Add PPDProvider barebones implementation and associated cache skeleton.

chromeos/printing/ppd_provider.h

Index: chromeos/printing/ppd_provider.h
diff --git a/chromeos/printing/ppd_provider.h b/chromeos/printing/ppd_provider.h
new file mode 100644
index 0000000000000000000000000000000000000000..16adc2379ace21c632cb4cde710979237213f9d1
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+++ b/chromeos/printing/ppd_provider.h
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+// 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 CHROMEOS_PRINTING_PPD_PROVIDER_H_
+#define CHROMEOS_PRINTING_PPD_PROVIDER_H_
+
+#include <memory>
+#include <string>
+
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "chromeos/chromeos_export.h"
+#include "chromeos/printing/printer_configuration.h"
+
+namespace net {
+class URLRequestContextGetter;
+}
+
+namespace chromeos {
+namespace printing {
+
+class PpdCache;
+
+// PpdProvider is responsible for mapping printer descriptions to
+// CUPS-PostScript Printer Description (PPD) files.  It provides PPDs that a
+// user previously identified for use, and falls back to querying quirksserver
+// based on manufacturer/model of the printer.
+class CHROMEOS_EXPORT PpdProvider {
+ public:
+  // Possible results of a Resolve* call.
+  enum ResolveResult {
+    // Found a PPD
+    SUCCESS,
+
+    // TODO(justincarlson) - Should we have a "FALLBACK" result here indicating
+    // we found a PPD that we think will work, but wasn't an exact match?
+
+    // Looked for a PPD for this configuration, but couldn't find a match.
+    NOT_FOUND,
+
+    // Failed to contact an external server needed to finish resolution.
+    SERVER_ERROR,
+
+    // Other error that is not expected to be transient.
+    INTERNAL_ERROR,
+  };
+
+  // Result of a resolve function.  If ResolveResult is SUCCESS, then filepath
+  // holds the path to a PPD file (that may or may not be gzipped).  Otherwise,
+  // the FilePath will be empty.
+  using ResolveCallback = base::Callback<void(ResolveResult, base::FilePath)>;
+
+  // Construction-time options.  Everything in this structure should have
+  // a sane default.
+  struct Options {
+    Options() {}
+
+    // hostname of quirks server to query.
+    std::string quirks_server = "chromeosquirksserver-pa.googleapis.com";
+
+    // Maximum size of the contents of a PPD file.  Trying to use a PPD file

[Lei Zhang, 2016/10/24 22:26:24]

Presumably: ... of a PPD file in bytes.

[Carlson, 2016/10/24 22:48:44]

Done.

+    // bigger than this will cause INTERNAL_ERRORs at resolution time.
+    size_t max_ppd_contents_size_ = 100 * 1024;
+  };
+
+  // Create and return a new PpdProvider with the given cache and options.
+  static std::unique_ptr<PpdProvider> Create(
+      const std::string& api_key,
+      scoped_refptr<net::URLRequestContextGetter> url_context_getter,
+      std::unique_ptr<PpdCache> cache,
+      const Options& options = Options());
+
+  virtual ~PpdProvider() {}
+
+  // Given a PpdReference, attempt to resolve the PPD for printing.
+  //
+  // Must be called from a Sequenced Task context (i.e.
+  // base::SequencedTaskRunnerHandle::IsSet() must be true).
+  //
+  // |cb| will only be called after the task invoking Resolve() is finished.
+  //
+  // Only one Resolve call should be outstanding at a time.
+  virtual void Resolve(const Printer::PpdReference& ppd_reference,
+                       ResolveCallback cb) = 0;
+
+  // Abort any outstanding Resolve call.  After this returns, it is guaranteed
+  // that all no ResolveCallback will be called until the next time Resolve is
+  // called.  It is a nop to call this if no Resolve is outstanding.
+  virtual void AbortResolve() = 0;
+
+  // Most of the time, the cache is just an invisible backend to the Provider,
+  // consulted at Resolve time, but in the case of the user doing "Add Printer"
+  // and "Select PPD" locally, then we get into a state where we want to put
+  // whatever they give us directly into the cache without doing a resolve.
+  // This hook lets is do that.
+  virtual bool CachePpd(const Printer::PpdReference& ppd_reference,
+                        const base::FilePath& ppd_path) = 0;
+};
+
+}  // namespace printing
+}  // namespace chromeos
+
+#endif  // CHROMEOS_PRINTING_PPD_PROVIDER_H_