90 lines
2.6 KiB
C
90 lines
2.6 KiB
C
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// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_CRDTP_SPAN_H_
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#define V8_CRDTP_SPAN_H_
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#include <algorithm>
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#include <cstdint>
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#include <cstring>
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#include <string>
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#include <vector>
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namespace v8_crdtp {
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// =============================================================================
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// span - sequence of bytes
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// =============================================================================
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// This template is similar to std::span, which will be included in C++20.
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template <typename T>
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class span {
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public:
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using index_type = size_t;
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span() : data_(nullptr), size_(0) {}
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span(const T* data, index_type size) : data_(data), size_(size) {}
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const T* data() const { return data_; }
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const T* begin() const { return data_; }
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const T* end() const { return data_ + size_; }
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const T& operator[](index_type idx) const { return data_[idx]; }
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span<T> subspan(index_type offset, index_type count) const {
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return span(data_ + offset, count);
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}
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span<T> subspan(index_type offset) const {
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return span(data_ + offset, size_ - offset);
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}
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bool empty() const { return size_ == 0; }
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index_type size() const { return size_; }
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index_type size_bytes() const { return size_ * sizeof(T); }
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private:
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const T* data_;
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index_type size_;
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};
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template <typename T>
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span<T> SpanFrom(const std::vector<T>& v) {
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return span<T>(v.data(), v.size());
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}
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template <size_t N>
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span<uint8_t> SpanFrom(const char (&str)[N]) {
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return span<uint8_t>(reinterpret_cast<const uint8_t*>(str), N - 1);
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}
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inline span<uint8_t> SpanFrom(const char* str) {
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return str ? span<uint8_t>(reinterpret_cast<const uint8_t*>(str), strlen(str))
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: span<uint8_t>();
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}
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inline span<uint8_t> SpanFrom(const std::string& v) {
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return span<uint8_t>(reinterpret_cast<const uint8_t*>(v.data()), v.size());
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}
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// Less than / equality comparison functions for sorting / searching for byte
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// spans. These are similar to absl::string_view's < and == operators.
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inline bool SpanLessThan(span<uint8_t> x, span<uint8_t> y) noexcept {
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auto min_size = std::min(x.size(), y.size());
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const int r = min_size == 0 ? 0 : memcmp(x.data(), y.data(), min_size);
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return (r < 0) || (r == 0 && x.size() < y.size());
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}
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inline bool SpanEquals(span<uint8_t> x, span<uint8_t> y) noexcept {
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auto len = x.size();
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if (len != y.size())
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return false;
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return x.data() == y.data() || len == 0 ||
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std::memcmp(x.data(), y.data(), len) == 0;
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}
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} // namespace v8_crdtp
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#endif // V8_CRDTP_SPAN_H_
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