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e9313dc331
This introduces an alternative to basic_static_string designed for use in POD types: Trivially copyable, having a sizeof == N + 1, with no embedded NULs. Placed in example/ to gather user feedback before committing to a public API. See issue #23.
672 lines
16 KiB
C++
672 lines
16 KiB
C++
//
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// Copyright (c) 2025 Gennaro Prota (gennaro dot prota at gmail dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/boostorg/static_string
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//
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#include "static_cstring.hpp"
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#include <boost/core/lightweight_test.hpp>
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#include <climits>
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#include <cstring>
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#include <sstream>
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#include <string>
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#include <string_view>
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#include <type_traits>
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namespace boost {
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namespace static_strings {
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static
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void
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testCStringSizeGuarantee()
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{
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// Core guarantee: sizeof is exactly N + 1 (no size member).
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static_assert(sizeof(static_cstring<0>) == 1, "");
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static_assert(sizeof(static_cstring<1>) == 2, "");
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static_assert(sizeof(static_cstring<10>) == 11, "");
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static_assert(sizeof(static_cstring<63>) == 64, "");
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static_assert(sizeof(static_cstring<64>) == 65, "");
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static_assert(sizeof(static_cstring<127>) == 128, "");
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static_assert(sizeof(static_cstring<UCHAR_MAX>) == (UCHAR_MAX + 1), "");
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static_assert(sizeof(static_cstring<UCHAR_MAX + 1>) == (UCHAR_MAX + 2), "");
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static_assert(sizeof(static_cstring<1000>) == 1001, "");
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}
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static
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void
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testCStringRemainingCapacityTrick()
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{
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// Test the remaining-capacity optimization for N <= UCHAR_MAX.
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// Full capacity: Last byte is both null terminator AND remaining == 0.
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{
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static_cstring<5> full("12345");
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BOOST_TEST(full.size() == 5);
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BOOST_TEST(full.capacity() == 5);
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BOOST_TEST(full.data()[5] == '\0');
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BOOST_TEST(std::strcmp(full.c_str(), "12345") == 0);
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}
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// Partial fill: Null terminator at position size, remaining at position N.
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{
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static_cstring<10> partial("Hi");
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BOOST_TEST(partial.size() == 2);
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BOOST_TEST(partial.capacity() == 10);
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BOOST_TEST(partial.data()[2] == '\0');
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BOOST_TEST(static_cast<unsigned char>(partial.data()[10]) == 8);
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}
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// Empty string.
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{
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static_cstring<10> empty;
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BOOST_TEST(empty.size() == 0);
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BOOST_TEST(empty.capacity() == 10);
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BOOST_TEST(empty.data()[0] == '\0');
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BOOST_TEST(static_cast<unsigned char>(empty.data()[10]) == 10);
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}
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// Edge case: N == UCHAR_MAX (max for our trick).
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{
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static_cstring<UCHAR_MAX> large;
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large.assign(100, 'x');
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BOOST_TEST(large.size() == 100);
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BOOST_TEST(large.capacity() == UCHAR_MAX);
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BOOST_TEST(static_cast<unsigned char>(large.data()[UCHAR_MAX]) == (UCHAR_MAX - large.size()));
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}
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}
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template<typename S>
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struct CStringTypeTraits
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{
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static_assert(std::is_trivially_copyable<S>::value);
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static_assert(std::is_trivially_copy_constructible<S>::value);
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static_assert(std::is_trivially_move_constructible<S>::value);
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static_assert(std::is_trivially_copy_assignable<S>::value);
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static_assert(std::is_trivially_move_assignable<S>::value);
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static_assert(std::is_trivially_destructible<S>::value);
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};
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static
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void
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testCStringTypeTraits()
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{
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{
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using S = static_cstring<0>;
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CStringTypeTraits< S > check;
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static_cast<void>(check);
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}
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{
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using S = static_cstring<63>;
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CStringTypeTraits< S > check;
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static_cast<void>(check);
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}
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{
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using S = static_cstring<300>;
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CStringTypeTraits< S > check;
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static_cast<void>(check);
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}
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}
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static
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void
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testCStringConstruct()
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{
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// Default construction.
