1 #ifndef _MINISKETCH_H_
2 #define _MINISKETCH_H_ 1
3 4 #include <stdint.h>
5 #include <stdlib.h>
6 7 #ifdef _MSC_VER
8 # include <BaseTsd.h>
9 typedef SSIZE_T ssize_t;
10 #else
11 # include <unistd.h>
12 #endif
13 14 #ifndef MINISKETCH_API
15 # if defined(_WIN32)
16 # ifdef MINISKETCH_BUILD
17 # define MINISKETCH_API __declspec(dllexport)
18 # else
19 # define MINISKETCH_API
20 # endif
21 # elif defined(__GNUC__) && (__GNUC__ >= 4) && defined(MINISKETCH_BUILD)
22 # define MINISKETCH_API __attribute__ ((visibility ("default")))
23 # else
24 # define MINISKETCH_API
25 # endif
26 #endif
27 28 #ifdef __cplusplus
29 # if __cplusplus >= 201103L
30 # include <memory>
31 # include <vector>
32 # include <cassert>
33 # if __cplusplus >= 201703L
34 # include <optional>
35 # endif // __cplusplus >= 201703L
36 # endif // __cplusplus >= 201103L
37 extern "C" {
38 #endif // __cplusplus
39 40 /** Opaque type for decoded sketches. */
41 typedef struct minisketch minisketch;
42 43 /** Determine whether support for elements of `bits` bits was compiled in. */
44 MINISKETCH_API int minisketch_bits_supported(uint32_t bits);
45 46 /** Determine the maximum number of implementations available.
47 *
48 * Multiple implementations may be available for a given element size, with
49 * different performance characteristics on different hardware.
50 *
51 * Each implementation is identified by a number from 0 to the output of this
52 * function call, inclusive. Note that not every combination of implementation
53 * and element size may exist (see further).
54 */
55 MINISKETCH_API uint32_t minisketch_implementation_max(void);
56 57 /** Determine if the a combination of bits and implementation number is available.
58 *
59 * Returns 1 if it is, 0 otherwise.
60 */
61 MINISKETCH_API int minisketch_implementation_supported(uint32_t bits, uint32_t implementation);
62 63 /** Construct a sketch for a given element size, implementation and capacity.
64 *
65 * If the combination of `bits` and `implementation` is unavailable, or when
66 * OOM occurs, NULL is returned. If minisketch_implementation_supported
67 * returns 1 for the specified bits and implementation, this will always succeed
68 * (except when allocation fails).
69 *
70 * If the result is not NULL, it must be destroyed using minisketch_destroy.
71 */
72 MINISKETCH_API minisketch* minisketch_create(uint32_t bits, uint32_t implementation, size_t capacity);
73 74 /** Get the element size of a sketch in bits. */
75 MINISKETCH_API uint32_t minisketch_bits(const minisketch* sketch);
76 77 /** Get the capacity of a sketch. */
78 MINISKETCH_API size_t minisketch_capacity(const minisketch* sketch);
79 80 /** Get the implementation of a sketch. */
81 MINISKETCH_API uint32_t minisketch_implementation(const minisketch* sketch);
82 83 /** Set the seed for randomizing algorithm choices to a fixed value.
84 *
85 * By default, sketches are initialized with a random seed. This is important
86 * to avoid scenarios where an attacker could force worst-case behavior.
87 *
88 * This function initializes the seed to a user-provided value (any 64-bit
89 * integer is acceptable, regardless of field size).
90 *
91 * When seed is -1, a fixed internal value with predictable behavior is
92 * used. It is only intended for testing.
93 */
94 MINISKETCH_API void minisketch_set_seed(minisketch* sketch, uint64_t seed);
95 96 /** Clone a sketch.
97 *
98 * The result must be destroyed using minisketch_destroy.
99 */
100 MINISKETCH_API minisketch* minisketch_clone(const minisketch* sketch);
101 102 /** Destroy a sketch.
103 *
104 * The pointer that was passed in may not be used anymore afterwards.
