1//===-- Implementation of a class for mapping errors to strings -----------===//
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#include "error_to_string.h"
10#include "platform_errors.h"
11
12#include "src/__support/CPP/span.h"
13#include "src/__support/CPP/string_view.h"
14#include "src/__support/CPP/stringstream.h"
15#include "src/__support/StringUtil/message_mapper.h"
16#include "src/__support/integer_to_string.h"
17#include "src/__support/macros/attributes.h"
18#include "src/__support/macros/config.h"
19
20#include <stddef.h>
21
22namespace LIBC_NAMESPACE_DECL {
23namespace internal {
24
25constexpr size_t max_buff_size() {
26 constexpr size_t unknown_str_len = sizeof("Unknown error");
27 // the buffer should be able to hold "Unknown error" + ' ' + num_str
28 return (unknown_str_len + 1 + IntegerToString<int>::buffer_size()) *
29 sizeof(char);
30}
31
32// This is to hold error strings that have to be custom built. It may be
33// rewritten on every call to strerror (or other error to string function).
34constexpr size_t ERR_BUFFER_SIZE = max_buff_size();
35LIBC_THREAD_LOCAL char error_buffer[ERR_BUFFER_SIZE];
36
37constexpr size_t TOTAL_STR_LEN = total_str_len(PLATFORM_ERRORS);
38
39// Since the StringMappings array is a map from error numbers to their
40// corresponding strings, we have to have an array large enough we can use the
41// error numbers as indexes. The current linux configuration has 132 values with
42// the maximum value being 133 (41 and 58 are skipped). If other platforms use
43// negative numbers or discontiguous ranges, then the array should be turned
44// into a proper hashmap.
45constexpr size_t ERR_ARRAY_SIZE = max_key_val(PLATFORM_ERRORS) + 1;
46
47constexpr MessageMapper<ERR_ARRAY_SIZE, TOTAL_STR_LEN>
48 ERROR_MAPPER(PLATFORM_ERRORS);
49
50constexpr MessageMapper<ERR_ARRAY_SIZE, TOTAL_STR_LEN>
51 ERRNO_NAME_MAPPER(PLATFORM_ERRNO_NAMES);
52
53cpp::string_view build_error_string(int err_num, cpp::span<char> buffer) {
54 // if the buffer can't hold "Unknown error" + ' ' + num_str, then just
55 // return "Unknown error".
56 if (buffer.size() <
57 (sizeof("Unknown error") + 1 + IntegerToString<int>::buffer_size()))
58 return const_cast<char *>("Unknown error");
59
60 cpp::StringStream buffer_stream(
61 {const_cast<char *>(buffer.data()), buffer.size()});
62 buffer_stream << "Unknown error" << ' ' << err_num << '\0';
63 return buffer_stream.str();
64}
65
66} // namespace internal
67
68cpp::string_view get_error_string(int err_num) {
69 return get_error_string(err_num,
70 {internal::error_buffer, internal::ERR_BUFFER_SIZE});
71}
72
73cpp::string_view get_error_string(int err_num, cpp::span<char> buffer) {
74 auto opt_str = internal::ERROR_MAPPER.get_str(err_num);
75 if (opt_str)
76 return *opt_str;
77 else
78 return internal::build_error_string(err_num, buffer);
79}
80
81cpp::optional<cpp::string_view> try_get_errno_name(int err_num) {
82 return internal::ERRNO_NAME_MAPPER.get_str(err_num);
83}
84
85} // namespace LIBC_NAMESPACE_DECL
86

source code of libc/src/__support/StringUtil/error_to_string.cpp