21768358452

Committed 06 Feb 2026 10:35PM UTC coverage: 90.064% (-0.003%) from 90.067%

Build # 21768358452

Build Type

Pull #5289

github

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web-flow

Commit Message

Merge f589db195 into 8ea0ca252

Pull Request Pull Request #5289: Further misc header reductions, forward declarations, etc

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92.45

/src/lib/utils/alignment_buffer.h

/*
 * Alignment buffer helper
 * (C) 2023 Jack Lloyd
 *     2023 René Meusel - Rohde & Schwarz Cybersecurity
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */

#ifndef BOTAN_ALIGNMENT_BUFFER_H_
#define BOTAN_ALIGNMENT_BUFFER_H_

#include <botan/internal/buffer_slicer.h>
#include <botan/internal/mem_utils.h>
#include <array>
#include <optional>
#include <span>

namespace Botan {

/**
 * Defines the strategy for handling the final block of input data in the
 * handle_unaligned_data() method of the AlignmentBuffer<>.
 *
 * - is_not_special:   the final block is treated like any other block
 * - must_be_deferred: the final block is not emitted while bulk processing (typically add_data())
 *                     but is deferred until manually consumed (typically final_result())
 *
 * The AlignmentBuffer<> assumes data to be "the final block" if no further
 * input data is available in the BufferSlicer<>. This might result in some
 * performance overhead when using the must_be_deferred strategy.
 */
enum class AlignmentBufferFinalBlock : uint8_t {
   is_not_special = 0,
   must_be_deferred = 1,
};

/**
 * @brief Alignment buffer helper
 *
 * Many algorithms have an intrinsic block size in which they consume input
 * data. When streaming arbitrary data chunks to such algorithms we must store
 * some data intermittently to honor the algorithm's alignment requirements.
 *
 * This helper encapsulates such an alignment buffer. The API of this class is
 * designed to minimize user errors in the algorithm implementations. Therefore,
 * it is strongly opinionated on its use case. Don't try to use it for anything
 * but the described circumstance.
 *
 * @tparam T                     the element type of the internal buffer
 * @tparam BLOCK_SIZE            the buffer size to use for the alignment buffer
 * @tparam FINAL_BLOCK_STRATEGY  defines whether the final input data block is
 *                               retained in handle_unaligned_data() and must be
 *                               manually consumed
 */
template <typename T,
          size_t BLOCK_SIZE,
          AlignmentBufferFinalBlock FINAL_BLOCK_STRATEGY = AlignmentBufferFinalBlock::is_not_special>
   requires(BLOCK_SIZE > 0)
class AlignmentBuffer {
   public:
      AlignmentBuffer() = default;

      ~AlignmentBuffer() { secure_zeroize_buffer(m_buffer.data(), sizeof(T) * m_buffer.size()); }

      AlignmentBuffer(const AlignmentBuffer& other) = default;
      AlignmentBuffer(AlignmentBuffer&& other) noexcept = default;
      AlignmentBuffer& operator=(const AlignmentBuffer& other) = default;
      AlignmentBuffer& operator=(AlignmentBuffer&& other) noexcept = default;

      void clear() {
         zeroize_buffer(m_buffer.data(), m_buffer.size());
         m_position = 0;
      }

      /**
       * Fills the currently unused bytes of the buffer with zero bytes
       */
      void fill_up_with_zeros() {
         if(!ready_to_consume()) {
            zeroize_buffer(&m_buffer[m_position], elements_until_alignment());
            m_position = m_buffer.size();
         }
      }

      /**
       * Appends the provided @p elements to the buffer. The user has to make
       * sure that @p elements fits in the remaining capacity of the buffer.
       */
      void append(std::span<const T> elements) {
         BOTAN_ASSERT_NOMSG(elements.size() <= elements_until_alignment());
         std::copy(elements.begin(), elements.end(), m_buffer.begin() + m_position);
         m_position += elements.size();
      }

