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|---|---|---|---|
| 1 | // | ||
| 2 | // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com) | ||
| 3 | // | ||
| 4 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | ||
| 5 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | ||
| 6 | // | ||
| 7 | // Official repository: https://github.com/cppalliance/buffers | ||
| 8 | // | ||
| 9 | |||
| 10 | #ifndef BOOST_BUFFERS_SLICE_HPP | ||
| 11 | #define BOOST_BUFFERS_SLICE_HPP | ||
| 12 | |||
| 13 | #include <boost/buffers/detail/config.hpp> | ||
| 14 | #include <boost/buffers/buffer.hpp> | ||
| 15 | #include <boost/buffers/range.hpp> | ||
| 16 | #include <boost/assert.hpp> | ||
| 17 | #include <array> | ||
| 18 | #include <iterator> | ||
| 19 | #include <type_traits> | ||
| 20 | |||
| 21 | namespace boost { | ||
| 22 | namespace buffers { | ||
| 23 | |||
| 24 | template<class T> class slice_of; | ||
| 25 | |||
| 26 | namespace detail { | ||
| 27 | |||
| 28 | template<class T, class = void> | ||
| 29 | struct has_tag_invoke : std::false_type {}; | ||
| 30 | |||
| 31 | template<class T> | ||
| 32 | struct has_tag_invoke<T, decltype(tag_invoke( | ||
| 33 | std::declval<slice_tag const&>(), | ||
| 34 | std::declval<T&>(), | ||
| 35 | std::declval<slice_how>(), | ||
| 36 | std::declval<std::size_t>()))> | ||
| 37 | : std::true_type {}; | ||
| 38 | |||
| 39 | } // detail | ||
| 40 | |||
| 41 | /** Alias for the type representing a slice of T | ||
| 42 | */ | ||
| 43 | template<class T> | ||
| 44 | using slice_type = typename std::conditional< | ||
| 45 | detail::has_tag_invoke<T>::value, | ||
| 46 | T, slice_of<T> >::type; | ||
| 47 | |||
| 48 | //------------------------------------------------ | ||
| 49 | |||
| 50 | /** A wrapper enabling a buffer sequence to be consumed | ||
| 51 | */ | ||
| 52 | template<class BufferSequence> | ||
| 53 | class slice_of | ||
| 54 | { | ||
| 55 | static_assert(! std::is_const<BufferSequence>::value, | ||
| 56 | "BufferSequence can't be const"); | ||
| 57 | |||
| 58 | static_assert(! std::is_reference<BufferSequence>::value, | ||
| 59 | "BufferSequence can't be a reference"); | ||
| 60 | |||
| 61 | static_assert(is_const_buffer_sequence<BufferSequence>::value, | ||
| 62 | "BufferSequence does not meet type requirements"); | ||
| 63 | |||
| 64 | using iter_type = decltype( | ||
| 65 | std::declval<BufferSequence const&>().begin()); | ||
| 66 | |||
| 67 | BufferSequence bs_; | ||
| 68 | iter_type begin_; | ||
| 69 | iter_type end_; | ||
| 70 | std::size_t len_ = 0; // length of bs_ | ||
| 71 | std::size_t size_ = 0; // total bytes | ||
| 72 | std::size_t prefix_ = 0; // used prefix bytes | ||
| 73 | std::size_t suffix_ = 0; // used suffix bytes | ||
| 74 | |||
| 75 | public: | ||
| 76 | /** The type of values returned by iterators | ||
| 77 | */ | ||
| 78 | using value_type = typename std::conditional< | ||
| 79 | is_mutable_buffer_sequence<BufferSequence>::value, | ||
| 80 | mutable_buffer, const_buffer>::type; | ||
| 81 | |||
| 82 | /** The type of returned iterators | ||
| 83 | */ | ||
| 84 | class const_iterator; | ||
| 85 | |||
| 86 | /** Constructor | ||
| 87 | */ | ||
| 88 | slice_of() = default; | ||
| 89 | |||
| 90 | /** Constructor | ||
| 91 | */ | ||
