Simple string operations?
Author
I''m working on a learning by doing opengl-c++ engine and I have to know how I can check whether a file is a jpg or a bitmap reading the extensions.
in vb is made by calling right$(filename,len(filename),3).
filename is clear. len gives the length of the string and 3 is the number of characters to get from the right.
who can I get those with c++?
In C:
Returns NULL on failure.
const char *GetFileExtension(const char *filepath) { int found_period = 0; for( ; *filepath != ''\0''; ++filepath) { if(*filepath == ''.'') { found_period = 1; break; } } if(found_period == 0) return NULL; while(*filepath != ''\0'') ++filepath; while(*filepath != ''.'') --filepath; return &filepath[1];} Returns NULL on failure.
Author
ok, the function works but I still have a problem with it.
When I use
MessageBox(NULL, GetFileExtension(strFileName), "CreateTexture", MB_OK);
to print the extension "jpg" appears without the quotation marks.
Thats fine. But when I try to compare GetFileExtension(strFileName) with "jpg" I get wrong results.
if (GetFileExtension(strFileName)=="jpg")
{
MessageBox(NULL, "Works", "Create Tex", MB_OK);
}
else
{
MessageBox(NULL, "Doesn''t Work", "Create Tex", MB_OK);
}
When I use
MessageBox(NULL, GetFileExtension(strFileName), "CreateTexture", MB_OK);
to print the extension "jpg" appears without the quotation marks.
Thats fine. But when I try to compare GetFileExtension(strFileName) with "jpg" I get wrong results.
if (GetFileExtension(strFileName)=="jpg")
{
MessageBox(NULL, "Works", "Create Tex", MB_OK);
}
else
{
MessageBox(NULL, "Doesn''t Work", "Create Tex", MB_OK);
}
You can clearly see you have a VB background 
Use the strncmp() function,.. it compares two strings of characters with a fixed length. It returns zero if the strings are equal...
You can't compare two strings directly in C/C++, you will end up comparing the addresses..
-Crawl
[edited by - Crawl on June 10, 2002 6:39:03 AM]
Use the strncmp() function,.. it compares two strings of characters with a fixed length. It returns zero if the strings are equal...
if ( strncmp( GetFileExtension(strFileName), "jpg", 3 ) == 0 ){ MessageBox(NULL, "Works", "Create Tex", MB_OK);} else{ MessageBox(NULL, "Doesn't Work", "Create Tex", MB_OK);} You can't compare two strings directly in C/C++, you will end up comparing the addresses..
-Crawl
[edited by - Crawl on June 10, 2002 6:39:03 AM]
Author
I worked with VB for 4 years 
I used the strncmp() function some time ago and I searched for it the last hour because I thought its name is cmpstr() ....
thankx a lott!
you can also find the extension like this...
void LoadTexture(char *filename){ char *Ext; Ext = strchr(filename, ''.''); Ext++; strupr(Ext); if((strcmpi(Ext,"BMP" == 0)) LoadBMP(...); ...} quote:Original post by Anonymous Poster... Ext = strchr(filename, '.');...
you need to use strrchr, otherwise you get bad results for eg.
manRunning.1.jpg
also, don't rely on the extension being 3 characters, some people use .jpeg
[edited by - dagarach on June 10, 2002 7:41:20 AM]
Author
Of course, but for the first time this test-engine is just for my purpose and I will hold my own conventions
But of course you''re right!
I think *.jpg is the standard extension for jpegs. I''m not sure but I think there is an API to get the extension... I will check that later on.
But of course you''re right!
I think *.jpg is the standard extension for jpegs. I''m not sure but I think there is an API to get the extension... I will check that later on.
This topic is closed to new replies.
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