Add CertIssuerSource interface and CertIssuerSourceStatic implementation.

net/cert/internal/cert_issuer_source.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 NET_CERT_INTERNAL_CERT_ISSUER_SOURCE_H_
+#define NET_CERT_INTERNAL_CERT_ISSUER_SOURCE_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/callback.h"
+#include "net/base/net_export.h"
+#include "net/cert/internal/completion_status.h"
+
+namespace net {
+
+class ParsedCertificate;
+
+// Interface for looking up issuers of a certificate during path building.
+// Provides a synchronous and asynchronous method for retrieving issuers, so the
+// path builder can try to complete synchronously first. The caller is expected
+// to call SyncGetIssuersOf first, see if it can make progress with those
+// results, and if not, then fall back to calling AsyncGetIssuersOf.
+// An implementations may choose to return results from either one of the Get

[eroman, 2016/06/01 23:30:23]

i think the interface may need more specificity for conveying completion
synchronously, and being more opinionated on whether async is a superset of sync
results etc.

But can leave those comments to the integration CL :)

Has the WIP been updated to use this?

[mattm, 2016/06/01 23:48:33]

ack.
Just uploaded a new patchset.

+// methods, or from both.
+class NET_EXPORT CertIssuerSource {
+ public:
+  class NET_EXPORT Request {
+   public:
+    // Destruction of the Request cancels it.
+    virtual ~Request() = default;
+
+    // Retrieves the next issuer.
+    //
+    // If one is available it will be stored in |out_cert| and SYNC will be
+    // returned. GetNext should be called again to retrieve any remaining
+    // issuers.
+    //
+    // If no issuers are currently available, |out_cert| will be cleared and the
+    // return value will indicate if the Request is exhausted. If the return
+    // value is ASYNC, the |issuers_callback| that was passed to
+    // AsyncGetIssuersOf will be called again (unless the Request is destroyed
+    // first). If the return value is SYNC, the Request is complete and the
+    // |issuers_callback| will not be called again.
+    virtual CompletionStatus GetNext(
+        scoped_refptr<ParsedCertificate>* out_cert) = 0;
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(Request);
+  };
+
+  using IssuerCallback = base::Callback<void(Request*)>;
+
+  virtual ~CertIssuerSource() = default;
+
+  // Finds certificates whose Subject matches |cert|'s Issuer.
+  // Matches are appended to |issuers|. Any existing contents of |issuers| will
+  // not be modified. If the implementation does not support synchronous
+  // lookups, or if there are no matches, |issuers| is not modified.
+  virtual void SyncGetIssuersOf(
+      const ParsedCertificate* cert,
+      std::vector<scoped_refptr<ParsedCertificate>>* issuers) = 0;
+
+  // Finds certificates whose Subject matches |cert|'s Issuer.
+  // If an async callback will be made |*out_req| is filled with a Request
+  // object which may be destroyed to cancel the callback. If the implementation
+  // does not support asynchronous lookups or can determine synchronously that
+  // it would return no results, |*out_req| will be set to nullptr.
+  //
+  // When matches are available or the request is complete, |issuers_callback|
+  // will be called with a pointer to the same Request. The Request::GetNext
+  // method may then be used to iterate through the retrieved issuers. Note that
+  // |issuers_callback| may be called multiple times. See the documentation for
+  // Request::GetNext for more details.
+  virtual void AsyncGetIssuersOf(const ParsedCertificate* cert,
+                                 const IssuerCallback& issuers_callback,
+                                 std::unique_ptr<Request>* out_req) = 0;
+};
+
+}  // namespace net
+
+#endif  // NET_CERT_INTERNAL_CERT_ISSUER_SOURCE_H_