| 92 | 278809 | slice_of( | |
| 93 | BufferSequence const& bs) | ||
| 94 | 278809 | : bs_(bs) | |
| 95 | 278809 | , begin_(buffers::begin(bs_)) | |
| 96 | 278809 | , end_(buffers::end(bs_)) | |
| 97 | { | ||
| 98 | 278809 | auto it = begin_; | |
| 99 |
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836979 | while(it != end_) |
| 100 | { | ||
| 101 | 558170 | value_type b(*it); | |
| 102 | 558170 | size_ += b.size(); | |
| 103 | 558170 | ++len_; | |
| 104 | 558170 | ++it; | |
| 105 | } | ||
| 106 | 278809 | } | |
| 107 | |||
| 108 | /** Return an iterator to the beginning of the sequence | ||
| 109 | */ | ||
| 110 | const_iterator | ||
| 111 | begin() const noexcept; | ||
| 112 | |||
| 113 | /** Return an iterator to the end of the sequence | ||
| 114 | */ | ||
| 115 | const_iterator | ||
| 116 | end() const noexcept; | ||
| 117 | |||
| 118 | friend | ||
| 119 | void | ||
| 120 | 266505 | tag_invoke( | |
| 121 | slice_tag const&, | ||
| 122 | slice_of<BufferSequence>& bs, | ||
| 123 | slice_how how, | ||
| 124 | std::size_t n) | ||
| 125 | { | ||
| 126 | 266505 | bs.slice_impl(how, n); | |
| 127 | 266505 | } | |
| 128 | |||
| 129 | private: | ||
| 130 | void | ||
| 131 | 131194 | remove_prefix_impl( | |
| 132 | std::size_t n) | ||
| 133 | { | ||
| 134 | // nice hack to simplify the loop (M. Nejati) | ||
| 135 | 131194 | n += prefix_; | |
| 136 | 131194 | size_ += prefix_; | |
| 137 | 131194 | prefix_ = 0; | |
| 138 | |||
| 139 |
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201047 | while(n > 0 && begin_ != end_) |
| 140 | { | ||
| 141 | 178351 | value_type b = *begin_; | |
| 142 |
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178351 | if(n < b.size()) |
| 143 | { | ||
| 144 | 108498 | prefix_ = n; | |
| 145 | 108498 | size_ -= n; | |
| 146 | 108498 | break; | |
| 147 | } | ||
| 148 | 69853 | n -= b.size(); | |
| 149 | 69853 | size_ -= b.size(); | |
| 150 | 69853 | ++begin_; | |
| 151 | 69853 | --len_; | |
| 152 | } | ||
| 153 | 131194 | } | |
| 154 | |||
| 155 | void | ||
| 156 | 114791 | remove_suffix_impl( | |
| 157 | std::size_t n) | ||
| 158 | { | ||
| 159 |
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114791 | if(size_ == 0) |
| 160 | { | ||
| 161 | ✗ | BOOST_ASSERT(begin_ == end_); | |
| 162 | 114791 | return; | |
| 163 | } | ||
| 164 |
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114791 | BOOST_ASSERT(begin_ != end_); |
| 165 | 114791 | n += suffix_; | |
| 166 | 114791 | size_ += suffix_; | |
| 167 | 114791 | suffix_ = 0; | |
| 168 | 114791 | iter_type it = end_; | |
| 169 | 114791 | --it; | |
| 170 |
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188842 | while(it != begin_) |
| 171 | { | ||
| 172 | 114885 | value_type b = *it; | |
| 173 |
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114885 | if(n < b.size()) |
| 174 | { | ||
| 175 | 40834 | suffix_ = n; | |
| 176 | 40834 | size_ -= n; | |
| 177 | 40834 | return; | |
| 178 | } | ||
| 179 | 74051 | n -= b.size(); | |
| 180 | 74051 | size_ -= b.size(); | |
| 181 | 74051 | --it; | |
| 182 | 74051 | --end_; | |
| 183 | 74051 | --len_; | |
| 184 | } | ||
| 185 | 73957 | value_type b = *it; | |
| 186 | 73957 | auto m = b.size() - prefix_; | |
| 187 |
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73957 | if(n < m) |
