Create a new print backend for the updated CUPS APIs

printing/backend/cups_connection.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PRINTING_BACKEND_CUPS_CONNECTION_H_
+#define PRINTING_BACKEND_CUPS_CONNECTION_H_
+
+#include <cups/cups.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "printing/backend/cups_deleters.h"
+#include "printing/backend/cups_printer.h"
+#include "printing/printing_export.h"
+#include "url/gurl.h"
+
+namespace printing {
+
+// Represents a connection to a CUPS server.
+class PRINTING_EXPORT CupsConnection {
+ public:
+  CupsConnection(const GURL& print_server_url,
+                 http_encryption_t encryption,
+                 bool blocking);
+
+  CupsConnection(CupsConnection&& connection);
+
+  ~CupsConnection();
+
+  // Returns a vector of all the printers configure on the CUPS server.
+  std::vector<CupsPrinter> GetDests();
+
+  // Returns a printer for |printer_name| from the connected server.
+  std::unique_ptr<CupsPrinter> GetPrinter(const std::string& printer_name);
+
+  std::string server_name() const;
+
+  int last_error() const;
+
+ private:
+  class Impl {
+   public:
+    explicit Impl(http_t* http);
+    ~Impl();
+
+    base::WeakPtr<http_t> GetHttp();
+
+   private:
+    std::unique_ptr<http_t, HttpDeleter> cups_http_;
+    base::WeakPtrFactory<http_t> http_factory_;
+
+    DISALLOW_COPY_AND_ASSIGN(Impl);
+  };
+
+  // lazily initialize http connection
+  bool Connect();
+
+  GURL print_server_url_;
+  http_encryption_t cups_encryption_;
+  bool blocking_;
+
+  std::unique_ptr<Impl> impl_;
+  base::WeakPtr<http_t> cups_http_;

[Lei Zhang, 2016/07/19 22:49:17]

Since CupsConnection owns |impl_|, as written |CuspConnection::cups_http_| is
always valid during its lifetime because destruction happens in reverse order.
This gets destroyed first before |Impl::cups_http_|. Also, nobody ever calls
impl_.reset(), and all the std::move(impl_) calls have corresponding
std::move(cups_http_) calls at the same time.

+
+  DISALLOW_COPY_AND_ASSIGN(CupsConnection);
+};
+
+}  // namespace printing
+
+#endif  // PRINTING_BACKEND_CUPS_CONNECTION_H_