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{
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static_cstring<1> s;
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BOOST_TEST(s.empty());
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BOOST_TEST(s.size() == 0);
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BOOST_TEST(s == "");
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BOOST_TEST(*s.end() == 0);
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}
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// Construct with count and char.
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{
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static_cstring<4> s1(3, 'x');
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BOOST_TEST(!s1.empty());
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BOOST_TEST(s1.size() == 3);
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BOOST_TEST(s1 == "xxx");
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BOOST_TEST(*s1.end() == 0);
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BOOST_TEST_THROWS(
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(static_cstring<2>(3, 'x')),
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std::length_error);
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}
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// Construct from a C string.
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{
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static_cstring<5> s1("12345");
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BOOST_TEST(s1.size() == 5);
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BOOST_TEST(s1 == "12345");
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BOOST_TEST(*s1.end() == 0);
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BOOST_TEST_THROWS(
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(static_cstring<4>("12345")),
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std::length_error);
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}
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// Construct from a C string with count.
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{
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static_cstring<5> s1("UVXYZ", 3);
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BOOST_TEST(s1 == "UVX");
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BOOST_TEST(*s1.end() == 0);
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}
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// Copy construction.
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{
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static_cstring<5> s1("12345");
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static_cstring<5> s2(s1);
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BOOST_TEST(s2 == "12345");
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BOOST_TEST(*s2.end() == 0);
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}
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}
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static
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void
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testCStringAssignment()
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{
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// assign(size_type count, CharT ch).
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BOOST_TEST(static_cstring<3>{}.assign(1, '*') == "*");
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BOOST_TEST(static_cstring<3>{}.assign(3, '*') == "***");
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BOOST_TEST(static_cstring<3>{"abc"}.assign(3, '*') == "***");
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BOOST_TEST_THROWS(static_cstring<1>{"a"}.assign(2, '*'), std::length_error);
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// assign(CharT const* s, size_type count).
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BOOST_TEST(static_cstring<3>{}.assign("abc", 3) == "abc");
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BOOST_TEST(static_cstring<3>{"*"}.assign("abc", 3) == "abc");
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BOOST_TEST_THROWS(static_cstring<1>{}.assign("abc", 3), std::length_error);
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// assign(CharT const* s).
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BOOST_TEST(static_cstring<3>{}.assign("abc") == "abc");
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BOOST_TEST(static_cstring<3>{"*"}.assign("abc") == "abc");
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BOOST_TEST_THROWS(static_cstring<1>{}.assign("abc"), std::length_error);
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// operator=(const CharT* s).
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{
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static_cstring<3> s1;
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s1 = "123";
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BOOST_TEST(s1 == "123");
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BOOST_TEST(*s1.end() == 0);
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static_cstring<1> s2;
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BOOST_TEST_THROWS(
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s2 = "123",
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std::length_error);
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}
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// Copy assignment.
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{
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static_cstring<3> s1("123");
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static_cstring<3> s2;
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s2 = s1;
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BOOST_TEST(s2 == "123");
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BOOST_TEST(*s2.end() == 0);
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}
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}
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static
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void
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testCStringElements()
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{
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using ccs3 = static_cstring<3> const;
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// at(size_type pos).
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BOOST_TEST(static_cstring<3>{"abc"}.at(0) == 'a');
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BOOST_TEST(static_cstring<3>{"abc"}.at(2) == 'c');
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BOOST_TEST_THROWS(static_cstring<3>{""}.at(0), std::out_of_range);
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BOOST_TEST_THROWS(static_cstring<3>{"abc"}.at(4), std::out_of_range);
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// at(size_type pos) const.
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BOOST_TEST(ccs3{"abc"}.at(0) == 'a');
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BOOST_TEST(ccs3{"abc"}.at(2) == 'c');
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BOOST_TEST_THROWS(ccs3{""}.at(0), std::out_of_range);
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// operator[](size_type pos).
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BOOST_TEST(static_cstring<3>{"abc"}[0] == 'a');
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BOOST_TEST(static_cstring<3>{"abc"}[2] == 'c');
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BOOST_TEST(static_cstring<3>{"abc"}[3] == 0);
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BOOST_TEST(static_cstring<3>{""}[0] == 0);
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// front() / back().
