]] nsresult Write(const nsACString& aStr);
  52
  53   /**
  54    * Write |length| bytes of |str| to the file.
  55    */
  56   [[nodiscard]] nsresult Write(const char* aStr, uint32_t aLen) {
  57     return Write(nsDependentCSubstring(aStr, aLen));
  58   }
  59
  60   /**
  61    * Close this nsGZFileWriter. This method will be run when the underlying
  62    * object is destroyed, so it's not strictly necessary to explicitly call it
  63    * from your code.
  64    *
  65    * It's an error to call this method twice, and it's an error to call Write()
  66    * after Finish() has been called.
  67    */
  68   nsresult Finish();
  69
  70  private:
  71   bool mInitialized;
  72   bool mFinished;
  73   FILE* mGZFile;
  74   z_stream mZStream = {};
  75   Bytef mBuffer[8192];
  76 };
  77
  78 #endif