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// 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 <iosfwd>
#include "base/hash_tables.h"
#include "content/common/content_export.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:
static DownloadId Invalid() { return DownloadId(NULL, -1); }
DownloadId(const DownloadManager* manager, int32 local_id)
: 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)); }
// The following methods (operator==, hash(), copy, and assign) provide
// support for STL containers such as hash_map.
bool operator==(const DownloadId& that) const {
return ((that.local_id_ == local_id_) &&
(that.manager_ == manager_));
}
bool operator<(const DownloadId& that) const {
// Even though DownloadManager* < DownloadManager* is not well defined and
// GCC does not require it for hash_map, MSVC requires operator< for
// hash_map. We don't ifdef it out here because we will probably make a
// set<DownloadId> at some point, when GCC will require it.
return ((manager_ < that.manager_) ||
((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 CONTENT_EXPORT std::ostream& operator<<(std::ostream& out,
const DownloadId& global_id);
// Allow copy and assign.
};
// Allow logging DownloadIds. Looks like "0x01234567:42".
CONTENT_EXPORT 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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