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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_UUID_H_
#define BASE_UUID_H_
#include <stdint.h>
#include <compare>
#include <iosfwd>
#include <string>
#include "base/base_export.h"
#include "base/containers/span.h"
#include "base/strings/string_piece.h"
#include "base/types/pass_key.h"
#include "build/build_config.h"
namespace content {
class FileSystemAccessManagerImpl;
}
namespace base {
class BASE_EXPORT Uuid {
public:
// Length in bytes of the input required to format the input as a Uuid in the
// form of version 4.
static constexpr size_t kGuidV4InputLength = 16;
// Generate a 128-bit random Uuid in the form of version 4. see RFC 4122,
// section 4.4. The format of Uuid version 4 must be
// xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where y is one of [8, 9, a, b]. The
// hexadecimal values "a" through "f" are output as lower case characters.
// A cryptographically secure random source will be used, but consider using
// UnguessableToken for greater type-safety if Uuid format is unnecessary.
static Uuid GenerateRandomV4();
// Formats a sequence of 16 random bytes as a Uuid in the form of version 4.
// `input` must:
// - have been randomly generated (e.g. created from an UnguessableToken), and
// - be of length 16 (this is checked at compile-time).
// Despite taking 128 bits of randomness, certain bits will always be
// masked over to adhere to the V4 Uuid format.
// Useful in cases where an opaque identifier that is generated from stable
// inputs needs to be formatted as a V4 Uuid. Currently only exposed to the
// File System Access API to return a V4 Uuid for the getUniqueId() method.
static Uuid FormatRandomDataAsV4(
base::span<const uint8_t, kGuidV4InputLength> input,
base::PassKey<content::FileSystemAccessManagerImpl> pass_key);
static Uuid FormatRandomDataAsV4ForTesting(
base::span<const uint8_t, kGuidV4InputLength> input);
// Returns a valid Uuid if the input string conforms to the Uuid format, and
// an invalid Uuid otherwise. Note that this does NOT check if the hexadecimal
// values "a" through "f" are in lower case characters.
static Uuid ParseCaseInsensitive(StringPiece input);
static Uuid ParseCaseInsensitive(StringPiece16 input);
// Similar to ParseCaseInsensitive(), but all hexadecimal values "a" through
// "f" must be lower case characters.
static Uuid ParseLowercase(StringPiece input);
static Uuid ParseLowercase(StringPiece16 input);
// Constructs an invalid Uuid.
Uuid();
Uuid(const Uuid& other);
Uuid& operator=(const Uuid& other);
Uuid(Uuid&& other);
Uuid& operator=(Uuid&& other);
bool is_valid() const { return !lowercase_.empty(); }
// Returns the Uuid in a lowercase string format if it is valid, and an empty
// string otherwise. The returned value is guaranteed to be parsed by
// ParseLowercase().
//
// NOTE: While AsLowercaseString() is currently a trivial getter, callers
// should not treat it as such. When the internal type of base::Uuid changes,
// this will be a non-trivial converter. See the TODO above `lowercase_` for
// more context.
const std::string& AsLowercaseString() const;
// Invalid Uuids are equal.
friend bool operator==(const Uuid&, const Uuid&) = default;
// Uuids are 128bit chunks of data so must be indistinguishable if equivalent.
friend std::strong_ordering operator<=>(const Uuid&, const Uuid&) = default;
private:
static Uuid FormatRandomDataAsV4Impl(
base::span<const uint8_t, kGuidV4InputLength> input);
// TODO(crbug.com/1026195): Consider using a different internal type.
// Most existing representations of Uuids in the codebase use std::string,
// so matching the internal type will avoid inefficient string conversions
// during the migration to base::Uuid.
//
// The lowercase form of the Uuid. Empty for invalid Uuids.
std::string lowercase_;
};
// For runtime usage only. Do not store the result of this hash, as it may
// change in future Chromium revisions.
struct BASE_EXPORT UuidHash {
size_t operator()(const Uuid& uuid) const;
};
// Stream operator so Uuid objects can be used in logging statements.
BASE_EXPORT std::ostream& operator<<(std::ostream& out, const Uuid& uuid);
} // namespace base
#endif // BASE_UUID_H_
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