Useful includes
#include <stdlib.h> #include <string> // for string, substring #include <sstream> // for stringstream #include <iostream> // for cout, puts etc. #include <stdio.h> // for sprintf, printf( "%lf\n", accum ); #include <time.h> // time #include <fcntl.h> // open() #include <unistd.h> // read() #include <iomanip> // for setw #include <fstream> // for ifstream #include <cstring> // for memcpy, placed in the std namespace #include <cstddef> // for size_t #include <stdint.h> // uint8_t, uint32_t, etc. using namespace std; // allows get rid of std:: prefix.
Formatting of the string
Formatting of the string
double val = 12345.26374859560; std::stringstream ss; ss << std::setw(8) << std::setprecision(8) << std::right << val; std::string s = ss.str();
Input from stringstream
std::string s("121 151 225 456");
std::stringstream ss(s);
T val;
do { ss >> val; cout << val << endl; } while( ss.good() );
String methods
#include <string>
std::string basename(const std::string& path)
{
size_t pos = path.find_last_of('/');
//if (pos == std::string::npos) return std::string();
if (pos < path.size()-1) return std::string(path,pos+1);
else return std::string();
}
Input from file value by value
#include <fstream> // for ifstream
std::ifstream f("file.txt");
std::string val;
while (f>>val) {
std::cout << "val: " << val << '\n';
}
f.close();
Input from file line by line
#include <fstream> // for ifstream
std::ifstream f("file.txt");
std::string line;
while (std::getline(f, line)) {
std::cout << "line: " << line << '\n';
}
f.close();
Print long space or repeated character
std::cout << std::setw(80) << " " << std::setw(4);
std::cout << std::setw(20) << setfill('=') << '=';
Bit operations
Check if the n-th bit is on: if( m_print_bits & (1 << n) ) ...
Set n-th bit: mask |= (1 << n)
Clear n-th bit: bit_fld &= ~(1 << n)
Toggle (swap 0<->1) n-th bit: bit_fld ^= (1 << n)
Check if the element is in the vector or list
T element = <instatiation>;
std::vector<T> v; v=<initialization>;
if (std::find(v.begin(), v.end(), element) != v.end()) {/*element is in v*/}
else {/* is not there */}
Add the element to the vector or list if it is not there
T element = <instatiation>; std::vector<T> v; v=<initialization>; if (std::find(v.begin(), v.end(), element) == v.end()) v.push_back(element);
Time
#include <stdio.h> // for printf
#include <time.h>
#include <iostream> // for cout
using namespace std;
int main ()
{
// Get current time in seconds since January 1, 1970:
time_t seconds;
seconds = time (NULL);
cout << seconds << " sec since January 1, 1970\n";
// Another form of the time access method:
time_t time_sec;
time ( &time_sec );
struct tm* timeinfo; timeinfo = localtime ( &time_sec );
cout << "time_sec = " << time_sec << endl;
cout << "ctime - converts time_sec in char* : " << ctime (&time_sec);
char* p_buf = asctime(timeinfo);
cout << "asctime - converts struct tm* in char*: " << p_buf;
char c_time_buf[80]; strftime (c_time_buf,80,"%Y-%m-%d %H:%M",timeinfo);
cout << "strftime - user-formatted time char* : " << c_time_buf << endl;
printf ( "struct tm* members:\n");
printf ( "sec = %d\n", timeinfo->tm_sec );
printf ( "min = %d\n", timeinfo->tm_min );
printf ( "hour = %d\n", timeinfo->tm_hour );
printf ( "mday = %d\n", timeinfo->tm_mday );
printf ( "mon = %d\n", timeinfo->tm_mon );
printf ( "year = %d\n", timeinfo->tm_year );
printf ( "wday = %d\n", timeinfo->tm_wday );
printf ( "yday = %d\n", timeinfo->tm_yday );
printf ( "isdst= %d\n", timeinfo->tm_isdst);
return ( EXIT_SUCCESS );
}
Precise time
Use another time structure, which accounts for sec and nsec.
