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How to make the c ++ application work with the browser. I mean a program that retrieves data from a given page (let's assume that the page displays a string) and then performs some reaction on the page. For example, the page displays a random string, and the program enters the length of the string into the form.
I am a novice programmer, so I care about information and advice on where to start. Thanks in advance for any help.
As I already promised to OP in comments, posting Partial answer, which doesn't answer all questions, but only provides handy tool to wrap (call) any Python code inside C++ program.
In my code snippet I don't even do anything with browsers, but instead show only example of computing Greatest Common Divisor using Python's standard function math.gcd().
I decided to introduce this Python-in-C++ bridge only because there exist many beautiful Python modules that work with browsers or with parsing/composing HTML, hence it is much easier to write such tools in Python instead of C++.
But expert without knowledge of default Python C API, it is not that easy to implement even simple use case - compile text of Python code, pass to it any arguments from C++, receive response arguments, return arguments back to C++. Only these simple actions need usage of a dozen of different Python C API functions. That's why I decided to show how to do it, as I know.
I implemented from scratch (specifically for OP's question) handy class PyRunner which does all the magic, usage of this class is simple:
PyRunner pyrun;
std::string code = R"(
def gcd(a, b):
import math
return math.gcd(a, b)
res = gcd(*arg)
print('GCD of', arg[0], 'and', arg[1], 'is', res, flush = True)
)";
std::cout << pyrun.Run(code, "(2 * 3 * 5, 2 * 3 * 7)") << std::endl;
std::cout << pyrun.Run(code, "(5 * 7 * 11, 5 * 7 * 13)") << std::endl;
Basically you just pass any Python code snippet to PyRunner::Run() method and also any argument (represented as Python object converted to string). Result of this call is also a returned Python object converted to string. You can also use JSON to pass any large argument as string and parse returned argument, as any JSON string is also a valid stringized Python object.
Of course you need a knowledge of Python to be able to write complex code snippets inside C++.
One drawback of my PyRunner class is that for some reason (that I didn't yet understand), you can't import Python module inside global scope, as you can see I did import math within function scope. But this is not a big deal, I think, and maybe some experts will clarify the reason.
To compile and run code you need to have pre-installed Python, and pass Python's include folder and library file as compiler arguments. For example in Windows CLang you do following:
clang.exe -std=c++20 -O3 -Id:/bin/Python39/include/ d:/bin/Python39/libs/python39.lib prog.cpp
and in Linux:
clang -std=c++20 -O3 -I/usr/include/ -lpython3.9 prog.cpp
To run the program either you should provide environment variables PYTHONHOME or PYTHONPATH or run program from Python folder (like d:/bin/Python39/) or do sys.path.append("d:/bin/Python39/") on first lines of Python code snippet embedded in C++. Without these paths Python can't find location of its standard library.
PyRunner class is thread-safe, but only single-threaded always. It means that two calls to .Run() inside two threads will be exclusively blocked by mutex. I use std::mutex instead of Python's GIL to protect from multi-threading, because it is quite alright (and faster), if you don't use Python C API in any other threads simultaneously. Also it is not allowed right now to have two instances of PyRunner objects as it does Py_Initialize() and Py_FinalizeEx() in constructor and destructor, which should be done globally only once. Hence PyRunner should be a singleton.
Below is full C++ code with implementation of PyRunner class and its usage (usage is inside main()). See console output after code below. Click Try it online! link to see compile/run of this code on free GodBolt online Linux servers.
Try it online!
