diff options
Diffstat (limited to 'src/prevector.h')
| -rw-r--r-- | src/prevector.h | 114 |
1 files changed, 63 insertions, 51 deletions
diff --git a/src/prevector.h b/src/prevector.h index f8d6a09145..103ead82cc 100644 --- a/src/prevector.h +++ b/src/prevector.h @@ -10,9 +10,12 @@ #include <stdint.h> #include <string.h> +#include <cstddef> #include <iterator> #include <type_traits> +#include <compat.h> + #pragma pack(push, 1) /** Implements a drop-in replacement for std::vector<T> which stores up to N * elements directly (without heap allocation). The types Size and Diff are @@ -194,16 +197,42 @@ private: T* item_ptr(difference_type pos) { return is_direct() ? direct_ptr(pos) : indirect_ptr(pos); } const T* item_ptr(difference_type pos) const { return is_direct() ? direct_ptr(pos) : indirect_ptr(pos); } + void fill(T* dst, ptrdiff_t count) { + if (IS_TRIVIALLY_CONSTRUCTIBLE<T>::value) { + // The most common use of prevector is where T=unsigned char. For + // trivially constructible types, we can use memset() to avoid + // looping. + ::memset(dst, 0, count * sizeof(T)); + } else { + for (auto i = 0; i < count; ++i) { + new(static_cast<void*>(dst + i)) T(); + } + } + } + + void fill(T* dst, ptrdiff_t count, const T& value) { + for (auto i = 0; i < count; ++i) { + new(static_cast<void*>(dst + i)) T(value); + } + } + + template<typename InputIterator> + void fill(T* dst, InputIterator first, InputIterator last) { + while (first != last) { + new(static_cast<void*>(dst)) T(*first); + ++dst; + ++first; + } + } + public: void assign(size_type n, const T& val) { clear(); if (capacity() < n) { change_capacity(n); } - while (size() < n) { - _size++; - new(static_cast<void*>(item_ptr(size() - 1))) T(val); - } + _size += n; + fill(item_ptr(0), n, val); } template<typename InputIterator> @@ -213,11 +242,8 @@ public: if (capacity() < n) { change_capacity(n); } - while (first != last) { - _size++; - new(static_cast<void*>(item_ptr(size() - 1))) T(*first); - ++first; - } + _size += n; + fill(item_ptr(0), first, last); } prevector() : _size(0), _union{{}} {} @@ -228,31 +254,23 @@ public: explicit prevector(size_type n, const T& val = T()) : _size(0) { change_capacity(n); - while (size() < n) { - _size++; - new(static_cast<void*>(item_ptr(size() - 1))) T(val); - } + _size += n; + fill(item_ptr(0), n, val); } template<typename InputIterator> prevector(InputIterator first, InputIterator last) : _size(0) { size_type n = last - first; change_capacity(n); - while (first != last) { - _size++; - new(static_cast<void*>(item_ptr(size() - 1))) T(*first); - ++first; - } + _size += n; + fill(item_ptr(0), first, last); } prevector(const prevector<N, T, Size, Diff>& other) : _size(0) { - change_capacity(other.size()); - const_iterator it = other.begin(); - while (it != other.end()) { - _size++; - new(static_cast<void*>(item_ptr(size() - 1))) T(*it); - ++it; - } + size_type n = other.size(); + change_capacity(n); + _size += n; + fill(item_ptr(0), other.begin(), other.end()); } prevector(prevector<N, T, Size, Diff>&& other) : _size(0) { @@ -263,14 +281,7 @@ public: if (&other == this) { return *this; } - resize(0); - change_capacity(other.size()); - const_iterator it = other.begin(); - while (it != other.end()) { - _size++; - new(static_cast<void*>(item_ptr(size() - 1))) T(*it); - ++it; - } + assign(other.begin(), other.end()); return *this; } @@ -314,16 +325,20 @@ public: } void resize(size_type new_size) { - if (size() > new_size) { + size_type cur_size = size(); + if (cur_size == new_size) { + return; + } + if (cur_size > new_size) { erase(item_ptr(new_size), end()); + return; } if (new_size > capacity()) { change_capacity(new_size); } - while (size() < new_size) { - _size++; - new(static_cast<void*>(item_ptr(size() - 1))) T(); - } + ptrdiff_t increase = new_size - cur_size; + fill(item_ptr(cur_size), increase); + _size += increase; } void reserve(size_type new_capacity) { @@ -346,10 +361,11 @@ public: if (capacity() < new_size) { change_capacity(new_size + (new_size >> 1)); } - memmove(item_ptr(p + 1), item_ptr(p), (size() - p) * sizeof(T)); + T* ptr = item_ptr(p); + memmove(ptr + 1, ptr, (size() - p) * sizeof(T)); _size++; - new(static_cast<void*>(item_ptr(p))) T(value); - return iterator(item_ptr(p)); + new(static_cast<void*>(ptr)) T(value); + return iterator(ptr); } void insert(iterator pos, size_type count, const T& value) { @@ -358,11 +374,10 @@ public: if (capacity() < new_size) { change_capacity(new_size + (new_size >> 1)); } - memmove(item_ptr(p + count), item_ptr(p), (size() - p) * sizeof(T)); + T* ptr = item_ptr(p); + memmove(ptr + count, ptr, (size() - p) * sizeof(T)); _size += count; - for (size_type i = 0; i < count; i++) { - new(static_cast<void*>(item_ptr(p + i))) T(value); - } + fill(item_ptr(p), count, value); } template<typename InputIterator> @@ -373,13 +388,10 @@ public: if (capacity() < new_size) { change_capacity(new_size + (new_size >> 1)); } - memmove(item_ptr(p + count), item_ptr(p), (size() - p) * sizeof(T)); + T* ptr = item_ptr(p); + memmove(ptr + count, ptr, (size() - p) * sizeof(T)); _size += count; - while (first != last) { - new(static_cast<void*>(item_ptr(p))) T(*first); - ++p; - ++first; - } + fill(ptr, first, last); } iterator erase(iterator pos) { |