#include <time.h> // time
struct timespec start, stop;
int gettimeStatus = clock_gettime( CLOCK_REALTIME, &start );
printf ( "gettimeStatus: %d \n", gettimeStatus );
printf ( "start.tv_sec = %d start.tv_nsec = %d \n", start.tv_sec, start.tv_nsec );
gettimeStatus = clock_gettime( CLOCK_REALTIME, &stop );
printf ( " stop.tv_sec = %d stop.tv_nsec = %d \n", stop.tv_sec, stop.tv_nsec );
printf ( " dt_sec = %d dt_nsec = %d \n", stop.tv_sec - start.tv_sec,
stop.tv_nsec- start.tv_nsec);
Direct access to command line parameters in C++
#include <iostream>
using namespace std;
int main(int argc, char* argv[]) {
cout << "argc = " << argc << endl;
for(int i = 0; i < argc; i++)
cout << "argv[" << i << "] = " << argv[i] << endl;
return 0;
}
Input parameters parsing with getopt
getopt has potential problem: it does not detect the missing argument and pick-up the next available option as an argument...
RETURN VALUE:
- The getopt() function shall return the next option character specified on the command line.
- A colon ( ':' ) shall be returned if getopt() detects a missing argument and the first character of optstring was a colon ( ':' ).
- A question mark ( '?' ) shall be returned if getopt() encounters an option character not in optstring or detects a missing argument and the first character of optstring was not a colon ( ':' ).
- Otherwise, getopt() shall return -1 when all command line options are parsed.
#include <getopt.h>
#include <stdio.h>
#include <iostream>
//===================
void usage(char* name) {
std::cout << "Usage: " << name << " [-a <aaa>] [-b <bbb>] [-c <ccc>] [-h] <p1> [<p2> [<p3> ...]] \n";
}
//===================
int main (int argc, char **argv)
{
char *avalue = NULL;
char *bvalue = NULL;
char *cvalue = NULL;
int index;
int c;
extern char *optarg;
extern int optind, optopt, opterr;
while ((c = getopt (argc, argv, ":a:b:c:h")) != -1)
switch (c)
{
case 'a':
avalue = optarg;
printf ("a: avalue = %s\n",avalue);
break;
case 'b':
bvalue = optarg;
printf ("b: bvalue = %s\n",bvalue);
break;
case 'c':
cvalue = optarg;
printf ("c: cvalue = %s\n",cvalue);
break;
case 'h':
printf ("h: ");
usage(argv[0]);
break;
case ':':
printf ("(:) Option -%c requires an argument.\n", optopt);
usage(argv[0]);
return EXIT_FAILURE;
case '?':
printf ("?: Option -%c requires an argument.\n", optopt);
usage(argv[0]);
return EXIT_FAILURE;
default:
printf ("default: You should not get here... option -%c .\n", optopt);
abort ();
}
printf ("End of options: avalue = %s, bvalue = %s, cvalue = %s\n",
avalue, bvalue, cvalue);
for (index = optind; index < argc; index++)
printf ("Non-option argument %s\n", argv[index]);
return EXIT_SUCCESS;
}
Check if directory exists
#include <sys/stat.h>
bool dir_exists(const std::string& dir)
{
struct stat st;
if( (stat(dir.c_str(),&st) == 0) && (((st.st_mode) & S_IFMT) == S_IFDIR) ) return true;
return false;
}
Check if file exists
#include <fstream> // for ifstream
std::ifstream f("file.txt");
if(not f.good()) ...