105 */
106 MINISKETCH_API void minisketch_destroy(minisketch* sketch);
107 108 /** Compute the size in bytes for serializing a given sketch. */
109 MINISKETCH_API size_t minisketch_serialized_size(const minisketch* sketch);
110 111 /** Serialize a sketch to bytes. */
112 MINISKETCH_API void minisketch_serialize(const minisketch* sketch, unsigned char* output);
113 114 /** Deserialize a sketch from bytes. */
115 MINISKETCH_API void minisketch_deserialize(minisketch* sketch, const unsigned char* input);
116 117 /** Add an element to a sketch.
118 *
119 * If the element to be added is too large for the sketch, the most significant
120 * bits of the element are dropped. More precisely, if the element size of
121 * `sketch` is b bits, then this function adds the unsigned integer represented
122 * by the b least significant bits of `element` to `sketch`.
123 *
124 * If the element to be added is 0 (after potentially dropping the most significant
125 * bits), then this function is a no-op. Sketches cannot contain an element with
126 * the value 0.
127 *
128 * Note that adding the same element a second time removes it again.
129 */
130 MINISKETCH_API void minisketch_add_uint64(minisketch* sketch, uint64_t element);
131 132 /** Merge the elements of another sketch into this sketch.
133 *
134 * After merging, `sketch` will contain every element that existed in one but not
135 * both of the input sketches. It can be seen as an exclusive or operation on
136 * the set elements. If the capacity of `other_sketch` is lower than `sketch`'s,
137 * merging reduces the capacity of `sketch` to that of `other_sketch`.
138 *
139 * This function returns the capacity of `sketch` after merging has been performed
140 * (where this capacity is at least 1), or 0 to indicate that merging has failed because
141 * the two input sketches differ in their element size or implementation. If 0 is
142 * returned, `sketch` (and its capacity) have not been modified.
143 *
144 * It is also possible to perform this operation directly on the serializations
145 * of two sketches with the same element size and capacity by performing a bitwise XOR
146 * of the serializations.
147 */
148 MINISKETCH_API size_t minisketch_merge(minisketch* sketch, const minisketch* other_sketch);
149 150 /** Decode a sketch.
151 *
152 * `output` is a pointer to an array of `max_element` uint64_t's, which will be
153 * filled with the elements in this sketch.
154 *
155 * The return value is the number of decoded elements, or -1 if decoding failed.
156 */
157 MINISKETCH_API ssize_t minisketch_decode(const minisketch* sketch, size_t max_elements, uint64_t* output);
158 159 /** Compute the capacity needed to achieve a certain rate of false positives.
160 *
161 * A sketch with capacity c and no more than c elements can always be decoded
162 * correctly. However, if it has more than c elements, or contains just random
163 * bytes, it is possible that it will still decode, but the result will be
164 * nonsense. This can be counteracted by increasing the capacity slightly.
165 *
166 * Given a field size bits, an intended number of elements that can be decoded
167 * max_elements, and a false positive probability of 1 in 2**fpbits, this
168 * function computes the necessary capacity. It is only guaranteed to be
169 * accurate up to fpbits=256.
170 */
171 MINISKETCH_API size_t minisketch_compute_capacity(uint32_t bits, size_t max_elements, uint32_t fpbits);
172 173 /** Compute what max_elements can be decoded for a certain rate of false positives.
174 *
175 * This is the inverse operation of minisketch_compute_capacity. It determines,
176 * given a field size bits, a capacity of a sketch, and an acceptable false
177 * positive probability of 1 in 2**fpbits, what the maximum allowed
178 * max_elements value is. If no value of max_elements would give the desired
179 * false positive probability, 0 is returned.
180 *
181 * Note that this is not an exact inverse of minisketch_compute_capacity. For
182 * example, with bits=32, fpbits=16, and max_elements=8,
183 * minisketch_compute_capacity will return 9, as capacity 8 would only have a
184 * false positive chance of 1 in 2^15.3. Increasing the capacity to 9 however
185 * decreases the fp chance to 1 in 2^47.3, enough for max_elements=9 (with fp
186 * chance of 1 in 2^18.5). Therefore, minisketch_compute_max_elements with
187 * capacity=9 will return 9.