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BOOST_TEST(static_cstring<3>{"abc"}.front() == 'a');
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BOOST_TEST(static_cstring<3>{"abc"}.back() == 'c');
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// data() / c_str().
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{
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static_cstring<3> s("123");
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BOOST_TEST(std::memcmp(s.data(), "123", 3) == 0);
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BOOST_TEST(std::memcmp(s.c_str(), "123\0", 4) == 0);
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}
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// Modification through element access.
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{
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static_cstring<5> s("12345");
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s[1] = '_';
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BOOST_TEST(s == "1_345");
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s.front() = 'A';
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BOOST_TEST(s == "A_345");
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s.back() = 'Z';
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BOOST_TEST(s == "A_34Z");
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}
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}
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static
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void
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testCStringIterators()
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{
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{
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static_cstring<3> s;
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BOOST_TEST(std::distance(s.begin(), s.end()) == 0);
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s = "123";
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BOOST_TEST(std::distance(s.begin(), s.end()) == 3);
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}
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{
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static_cstring<3> const s("123");
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BOOST_TEST(std::distance(s.begin(), s.end()) == 3);
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BOOST_TEST(std::distance(s.cbegin(), s.cend()) == 3);
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}
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// Iteration.
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{
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static_cstring<5> s("hello");
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std::string result;
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for (const char c : s)
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{
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result += c;
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}
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BOOST_TEST(result == "hello");
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}
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}
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static
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void
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testCStringCapacity()
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{
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// empty().
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BOOST_TEST(static_cstring<0>{}.empty());
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BOOST_TEST(static_cstring<1>{}.empty());
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BOOST_TEST(!static_cstring<1>{"a"}.empty());
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// size().
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BOOST_TEST(static_cstring<0>{}.size() == 0);
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BOOST_TEST(static_cstring<1>{"a"}.size() == 1);
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BOOST_TEST(static_cstring<5>{"abc"}.size() == 3);
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// length().
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BOOST_TEST(static_cstring<0>{}.length() == 0);
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BOOST_TEST(static_cstring<3>{"abc"}.length() == 3);
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// max_size().
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BOOST_TEST(static_cstring<0>{}.max_size() == 0);
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BOOST_TEST(static_cstring<5>{"abc"}.max_size() == 5);
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// capacity().
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BOOST_TEST(static_cstring<0>{}.capacity() == 0);
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BOOST_TEST(static_cstring<5>{"abc"}.capacity() == 5);
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}
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static
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void
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testCStringClear()
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{
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static_cstring<3> s("123");
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BOOST_TEST(!s.empty());
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s.clear();
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BOOST_TEST(s.empty());
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BOOST_TEST(s.size() == 0);
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BOOST_TEST(*s.end() == 0);
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BOOST_TEST(s == "");
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}
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static
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void
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testCStringPushPop()
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{
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// push_back().
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{
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static_cstring<5> s("abc");
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s.push_back('d');
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BOOST_TEST(s == "abcd");
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BOOST_TEST(s.size() == 4);
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BOOST_TEST(*s.end() == 0);
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s.push_back('e');
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BOOST_TEST(s == "abcde");
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BOOST_TEST(s.size() == 5);
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BOOST_TEST_THROWS(s.push_back('f'), std::length_error);
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}
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// pop_back().
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{
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static_cstring<5> s("abcde");
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s.pop_back();
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BOOST_TEST(s == "abcd");
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BOOST_TEST(s.size() == 4);
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BOOST_TEST(*s.end() == 0);
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s.pop_back();
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s.pop_back();
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s.pop_back();
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s.pop_back();
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BOOST_TEST(s.empty());
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}
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}
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static
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void
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testCStringAppend()
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{
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// append(const CharT* s).
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{
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static_cstring<12> s("Hello");
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s.append(", World");
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BOOST_TEST(s == "Hello, World");
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BOOST_TEST(*s.end() == 0);
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}
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{
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static_cstring<5> s("abc");
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BOOST_TEST_THROWS(s.append("def"), std::length_error);
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}
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// append(const CharT* s, size_type count)
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{
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static_cstring<10> s("abc");
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s.append("defgh", 3);
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BOOST_TEST(s == "abcdef");
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BOOST_TEST(*s.end() == 0);
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}
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// append(size_type count, CharT ch)
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{
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static_cstring<10> s("abc");
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s.append(3, 'x');
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BOOST_TEST(s == "abcxxx");
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BOOST_TEST(*s.end() == 0);
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BOOST_TEST_THROWS(s.append(5, 'y'), std::length_error);
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}
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// operator+=()
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{
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static_cstring<10> s("abc");
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s += "def";
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BOOST_TEST(s == "abcdef");
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s += 'g';
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BOOST_TEST(s == "abcdefg");
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BOOST_TEST(*s.end() == 0);
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}
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}
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static
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void
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testCStringComparison()
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{
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// operator==() / operator!=().