      /**
       * Allows direct modification of the first @p elements in the buffer.
       * This is a low-level accessor that neither takes the buffer's current
       * capacity into account nor does it change the internal cursor.
       * Beware not to overwrite unconsumed bytes.
       */
      std::span<T> directly_modify_first(size_t elements) {
         BOTAN_ASSERT_NOMSG(size() >= elements);
         return std::span(m_buffer).first(elements);
      }

      /**
       * Allows direct modification of the last @p elements in the buffer.
       * This is a low-level accessor that neither takes the buffer's current
       * capacity into account nor does it change the internal cursor.
       * Beware not to overwrite unconsumed bytes.
       */
      std::span<T> directly_modify_last(size_t elements) {
         BOTAN_ASSERT_NOMSG(size() >= elements);
         return std::span(m_buffer).last(elements);
      }

      /**
       * Once the buffer reached alignment, this can be used to consume as many
       * input bytes from the given @p slider as possible. The output always
       * contains data elements that are a multiple of the intrinsic block size.
       *
       * @returns a view onto the aligned data from @p slicer and the number of
       *          full blocks that are represented by this view.
       */
      [[nodiscard]] std::tuple<std::span<const uint8_t>, size_t> aligned_data_to_process(BufferSlicer& slicer) const {
         BOTAN_ASSERT_NOMSG(in_alignment());

         // When the final block is to be deferred, the last block must not be
         // selected for processing if there is no (unaligned) extra input data.
         const size_t defer = (defers_final_block()) ? 1 : 0;
         const size_t full_blocks_to_process = (slicer.remaining() - defer) / m_buffer.size();
         return {slicer.take(full_blocks_to_process * m_buffer.size()), full_blocks_to_process};
      }

      /**
       * Once the buffer reached alignment, this can be used to consume full
       * blocks from the input data represented by @p slicer.
       *
       * @returns a view onto the next full block from @p slicer or std::nullopt
       *          if not enough data is available in @p slicer.
       */
      [[nodiscard]] std::optional<std::span<const uint8_t>> next_aligned_block_to_process(BufferSlicer& slicer) const {
         BOTAN_ASSERT_NOMSG(in_alignment());

         // When the final block is to be deferred, the last block must not be
         // selected for processing if there is no (unaligned) extra input data.
         const size_t defer = (defers_final_block()) ? 1 : 0;
         if(slicer.remaining() < m_buffer.size() + defer) {
            return std::nullopt;
         }

         return slicer.take(m_buffer.size());
      }

      /**
       * Intermittently buffers potentially unaligned data provided in @p
       * slicer. If the internal buffer already contains some elements, data is
       * appended. Once a full block is collected, it is returned to the caller
       * for processing.
       *
       * @param slicer the input data source to be (partially) consumed
       * @returns a view onto a full block once enough data was collected, or
       *          std::nullopt if no full block is available yet
       */
      [[nodiscard]] std::optional<std::span<const T>> handle_unaligned_data(BufferSlicer& slicer) {
         // When the final block is to be deferred, we would need to store and
         // hold a buffer that contains exactly one block until more data is
         // passed or it is explicitly consumed.
         const size_t defer = (defers_final_block()) ? 1 : 0;

         if(in_alignment() && slicer.remaining() >= m_buffer.size() + defer) {
            // We are currently in alignment and the passed-in data source
            // contains enough data to benefit from aligned processing.
            // Therefore, we don't copy anything into the intermittent buffer.
            return std::nullopt;
         }

         // Fill the buffer with as much input data as needed to reach alignment
         // or until the input source is depleted.
         const auto elements_to_consume = std::min(m_buffer.size() - m_position, slicer.remaining());
         append(slicer.take(elements_to_consume));

         // If we collected enough data, we push out one full block. When
         // deferring the final block is enabled, we additionally check that
         // more input data is available to continue processing a consecutive
         // block.
         if(ready_to_consume() && (!defers_final_block() || !slicer.empty())) {
            return consume();
         } else {
            return std::nullopt;
         }
      }

