1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9// UNSUPPORTED: c++03, c++11, c++14, c++17
10// UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
11
12// XFAIL: availability-fp_to_chars-missing
13
14// <format>
15
16// template<class Out, class... Args>
17// format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
18// format-string<Args...> fmt, const Args&... args);
19// template<class Out, class... Args>
20// format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
21// wformat-string<Args...> fmt, const Args&... args);
22
23#include <format>
24#include <algorithm>
25#include <cassert>
26#include <iterator>
27#include <list>
28#include <vector>
29
30#include "test_macros.h"
31#include "format_tests.h"
32#include "string_literal.h"
33#include "test_format_string.h"
34
35auto test = []<class CharT, class... Args>(
36 std::basic_string_view<CharT> expected,
37 test_format_string<CharT, Args...> fmt,
38 Args&&... args) constexpr {
39 {
40 std::list<CharT> out;
41 std::format_to_n_result result = std::format_to_n(std::back_inserter(out), 0, fmt, std::forward<Args>(args)...);
42 // To avoid signedness warnings make sure formatted_size uses the same type
43 // as result.size.
44 using diff_type = decltype(result.size);
45 diff_type formatted_size = std::formatted_size(fmt, std::forward<Args>(args)...);
46
47 assert(result.size == formatted_size);
48 assert(out.empty());
49 }
50 {
51 std::vector<CharT> out;
52 std::format_to_n_result result = std::format_to_n(std::back_inserter(out), 5, fmt, std::forward<Args>(args)...);
53 using diff_type = decltype(result.size);
54 diff_type formatted_size = std::formatted_size(fmt, std::forward<Args>(args)...);
55 diff_type size = std::min<diff_type>(5, formatted_size);
56
57 assert(result.size == formatted_size);
58 assert(std::equal(out.begin(), out.end(), expected.begin(), expected.begin() + size));
59 }
60 {
61 std::basic_string<CharT> out;
62 std::format_to_n_result result = std::format_to_n(std::back_inserter(out), 1000, fmt, std::forward<Args>(args)...);
63 using diff_type = decltype(result.size);
64 diff_type formatted_size = std::formatted_size(fmt, std::forward<Args>(args)...);
65 diff_type size = std::min<diff_type>(1000, formatted_size);
66
67 assert(result.size == formatted_size);
68 assert(out == expected.substr(0, size));
69 }
70 {
71 // Test the returned iterator.
72 std::basic_string<CharT> out(10, CharT(' '));
73 std::format_to_n_result result = std::format_to_n(out.begin(), 10, fmt, std::forward<Args>(args)...);
74 using diff_type = decltype(result.size);
75 diff_type formatted_size = std::formatted_size(fmt, std::forward<Args>(args)...);
76 diff_type size = std::min<diff_type>(10, formatted_size);
77
78 assert(result.size == formatted_size);
79 assert(result.out == out.begin() + size);
80 assert(out.substr(0, size) == expected.substr(0, size));
81 }
82 {
83 static_assert(std::is_signed_v<std::iter_difference_t<CharT*>>,
84 "If the difference type isn't negative the test will fail "
85 "due to using a large positive value.");
86 CharT buffer[1] = {CharT(0)};
87 std::format_to_n_result result = std::format_to_n(buffer, -1, fmt, std::forward<Args>(args)...);
88 using diff_type = decltype(result.size);
89 diff_type formatted_size = std::formatted_size(fmt, std::forward<Args>(args)...);
90
91 assert(result.size == formatted_size);
92 assert(result.out == buffer);
93 assert(buffer[0] == CharT(0));
94 }
95};
96
97auto test_exception = []<class CharT, class... Args>(std::string_view, std::basic_string_view<CharT>, Args&&...) {
98 // After P2216 most exceptions thrown by std::format_to_n become ill-formed.
99 // Therefore this tests does nothing.
100 // A basic ill-formed test is done in format_to_n.verify.cpp
101 // The exceptions are tested by other functions that don't use the basic-format-string as fmt argument.
102};
103
104int main(int, char**) {
105 format_tests<char, execution_modus::partial>(check: test, check_exception: test_exception);
106
107#ifndef TEST_HAS_NO_WIDE_CHARACTERS
108 format_tests_char_to_wchar_t(check: test);
109 format_tests<wchar_t, execution_modus::partial>(check: test, check_exception: test_exception);
110#endif
111
112 return 0;
113}
114

source code of libcxx/test/std/utilities/format/format.functions/format_to_n.pass.cpp