#include <iostream>
#include <functional>
#include <string>
#include <string_view>
#include <stdexcept>
#include <memory>
#include <mutex>
#include <Python.h>
#define ASSERT_MSG(cond, msg) { if (!(cond)) throw std::runtime_error("Assertion (" #cond ") failed at line " + std::to_string(__LINE__) + "! Msg: '" + std::string(msg) + "'."); }
#define ASSERT(cond) ASSERT_MSG(cond, "")
#define PY_ASSERT_MSG(cond, msg) { if (!(cond) || PyErr_Occurred()) { PyErr_Print(); ASSERT_MSG(false && #cond, msg); } }
#define PY_ASSERT(cond) PY_ASSERT_MSG(cond, "")
#define LN { std::cout << "LN " << __LINE__ << std::endl << std::flush; }
class PyRunner {
private:
class PyObj {
public:
PyObj(PyObject * pobj, bool inc_ref = false) : p_(pobj) {
if (inc_ref)
Py_XINCREF(p_);
PY_ASSERT_MSG(p_, "NULL PyObject* passed!");
}
PyObject * Get() { return p_; }
~PyObj() {
Py_XDECREF(p_);
p_ = nullptr;
}
private:
PyObject * p_ = nullptr;
};
public:
PyRunner() {
Py_SetProgramName(L"prog.py");
Py_Initialize();
}
~PyRunner() {
codes_.clear();
Py_FinalizeEx();
}
std::string Run(std::string code, std::string const & arg = "None") {
std::unique_lock<std::mutex> lock(mutex_);
code = StrUnIndent(code);
if (!codes_.count(code))
codes_.insert(std::pair{code, std::make_shared<PyObj>(Py_CompileString(code.c_str(), "script.py", Py_file_input))});
PyObj & compiled = *codes_.at(code);
PyObj globals_arg_mod = PyModule_New("arg"), globals_arg = PyModule_GetDict(globals_arg_mod.Get()), locals_arg = PyDict_New(),
globals_mod = PyModule_New("__main__"), globals = PyModule_GetDict(globals_mod.Get()), locals = PyDict_New();
// py_arg = PyUnicode_FromString(arg.c_str()),
PyObj py_arg = PyRun_String(arg.c_str(), Py_eval_input, globals_arg.Get(), locals_arg.Get());
PY_ASSERT(PyDict_SetItemString(locals.Get(), "arg", py_arg.Get()) == 0);
#if 0
PyObj result = PyEval_EvalCode(compiled.Get(), globals.Get(), locals.Get());
#else
PyObj builtins(PyEval_GetBuiltins(), true), exec(PyDict_GetItemString(builtins.Get(), "exec"), true);
PyObj exec_args = PyTuple_Pack(3, compiled.Get(), globals.Get(), locals.Get());
PyObj result = PyObject_CallObject(exec.Get(), exec_args.Get());
#endif
PyObj res(PyDict_GetItemString(locals.Get(), "res"), true), res_str = PyObject_Str(res.Get());
char const * cres = nullptr;
PY_ASSERT(cres = PyUnicode_AsUTF8(res_str.Get()));
return cres;
}
private:
static std::string StrUnIndent(std::string_view const & s) {
auto lines = StrSplit(s, "\n");
size_t min_off = size_t(-1);
for (auto const & line: lines) {
if (StrTrim(line).empty())
continue;
min_off = std::min<size_t>(min_off, line.find_first_not_of("\t\n\v\f\r "));
}
ASSERT(min_off < 10000ULL);
std::string res;
for (auto const & line: lines)
res += line.substr(std::min<size_t>(min_off, line.size())) + "\n";
return res;
}
static std::string StrTrim(std::string s) {
s.erase(0, s.find_first_not_of("\t\n\v\f\r ")); // left trim
s.erase(s.find_last_not_of("\t\n\v\f\r ") + 1); // right trim
return s;
}
static std::vector<std::string> StrSplit(std::string_view const & s, std::string_view const & delim) {
std::vector<std::string> res;
size_t start = 0;
while (true) {
size_t pos = s.find(delim, start);
if (pos == std::string::npos)
pos = s.size();
res.emplace_back(s.substr(start, pos - start));
if (pos >= s.size())
break;
start = pos + delim.size();
}
return res;
}
private:
std::unordered_map<std::string, std::shared_ptr<PyObj>> codes_;
std::mutex mutex_;
};
int main() {
try {
PyRunner pyrun;
std::string code = R"(
def gcd(a, b):
import math
return math.gcd(a, b)
res = gcd(*arg)
print('GCD of', arg[0], 'and', arg[1], 'is', res, flush = True)
)";
std::cout << pyrun.Run(code, "(2 * 3 * 5, 2 * 3 * 7)") << std::endl;
std::cout << pyrun.Run(code, "(5 * 7 * 11, 5 * 7 * 13)") << std::endl;
return 0;
} catch (std::exception const & ex) {
std::cout << "Exception: " << ex.what() << std::endl;
return -1;
}
}
Console output:
GCD of 30 and 42 is 6
6
GCD of 385 and 455 is 35
35
I've made a simple .acf file to .json file formatter. But for some reason it runs correctly under Windows with GCC using msys2 - But after executing a string insert or replace - it segmentation faults every time.
