Bug 788021 - Part 1: Add nsGZFileWriter. r=bsmedberg

xpcom/base/Makefile.in

@@ -40,6 +40,7 @@ CPPSRCS		= \
 		ClearOnShutdown.cpp \
 		VisualEventTracer.cpp \
 		nsErrorAsserts.cpp \
+		nsGZFileWriter.cpp \
 		$(NULL)
 
 ifeq ($(OS_ARCH),Linux)
@@ -64,6 +65,7 @@ EXPORTS		= \
 		nsWeakPtr.h \
 		nsInterfaceRequestorAgg.h \
 		dmd.h \
+		nsGZFileWriter.h \
 		$(NULL)
 
 EXPORTS_NAMESPACES = mozilla
@@ -130,6 +132,7 @@ XPIDLSRCS	= \
 		nsIUUIDGenerator.idl \
 		nsIMutable.idl \
 		nsIMemoryReporter.idl \
+		nsIGZFileWriter.idl \
 		$(NULL)
 
 ifeq (cocoa,$(MOZ_WIDGET_TOOLKIT))

xpcom/base/nsGZFileWriter.cpp

@@ -0,0 +1,90 @@
+/* -*- Mode: C++; tab-width: 50; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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
+
+NS_IMPL_ISUPPORTS1(nsGZFileWriter, nsIGZFileWriter)
+
+nsGZFileWriter::nsGZFileWriter()
+  : mInitialized(false)
+  , mFinished(false)
+{}
+
+nsGZFileWriter::~nsGZFileWriter()
+{
+  if (mInitialized && !mFinished) {
+    Finish();
+  }
+}
+
+NS_IMETHODIMP
+nsGZFileWriter::Init(nsIFile* aFile)
+{
+  NS_ENSURE_FALSE(mInitialized, NS_ERROR_FAILURE);
+  NS_ENSURE_FALSE(mFinished, 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("w", &file);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mGZFile = gzdopen(dup(fileno(file)), "w");
+  fclose(file);
+
+  // gzdopen returns NULL on error.
+  NS_ENSURE_TRUE(mGZFile, NS_ERROR_FAILURE);
+  mInitialized = true;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsGZFileWriter::Write(const nsACString& aStr)
+{
+  NS_ENSURE_TRUE(mInitialized, NS_ERROR_NOT_INITIALIZED);
+  NS_ENSURE_FALSE(mFinished, 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());
+  NS_ENSURE_TRUE(rv == static_cast<int>(aStr.Length()), NS_ERROR_FAILURE);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsGZFileWriter::Finish()
+{
+  NS_ENSURE_TRUE(mInitialized, NS_ERROR_NOT_INITIALIZED);
+  NS_ENSURE_FALSE(mFinished, 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;
+}

xpcom/base/nsGZFileWriter.h

@@ -0,0 +1,41 @@
+/* -*- Mode: C++; tab-width: 50; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 "nsIGZFileWriter.h"
+#include <stdio.h>
+#include "zlib.h"
+
+/**
+ * A simple class for writing .gz files.
+ */
+class nsGZFileWriter : public nsIGZFileWriter
+{
+public:
+  nsGZFileWriter();
+  virtual ~nsGZFileWriter();
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGZFILEWRITER
+
+  /**
+   * nsIGZFileWriter exposes two non-virtual overloads of Write().  We
+   * duplicate them here so that you can call these overloads on a pointer to
+   * the concrete nsGZFileWriter class.
+   */
+  nsresult Write(const char* aStr)
+  {
+    return nsIGZFileWriter::Write(aStr);
+  }
+
+  nsresult Write(const char* aStr, uint32_t aLen)
+  {
+    return nsIGZFileWriter::Write(aStr, aLen);
+  }
+
+private:
+  bool mInitialized;
+  bool mFinished;
+  gzFile mGZFile;
+};

xpcom/base/nsIGZFileWriter.idl

@@ -0,0 +1,73 @@
+/* -*- Mode: C++; tab-width: 50; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 "nsISupports.idl"
+
+%{C++
+#include "nsDependentString.h"
+%}
+
+interface nsIFile;
+
+/**
+ * A simple interface 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.
+ */
+[scriptable, uuid(a256f26a-c603-459e-b5a4-53b4877f2cd8)]
+interface nsIGZFileWriter : nsISupports
+{
+  /**
+   * 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().
+   */
+  void init(in nsIFile file);
+
+  /**
+   * Write the given string to the file.
+   */
+  void write(in AUTF8String str);
+
+  /*
+   * The following two overloads of Write() are C++ because we can't overload
+   * methods in XPIDL.  Anyway, they don't add much functionality for JS
+   * callers.
+   */
+  %{C++
+  /**
+   * Write the given char* to the file (not including the null-terminator).
+   */
+  nsresult Write(const char* str)
+  {
+    return Write(str, strlen(str));
+  }
+
+  /**
+   * Write |length| bytes of |str| to the file.
+   */
+  nsresult Write(const char* str, uint32_t len)
+  {
+    return Write(nsDependentCString(str, len));
+  }
+  %}
+
+  /**
+   * Close this nsIGZFileWriter.  This method is 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.
+   */
+  void finish();
+};