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{
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static_cstring<10> a("abc");
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static_cstring<10> b("abc");
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static_cstring<10> c("abd");
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BOOST_TEST(a == b);
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BOOST_TEST(!(a == c));
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BOOST_TEST(a != c);
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BOOST_TEST(!(a != b));
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}
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// operator<(), <=(), >(), >=().
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{
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static_cstring<10> a("abc");
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static_cstring<10> b("abd");
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BOOST_TEST(a < b);
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BOOST_TEST(a <= b);
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BOOST_TEST(a <= a);
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BOOST_TEST(b > a);
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BOOST_TEST(b >= a);
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BOOST_TEST(b >= b);
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}
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// Comparison with CharT const*.
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{
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static_cstring<10> s("hello");
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BOOST_TEST(s == "hello");
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BOOST_TEST("hello" == s);
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BOOST_TEST(s != "world");
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BOOST_TEST("world" != s);
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}
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// compare().
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{
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static_cstring<10> s("abc");
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BOOST_TEST(s.compare("abc") == 0);
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BOOST_TEST(s.compare("abd") < 0);
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BOOST_TEST(s.compare("abb") > 0);
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}
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}
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static
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void
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testCStringConversion()
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{
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// operator string_view().
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{
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static_cstring<10> s("hello");
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std::string_view sv = s;
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BOOST_TEST(sv == "hello");
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BOOST_TEST(sv.size() == 5);
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}
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// str().
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{
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static_cstring<10> s("hello");
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std::string str = s.str();
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BOOST_TEST(str == "hello");
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BOOST_TEST(str.size() == 5);
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}
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}
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static
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void
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testCStringStream()
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{
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static_cstring<10> s("hello");
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std::ostringstream oss;
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oss << s;
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BOOST_TEST(oss.str() == "hello");
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}
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static
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void
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testCStringSwap()
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{
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static_cstring<10> a("hello");
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static_cstring<10> b("world");
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a.swap(b);
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BOOST_TEST(a == "world");
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BOOST_TEST(b == "hello");
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}
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static
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void
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testCStringConstexpr()
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{
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// constexpr construction and operations.
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constexpr static_cstring<10> ce("test");
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static_assert(ce.size() == 4, "");
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static_assert(ce[0] == 't', "");
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static_assert(ce[1] == 'e', "");
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static_assert(ce[2] == 's', "");
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static_assert(ce[3] == 't', "");
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static_assert(!ce.empty(), "");
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static_assert(ce.max_size() == 10, "");
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static_assert(ce.capacity() == 10, "");
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constexpr static_cstring<5> ce_empty;
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static_assert(ce_empty.empty(), "");
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static_assert(ce_empty.size() == 0, "");
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}
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// Helper struct to test NTTP.
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template<basic_static_cstring S>
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struct NTTPHelper
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{
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static constexpr std::size_t size() noexcept
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{
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return S.size();
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}
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static constexpr const char* c_str() noexcept
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{
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return S.c_str();
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}
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};
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static
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void
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testCStringNTTP()
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{
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// Test non-type template parameter usage (C++20).