What it does is convert the below file into a json compatible format. It appends commas after each entry, applies attribute set symbol and puts braces around it.
Save as test.acf:
"AppState"
{
"appid" "730"
"Universe" "1"
"name" "Counter-Strike: Global Offensive"
"StateFlags" "4"
"installdir" "Counter-Strike Global Offensive"
"LastUpdated" "1462547468"
"UpdateResult" "0"
"SizeOnDisk" "14990577143"
"buildid" "1110931"
"LastOwner" "76561198013962068"
"BytesToDownload" "8768"
"BytesDownloaded" "8768"
"AutoUpdateBehavior" "1"
"AllowOtherDownloadsWhileRunning" "0"
"UserConfig"
{
"Language" "english"
}
"MountedDepots"
{
"731" "205709710082221598"
"734" "5169984513691014102"
}
}
Minimal main code with defects triple slashed:
#include <iostream>
#include <fstream>
#include <string>
int main(int argc, char* argv[])
{
file.open("test.acf");
std::string data((std::istreambuf_iterator<char>(file)), (std::istreambuf_iterator<char>()));
int indexQuote = 0;
int index[4];
int insertCommaNext = -1;
string delims = "\"{}"; // It skips between braces and quotes only
std::size_t found = data.find_first_of(delims);
while(found != std::string::npos)
{
int inc = 1; // 0-4 depending on the quote - 0"key1" 2"value3" 4{
char c = data.at(found);
if (c != '"') {
if (c == '}')
insertCommaNext = found + 1; // Record index to insert comma after (following closing brace)
else if (c == '{') {
///data.insert(index[1] + 1, ":");
///inc++;
}
indexQuote = 0;
} else {
if (insertCommaNext != -1) {
///data.insert(insertCommaNext, ",");
///inc++;
insertCommaNext = -1;
}
index[indexQuote] = found;
if (indexQuote == 2) { // Join 'key: value' by placing the comma
///data.replace(index[1] + 1, 1, ":");
} else if (indexQuote == 4) { // Add comma after each key/value entry
indexQuote = 0;
///data.insert(index[3] + 1, ",");
///inc++;
}
indexQuote++;
}
found = data.find_first_of(delims, found + inc);
}
data = "{" + data + "}";
}
If you uncomment any of the triple slashed /// lines - containing an insert/replace, it will crash.
I'm certian the code quality is not great, there's probably better ways to achieve this. Cheers.
The problem is that indexQuote gets higher than 3, so index[indexQuote] = found; goes out of bounds. You have the case below that resets indexQuote to 0, you have to do that before you try to call index[indexQuote].
For reference, I debugged this by adding prints everywhere and printing all the variables until I found where it crashed.
Given a string "filename.conf", how to I verify the extension part?
I need a cross platform solution.
Is this too simple of a solution?
#include <iostream>
#include <string>
int main()
{
std::string fn = "filename.conf";
if(fn.substr(fn.find_last_of(".") + 1) == "conf") {
std::cout << "Yes..." << std::endl;
} else {
std::cout << "No..." << std::endl;
}
}
The best way is to not write any code that does it but call existing methods. In windows, the PathFindExtension method is probably the simplest.
