1 files changed, 97 insertions, 0 deletions
diff --git a/xpcom/base/nsGZFileWriter.cpp b/xpcom/base/nsGZFileWriter.cpp
new file mode 100644
index 0000000000..2d8e14e944
--- /dev/null
+++ b/xpcom/base/nsGZFileWriter.cpp
@@ -0,0 +1,97 @@
+/* -*- 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 "nsGZFileWriter.h"
+#include "nsIFile.h"
+#include "nsString.h"
+#include "zlib.h"
+
+#ifdef XP_WIN
+#  include <io.h>
+#  define _dup dup
+#else
+#  include <unistd.h>
+#endif
+
+nsGZFileWriter::nsGZFileWriter(Operation aMode)
+    : mMode(aMode), mInitialized(false), mFinished(false), mGZFile(nullptr) {}
+
+nsGZFileWriter::~nsGZFileWriter() {
+  if (mInitialized && !mFinished) {
+    Finish();
+  }
+}
+
+nsresult nsGZFileWriter::Init(nsIFile* aFile) {
+  if (NS_WARN_IF(mInitialized) || NS_WARN_IF(mFinished)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Get a FILE out of our nsIFile.  Convert that into a file descriptor which
+  // gzip can own.  Then close our FILE, leaving only gzip's fd open.
+
+  FILE* file;
+  nsresult rv = aFile->OpenANSIFileDesc(mMode == Create ? "wb" : "ab", &file);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  return InitANSIFileDesc(file);
+}
+
+nsresult nsGZFileWriter::InitANSIFileDesc(FILE* aFile) {
+  if (NS_WARN_IF(mInitialized) || NS_WARN_IF(mFinished)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mGZFile = gzdopen(dup(fileno(aFile)), mMode == Create ? "wb" : "ab");
+  fclose(aFile);
+
+  // gzdopen returns nullptr on error.
+  if (NS_WARN_IF(!mGZFile)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mInitialized = true;
+
+  return NS_OK;
+}
+
+nsresult nsGZFileWriter::Write(const nsACString& aStr) {
+  if (NS_WARN_IF(!mInitialized) || NS_WARN_IF(mFinished)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // gzwrite uses a return value of 0 to indicate failure.  Otherwise, it
+  // returns the number of uncompressed bytes written.  To ensure we can
+  // distinguish between success and failure, don't call gzwrite when we have 0
+  // bytes to write.
+  if (aStr.IsEmpty()) {
+    return NS_OK;
+  }
+
+  // gzwrite never does a short write -- that is, the return value should
+  // always be either 0 or aStr.Length(), and we shouldn't have to call it
+  // multiple times in order to get it to read the whole buffer.
+  int rv = gzwrite(mGZFile, aStr.BeginReading(), aStr.Length());
+  if (NS_WARN_IF(rv != static_cast<int>(aStr.Length()))) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+nsresult nsGZFileWriter::Finish() {
+  if (NS_WARN_IF(!mInitialized) || NS_WARN_IF(mFinished)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mFinished = true;
+  gzclose(mGZFile);
+
+  // Ignore errors from gzclose; it's not like there's anything we can do about
+  // it, at this point!
+  return NS_OK;
+}