188 */
189 MINISKETCH_API size_t minisketch_compute_max_elements(uint32_t bits, size_t capacity, uint32_t fpbits);
190 191 #ifdef __cplusplus
192 }
193 194 #if __cplusplus >= 201103L
195 /** Simple RAII C++11 wrapper around the minisketch API. */
196 class Minisketch
197 {
198 struct Deleter
199 {
200 void operator()(minisketch* ptr) const
201 {
202 minisketch_destroy(ptr);
203 }
204 };
205 206 std::unique_ptr<minisketch, Deleter> m_minisketch;
207 208 public:
209 /** Check whether the library supports fields of the given size. */
210 static bool BitsSupported(uint32_t bits) noexcept { return minisketch_bits_supported(bits); }
211 212 /** Get the highest supported implementation number. */
213 static uint32_t MaxImplementation() noexcept { return minisketch_implementation_max(); }
214 215 /** Check whether the library supports fields with a given size and implementation number.
216 * If a particular field size `bits` is supported, implementation 0 is always supported for it.
217 * Higher implementation numbers may or may not be available as well, up to MaxImplementation().
218 */
219 static bool ImplementationSupported(uint32_t bits, uint32_t implementation) noexcept { return minisketch_implementation_supported(bits, implementation); }
220 221 /** Given field size and a maximum number of decodable elements n, compute what capacity c to
222 * use so that sketches with more elements than n have a chance no higher than 2^-fpbits of
223 * being decoded incorrectly (and will instead fail when decoding for up to n elements).
224 *
225 * See minisketch_compute_capacity for more details. */
226 static size_t ComputeCapacity(uint32_t bits, size_t max_elements, uint32_t fpbits) noexcept { return minisketch_compute_capacity(bits, max_elements, fpbits); }
227 228 /** Reverse operation of ComputeCapacity. See minisketch_compute_max_elements. */
229 static size_t ComputeMaxElements(uint32_t bits, size_t capacity, uint32_t fpbits) noexcept { return minisketch_compute_max_elements(bits, capacity, fpbits); }
230 231 /** Construct a clone of the specified sketch. */
232 Minisketch(const Minisketch& sketch) noexcept
233 {
234 if (sketch.m_minisketch) {
235 m_minisketch = std::unique_ptr<minisketch, Deleter>(minisketch_clone(sketch.m_minisketch.get()));
236 }
237 }
238 239 /** Make this Minisketch a clone of the specified one. */
240 Minisketch& operator=(const Minisketch& sketch) noexcept
241 {
242 if (this != &sketch && sketch.m_minisketch) {
243 m_minisketch = std::unique_ptr<minisketch, Deleter>(minisketch_clone(sketch.m_minisketch.get()));
244 }
245 return *this;
246 }
247 248 /** Check whether this Minisketch object is valid. */
249 explicit operator bool() const noexcept { return bool{m_minisketch}; }
250 251 /** Default constructor is deleted. */
252 Minisketch() noexcept = delete;
253 254 /** Move constructor. */
255 Minisketch(Minisketch&&) noexcept = default;
256 257 /** Move assignment. */
258 Minisketch& operator=(Minisketch&&) noexcept = default;
259 260 /** Construct a Minisketch object with the specified parameters.
261 *
262 * If bits is not BitsSupported(), or the combination of bits and capacity is not
263 * ImplementationSupported(), or OOM occurs internally, an invalid Minisketch
264 * object will be constructed. Use operator bool() to check that this isn't the
265 * case before performing any other operations. */
266 Minisketch(uint32_t bits, uint32_t implementation, size_t capacity) noexcept
267 {
268 m_minisketch = std::unique_ptr<minisketch, Deleter>(minisketch_create(bits, implementation, capacity));
269 }
270 271 /** Create a Minisketch object sufficiently large for the specified number of elements at given fpbits.
