C++ fwrite() writes more than expected

Question

I have problem when copying files code: ``` bool done; FILE* fin; FILE* fout; const int bs = 1024*64;//64 kb char* buffer[bs]; int er, ew, br, bw; long long int size = 0; long long int sizew = 0; er = fopen_s(&fin,s.c_str(),"rb"); ew = fopen_s(&fout,s2.c_str(),"wb"); if(er == 0 && ew == 0){ while(br = fread(buffer,1,bs,fin)){ size += br; sizew += fwrite(buffer,1,bs,fout); } done = true; }else{ done = false; } if(fin != NULL)fclose(fin); if(fout != NULL)fclose(fout); ``` Somehow fwrite writes whole buffer ignoring count value (br) Some examples how: ``` Copying 595 file of 635 DONE. 524288/524288 B Copying 596 file of 635 DONE. 524288/524288 B Copying 597 file of 635 DONE. 65536/145 B Copying 598 file of 635 DONE. 65536/16384 B Copying 599 file of 635 DONE. 65536/145 B Copying 600 file of 635 DONE. 65536/67 B Copying 601 file of 635 DONE. 65536/32768 B Copying 602 file of 635 DONE. 65536/67 B ``` Anyone knows where is the problem?

Accepted Answer

You should do

```
        sizew += fwrite(buffer,1,br,fout);
```

You were passing `bs`, which was the maximum amount that `fread` was allowed to read. `br` was the amount that `fread` actually did read.

C++ fwrite() writes more than expected

Solution

Problem