So why would you not write your own?
Well, take the strrchr example, what happens when you use that method on the following string "c:\program files\AppleGate.Net\readme"? Is ".Net\readme" the extension? It is easy to write something that works for a few example cases, but can be much harder to write something that works for all cases.
With C++17 and its std::filesystem::path::extension (the library is the successor to boost::filesystem) you would make your statement more expressive than using e.g. std::string.
#include <iostream>
#include <filesystem> // C++17
namespace fs = std::filesystem;
int main()
{
fs::path filePath = "my/path/to/myFile.conf";
if (filePath.extension() == ".conf") // Heed the dot.
{
std::cout << filePath.stem() << " is a valid type."; // Output: "myFile is a valid type."
}
else
{
std::cout << filePath.filename() << " is an invalid type."; // Output: e.g. "myFile.cfg is an invalid type"
}
}
See also std::filesystem::path::stem, std::filesystem::path::filename.
You have to make sure you take care of file names with more then one dot.
example: c:\.directoryname\file.name.with.too.many.dots.ext would not be handled correctly by strchr or find.
My favorite would be the boost filesystem library that have an extension(path) function
Assuming you have access to STL:
std::string filename("filename.conf");
std::string::size_type idx;
idx = filename.rfind('.');
if(idx != std::string::npos)
{
std::string extension = filename.substr(idx+1);
}
else
{
// No extension found
}
Edit: This is a cross platform solution since you didn't mention the platform. If you're specifically on Windows, you'll want to leverage the Windows specific functions mentioned by others in the thread.
Someone else mentioned boost but I just wanted to add the actual code to do this:
#include <boost/filesystem.hpp>
using std::string;
string texture = foo->GetTextureFilename();
string file_extension = boost::filesystem::extension(texture);
cout << "attempting load texture named " << texture
<< " whose extensions seems to be "
<< file_extension << endl;
// Use JPEG or PNG loader function, or report invalid extension
actually the STL can do this without much code, I advise you learn a bit about the STL because it lets you do some fancy things, anyways this is what I use.
std::string GetFileExtension(const std::string& FileName)
{
if(FileName.find_last_of(".") != std::string::npos)
return FileName.substr(FileName.find_last_of(".")+1);
return "";
}
this solution will always return the extension even on strings like "this.a.b.c.d.e.s.mp3" if it cannot find the extension it will return "".
Actually, the easiest way is
char* ext;
ext = strrchr(filename,'.')
One thing to remember: if '.' doesn't exist in filename, ext will be NULL.
I've stumbled onto this question today myself, even though I already had a working code I figured out that it wouldn't work in some cases.
While some people already suggested using some external libraries, I prefer to write my own code for learning purposes.
Some answers included the method I was using in the first place (looking for the last "."), but I remembered that on linux hidden files/folders start with ".".
So if file file is hidden and has no extension, the whole file name would be taken for extension.
To avoid that I wrote this piece of code:
bool getFileExtension(const char * dir_separator, const std::string & file, std::string & ext)
{
std::size_t ext_pos = file.rfind(".");
std::size_t dir_pos = file.rfind(dir_separator);
if(ext_pos>dir_pos+1)
{
ext.append(file.begin()+ext_pos,file.end());
return true;
}
return false;
}
I haven't tested this fully, but I think that it should work.
I'd go with boost::filesystem::extension (std::filesystem::path::extension with C++17) but if you cannot use Boost and you just have to verify the extension, a simple solution is:
bool ends_with(const std::string &filename, const std::string &ext)
{
return ext.length() <= filename.length() &&
std::equal(ext.rbegin(), ext.rend(), filename.rbegin());
}
if (ends_with(filename, ".conf"))
{ /* ... */ }
Using std::string's find/rfind solves THIS problem, but if you work a lot with paths then you should look at boost::filesystem::path since it will make your code much cleaner than fiddling with raw string indexes/iterators.
