chromium/components/visitedlink/common/visitedlink_common.h

// Copyright 2006-2008 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_VISITEDLINK_COMMON_VISITEDLINK_COMMON_H_
#define COMPONENTS_VISITEDLINK_COMMON_VISITEDLINK_COMMON_H_

#include <stddef.h>
#include <stdint.h>

#include <string_view>
#include <vector>

#include "base/memory/raw_ptr.h"
#include "components/visitedlink/core/visited_link.h"

class GURL;

namespace net {
class SchemefulSite;
}

namespace url {
class Origin;
}

namespace visitedlink {

// number of bytes in the salt
#define LINK_SALT_LENGTH …

// A multiprocess-safe database of the visited links for the browser. There
// should be exactly one process that has write access (implemented by
// VisitedLinkWriter), while all other processes should be read-only
// (implemented by VisitedLinkReader). These other processes add links by
// calling the writer process to add them for it. The writer may also notify the
// readers to replace their table when the table is resized.
//
// IPC is not implemented in these classes. This is done through callback
// functions supplied by the creator of these objects to allow more flexibility,
// especially for testing.
//
// This class defines the common base for these others. We implement accessors
// for looking things up in the hash table, and for computing hash values and
// fingerprints. Both the writer and the reader inherit from this, and add their
// own code to set up and change these values as their design requires. The
// reader pretty much just sets up the shared memory and saves the pointer. The
// writer does a lot of work to manage the table, reading and writing it to and
// from disk, and resizing it when it gets too full.
//
// To ask whether a page is in history, we compute a 64-bit fingerprint of the
// URL. This URL is hashed and we see if it is in the URL hashtable. If it is,
// we consider it visited. Otherwise, it is unvisited. Note that it is possible
// to get collisions, which is the penalty for not storing all URL strings in
// memory (which could get to be more than we want to have in memory). We use
// a salt value for the links on one computer so that an attacker can not
// manually create a link that causes a collision.
class VisitedLinkCommon { … };

}  // namespace visitedlink

#endif  // COMPONENTS_VISITEDLINK_COMMON_VISITEDLINK_COMMON_H_