      /**
       * Explicitly consume the currently collected block. It is the caller's
       * responsibility to ensure that the buffer is filled fully. After
       * consumption, the buffer is cleared and ready to collect new data.
       */
      [[nodiscard]] std::span<const T> consume() {
         BOTAN_ASSERT_NOMSG(ready_to_consume());
         m_position = 0;
         return m_buffer;
      }

      /**
       * Explicitly consumes however many bytes are currently stored in the
       * buffer. After consumption, the buffer is cleared and ready to collect
       * new data.
       */
      [[nodiscard]] std::span<const T> consume_partial() {
         const auto elements = elements_in_buffer();
         m_position = 0;
         return std::span(m_buffer).first(elements);
      }

      constexpr size_t size() const { return m_buffer.size(); }

      size_t elements_in_buffer() const { return m_position; }

      size_t elements_until_alignment() const { return m_buffer.size() - m_position; }

      /**
       * @returns true if the buffer is empty (i.e. contains no unaligned data)
       */
      bool in_alignment() const { return m_position == 0; }

      /**
       * @returns true if the buffer is full (i.e. a block is ready to be consumed)
       */
      bool ready_to_consume() const { return m_position == m_buffer.size(); }

      constexpr bool defers_final_block() const {
         return FINAL_BLOCK_STRATEGY == AlignmentBufferFinalBlock::must_be_deferred;
      }

   private:
      std::array<T, BLOCK_SIZE> m_buffer = {};
      size_t m_position = 0;
};