I suggest boost since it's a high quality, well tested, (open source and commercially) free and fully portable library.
For char array-type strings you can use this:
#include <ctype.h>
#include <string.h>
int main()
{
char filename[] = "apples.bmp";
char extension[] = ".jpeg";
if(compare_extension(filename, extension) == true)
{
// .....
} else {
// .....
}
return 0;
}
bool compare_extension(char *filename, char *extension)
{
/* Sanity checks */
if(filename == NULL || extension == NULL)
return false;
if(strlen(filename) == 0 || strlen(extension) == 0)
return false;
if(strchr(filename, '.') == NULL || strchr(extension, '.') == NULL)
return false;
/* Iterate backwards through respective strings and compare each char one at a time */
for(int i = 0; i < strlen(filename); i++)
{
if(tolower(filename[strlen(filename) - i - 1]) == tolower(extension[strlen(extension) - i - 1]))
{
if(i == strlen(extension) - 1)
return true;
} else
break;
}
return false;
}
Can handle file paths in addition to filenames. Works with both C and C++. And cross-platform.
If you use Qt library, you can give a try to QFileInfo's suffix()
Good answers but I see most of them has some problems:
First of all I think a good answer should work for complete file names which have their path headings, also it should work for linux or windows or as mentioned it should be cross platform. For most of answers; file names with no extension but a path with a folder name including dot, the function will fail to return the correct extension: examples of some test cases could be as follow:
const char filename1 = {"C:\\init.d\\doc"}; // => No extention
const char filename2 = {"..\\doc"}; //relative path name => No extention
const char filename3 = {""}; //emputy file name => No extention
const char filename4 = {"testing"}; //only single name => No extention
const char filename5 = {"tested/k.doc"}; // normal file name => doc
const char filename6 = {".."}; // parent folder => No extention
const char filename7 = {"/"}; // linux root => No extention
const char filename8 = {"/bin/test.d.config/lx.wize.str"}; // ordinary path! => str
"brian newman" suggestion will fail for filename1 and filename4.
and most of other answers which are based on reverse find will fail for filename1.
I suggest including the following method in your source:
which is function returning index of first character of extension or the length of given string if not found.
size_t find_ext_idx(const char* fileName)
{
size_t len = strlen(fileName);
size_t idx = len-1;
for(size_t i = 0; *(fileName+i); i++) {
if (*(fileName+i) == '.') {
idx = i;
} else if (*(fileName + i) == '/' || *(fileName + i) == '\\') {
idx = len - 1;
}
}
return idx+1;
}
you could use the above code in your c++ application like below:
std::string get_file_ext(const char* fileName)
{
return std::string(fileName).substr(find_ext_idx(fileName));
}
The last point in some cases the a folder is given to file name as argument and includes a dot in the folder name the function will return folder's dot trailing so better first to user check that the given name is a filename and not folder name.
This is a solution I came up with. Then, I noticed that it is similar to what #serengeor posted.
It works with std::string and find_last_of, but the basic idea will also work if modified to use char arrays and strrchr.
It handles hidden files, and extra dots representing the current directory. It is platform independent.
string PathGetExtension( string const & path )
{
string ext;
// Find the last dot, if any.
size_t dotIdx = path.find_last_of( "." );
if ( dotIdx != string::npos )
{
// Find the last directory separator, if any.
size_t dirSepIdx = path.find_last_of( "/\\" );
// If the dot is at the beginning of the file name, do not treat it as a file extension.
// e.g., a hidden file: ".alpha".
// This test also incidentally avoids a dot that is really a current directory indicator.