| 188 | { | ||
| 189 | 73957 | suffix_ = n; | |
| 190 | 73957 | size_ -= n; | |
| 191 | 73957 | return; | |
| 192 | } | ||
| 193 | ✗ | end_ = begin_; | |
| 194 | ✗ | len_ = 0; | |
| 195 | } | ||
| 196 | |||
| 197 | void | ||
| 198 | 135311 | keep_prefix_impl( | |
| 199 | std::size_t n) | ||
| 200 | { | ||
| 201 |
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135311 | if(n >= size_) |
| 202 | 8217 | return; | |
| 203 |
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127094 | if(n == 0) |
| 204 | { | ||
| 205 | 12303 | end_ = begin_; | |
| 206 | 12303 | len_ = 0; | |
| 207 | 12303 | size_ = 0; | |
| 208 | 12303 | return; | |
| 209 | } | ||
| 210 | 114791 | remove_suffix_impl(size_ - n); | |
| 211 | } | ||
| 212 | |||
| 213 | void | ||
| 214 | keep_suffix_impl( | ||
| 215 | std::size_t n) | ||
| 216 | { | ||
| 217 | if(n >= size_) | ||
| 218 | return; | ||
| 219 | if(n == 0) | ||
| 220 | { | ||
| 221 | begin_ = end_; | ||
| 222 | len_ = 0; | ||
| 223 | size_ = 0; | ||
| 224 | return; | ||
| 225 | } | ||
| 226 | remove_prefix_impl(size_ - n); | ||
| 227 | } | ||
| 228 | |||
| 229 | void | ||
| 230 | 266505 | slice_impl( | |
| 231 | slice_how how, | ||
| 232 | std::size_t n) | ||
| 233 | { | ||
| 234 |
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266505 | switch(how) |
| 235 | { | ||
| 236 | 131194 | case slice_how::remove_prefix: | |
| 237 | { | ||
| 238 | 131194 | remove_prefix_impl(n); | |
| 239 | 131194 | break; | |
| 240 | } | ||
| 241 | 135311 | case slice_how::keep_prefix: | |
| 242 | { | ||
| 243 | 135311 | keep_prefix_impl(n); | |
| 244 | 135311 | break; | |
| 245 | } | ||
| 246 | } | ||
| 247 | 266505 | } | |
| 248 | }; | ||
| 249 | |||
| 250 | //------------------------------------------------ | ||
| 251 | |||
| 252 | template<class BufferSequence> | ||
| 253 | class slice_of<BufferSequence>:: | ||
| 254 | const_iterator | ||
| 255 | { | ||
| 256 | using iter_type = typename | ||
| 257 | slice_of::iter_type; | ||
| 258 | |||
| 259 | iter_type it_; | ||
| 260 | // VFALCO we could just point back to | ||
| 261 | // the original sequence to save size | ||
| 262 | std::size_t prefix_ = 0; | ||
| 263 | std::size_t suffix_ = 0; | ||
| 264 | std::size_t i_ = 0; | ||
| 265 | std::size_t n_ = 0; | ||
| 266 | |||
| 267 | friend class slice_of<BufferSequence>; | ||
| 268 | |||
| 269 | 6412252 | const_iterator( | |
| 270 | iter_type it, | ||
| 271 | std::size_t prefix__, | ||
| 272 | std::size_t suffix__, | ||
| 273 | std::size_t i, | ||
| 274 | std::size_t n) noexcept | ||
| 275 | 6412252 | : it_(it) | |
| 276 | 6412252 | , prefix_(prefix__) | |
| 277 | 6412252 | , suffix_(suffix__) | |
| 278 | 6412252 | , i_(i) | |
| 279 | 6412252 | , n_(n) | |
| 280 | { | ||
| 281 | // n_ is the index of the end iterator | ||
| 282 | 6412252 | } | |
| 283 | |||
| 284 | public: | ||
| 285 | using value_type = typename slice_of::value_type; | ||
| 286 | using reference = value_type; | ||
| 287 | using pointer = void; | ||
| 288 | using difference_type = std::ptrdiff_t; | ||
| 289 | using iterator_category = | ||
| 290 | std::bidirectional_iterator_tag; | ||
| 291 | #if defined(__cpp_concepts) || defined(__cpp_lib_concepts) | ||
| 292 | using iterator_concept = std::bidirectional_iterator_tag; // (since C++20) | ||
