Add a method to query IPP printers for attributes.

chrome/browser/chromeos/printing/printer_info_cups.cc

+// Copyright 2017 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.
+
+#include "chrome/browser/chromeos/printing/printer_info.h"
+
+#include <algorithm>
+#include <string>
+
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "base/strings/string_piece.h"
+#include "base/task_runner_util.h"
+#include "base/task_scheduler/post_task.h"
+#include "base/task_scheduler/task_traits.h"
+#include "printing/backend/cups_jobs.h"
+
+namespace {
+
+// Returns true if any of the |ipp_versions| are greater than or equal to 2.0.

[Carlson, 2017/05/25 19:04:35]

what's the pair?  <major, minor>  ?

[skau, 2017/05/27 02:01:19]

Done.

+bool AllowedIpp(const std::vector<std::pair<int, int>>& ipp_versions) {
+  auto found = std::find_if(
+      ipp_versions.begin(), ipp_versions.end(),
+      [](const std::pair<int, int>& version) { return version.first >= 2; });
+
+  return found != ipp_versions.end();
+}
+
+// Returns true if |info| describes a printer for which we want to attempt
+// automatic configuration.
+bool IsAutoconf(const ::printing::PrinterInfo& info) {
+  return info.ipp_everywhere || AllowedIpp(info.ipp_versions);
+}
+
+std::unique_ptr<::printing::PrinterInfo> QueryPrinterImpl(

[Carlson, 2017/05/25 19:04:35]

Function comment?

[skau, 2017/05/27 02:01:19]

Done.

+    const std::string& host,
+    const int port,
+    const std::string& path) {
+  auto info = base::MakeUnique<::printing::PrinterInfo>();
+  if (!::printing::GetPrinterInfo(host, port, path, info.get())) {
+    LOG(ERROR) << "Could not retrieve printer info";
+    return nullptr;
+  }
+
+  return info;
+}
+
+void OnPrinterQueried(const chromeos::PrinterInfoCallback& callback,
+                      std::unique_ptr<::printing::PrinterInfo> info) {
+  if (!info) {
+    VLOG(1) << "Could not reach printer";
+    callback.Run(false, std::string(), std::string(), false);
+    return;
+  }
+
+  // TODO(skau): Handle manufacturers with two word names.
+  base::StringPiece make_and_model(info->make_and_model);
+  base::StringPiece make;
+  base::StringPiece model;
+
+  size_t first_space = make_and_model.find(" ");
+  if (first_space != base::BaseStringPiece::npos &&
+      (first_space + 1) < make_and_model.length()) {

[Carlson, 2017/05/25 19:04:36]

I don't think the second half of this conditional is needed?

If we found a space, then first_space will be between [0, length-1].  

If first_space is length-1, then first_space+1 is length, which would cause
make_and_model.substr(first_space + 1) to be an empty string(piece), which is
what you want.

Am I missing something?

[skau, 2017/05/27 02:01:19]

Yes.  You are correct.  The primary concern is a trailing space which would
result in an empty string.

+    make = make_and_model.substr(0, first_space);
+    model = make_and_model.substr(first_space + 1);
+  } else {
+    // If there's only one word or an empty string, use it.
+    model = make_and_model;
+  }
+
+  callback.Run(true, make.as_string(), model.as_string(), IsAutoconf(*info));
+}
+
+}  // namespace
+
+namespace chromeos {
+
+void QueryPrinter(const std::string& host,
+                  const int port,
+                  const std::string& path,
+                  const PrinterInfoCallback& callback) {
+  DCHECK(!host.empty());
+

[Carlson, 2017/05/25 19:04:35]

A comment on why you want these specific traits would be useful.

[skau, 2017/05/27 02:01:19]

Done.

+  base::PostTaskWithTraitsAndReplyWithResult(
+      FROM_HERE,
+      base::TaskTraits(base::TaskPriority::USER_VISIBLE, base::MayBlock()),
+      base::Bind(&QueryPrinterImpl, host, port, path),
+      base::Bind(&OnPrinterQueried, callback));
+}
+
+}  // namespace chromeos