// e.g.: "alpha/./bravo"
if ( dotIdx > dirSepIdx + 1 )
{
ext = path.substr( dotIdx );
}
}
return ext;
}
Unit test:
int TestPathGetExtension( void )
{
int errCount = 0;
string tests[][2] =
{
{ "/alpha/bravo.txt", ".txt" },
{ "/alpha/.bravo", "" },
{ ".alpha", "" },
{ "./alpha.txt", ".txt" },
{ "alpha/./bravo", "" },
{ "alpha/./bravo.txt", ".txt" },
{ "./alpha", "" },
{ "c:\\alpha\\bravo.net\\charlie.txt", ".txt" },
};
int n = sizeof( tests ) / sizeof( tests[0] );
for ( int i = 0; i < n; ++i )
{
string ext = PathGetExtension( tests[i][0] );
if ( ext != tests[i][1] )
{
++errCount;
}
}
return errCount;
}
A NET/CLI version using System::String
System::String^ GetFileExtension(System::String^ FileName)
{
int Ext=FileName->LastIndexOf('.');
if( Ext != -1 )
return FileName->Substring(Ext+1);
return "";
}
_splitpath, _wsplitpath, _splitpath_s, _wsplitpath_w
This is Windows (Platform SDK) only
You can use strrchr() to find last occurence of .(dot) and get .(dot) based extensions files.
Check the below code for example.
#include<stdio.h>
void GetFileExtension(const char* file_name) {
int ext = '.';
const char* extension = NULL;
extension = strrchr(file_name, ext);
if(extension == NULL){
printf("Invalid extension encountered\n");
return;
}
printf("File extension is %s\n", extension);
}
int main()
{
const char* file_name = "c:\\.directoryname\\file.name.with.too.many.dots.ext";
GetFileExtension(file_name);
return 0;
}
Here's a function that takes a path/filename as a string and returns the extension as a string. It is all standard c++, and should work cross-platform for most platforms.
Unlike several other answers here, it handles the odd cases that windows' PathFindExtension handles, based on PathFindExtensions's documentation.
wstring get_file_extension( wstring filename )
{
size_t last_dot_offset = filename.rfind(L'.');
// This assumes your directory separators are either \ or /
size_t last_dirsep_offset = max( filename.rfind(L'\\'), filename.rfind(L'/') );
// no dot = no extension
if( last_dot_offset == wstring::npos )
return L"";
// directory separator after last dot = extension of directory, not file.
// for example, given C:\temp.old\file_that_has_no_extension we should return "" not "old"
if( (last_dirsep_offset != wstring::npos) && (last_dirsep_offset > last_dot_offset) )
return L"";
return filename.substr( last_dot_offset + 1 );
}
I use these two functions to get the extension and filename without extension:
std::string fileExtension(std::string file){
std::size_t found = file.find_last_of(".");
return file.substr(found+1);
}
std::string fileNameWithoutExtension(std::string file){
std::size_t found = file.find_last_of(".");
return file.substr(0,found);
}
And these regex approaches for certain extra requirements:
std::string fileExtension(std::string file){
std::regex re(".*[^\\.]+\\.([^\\.]+$)");
std::smatch result;
if(std::regex_match(file,result,re))return result[1];
else return "";
}
std::string fileNameWithoutExtension(std::string file){
std::regex re("(.*[^\\.]+)\\.[^\\.]+$");
std::smatch result;
if(std::regex_match(file,result,re))return result[1];
else return file;
}
Extra requirements that are met by the regex method:
If filename is like .config or something like this, extension will be an empty string and filename without extension will be .config.
If filename doesn't have any extension, extention will be an empty string, filename without extension will be the filename unchanged.
EDIT:
The extra requirements can also be met by the following:
std::string fileExtension(const std::string& file){
std::string::size_type pos=file.find_last_of('.');
if(pos!=std::string::npos&&pos!=0)return file.substr(pos+1);
else return "";
}
std::string fileNameWithoutExtension(const std::string& file){
std::string::size_type pos=file.find_last_of('.');
if(pos!=std::string::npos&&pos!=0)return file.substr(0,pos);
else return file;
}
Note:
Pass only the filenames (not path) in the above functions.
