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Unified Diff: chrome/browser/download/download_id.h

Issue 7237034: sql::MetaTable.next_download_id, DownloadManager::GetNextId() (Closed) Base URL: http://git.chromium.org/git/chromium.git@trunk
Patch Set: " Created 9 years, 4 months ago
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Index: chrome/browser/download/download_id.h
diff --git a/chrome/browser/download/download_id.h b/chrome/browser/download/download_id.h
new file mode 100644
index 0000000000000000000000000000000000000000..bdfe5439e11da85c0a154033fe13059901d8ebef
--- /dev/null
+++ b/chrome/browser/download/download_id.h
@@ -0,0 +1,90 @@
+// Copyright (c) 2011 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 CHROME_BROWSER_DOWNLOAD_DOWNLOAD_ID_H_
+#define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_ID_H_
+#pragma once
+
+#include <iostream>
+
+#include "base/hash_tables.h"
+
+class DownloadManager;
+
+// DownloadId combines per-profile Download ids with an indication of which
+// profile in order to be globally unique. DownloadIds are not persistent across
+// sessions, but their local() field is.
+class DownloadId {
+ public:
+ explicit DownloadId(const DownloadManager* manager = NULL,
willchan no longer on Chromium 2011/08/06 14:08:36 http://google-styleguide.googlecode.com/svn/trunk/
benjhayden 2011/08/08 16:50:19 Done.
+ int32 local_id = -1)
+ : manager_(manager),
+ local_id_(local_id) {
+ }
+
+ // Return the per-profile and persistent part of this DownloadId.
+ int32 local() const { return local_id_; }
+
+ // Returns true if this DownloadId has been allocated and could possibly refer
+ // to a DownloadItem that exists.
+ bool IsValid() const { return ((manager_ != NULL) && (local_id_ >= 0)); }
+
+ // Returns true if this DownloadId was allocated by |manager|.
+ bool BelongsTo(const DownloadManager* manager) const {
+ return manager == manager_;
+ }
+
+ // The following methods (operator==, operator<, hash(), copy, and assign)
+ // provide support for STL containers such as hash_map and set.
+
+ // Returns true if this refers to the same DownloadItem as that.
willchan no longer on Chromium 2011/08/06 14:08:36 Where do you need this operator==?
benjhayden 2011/08/08 16:50:19 It looks like hash_map uses operator== on its keys
+ bool operator==(const DownloadId& that) const {
+ return ((that.local_id_ == local_id_) &&
+ (that.manager_ == manager_));
+ }
+ bool operator<(const DownloadId& that) const {
willchan no longer on Chromium 2011/08/06 14:08:36 operator< does not make sense and I'm not sure you
benjhayden 2011/08/08 16:50:19 Done.
+ return ((manager_ < that.manager_) ||
+ (local_id_ < that.local_id_));
+ }
+
+ size_t hash() const {
+ // The top half of manager is unlikely to be distinct, and the user is
+ // unlikely to have >64K downloads. If these assumptions are incorrect, then
+ // DownloadFileManager's hash_map might have a few collisions, but it will
+ // use operator== to safely disambiguate.
+ return reinterpret_cast<size_t>(manager_) +
+ (static_cast<size_t>(local_id_) << (4 * sizeof(size_t)));
+ }
+
+ private:
+ // DownloadId is used mostly off the UI thread, so manager's methods can't be
+ // called, but the pointer can be compared.
+ const DownloadManager* manager_;
+
+ int32 local_id_;
+
+ friend std::ostream& operator<<(std::ostream& out,
+ const DownloadId& global_id);
+
+ // Allow copy and assign.
+};
+
+// Allow logging DownloadIds. Looks like "0x01234567:42".
+std::ostream& operator<<(std::ostream& out, const DownloadId& global_id);
+
+// Allow using DownloadIds as keys in hash_maps.
+namespace BASE_HASH_NAMESPACE {
+#if defined(COMPILER_GCC)
+template<> struct hash<DownloadId> {
+ std::size_t operator()(const DownloadId& id) const {
+ return id.hash();
+ }
+};
+#elif defined(COMPILER_MSVC)
+inline size_t hash_value(const DownloadId& id) {
+ return id.hash();
+}
+#endif // COMPILER
+}
+#endif // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_ID_H_

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