diff options
Diffstat (limited to 'src/prevector.h')
| -rw-r--r-- | src/prevector.h | 31 |
1 files changed, 25 insertions, 6 deletions
diff --git a/src/prevector.h b/src/prevector.h index 75d6abfb0e..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 @@ -194,8 +197,21 @@ 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, size_type count, const T& value) { - for (size_type i = 0; i < count; ++i) { + 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); } } @@ -310,16 +326,19 @@ public: void resize(size_type 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); } - for (T* p = item_ptr(0); cur_size < new_size; cur_size++) { - _size++; - new(static_cast<void*>(p + cur_size)) T(); - } + ptrdiff_t increase = new_size - cur_size; + fill(item_ptr(cur_size), increase); + _size += increase; } void reserve(size_type new_capacity) { |