Try to use strstr
char* lastSlash;
lastSlash = strstr(filename, ".");
Or you can use this:
char *ExtractFileExt(char *FileName)
{
std::string s = FileName;
int Len = s.length();
while(TRUE)
{
if(FileName[Len] != '.')
Len--;
else
{
char *Ext = new char[s.length()-Len+1];
for(int a=0; a<s.length()-Len; a++)
Ext[a] = FileName[s.length()-(s.length()-Len)+a];
Ext[s.length()-Len] = '\0';
return Ext;
}
}
}
This code is cross-platform
So, using std::filesystem is the best answer, but if for whatever reason you don't have C++17 features available, this will work even if the input string includes directories:
string getextn (const string &fn) {
int sep = fn.find_last_of(".\\/");
return (sep >= 0 && fn[sep] == '.') ? fn.substr(sep) : "";
}
I'm adding this because the rest of the answers here are either strangely complicated or fail if the path to the file contains a dot and the file doesn't. I think the fact that find_last_of can look for multiple characters is often overlooked.
It works with both / and \ path separators. It fails if the extension itself contains a slash but that's usually too rare to matter. It doesn't do any filtering for filenames that start with a dot and contain no other dots -- if this matters to you then this is the least unreasonable answer here.
Example input / output:
/ => ''
./ => ''
./pathname/ => ''
./path.name/ => ''
pathname/ => ''
path.name/ => ''
c:\path.name\ => ''
/. => '.'
./. => '.'
./pathname/. => '.'
./path.name/. => '.'
pathname/. => '.'
path.name/. => '.'
c:\path.name\. => '.'
/.git_ignore => '.git_ignore'
./.git_ignore => '.git_ignore'
./pathname/.git_ignore => '.git_ignore'
./path.name/.git_ignore => '.git_ignore'
pathname/.git_ignore => '.git_ignore'
path.name/.git_ignore => '.git_ignore'
c:\path.name\.git_ignore => '.git_ignore'
/filename => ''
./filename => ''
./pathname/filename => ''
./path.name/filename => ''
pathname/filename => ''
path.name/filename => ''
c:\path.name\filename => ''
/filename. => '.'
./filename. => '.'
./pathname/filename. => '.'
./path.name/filename. => '.'
pathname/filename. => '.'
path.name/filename. => '.'
c:\path.name\filename. => '.'
/filename.tar => '.tar'
./filename.tar => '.tar'
./pathname/filename.tar => '.tar'
./path.name/filename.tar => '.tar'
pathname/filename.tar => '.tar'
path.name/filename.tar => '.tar'
c:\path.name\filename.tar => '.tar'
/filename.tar.gz => '.gz'
./filename.tar.gz => '.gz'
./pathname/filename.tar.gz => '.gz'
./path.name/filename.tar.gz => '.gz'
pathname/filename.tar.gz => '.gz'
path.name/filename.tar.gz => '.gz'
c:\path.name\filename.tar.gz => '.gz'
If you happen to use Poco libraries you can do:
#include <Poco/Path.h>
...
std::string fileExt = Poco::Path("/home/user/myFile.abc").getExtension(); // == "abc"
If you consider the extension as the last dot and the possible characters after it, but only if they don't contain the directory separator character, the following function returns the extension starting index, or -1 if no extension found. When you have that you can do what ever you want, like strip the extension, change it, check it etc.
long get_extension_index(string path, char dir_separator = '/') {
// Look from the end for the first '.',
// but give up if finding a dir separator char first
for(long i = path.length() - 1; i >= 0; --i) {
if(path[i] == '.') {
return i;
}
if(path[i] == dir_separator) {
return -1;
}
}
return -1;
}
I used PathFindExtension() function to know whether it is a valid tif file or not.
#include <Shlwapi.h>
bool A2iAWrapperUtility::isValidImageFile(string imageFile)
{
char * pStrExtension = ::PathFindExtension(imageFile.c_str());
if (pStrExtension != NULL && strcmp(pStrExtension, ".tif") == 0)
{
return true;
}
return false;
}