272 * It may construct an invalid object, which you may need to check for. */
273 static Minisketch CreateFP(uint32_t bits, uint32_t implementation, size_t max_elements, uint32_t fpbits) noexcept
274 {
275 return Minisketch(bits, implementation, ComputeCapacity(bits, max_elements, fpbits));
276 }
277 278 /** Return the field size for a (valid) Minisketch object. */
279 uint32_t GetBits() const noexcept { return minisketch_bits(m_minisketch.get()); }
280 281 /** Return the capacity for a (valid) Minisketch object. */
282 size_t GetCapacity() const noexcept { return minisketch_capacity(m_minisketch.get()); }
283 284 /** Return the implementation number for a (valid) Minisketch object. */
285 uint32_t GetImplementation() const noexcept { return minisketch_implementation(m_minisketch.get()); }
286 287 /** Set the seed for a (valid) Minisketch object. See minisketch_set_seed(). */
288 Minisketch& SetSeed(uint64_t seed) noexcept
289 {
290 minisketch_set_seed(m_minisketch.get(), seed);
291 return *this;
292 }
293 294 /** Add (or remove, if already present) an element to a (valid) Minisketch object.
295 * See minisketch_add_uint64(). */
296 Minisketch& Add(uint64_t element) noexcept
297 {
298 minisketch_add_uint64(m_minisketch.get(), element);
299 return *this;
300 }
301 302 /** Merge sketch into *this; both have to be valid Minisketch objects.
303 * See minisketch_merge for details. */
304 Minisketch& Merge(const Minisketch& sketch) noexcept
305 {
306 minisketch_merge(m_minisketch.get(), sketch.m_minisketch.get());
307 return *this;
308 }
309 310 /** Decode this (valid) Minisketch object into the result vector, up to as many elements as the
311 * vector's size permits. */
312 bool Decode(std::vector<uint64_t>& result) const
313 {
314 ssize_t ret = minisketch_decode(m_minisketch.get(), result.size(), result.data());
315 if (ret == -1) return false;
316 result.resize(ret);
317 return true;
318 }
319 320 /** Get the serialized size in bytes for this (valid) Minisketch object.. */
321 size_t GetSerializedSize() const noexcept { return minisketch_serialized_size(m_minisketch.get()); }
322 323 /** Serialize this (valid) Minisketch object as a byte vector. */
324 std::vector<unsigned char> Serialize() const
325 {
326 std::vector<unsigned char> result(GetSerializedSize());
327 minisketch_serialize(m_minisketch.get(), result.data());
328 return result;
329 }
330 331 /** Deserialize into this (valid) Minisketch from an object containing its bytes (which has data()
332 * and size() members). */
333 template<typename T>
334 Minisketch& Deserialize(
335 const T& obj,
336 typename std::enable_if<
337 std::is_convertible<typename std::remove_pointer<decltype(obj.data())>::type (*)[], const unsigned char (*)[]>::value &&
338 std::is_convertible<decltype(obj.size()), std::size_t>::value,
339 std::nullptr_t
340 >::type = nullptr) noexcept
341 {
342 assert(GetSerializedSize() == obj.size());
343 minisketch_deserialize(m_minisketch.get(), obj.data());
344 return *this;
345 }
346 347 #if __cplusplus >= 201703L
348 /** C++17 only: like Decode(), but up to a specified number of elements into an optional vector. */
349 std::optional<std::vector<uint64_t>> Decode(size_t max_elements) const
350 {
351 std::vector<uint64_t> result(max_elements);
352 ssize_t ret = minisketch_decode(m_minisketch.get(), max_elements, result.data());
353 if (ret == -1) return {};
354 result.resize(ret);
355 return result;
356 }
357 358 /** C++17 only: similar to Decode(), but with specified false positive probability. */
359 std::optional<std::vector<uint64_t>> DecodeFP(uint32_t fpbits) const
360 {
361 return Decode(ComputeMaxElements(GetBits(), GetCapacity(), fpbits));
362 }
363 #endif // __cplusplus >= 201703L
364 };
365 #endif // __cplusplus >= 201103L
366 #endif // __cplusplus
367 368 #endif // _MINISKETCH_H_
369