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- // Copyright 2015 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_DER_INPUT_H_
- #define NET_DER_INPUT_H_
- #include <stddef.h>
- #include <stdint.h>
- #include <string>
- #include "base/containers/span.h"
- #include "base/strings/string_piece.h"
- #include "net/base/net_export.h"
- namespace net::der {
- // An opaque class that represents a fixed buffer of data of a fixed length,
- // to be used as an input to other operations. An Input object does not own
- // the data it references, so callers are responsible for making sure that
- // the data outlives the Input object and any other associated objects.
- //
- // All data access for an Input should be done through the ByteReader class.
- // This class and associated classes are designed with safety in mind to make it
- // difficult to read memory outside of an Input. ByteReader provides a simple
- // API for reading through the Input sequentially. For more complicated uses,
- // multiple instances of a ByteReader for a particular Input can be created.
- class NET_EXPORT_PRIVATE Input {
- public:
- // Creates an empty Input, one from which no data can be read.
- constexpr Input() = default;
- // Creates an Input from a constant array |data|.
- template <size_t N>
- constexpr explicit Input(const uint8_t (&data)[N]) : data_(data), len_(N) {}
- // Creates an Input from the given |data| and |len|.
- constexpr explicit Input(const uint8_t* data, size_t len)
- : data_(data), len_(len) {}
- // Creates an Input from a base::StringPiece.
- explicit Input(const base::StringPiece& sp);
- // Creates an Input from a std::string. The lifetimes are a bit subtle when
- // using this function: The constructed Input is only valid so long as |s| is
- // still alive and not mutated.
- explicit Input(const std::string* s);
- // Returns the length in bytes of an Input's data.
- constexpr size_t Length() const { return len_; }
- // Returns a pointer to the Input's data. This method is marked as "unsafe"
- // because access to the Input's data should be done through ByteReader
- // instead. This method should only be used where using a ByteReader truly
- // is not an option.
- constexpr const uint8_t* UnsafeData() const { return data_; }
- // Returns a copy of the data represented by this object as a std::string.
- std::string AsString() const;
- // Returns a StringPiece pointing to the same data as the Input. The resulting
- // StringPiece must not outlive the data that was used to construct this
- // Input.
- base::StringPiece AsStringPiece() const;
- // Returns a base::span pointing to the same data as the Input. The resulting
- // base::span must not outlive the data that was used to construct this
- // Input.
- base::span<const uint8_t> AsSpan() const;
- private:
- // This constructor is deleted to prevent constructing an Input from a
- // std::string r-value. Since the Input points to memory owned by another
- // object, such an Input would point to invalid memory. Without this deleted
- // constructor, a std::string could be passed in to the base::StringPiece
- // constructor because of StringPiece's implicit constructor.
- Input(std::string) = delete;
- const uint8_t* data_ = nullptr;
- size_t len_ = 0;
- };
- // Return true if |lhs|'s data and |rhs|'s data are byte-wise equal.
- NET_EXPORT_PRIVATE bool operator==(const Input& lhs, const Input& rhs);
- // Return true if |lhs|'s data and |rhs|'s data are not byte-wise equal.
- NET_EXPORT_PRIVATE bool operator!=(const Input& lhs, const Input& rhs);
- // Returns true if |lhs|'s data is lexicographically less than |rhs|'s data.
- NET_EXPORT_PRIVATE constexpr bool operator<(const Input& lhs,
- const Input& rhs) {
- // This is `std::lexicographical_compare`, but that's not `constexpr` until
- // C++-20.
- auto* it1 = lhs.UnsafeData();
- auto* it2 = rhs.UnsafeData();
- const auto* end1 = lhs.UnsafeData() + lhs.Length();
- const auto* end2 = rhs.UnsafeData() + rhs.Length();
- for (; it1 != end1 && it2 != end2; ++it1, ++it2) {
- if (*it1 < *it2) {
- return true;
- } else if (*it2 < *it1) {
- return false;
- }
- }
- return it2 != end2;
- }
- // This class provides ways to read data from an Input in a bounds-checked way.
- // The ByteReader is designed to read through the input sequentially. Once a
- // byte has been read with a ByteReader, the caller can't go back and re-read
- // that byte with the same reader. Of course, the caller can create multiple
- // ByteReaders for the same input (or copy an existing ByteReader).
- //
- // For something simple like a single byte lookahead, the easiest way to do
- // that is to copy the ByteReader and call ReadByte() on the copy - the original
- // ByteReader will be unaffected and the peeked byte will be read through
- // ReadByte(). For other read patterns, it can be useful to mark where one is
- // in a ByteReader to be able to return to that spot.
- //
- // Some operations using Mark can also be done by creating a copy of the
- // ByteReader. By using a Mark instead, you use less memory, but more
- // importantly, you end up with an immutable object that matches the semantics
- // of what is intended.
- class NET_EXPORT_PRIVATE ByteReader {
- public:
- // Creates a ByteReader to read the data represented by an Input.
- explicit ByteReader(const Input& in);
- // Reads a single byte from the input source, putting the byte read in
- // |*byte_p|. If a byte cannot be read from the input (because there is
- // no input left), then this method returns false.
- [[nodiscard]] bool ReadByte(uint8_t* out);
- // Reads |len| bytes from the input source, and initializes an Input to
- // point to that data. If there aren't enough bytes left in the input source,
- // then this method returns false.
- [[nodiscard]] bool ReadBytes(size_t len, Input* out);
- // Returns how many bytes are left to read.
- size_t BytesLeft() const { return len_; }
- // Returns whether there is any more data to be read.
- bool HasMore();
- private:
- void Advance(size_t len);
- const uint8_t* data_;
- size_t len_;
- };
- } // namespace net::der
- #endif // NET_DER_INPUT_H_
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