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Diffstat (limited to 'apt-pkg/contrib/string_view.h')
| -rw-r--r-- | apt-pkg/contrib/string_view.h | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/apt-pkg/contrib/string_view.h b/apt-pkg/contrib/string_view.h new file mode 100644 index 0000000..04f6ff1 --- /dev/null +++ b/apt-pkg/contrib/string_view.h @@ -0,0 +1,163 @@ +/* + * 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) +#define APT_STRINGVIEW_H +#include <apt-pkg/macros.h> +#include <string> +#include <string.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 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()) {} + + /* Modifiers */ + void remove_prefix(size_t n) { data_ += n; size_ -= n; } + void remove_suffix(size_t n) { size_ -= n; } + void clear() { size_ = 0; } + + /* 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_; + } + + size_t find(APT::StringView const needle) const { + if (needle.empty()) + return npos; + if (needle.length() == 1) + return find(*needle.data()); + size_t found = 0; + while ((found = find(*needle.data(), found)) != npos) { + if (compare(found, needle.length(), needle) == 0) + return found; + ++found; + } + return found; + } + size_t find(APT::StringView const needle, size_t pos) const { + if (pos == 0) + return find(needle); + size_t const found = substr(pos).find(needle); + if (found == npos) + return npos; + return pos + found; + } + + /* 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()); +} + +static constexpr inline APT::StringView operator""_sv(const char *data, size_t size) +{ + return APT::StringView(data, size); +} +} + +inline bool operator ==(const char *other, APT::StringView that); +inline bool operator ==(const char *other, APT::StringView that) { return that.operator==(other); } +inline bool operator ==(std::string const &other, APT::StringView that); +inline bool operator ==(std::string const &other, APT::StringView that) { return that.operator==(other); } + +#endif |