/* * Basic implementation of string_view * * (C) 2015 Julian Andres Klode <jak@debian.org> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. */ #if !defined(APT_STRINGVIEW_H) && defined(APT_PKG_EXPOSE_STRING_VIEW) #define APT_STRINGVIEW_H #include <string.h> #include <string> #include <apt-pkg/macros.h> namespace APT { /** * \brief Simple subset of std::string_view from C++17 * * This is an internal implementation of the subset of std::string_view * used by APT. It is not meant to be used in programs, only inside the * library for performance critical paths. */ class APT_HIDDEN StringView { const char *data_; size_t size_; public: static constexpr size_t npos = static_cast<size_t>(-1); static_assert(APT::StringView::npos == std::string::npos, "npos values are different"); /* Constructors */ constexpr StringView() : data_(""), size_(0) {} constexpr StringView(const char *data, size_t size) : data_(data), size_(size) {} StringView(const char *data) : data_(data), size_(strlen(data)) {} StringView(std::string const & str): data_(str.data()), size_(str.size()) {} /* Viewers */ constexpr StringView substr(size_t pos, size_t n = npos) const { return StringView(data_ + pos, n > (size_ - pos) ? (size_ - pos) : n); } size_t find(int c, size_t pos) const { if (pos == 0) return find(c); size_t const found = substr(pos).find(c); if (found == npos) return npos; return pos + found; } size_t find(int c) const { const char *found = static_cast<const char*>(memchr(data_, c, size_)); if (found == NULL) return npos; return found - data_; } size_t rfind(int c, size_t pos) const { if (pos == npos) return rfind(c); return APT::StringView(data_, pos).rfind(c); } size_t rfind(int c) const { const char *found = static_cast<const char*>(memrchr(data_, c, size_)); if (found == NULL) return npos; return found - data_; } /* Conversions */ std::string to_string() const { return std::string(data_, size_); } /* Comparisons */ int compare(size_t pos, size_t n, StringView other) const { return substr(pos, n).compare(other); } int compare(StringView other) const { int res; res = memcmp(data_, other.data_, std::min(size_, other.size_)); if (res != 0) return res; if (size_ == other.size_) return res; return (size_ > other.size_) ? 1 : -1; } /* Optimization: If size not equal, string cannot be equal */ bool operator ==(StringView other) const { return size_ == other.size_ && compare(other) == 0; } bool operator !=(StringView other) const { return !(*this == other); } /* Accessors */ constexpr bool empty() const { return size_ == 0; } constexpr const char* data() const { return data_; } constexpr const char* begin() const { return data_; } constexpr const char* end() const { return data_ + size_; } constexpr char operator [](size_t i) const { return data_[i]; } constexpr size_t size() const { return size_; } constexpr size_t length() const { return size_; } }; /** * \brief Faster comparison for string views (compare size before data) * * Still stable, but faster than the normal ordering. */ static inline int StringViewCompareFast(StringView a, StringView b) { if (a.size() != b.size()) return a.size() - b.size(); return memcmp(a.data(), b.data(), a.size()); } } inline bool operator ==(const char *other, APT::StringView that); inline bool operator ==(const char *other, APT::StringView that) { return that.operator==(other); } #endif