}  // namespace Botan

#endif

1	/*
2	* Alignment buffer helper
3	* (C) 2023 Jack Lloyd
4	* 2023 René Meusel - Rohde & Schwarz Cybersecurity
5	*
6	* Botan is released under the Simplified BSD License (see license.txt)
7	*/
8
9	#ifndef BOTAN_ALIGNMENT_BUFFER_H_
10	#define BOTAN_ALIGNMENT_BUFFER_H_
11
12	#include <botan/internal/buffer_slicer.h>
13	#include <botan/internal/mem_utils.h>
14	#include <array>
15	#include <optional>
16	#include <span>
17
18	namespace Botan {
19
20	/**
21	* Defines the strategy for handling the final block of input data in the
22	* handle_unaligned_data() method of the AlignmentBuffer<>.
23	*
24	* - is_not_special: the final block is treated like any other block
25	* - must_be_deferred: the final block is not emitted while bulk processing (typically add_data())
26	* but is deferred until manually consumed (typically final_result())
27	*
28	* The AlignmentBuffer<> assumes data to be "the final block" if no further
29	* input data is available in the BufferSlicer<>. This might result in some
30	* performance overhead when using the must_be_deferred strategy.
31	*/
32	enum class AlignmentBufferFinalBlock : uint8_t {
33	is_not_special = 0,
34	must_be_deferred = 1,
35	};
36
37	/**
38	* @brief Alignment buffer helper
39	*
40	* Many algorithms have an intrinsic block size in which they consume input
41	* data. When streaming arbitrary data chunks to such algorithms we must store
42	* some data intermittently to honor the algorithm's alignment requirements.
43	*
44	* This helper encapsulates such an alignment buffer. The API of this class is
45	* designed to minimize user errors in the algorithm implementations. Therefore,
46	* it is strongly opinionated on its use case. Don't try to use it for anything
47	* but the described circumstance.
48	*
49	* @tparam T the element type of the internal buffer
50	* @tparam BLOCK_SIZE the buffer size to use for the alignment buffer
51	* @tparam FINAL_BLOCK_STRATEGY defines whether the final input data block is
52	* retained in handle_unaligned_data() and must be
53	* manually consumed
54	*/
55	template <typename T,
56	size_t BLOCK_SIZE,
57	AlignmentBufferFinalBlock FINAL_BLOCK_STRATEGY = AlignmentBufferFinalBlock::is_not_special>
58	requires(BLOCK_SIZE > 0)
59	class AlignmentBuffer {
60	public:
61	AlignmentBuffer() = default;	588,493✔
62
63	~AlignmentBuffer() { secure_zeroize_buffer(m_buffer.data(), sizeof(T) * m_buffer.size()); }	1,036✔
64
65	AlignmentBuffer(const AlignmentBuffer& other) = default;
66	AlignmentBuffer(AlignmentBuffer&& other) noexcept = default;
67	AlignmentBuffer& operator=(const AlignmentBuffer& other) = default;
68	AlignmentBuffer& operator=(AlignmentBuffer&& other) noexcept = default;
69
70	void clear() {	238,508,462✔
71	zeroize_buffer(m_buffer.data(), m_buffer.size());	238,508,462✔
72	m_position = 0;	924,228✔
73	}
74
75	/**
76	* Fills the currently unused bytes of the buffer with zero bytes
77	*/
78	void fill_up_with_zeros() {	248,218,338✔
79	if(!ready_to_consume()) {	248,218,338✔
80	zeroize_buffer(&m_buffer[m_position], elements_until_alignment());	248,215,946✔
81	m_position = m_buffer.size();	248,215,946✔
82	}
83	}
84
85	/**
86	* Appends the provided @p elements to the buffer. The user has to make
87	* sure that @p elements fits in the remaining capacity of the buffer.
88	*/
89	void append(std::span<const T> elements) {	960,111,677✔
90	BOTAN_ASSERT_NOMSG(elements.size() <= elements_until_alignment());	×
91	std::copy(elements.begin(), elements.end(), m_buffer.begin() + m_position);	960,111,677✔
92	m_position += elements.size();	960,111,677✔
93	}	960,111,677✔
94
95	/**
96	* Allows direct modification of the first @p elements in the buffer.
97	* This is a low-level accessor that neither takes the buffer's current
98	* capacity into account nor does it change the internal cursor.
99	* Beware not to overwrite unconsumed bytes.
100	*/
101	std::span<T> directly_modify_first(size_t elements) {	2,100✔
102	BOTAN_ASSERT_NOMSG(size() >= elements);	2,100✔
103	return std::span(m_buffer).first(elements);	2,100✔
104	}
105
106	/**
107	* Allows direct modification of the last @p elements in the buffer.
108	* This is a low-level accessor that neither takes the buffer's current
109	* capacity into account nor does it change the internal cursor.
110	* Beware not to overwrite unconsumed bytes.
111	*/
112	std::span<T> directly_modify_last(size_t elements) {	237,230,955✔
113	BOTAN_ASSERT_NOMSG(size() >= elements);	237,230,955✔
114	return std::span(m_buffer).last(elements);	237,230,955✔
115	}
116
117	/**
118	* Once the buffer reached alignment, this can be used to consume as many
119	* input bytes from the given @p slider as possible. The output always
120	* contains data elements that are a multiple of the intrinsic block size.
121	*
122	* @returns a view onto the aligned data from @p slicer and the number of
123	* full blocks that are represented by this view.
124	*/
125	[[nodiscard]] std::tuple<std::span<const uint8_t>, size_t> aligned_data_to_process(BufferSlicer& slicer) const {	222,674,624✔
