+/*
+ * Copyright (c) 2023 Philippe Proulx <pproulx@efficios.com>
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#ifndef LTTNG_C_STRING_VIEW_HPP
+#define LTTNG_C_STRING_VIEW_HPP
+
+#include <common/format.hpp>
+#include <common/type-traits.hpp>
+
+#include <cstddef>
+#include <cstring>
+#include <functional>
+#include <string>
+
+namespace lttng {
+
+/*
+ * A view on a constant null-terminated C string.
+ */
+class c_string_view final {
+public:
+ /*
+ * Builds an empty view (data() returns `nullptr`).
+ *
+ * Intentionally not explicit.
+ */
+ constexpr c_string_view() noexcept = default;
+
+ /*
+ * Builds a view of the C string `str` (may be `nullptr`).
+ *
+ * Intentionally not explicit.
+ */
+ /* NOLINTBEGIN(google-explicit-constructor) */
+ constexpr c_string_view(const char *const str) noexcept : _str{ str }
+ {
+ }
+ /* NOLINTEND(google-explicit-constructor) */
+
+ /*
+ * Builds a view of the string `str`.
+ */
+ /* NOLINTBEGIN(google-explicit-constructor) */
+ c_string_view(const std::string& str) noexcept : _str{ str.c_str() }
+ {
+ }
+ /* NOLINTEND */
+
+ /*
+ * Makes this view view the C string `str` (may be `nullptr`).
+ */
+ c_string_view& operator=(const char *const str) noexcept
+ {
+ _str = str;
+ return *this;
+ }
+
+ /*
+ * Viewed null-terminated C string (may be `nullptr`).
+ */
+ const char *data() const noexcept
+ {
+ return _str;
+ }
+
+ /*
+ * Alias of data().
+ */
+ operator const char *() const noexcept /* NOLINT(google-explicit-constructor) */
+ {
+ return this->data();
+ }
+
+ /*
+ * Evaluate as boolean (false means an empty string).
+ */
+ operator bool() const noexcept /* NOLINT(google-explicit-constructor) */
+ {
+ return *this->data();
+ }
+
+ /*
+ * Alias of data().
+ */
+ const char *operator*() const noexcept
+ {
+ return this->data();
+ }
+
+ /*
+ * Alias of data().
+ *
+ * data() must not return `nullptr`.
+ */
+ const char *begin() const noexcept
+ {
+ return this->data();
+ }
+
+ /*
+ * Pointer to the null character of the viewed C string.
+ *
+ * data() must not return `nullptr`.
+ */
+ const char *end() const noexcept
+ {
+ return _str + this->len();
+ }
+
+ /*
+ * Length of the viewed C string, excluding the null character.
+ *
+ * data() must not return `nullptr`.
+ */
+ std::size_t len() const noexcept
+ {
+ return std::strlen(_str);
+ }
+
+ /*
+ * Returns an `std::string` instance containing a copy of the viewed
+ * C string.
+ *
+ * data() must not return `nullptr`.
+ */
+ std::string str() const
+ {
+ return std::string{ _str };
+ }
+
+ /*
+ * Alias of str().
+ */
+ operator std::string() const /* NOLINT(google-explicit-constructor) */
+ {
+ return this->str();
+ }
+
+ /*
+ * Returns the character at index `i`.
+ *
+ * `i` must be less than what len() returns.
+ *
+ * data() must not return `nullptr`.
+ */
+ char operator[](const std::size_t i) const noexcept
+ {
+ return _str[i];
+ }
+
+ bool startsWith(const lttng::c_string_view prefix) const noexcept
+ {
+ return std::strncmp(_str, (const char *) prefix, prefix.len()) == 0;
+ }
+
+private:
+ const char *_str = nullptr;
+};
+
+inline const char *format_as(const c_string_view& str)
+{
+ return str ? *str : "(null)";
+}
+
+namespace internal {
+
+template <typename StrT>
+const char *as_const_char_ptr(StrT&& val) noexcept
+{
+ return val.data();
+}
+
+inline const char *as_const_char_ptr(const char *const val) noexcept
+{
+ return val;
+}
+
+template <typename StrT>
+using comparable_with_c_string_view = lttng::traits::
+ is_one_of<typename std::decay<StrT>::type, c_string_view, std::string, const char *>;
+
+} /* namespace internal */
+
+/*
+ * Returns true if `lhs` is equal to `rhs`.
+ *
+ * `LhsT` and `RhsT` may be any of:
+ *
+ * • `const char *`
+ * • `std::string`
+ * • `c_string_view`
+ *
+ * Both `lhs` and `rhs` must not have an underlying `nullptr` raw data.
+ */
+template <
+ typename LhsT,
+ typename RhsT,
+ typename =
+ typename std::enable_if<internal::comparable_with_c_string_view<LhsT>::value>::type,
+ typename =
+ typename std::enable_if<internal::comparable_with_c_string_view<RhsT>::value>::type>
+bool operator==(LhsT&& lhs, RhsT&& rhs) noexcept
+{
+ const auto raw_lhs = internal::as_const_char_ptr(lhs);
+ const auto raw_rhs = internal::as_const_char_ptr(rhs);
+
+ return std::strcmp(raw_lhs, raw_rhs) == 0;
+}
+
+/*
+ * Returns true if `lhs` is not equal to `rhs`.
+ *
+ * `LhsT` and `RhsT` may be any of:
+ *
+ * • `const char *`
+ * • `std::string`
+ * • `c_string_view`
+ *
+ * Both `lhs` and `rhs` must not have an underlying `nullptr` raw data.
+ */
+template <
+ typename LhsT,
+ typename RhsT,
+ typename =
+ typename std::enable_if<internal::comparable_with_c_string_view<LhsT>::value>::type,
+ typename =
+ typename std::enable_if<internal::comparable_with_c_string_view<RhsT>::value>::type>
+bool operator!=(LhsT&& lhs, RhsT&& rhs) noexcept
+{
+ return !(std::forward<LhsT>(lhs) == std::forward<RhsT>(rhs));
+}
+
+} /* namespace lttng */
+
+/*
+ * Appends `rhs` to `lhs`.
+ */
+inline void operator+=(std::string& lhs, lttng::c_string_view rhs)
+{
+ lhs += rhs.data();
+}
+
+namespace std {
+template <>
+struct hash<lttng::c_string_view> {
+ std::size_t operator()(const lttng::c_string_view& str) const
+ {
+ auto hash_value = std::hash<char>{}('\0');
+
+ for (auto character : str) {
+ hash_value ^= std::hash<decltype(character)>{}(character);
+ }
+
+ return hash_value;
+ }
+};
+} /* namespace std */
+
+#endif /* LTTNG_C_STRING_VIEW_HPP */
projects / lttng-tools.git / commitdiff
