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