126	BOTAN_ASSERT_NOMSG(in_alignment());	×
127
128	// When the final block is to be deferred, the last block must not be
129	// selected for processing if there is no (unaligned) extra input data.
130	const size_t defer = (defers_final_block()) ? 1 : 0;	222,674,624✔
131	const size_t full_blocks_to_process = (slicer.remaining() - defer) / m_buffer.size();	222,674,624✔
132	return {slicer.take(full_blocks_to_process * m_buffer.size()), full_blocks_to_process};	222,674,624✔
133	}
134
135	/**
136	* Once the buffer reached alignment, this can be used to consume full
137	* blocks from the input data represented by @p slicer.
138	*
139	* @returns a view onto the next full block from @p slicer or std::nullopt
140	* if not enough data is available in @p slicer.
141	*/
142	[[nodiscard]] std::optional<std::span<const uint8_t>> next_aligned_block_to_process(BufferSlicer& slicer) const {	6,276✔
143	BOTAN_ASSERT_NOMSG(in_alignment());	×
144
145	// When the final block is to be deferred, the last block must not be
146	// selected for processing if there is no (unaligned) extra input data.
147	const size_t defer = (defers_final_block()) ? 1 : 0;	6,276✔
148	if(slicer.remaining() < m_buffer.size() + defer) {	6,276✔
149	return std::nullopt;	2,751✔
150	}
151
152	return slicer.take(m_buffer.size());	3,525✔
153	}
154
155	/**
156	* Intermittently buffers potentially unaligned data provided in @p
157	* slicer. If the internal buffer already contains some elements, data is
158	* appended. Once a full block is collected, it is returned to the caller
159	* for processing.
160	*
161	* @param slicer the input data source to be (partially) consumed
162	* @returns a view onto a full block once enough data was collected, or
163	* std::nullopt if no full block is available yet
164	*/
165	[[nodiscard]] std::optional<std::span<const T>> handle_unaligned_data(BufferSlicer& slicer) {	830,952,847✔
166	// When the final block is to be deferred, we would need to store and
167	// hold a buffer that contains exactly one block until more data is
168	// passed or it is explicitly consumed.
169	const size_t defer = (defers_final_block()) ? 1 : 0;	830,952,847✔
170
171	if(in_alignment() && slicer.remaining() >= m_buffer.size() + defer) {	457,054,279✔
172	// We are currently in alignment and the passed-in data source
173	// contains enough data to benefit from aligned processing.
174	// Therefore, we don't copy anything into the intermittent buffer.
175	return std::nullopt;	108,079,650✔
176	}
177
178	// Fill the buffer with as much input data as needed to reach alignment
179	// or until the input source is depleted.
180	const auto elements_to_consume = std::min(m_buffer.size() - m_position, slicer.remaining());	722,873,197✔
181	append(slicer.take(elements_to_consume));	722,873,197✔
182
183	// If we collected enough data, we push out one full block. When
184	// deferring the final block is enabled, we additionally check that
185	// more input data is available to continue processing a consecutive
186	// block.
187	if(ready_to_consume() && (!defers_final_block() \|\| !slicer.empty())) {	722,452,591✔
188	return consume();	114,597,721✔
189	} else {
190	return std::nullopt;	608,275,476✔
191	}
192	}
193
194	/**
195	* Explicitly consume the currently collected block. It is the caller's
196	* responsibility to ensure that the buffer is filled fully. After
197	* consumption, the buffer is cleared and ready to collect new data.
198	*/
199	[[nodiscard]] std::span<const T> consume() {	362,816,060✔
200	BOTAN_ASSERT_NOMSG(ready_to_consume());	×
201	m_position = 0;	362,816,060✔
202	return m_buffer;	362,816,060✔
203	}
204
205	/**
206	* Explicitly consumes however many bytes are currently stored in the
207	* buffer. After consumption, the buffer is cleared and ready to collect
208	* new data.
209	*/
210	[[nodiscard]] std::span<const T> consume_partial() {	3✔
211	const auto elements = elements_in_buffer();	3✔
212	m_position = 0;	3✔
213	return std::span(m_buffer).first(elements);	3✔
214	}
215
216	constexpr size_t size() const { return m_buffer.size(); }	237,235,217✔
217
218	size_t elements_in_buffer() const { return m_position; }	230,451✔
219
220	size_t elements_until_alignment() const { return m_buffer.size() - m_position; }	1,219,063,844✔
221
222	/**
223	* @returns true if the buffer is empty (i.e. contains no unaligned data)
224	*/
225	bool in_alignment() const { return m_position == 0; }	1,884,735,409✔
226
227	/**
228	* @returns true if the buffer is full (i.e. a block is ready to be consumed)
229	*/
230	bool ready_to_consume() const { return m_position == m_buffer.size(); }	1,571,138,572✔
231
232	constexpr bool defers_final_block() const {
233	return FINAL_BLOCK_STRATEGY == AlignmentBufferFinalBlock::must_be_deferred;
234	}
235
236	private:
237	std::array<T, BLOCK_SIZE> m_buffer = {};
238	size_t m_position = 0;
239	};
240
241	} // namespace Botan
242
243	#endif

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