| 293 | #endif | ||
| 294 | |||
| 295 | const_iterator() = default; | ||
| 296 | |||
| 297 | bool | ||
| 298 | 7768114 | operator==( | |
| 299 | const_iterator const& other) const noexcept | ||
| 300 | { | ||
| 301 | return | ||
| 302 | 10974239 | it_ == other.it_ && | |
| 303 |
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3206125 | prefix_ == other.prefix_ && |
| 304 |
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3206125 | suffix_ == other.suffix_ && |
| 305 |
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14180364 | i_ == other.i_ && |
| 306 |
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10974239 | n_ == other.n_; |
| 307 | } | ||
| 308 | |||
| 309 | bool | ||
| 310 | 7768114 | operator!=( | |
| 311 | const_iterator const& other) const noexcept | ||
| 312 | { | ||
| 313 | 7768114 | return !(*this == other); | |
| 314 | } | ||
| 315 | |||
| 316 | reference | ||
| 317 | 4561989 | operator*() const noexcept | |
| 318 | { | ||
| 319 | 4561989 | value_type v = *it_; | |
| 320 | using P = typename std::conditional< | ||
| 321 | is_mutable_buffer_sequence<BufferSequence>::value, | ||
| 322 | char*, char const*>::type; | ||
| 323 | 4561989 | auto p = reinterpret_cast<P>(v.data()); | |
| 324 | 4561989 | auto n = v.size(); | |
| 325 |
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4561989 | if(i_ == 0) |
| 326 | { | ||
| 327 | 2956579 | p += prefix_; | |
| 328 | 2956579 | n -= prefix_; | |
| 329 | } | ||
| 330 |
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4561989 | if(i_ == n_ - 1) |
| 331 | 2956579 | n -= suffix_; | |
| 332 | 4561989 | return value_type(p, n); | |
| 333 | } | ||
| 334 | |||
| 335 | const_iterator& | ||
| 336 | 3004622 | operator++() noexcept | |
| 337 | { | ||
| 338 |
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3004622 | BOOST_ASSERT(i_ < n_); |
| 339 | 3004622 | ++it_; | |
| 340 | 3004622 | ++i_; | |
| 341 | 3004622 | return *this; | |
| 342 | } | ||
| 343 | |||
| 344 | const_iterator | ||
| 345 | 778684 | operator++(int) noexcept | |
| 346 | { | ||
| 347 | 778684 | auto temp = *this; | |
| 348 | 778684 | ++(*this); | |
| 349 | 778684 | return temp; | |
| 350 | } | ||
| 351 | |||
| 352 | const_iterator& | ||
| 353 | 1557368 | operator--() noexcept | |
| 354 | { | ||
| 355 |
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1557368 | BOOST_ASSERT(i_ > 0); |
| 356 | 1557368 | --it_; | |
| 357 | 1557368 | --i_; | |
| 358 | 1557368 | return *this; | |
| 359 | } | ||
| 360 | |||
| 361 | const_iterator | ||
| 362 | 778684 | operator--(int) noexcept | |
| 363 | { | ||
| 364 | 778684 | auto temp = *this; | |
| 365 | 778684 | --(*this); | |
| 366 | 778684 | return temp; | |
| 367 | } | ||
| 368 | }; | ||
| 369 | |||
| 370 | //------------------------------------------------ | ||
| 371 | |||
| 372 | template<class BufferSequence> | ||
| 373 | auto | ||
| 374 | 3206127 | slice_of<BufferSequence>:: | |
| 375 | begin() const noexcept -> | ||
| 376 | const_iterator | ||
| 377 | { | ||
| 378 | return const_iterator( | ||
| 379 | 3206127 | this->begin_, prefix_, suffix_, 0, len_); | |
| 380 | } | ||
| 381 | |||
| 382 | template<class BufferSequence> | ||
| 383 | auto | ||
| 384 | 3206125 | slice_of<BufferSequence>:: | |
| 385 | end() const noexcept -> | ||
