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1//
2// strtok_s.cpp
3//
4// Copyright (c) Microsoft Corporation. All rights reserved.
5//
6// Defines strtok_s(), which tokenizes a string via repeated calls. See strtok()
7// for more details. This more secure function uses a caller-provided context
8// instead of the thread-local tokenization state.
9//
10#include <string.h>
11#include <corecrt_internal_securecrt.h>
12
13
14
15// This common implementation is used by both strtok() and strtok_s()
16extern "C" char* __cdecl __acrt_strtok_s_novalidation(
17 _Inout_opt_z_ char* string,
18 _In_z_ char const* control,
19 _Inout_ _Deref_prepost_opt_z_ char** context
20 )
21{
22 // Clear control map. The control characters are stored in a bitmap, one
23 // bit per character. The null character is always a control character.
24 unsigned char map[32];
25 for (int count = 0; count < 32; count++)
26 {
27 map[count] = 0;
28 }
29
30 // Set bits in delimiter table
31 unsigned char const* unsigned_control = reinterpret_cast<unsigned char const*>(control);
32 do
33 {
34 map[*unsigned_control >> 3] |= (1 << (*unsigned_control & 7));
35 }
36 while (*unsigned_control++);
37
38 // If string is null, set the iterator to the saved pointer (i.e., continue
39 // breaking tokens out of the string from the last strtok call):
40 char* it = string != nullptr
41 ? string
42 : *context;
43
44 unsigned char*& unsigned_it = reinterpret_cast<unsigned char*&>(it);
45
46 // Find beginning of token (skip over leading delimiters). Note that
47 // there is no token iff this loop sets it to point to the terminal
48 // null (*it == '\0')
49 while ((map[*unsigned_it >> 3] & (1 << (*unsigned_it & 7))) && *it)
50 {
51 ++it;
52 }
53
54 char* const token_first = it;
55
56 // Find the end of the token. If it is not the end of the string,
57 // put a null there.
58 for (; *it; ++it)
59 {
60 if (map[*unsigned_it >> 3] & (1 << (*unsigned_it & 7)))
61 {
62 *it++ = '\0';
63 break;
64 }
65 }
66
67 // Update the saved pointer:
68 *context = it;
69
70 // Determine if a token has been found.
71 return it != token_first ? token_first : nullptr;
72}
73
74
75
76extern "C" char* __cdecl strtok_s(char* string, char const* control, char** context)
77{
78 _VALIDATE_POINTER_ERROR_RETURN(context, EINVAL, nullptr);
79 _VALIDATE_POINTER_ERROR_RETURN(control, EINVAL, nullptr);
80 _VALIDATE_CONDITION_ERROR_RETURN(string != nullptr || *context != nullptr, EINVAL, nullptr);
81
82 return __acrt_strtok_s_novalidation(string, control, context);
83}