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|
// Test size deduction from string literals.
|
|
BOOST_TEST(NTTPHelper<"hello">::size() == 5);
|
|
BOOST_TEST(NTTPHelper<"">::size() == 0);
|
|
BOOST_TEST(NTTPHelper<"test">::size() == 4);
|
|
|
|
// Test that different strings create different types
|
|
constexpr bool same_type = std::is_same_v<
|
|
NTTPHelper<"hello">,
|
|
NTTPHelper<"hello">>;
|
|
BOOST_TEST(same_type);
|
|
|
|
constexpr bool different_type = !std::is_same_v<
|
|
NTTPHelper<"hello">,
|
|
NTTPHelper<"world">>;
|
|
BOOST_TEST(different_type);
|
|
|
|
// Test constexpr access.
|
|
constexpr std::size_t len = NTTPHelper<"constexpr">::size();
|
|
static_assert(len == 9, "");
|
|
}
|
|
|
|
static
|
|
void
|
|
testCStringPODUsage()
|
|
{
|
|
// Test usage in POD types (the original motivation).
|
|
struct UserRecord
|
|
{
|
|
int id;
|
|
static_cstring<63> name;
|
|
unsigned int flags;
|
|
};
|
|
|
|
static_assert(sizeof(static_cstring<63>) == 64, "");
|
|
static_assert(std::is_trivially_copyable<UserRecord>::value, "");
|
|
|
|
UserRecord user{};
|
|
user.id = 42;
|
|
user.name = "Alice";
|
|
user.flags = 0xFF;
|
|
|
|
BOOST_TEST(user.id == 42);
|
|
BOOST_TEST(user.name.size() == 5);
|
|
BOOST_TEST(user.name == "Alice");
|
|
BOOST_TEST(user.flags == 0xFF);
|
|
|
|
// Copy the struct.
|
|
UserRecord copy = user;
|
|
BOOST_TEST(copy.name == "Alice");
|
|
|
|
// memcpy() should work.
|
|
UserRecord memcpy_dest;
|
|
std::memcpy(&memcpy_dest, &user, sizeof(UserRecord));
|
|
BOOST_TEST(memcpy_dest.name == "Alice");
|
|
}
|
|
|
|
static
|
|
void
|
|
testCStringLargeCapacity()
|
|
{
|
|
// Test strings with N > UCHAR_MAX (no remaining-capacity trick).
|
|
{
|
|
static_cstring<300> s;
|
|
BOOST_TEST(s.empty());
|
|
BOOST_TEST(s.size() == 0);
|
|
|
|
s = "This is a test string";
|
|
BOOST_TEST(s.size() == 21);
|
|
BOOST_TEST(s == "This is a test string");
|
|
|
|
s.clear();
|
|
BOOST_TEST(s.empty());
|
|
}
|
|
|
|
// Large string operations.
|
|
{
|
|
static_cstring<500> s;
|
|
s.assign(400, 'x');
|
|
BOOST_TEST(s.size() == 400);
|
|
BOOST_TEST(s[0] == 'x');
|
|
BOOST_TEST(s[399] == 'x');
|
|
BOOST_TEST(*s.end() == 0);
|
|
}
|
|
}
|
|
|
|
static
|
|
void
|
|
testCStringWideChar()
|
|
{
|
|
// Test with wchar_t.
|
|
{
|
|
static_wcstring<10> ws;
|
|
BOOST_TEST(ws.empty());
|
|
BOOST_TEST(ws.size() == 0);
|
|
}
|
|
|
|
{
|
|
static_wcstring<10> ws(L"hello");
|
|
BOOST_TEST(ws.size() == 5);
|
|
BOOST_TEST(ws[0] == L'h');
|
|
BOOST_TEST(ws[4] == L'o');
|
|
BOOST_TEST(*ws.end() == 0);
|
|
}
|
|
}
|
|
|
|
int
|
|
runTests()
|
|
{
|
|
testCStringSizeGuarantee();
|
|
testCStringRemainingCapacityTrick();
|
|
testCStringTypeTraits();
|
|
testCStringConstruct();
|
|
testCStringAssignment();
|
|
testCStringElements();
|
|
testCStringIterators();
|
|
testCStringCapacity();
|
|
testCStringClear();
|
|
testCStringPushPop();
|
|
testCStringAppend();
|
|
testCStringComparison();
|
|
testCStringConversion();
|
|
testCStringStream();
|
|
testCStringSwap();
|
|
testCStringConstexpr();
|
|
testCStringNTTP();
|
|
testCStringPODUsage();
|
|
testCStringLargeCapacity();
|
|
testCStringWideChar();
|
|
|
|
return report_errors();
|
|
}
|
|
}
|
|
}
|
|
|
|
int
|
|
main()
|
|
{
|
|
return boost::static_strings::runTests();
|
|
}
|