| 386 | const_iterator | ||
| 387 | { | ||
| 388 | return const_iterator( | ||
| 389 | 3206125 | this->end_, prefix_, suffix_, len_, len_); | |
| 390 | } | ||
| 391 | |||
| 392 | //------------------------------------------------ | ||
| 393 | |||
| 394 | // in-place modify return value | ||
| 395 | // ----------------------------- | ||
| 396 | // keep_prefix* prefix | ||
| 397 | // keep_suffix suffix | ||
| 398 | // remove_prefix* sans_prefix | ||
| 399 | // remove_suffix sans_suffix | ||
| 400 | |||
| 401 | /** Remove all but the first `n` bytes from a buffer sequence | ||
| 402 | */ | ||
| 403 | constexpr struct keep_prefix_mrdocs_workaround_t | ||
| 404 | { | ||
| 405 | template<class BufferSequence> | ||
| 406 | 412994 | auto operator()( | |
| 407 | BufferSequence& bs, | ||
| 408 | std::size_t n) const -> typename std::enable_if< | ||
| 409 | is_const_buffer_sequence<BufferSequence>::value && | ||
| 410 | detail::has_tag_invoke<BufferSequence>::value>::type | ||
| 411 | |||
| 412 | { | ||
| 413 |
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412994 | tag_invoke(slice_tag{}, bs, slice_how::keep_prefix, n); |
| 414 | 412994 | } | |
| 415 | } const keep_prefix{}; | ||
| 416 | |||
| 417 | /** Remove all but the last `n` bytes from a buffer sequence | ||
| 418 | */ | ||
| 419 | constexpr struct keep_suffix_mrdocs_workaround_t | ||
| 420 | { | ||
| 421 | template<class BufferSequence> | ||
| 422 | 140418 | auto operator()( | |
| 423 | BufferSequence& bs, | ||
| 424 | std::size_t n) const -> typename std::enable_if< | ||
| 425 | is_const_buffer_sequence<BufferSequence>::value && | ||
| 426 | detail::has_tag_invoke<BufferSequence>::value>::type | ||
| 427 | { | ||
| 428 | 140418 | auto n0 = size(bs); | |
| 429 |
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140418 | if(n < n0) |
| 430 |
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123896 | tag_invoke(slice_tag{}, bs, slice_how::remove_prefix, n0 - n); |
| 431 | 140418 | } | |
| 432 | } const keep_suffix{}; | ||
| 433 | |||
| 434 | /** Remove `n` bytes from the beginning of a buffer sequence | ||
| 435 | */ | ||
| 436 | constexpr struct remove_prefix_mrdocs_workaround_t | ||
| 437 | { | ||
| 438 | template<class BufferSequence> | ||
| 439 | 404679 | auto operator()( | |
| 440 | BufferSequence& bs, | ||
| 441 | std::size_t n) const -> typename std::enable_if< | ||
| 442 | is_const_buffer_sequence<BufferSequence>::value && | ||
| 443 | detail::has_tag_invoke<BufferSequence>::value>::type | ||
| 444 | { | ||
| 445 |
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404679 | tag_invoke(slice_tag{}, bs, slice_how::remove_prefix, n); |
| 446 | 404679 | } | |
| 447 | } const remove_prefix{}; | ||
| 448 | |||
| 449 | /** Remove `n` bytes from the end of a buffer sequence | ||
| 450 | */ | ||
| 451 | constexpr struct remove_suffix_mrdocs_workaround_t | ||
| 452 | { | ||
| 453 | template<class BufferSequence> | ||
| 454 | 140418 | auto operator()( | |
| 455 | BufferSequence& bs, | ||
| 456 | std::size_t n) const -> typename std::enable_if< | ||
| 457 | is_const_buffer_sequence<BufferSequence>::value && | ||
| 458 | detail::has_tag_invoke<BufferSequence>::value>::type | ||
| 459 | { | ||
| 460 | 140418 | auto n0 = size(bs); | |
| 461 |
