xpcom/base/nsGZFileWriter.cpp

   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 #include "nsGZFileWriter.h"
   8 #include "nsIFile.h"
   9 #include "nsString.h"
  10 #include "zlib.h"
  11
  12 #ifdef XP_WIN
  13 #  include <io.h>
  14 #  define _dup dup
  15 #else
  16 #  include <unistd.h>
  17 #endif
  18
  19 nsGZFileWriter::nsGZFileWriter(Operation aMode)
  20     : mMode(aMode), mInitialized(false), mFinished(false), mGZFile(nullptr) {}
  21
  22 nsGZFileWriter::~nsGZFileWriter() {
  23   if (mInitialized && !mFinished) {
  24     Finish();
  25   }
  26 }
  27
  28 nsresult nsGZFileWriter::Init(nsIFile* aFile) {
  29   if (NS_WARN_IF(mInitialized) || NS_WARN_IF(mFinished)) {
  30     return NS_ERROR_FAILURE;
  31   }
  32
  33   // Get a FILE out of our nsIFile.  Convert that into a file descriptor which
  34   // gzip can own.  Then close our FILE, leaving only gzip's fd open.
  35
  36   FILE* file;
  37   nsresult rv = aFile->OpenANSIFileDesc(mMode == Create ? "wb" : "ab", &file);
  38   if (NS_WARN_IF(NS_FAILED(rv))) {
  39     return rv;
  40   }
  41   return InitANSIFileDesc(file);
  42 }
  43
  44 nsresult nsGZFileWriter::InitANSIFileDesc(FILE* aFile) {
  45   if (NS_WARN_IF(mInitialized) || NS_WARN_IF(mFinished)) {
  46     return NS_ERROR_FAILURE;
  47   }
  48
  49   mGZFile = gzdopen(dup(fileno(aFile)), mMode == Create ? "wb" : "ab");
  50   fclose(aFile);
  51
  52   // gzdopen returns nullptr on error.
  53   if (NS_WARN_IF(!mGZFile)) {
  54     return NS_ERROR_FAILURE;
  55   }
  56
  57   mInitialized = true;
  58
  59   return NS_OK;
  60 }
  61
  62 nsresult nsGZFileWriter::Write(const nsACString& aStr) {
  63   if (NS_WARN_IF(!mInitialized) || NS_WARN_IF(mFinished)) {
  64     return NS_ERROR_FAILURE;
  65   }
  66
  67   // gzwrite uses a return value of 0 to indicate failure.  Otherwise, it
  68   // returns the number of uncompressed bytes written.  To ensure we can
  69   // distinguish between success and failure, don't call gzwrite when we have 0
  70   // bytes to write.
  71   if (aStr.IsEmpty()) {
  72     return NS_OK;
  73   }
  74
  75   // gzwrite never does a short write -- that is, the return value should
  76   // always be either 0 or aStr.Length(), and we shouldn't have to call it
  77   // multiple times in order to get it to read the whole buffer.
  78   int rv = gzwrite(mGZFile, aStr.BeginReading(), aStr.Length());
  79   if (NS_WARN_IF(rv != static_cast<int>(aStr.Length()))) {
  80     return NS_ERROR_FAILURE;
  81   }
  82
  83   return NS_OK;
  84 }
  85
  86 nsresult nsGZFileWriter::Finish() {
  87   if (NS_WARN_IF(!mInitialized) || NS_WARN_IF(mFinished)) {
  88     return NS_ERROR_FAILURE;
  89   }
  90
  91   mFinished = true;
  92   gzclose(mGZFile);
  93
  94   // Ignore errors from gzclose; it's not like there's anything we can do about
  95   // it, at this point!
  96   return NS_OK;
  97 }