Iterate over files in the directory
Using opendir, readdir, closedir from STL
#include <iostream>
#include <dirent.h>
using namespace std;
int main() {
DIR* dir;
dirent* pdir;
dir = opendir("."); // open current directory
while (pdir = readdir(dir)) {
cout << pdir->d_name << endl;
}
closedir(dir);
return 0;
}
Using boost
#include <boost/filesystem.hpp>
namespace fs = boost::filesystem;
fs::path path = "/reg/d/psdm/CXI/cxi49012/xtc/e158-r0150-s00-c01.xtc";
fs::path dir = path.parent_path(); // i.e.: /reg/d/psdm/CXI/cxi49012/xtc
typedef fs::directory_iterator dir_iter;
for (dir_iter dit = dir_iter(dir); dit != dir_iter(); ++ dit) {
std::cout << dit->path().stem().string() << "\n";
}
Other methods of fs::path
fs::path path = m_path; std::cout << "stem = " << path.stem().string() << "\n"; // e158-r0150-s00-c00 std::cout << "extension() = " << path.extension().string() << "\n"; // .xtc std::cout << "filename() = " << path.filename().string() << "\n"; // e158-r0150-s00-c00.xtc std::cout << "parent_path() = " << path.parent_path().string() << "\n"; // /reg/d/psdm/CXI/cxi49012/xtc
ndarray and shared pointer
Example of how to access ndarray data in psana module through the shared pointer and construct ndarray<const T,NDim>
shared_ptr< ndarray<T,NDim> > shp = evt.get(m_source, m_key, &m_src);
if (shp.get()) {
ndarray<T,NDim>* pnda = shp.get();
ndarray<const T,NDim> nda_const(pnda->data(), pnda->shape());
ndarray<const T,NDim> nda_const(shp->data(), shp->shape());
}
Singleton
InputParameters.h :
#include <iostream> // for cout
class InputParameters {
public:
static InputParameters* instance();
void print();
private:
InputParameters () ; // !!!!! Private so that it can not be called from outside
virtual ~InputParameters () {};
static InputParameters* m_pInstance; // !!!!! Singleton instance
// Copy constructor and assignment are disabled by default
InputParameters ( const InputParameters& ) ;
InputParameters& operator = ( const InputParameters& ) ;
};
InputParameters.cc :
#include "<Package>/InputParameters.h"
InputParameters* InputParameters::m_pInstance = NULL; // !!!!!! make global pointer !!!!!
//----------------
InputParameters::InputParameters ()
{
std::cout << "!!!!!!!! Single instance for singleton class InputParameters is created \n";
}
//----------------
InputParameters* InputParameters::instance()
{
if( !m_pInstance ) m_pInstance = new InputParameters();
return m_pInstance;
}
//----------------
void InputParameters::print() { std::cout << "InputParameters::print()\n"; }
Calls:
#include "<Package>/InputParameters.h"
int main(int argc, char *argv[])
{
InputParameters::instance()->print("xyz...");
}
Shortcuts:
#define PRINT InputParameters::instance()->print
int main(){
PRINT("This is a line of log");
return 0;
}
Declaration, Initialization, Definition of static const parameters
// *.h :
class A {
public:
static const int INT_PAR = 185;
static const double DOUBLE_PAR;
}
// *.cpp :
const int A::INT_PAR;
const double A::DOUBLE_PAR = 109.92;
Issue OS command from C++
Use method system
// int system (const char* command);
#include <stdlib.h> /* system, NULL, EXIT_FAILURE */
int status = system ("ls -l");
Use method popen
#include <string>
#include <iostream>
#include <stdio.h>
std::string exec(char* cmd) {
FILE* pipe = popen(cmd, "r");
if (!pipe) return "ERROR";
char buffer[128];
std::string result = "";
while(!feof(pipe)) {
if(fgets(buffer, 128, pipe) != NULL)
result += buffer;
}
pclose(pipe);
return result;
}
Valgrind - analysis of job memory consumption
valgrind --tool=massif --time-unit=B psana -n 1 -m ImgAlgos.PixCoordsProducer exp=cxi86415:run=62
this command runs the job and produces the file like massif.out.23864, which can be printed by command:
ms_print massif.out.23864
Building C/C++ library using distutils.core setup, Extension
http://stackoverflow.com/questions/16854066/using-distutils-and-build-clib-to-build-c-library
Instead of passing a library name as a string, pass a tuple with the sources to compile:
# setup.py
#__________
import sys
from distutils.core import setup
from distutils.command.build_clib import build_clib
from distutils.extension import Extension
from Cython.Distutils import build_ext
libhello = ('hello', {'sources': ['hello.c']}) # <<<<==============
ext_modules=[
Extension("demo", ["demo.pyx"])
]
setup(
name = 'demo',
libraries = [libhello],
cmdclass = {'build_clib': build_clib, 'build_ext': build_ext},
ext_modules = ext_modules
)
#__________
Using C++ in Cython
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