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140418 | if(n > 0) |
| 462 | { | ||
| 463 |
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132157 | if( n > n0) |
| 464 | 8261 | n = n0; | |
| 465 |
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132157 | tag_invoke(slice_tag{}, bs, slice_how::keep_prefix, n0 - n); |
| 466 | } | ||
| 467 | 140418 | } | |
| 468 | } const remove_suffix{}; | ||
| 469 | |||
| 470 | //------------------------------------------------ | ||
| 471 | |||
| 472 | /** Return a sequence representing the first `n` bytes of a buffer sequence | ||
| 473 | */ | ||
| 474 | constexpr struct prefix_mrdocs_workaround_t | ||
| 475 | { | ||
| 476 | template<class BufferSequence> | ||
| 477 | 108 | auto operator()( | |
| 478 | BufferSequence const& bs, | ||
| 479 | std::size_t n) const noexcept -> typename std::enable_if< | ||
| 480 | is_const_buffer_sequence<BufferSequence>::value, | ||
| 481 | slice_type<BufferSequence>>::type | ||
| 482 | { | ||
| 483 | 108 | slice_type<BufferSequence> result(bs); | |
| 484 | 108 | keep_prefix(result, n); | |
| 485 | 108 | return result; | |
| 486 | } | ||
| 487 | } prefix{}; | ||
| 488 | |||
| 489 | /** Return a sequence representing the last `n` bytes of a buffer sequence | ||
| 490 | */ | ||
| 491 | constexpr struct suffix_mrdocs_workaround_t | ||
| 492 | { | ||
| 493 | template<class BufferSequence> | ||
| 494 | auto operator()( | ||
| 495 | BufferSequence const& bs, | ||
| 496 | std::size_t n) const noexcept -> typename std::enable_if< | ||
| 497 | is_const_buffer_sequence<BufferSequence>::value, | ||
| 498 | slice_type<BufferSequence>>::type | ||
| 499 | { | ||
| 500 | slice_type<BufferSequence> result(bs); | ||
| 501 | keep_suffix(result, n); | ||
| 502 | return result; | ||
| 503 | } | ||
| 504 | } suffix{}; | ||
| 505 | |||
| 506 | /** Return a sequence representing all but the first `n` bytes of a buffer sequence | ||
| 507 | */ | ||
| 508 | constexpr struct sans_prefix_mrdocs_workaround_t | ||
| 509 | { | ||
| 510 | template<class BufferSequence> | ||
| 511 | 69 | auto operator()( | |
| 512 | BufferSequence const& bs, | ||
| 513 | std::size_t n) const noexcept -> typename std::enable_if< | ||
| 514 | is_const_buffer_sequence<BufferSequence>::value, | ||
| 515 | slice_type<BufferSequence>>::type | ||
| 516 | { | ||
| 517 | 69 | slice_type<BufferSequence> result(bs); | |
| 518 | 69 | remove_prefix(result, n); | |
| 519 | 69 | return result; | |
| 520 | } | ||
| 521 | } sans_prefix{}; | ||
| 522 | |||
| 523 | /** Return a sequence representing all but the last `n` bytes of a buffer sequence | ||
| 524 | */ | ||
| 525 | constexpr struct sans_suffix_mrdocs_workaround_t | ||
| 526 | { | ||
| 527 | template<class BufferSequence> | ||
| 528 | auto operator()( | ||
| 529 | BufferSequence const& bs, | ||
| 530 | std::size_t n) const noexcept -> typename std::enable_if< | ||
| 531 | is_const_buffer_sequence<BufferSequence>::value, | ||
| 532 | slice_type<BufferSequence>>::type | ||
| 533 | { | ||
| 534 | slice_type<BufferSequence> result(bs); | ||
| 535 | remove_suffix(result, n); | ||
| 536 | return result; | ||
| 537 | } | ||
| 538 | } sans_suffix{}; | ||
| 539 | |||
| 540 | } // buffers | ||
| 541 | } // boost | ||
| 542 | |||
| 543 | #endif | ||
| 544 |