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78 lines
2.6 KiB
C++
78 lines
2.6 KiB
C++
// Copyright 2019 Roman Perepelitsa.
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//
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// This file is part of GitStatus.
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//
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// GitStatus is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// GitStatus is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with GitStatus. If not, see <https://www.gnu.org/licenses/>.
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#ifndef ROMKATV_GITSTATUS_STRING_VIEW_H_
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#define ROMKATV_GITSTATUS_STRING_VIEW_H_
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#include <algorithm>
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#include <cstddef>
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#include <cstring>
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#include <ostream>
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#include <string>
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namespace gitstatus {
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// WARNING: StringView must not have embedded null characters. Violations cause UB.
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struct StringView {
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StringView() : StringView("") {}
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// Requires: !memchr(s.data(), 0, s.size()).
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//
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// WARNING: The existence of this requirement and the fact that this constructor is implicit
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// means it's dangerous to have std::string instances with embedded null characters anywhere
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// in the program. If you have an std::string `s` with embedded nulls, an innocent-looking
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// `F(s)` might perform an implicit conversion to StringView and land you squarely in the
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// Undefined Behavior land.
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StringView(const std::string& s) : StringView(s.c_str(), s.size()) {}
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// Requires: !memchr(ptr, 0, len).
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StringView(const char* ptr, size_t len) : ptr(ptr), len(len) {}
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// Requires: end >= begin && !memchr(begin, 0, end - begin).
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StringView(const char* begin, const char* end) : StringView(begin, end - begin) {}
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// Requires: strchr(s, 0) == s + N.
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template <size_t N>
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StringView(const char (&s)[N]) : StringView(s, N - 1) {
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static_assert(N, "");
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}
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// Explicit because it's the only constructor that isn't O(1).
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// Are you sure you don't already known the strings's length?
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explicit StringView(const char* ptr) : StringView(ptr, ptr ? std::strlen(ptr) : 0) {}
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bool StartsWith(StringView prefix) const {
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return len >= prefix.len && !std::memcmp(ptr, prefix.ptr, prefix.len);
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}
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bool EndsWith(StringView suffix) const {
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return len >= suffix.len && !std::memcmp(ptr + (len - suffix.len), suffix.ptr, suffix.len);
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}
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const char* ptr;
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size_t len;
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};
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inline std::ostream& operator<<(std::ostream& strm, StringView s) {
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if (s.ptr) strm.write(s.ptr, s.len);
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return strm;
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}
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} // namespace gitstatus
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#endif // ROMKATV_GITSTATUS_STRING_VIEW_H_
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