Difference between revisions of "cpp/string/byte/memchr"
From cppreference.com
m (s/character/byte) |
Andreas Krug (Talk | contribs) m ({{c}}, headers sorted, fmt) |
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| − | {{cpp/title| memchr}} | + | {{cpp/title|memchr}} |
{{cpp/string/byte/navbar}} | {{cpp/string/byte/navbar}} | ||
{{dcl begin}} | {{dcl begin}} | ||
| − | {{dcl header | cstring}} | + | {{dcl header|cstring}} |
| − | {{dcl | | + | {{dcl| |
const void* memchr( const void* ptr, int ch, std::size_t count ); | const void* memchr( const void* ptr, int ch, std::size_t count ); | ||
}} | }} | ||
| − | {{dcl | 1= | + | {{dcl|1= |
void* memchr( void* ptr, int ch, std::size_t count ); | void* memchr( void* ptr, int ch, std::size_t count ); | ||
}} | }} | ||
{{dcl end}} | {{dcl end}} | ||
| − | Converts {{ | + | Converts {{c|ch}} to {{c|unsigned char}} and locates the first occurrence of that value in the initial {{c|count}} bytes (each interpreted as {{c|unsigned char}}) of the object pointed to by {{c|ptr}}. |
{{rrev|since=c++17| | {{rrev|since=c++17| | ||
| − | This function behaves as if it reads the bytes sequentially and stops as soon as a matching bytes is found: if the array pointed to by {{ | + | This function behaves as if it reads the bytes sequentially and stops as soon as a matching bytes is found: if the array pointed to by {{c|ptr}} is smaller than {{c|count}}, but the match is found within the array, the behavior is well-defined. |
}} | }} | ||
===Parameters=== | ===Parameters=== | ||
{{par begin}} | {{par begin}} | ||
| − | {{par | ptr | pointer to the object to be examined}} | + | {{par|ptr|pointer to the object to be examined}} |
| − | {{par | ch | byte to search for}} | + | {{par|ch|byte to search for}} |
| − | {{par | count | max number of bytes to examine}} | + | {{par|count|max number of bytes to examine}} |
{{par end}} | {{par end}} | ||
| Line 30: | Line 30: | ||
Search an array of characters. | Search an array of characters. | ||
{{example | {{example | ||
| − | + | |code= | |
| − | + | ||
#include <cstring> | #include <cstring> | ||
| + | #include <iostream> | ||
int main() | int main() | ||
{ | { | ||
| − | char arr[] = {'a','\0','a','A','a','a','A','a'}; | + | char arr[] = {'a', '\0', 'a', 'A', 'a', 'a', 'A', 'a'}; |
| − | char *pc = (char*)std::memchr(arr,'A',sizeof arr); | + | char *pc = (char*) std::memchr(arr, 'A', sizeof arr); |
if (pc != nullptr) | if (pc != nullptr) | ||
| − | + | std::cout << "search character found\n"; | |
else | else | ||
| − | + | std::cout << "search character not found\n"; | |
} | } | ||
| − | + | |output= | |
search character found | search character found | ||
}} | }} | ||
| Line 49: | Line 49: | ||
===See also=== | ===See also=== | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc inc | cpp/string/byte/dsc strchr}} | + | {{dsc inc|cpp/string/byte/dsc strchr}} |
| − | {{dsc inc | cpp/algorithm/dsc find}} | + | {{dsc inc|cpp/algorithm/dsc find}} |
| − | {{dsc see c | c/string/byte/memchr}} | + | {{dsc see c|c/string/byte/memchr}} |
{{dsc end}} | {{dsc end}} | ||
{{langlinks|de|es|fr|it|ja|pt|ru|zh}} | {{langlinks|de|es|fr|it|ja|pt|ru|zh}} | ||
Latest revision as of 09:14, 5 June 2023
| Defined in header <cstring>
|
||
| const void* memchr( const void* ptr, int ch, std::size_t count ); |
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| void* memchr( void* ptr, int ch, std::size_t count ); |
||
Converts ch to unsigned char and locates the first occurrence of that value in the initial count bytes (each interpreted as unsigned char) of the object pointed to by ptr.
|
This function behaves as if it reads the bytes sequentially and stops as soon as a matching bytes is found: if the array pointed to by ptr is smaller than count, but the match is found within the array, the behavior is well-defined. |
(since C++17) |
Contents |
[edit] Parameters
| ptr | - | pointer to the object to be examined |
| ch | - | byte to search for |
| count | - | max number of bytes to examine |
[edit] Return value
Pointer to the location of the byte, or a null pointer if no such byte is found.
[edit] Example
Search an array of characters.
Run this code
Output:
search character found
[edit] See also
| finds the first occurrence of a character (function) | |
| (C++11) |
finds the first element satisfying specific criteria (function template) |
| C documentation for memchr
| |
