本例是上例的延续，主要接着展示C语言中的各种string操作方法。
CMakeLists.txt
cmake_minimum_required(VERSION 3.3)
project(84_cstring_manipulation)
set(ENV{PKG_CONFIG_PATH} "$ENV{PKG_CONFIG_PATH}:/usr/local/lib/pkgconfig/")
set ( CMAKE_CXX_FLAGS "-pthread")
set(CMAKE_CXX_STANDARD 20)
add_definitions(-g)
include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)
conan_basic_setup()
include_directories(${INCLUDE_DIRS})
LINK_DIRECTORIES(${LINK_DIRS})
file( GLOB main_file_list ${CMAKE_CURRENT_SOURCE_DIR}/*.cpp)
foreach( main_file ${main_file_list} )
file(RELATIVE_PATH filename ${CMAKE_CURRENT_SOURCE_DIR} ${main_file})
string(REPLACE ".cpp" "" file ${filename})
add_executable(${file} ${main_file})
target_link_libraries(${file} ${CONAN_LIBS} pthread)
endforeach( main_file ${main_file_list})
conanfile.txt
[requires]
boost/1.72.0
[generators]
cmake
main.cpp
#include <iostream>
#include <cstring>
enum op_t {
STR_LEN,
STR_CMP,
STR_N_CMP,
STR_CHR,
STR_RCHR
};
struct c_string_demo_t {
void str_len_demo() {
char const message1[] {"The sky is blue."};
char const* message2 {"The sky is blue."};
//strlen ignores null character
std::cout << "strlen(message1): " << std::strlen(message1) << std::endl;
// Includes the null character
std::cout << "sizeof(message1): " << sizeof(message1) << std::endl;
//strlen still works with decayed arrays
std::cout << "strlen(message2): " << std::strlen(message2) << std::endl;
//Prints size of pointer
std::cout << "sizeof(message2): " << sizeof(message2) << std::endl;
}
void str_cmp_demo() {
// std::strcmp - signature : int strcmp( const char *lhs, const char *rhs );
//Returns negative value if lhs appears before rhs in lexicographical order,
//Zero if lhs and rhs compare equal.
//and Positive value if lhs appears after rhs in lexicographical order.
std::cout << std::endl;
std::cout << "std::strcmp: " << std::endl;
char const* str_data1 {"Alabama"};
char const* str_data2 {"Blabama"};
char str_data3[] {"Alabama"};
char str_data4[] {"Blabama"};
std::cout << "std::strcmp(" << str_data1 << "," << str_data2 << "): "
<< std::strcmp(str_data1, str_data2) << std::endl;
std::cout << "std::strcmp(" << str_data3 << "," << str_data4 << "): "
<< std::strcmp(str_data3, str_data4) << std::endl;
str_data1 = "Alabama";
str_data2 = "Alabamb";
std::cout << "std::strcmp(" << str_data1 << "," << str_data2 << "): "
<< std::strcmp(str_data1, str_data2) << std::endl;
str_data1 = "Alacama";
str_data2 = "Alabama";
std::cout << "std::strcmp(" << str_data1 << "," << str_data2 << "): "
<< std::strcmp(str_data1, str_data2) << std::endl;
str_data1 = "India";
str_data2 = "France";
std::cout << "std::strcmp(" << str_data1 << "," << str_data2 << "): "
<< std::strcmp(str_data1, str_data2) << std::endl;
str_data1 = "Kigali";
str_data2 = "Kigali";
std::cout << "std::strcmp(" << str_data1 << "," << str_data2 << "): "
<< std::strcmp(str_data1, str_data2) << std::endl;
}
void str_n_cmp_demo() {
//std::strncmp : int strncmp( const char *lhs, const char *rhs, std::size_t count );
//Compares n characters in the strings
//Returns : Negative value if lhs appears before rhs in lexicographical order.
//Zero if lhs and rhs compare equal, or if count is zero.
//Positive value if lhs appears after rhs in lexicographical order.
//Print out the comparison
char const* str_data1 {"Alabama"};
char const* str_data2 {"Blabama"};
std::size_t n{3};
std::cout << std::endl;
std::cout << "std::strncmp: " << std::endl;
std::cout << "std::strncmp(" << str_data1 << "," << str_data2 << "," << n << "):"
<< std::strncmp(str_data1, str_data2, n) << std::endl;
str_data1 = "aaaia";
str_data2 = "aaance";
std::cout << "std::strncmp(" << str_data1 << "," << str_data2 << "," << n << "):"
<< std::strncmp(str_data1, str_data2, n) << std::endl;
n = 5;
std::cout << "std::strncmp(" << str_data1 << "," << str_data2 << "," << n << "):"
<< std::strncmp(str_data1, str_data2, n) << std::endl;
str_data1 = "aaaoa";
str_data2 = "aaance";
std::cout << "std::strncmp(" << str_data1 << "," << str_data2 << "," << n << "):"
<< std::strncmp(str_data1, str_data2, n) << std::endl;
}
void str_chr_demo() {
char const* const str {"Try not. Do, or do not. There is no try."};
char target = 'T';
char const* result = str;
std::size_t iterations {};
while((result = std::strchr(result, target)) != nullptr) {
std::cout << "Found '" << target << "' starting at '"
<< result << "'\n";
// Increment result, otherwise we'll find target at the same location
++ result;
++ iterations;
}
}
void str_rchr_demo() {
std::cout << std::endl;
std::cout << "std::strrchr: " << std::endl;
char input[] = "/home/user/hello.cpp";
char* output = std::strrchr(input, '/');
if(output) {
//+1 because we want to start printing past
// the character found by std::strrchr.
std::cout << output + 1 << std::endl;
}
}
void operator()(op_t op) {
switch(op) {
case STR_LEN:
str_len_demo();
break;
case STR_CMP:
str_cmp_demo();
break;
case STR_N_CMP:
str_n_cmp_demo();
break;
case STR_CHR:
str_chr_demo();
break;
case STR_RCHR:
str_rchr_demo();
break;
}
}
};
int main(int argc, char* argv[]) {
c_string_demo_t c_s_demo;
c_s_demo(op_t::STR_LEN);
c_s_demo(op_t::STR_CMP);
c_s_demo(op_t::STR_N_CMP);
c_s_demo(op_t::STR_CHR);
c_s_demo(op_t::STR_RCHR);
return EXIT_SUCCESS;
}
程序输出如下，
image.png
image.png
