MSVC_example_fscanf_s_and_chars_wchars, C++ (vc++)

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//Microsoft (R) C/C++ Optimizing Compiler Version 19.00.23506 for x64

#include <iostream>

#include "stdio.h"
#include "wchar.h"  // provides e.g. swprintf

#if 0
#define bufsize     4u
#else
#define bufsize     16u
#endif

#define string1     "abcdefgh"
#define string2     "ijklmnop"

#define L_string1   L"abcdefgh"
#define L_string2   L"ijklmnop"

static void write_to_file (const char * file_name)
{
    FILE * hFile;

std::cout << "====" << __FUNCTION__ << "====" << std::endl;

errno_t eError = fopen_s (&hFile, file_name, "w");
    if (eError == 0)
    {
        int iCharsWritten = 0;

printf ("writing this data: %u %d %c %C %s %S\n", 123u, -456, 'c', L'd', string1, L_string2);           // write as chars to the screen
        printf ("as chars and as wchars\n");

iCharsWritten = fprintf (hFile, "%u %d %c %C %s %S\n", 123u, -456, 'c', L'd', string1, L_string2);      // write as chars
        std::cout << "Write to file as char. chars written = " << iCharsWritten << std::endl;

iCharsWritten = fwprintf (hFile, L"%u %d %c %C %s %S\n", 123u, -456, L'c', 'd', L_string1, string2);    // write as wchars
        std::cout << "Write to file as wchar. chars written = " << iCharsWritten << std::endl;

fclose (hFile);
    }
    else
    {
        std::cout << "fopen_s for create new file: FAILED!!! error = " << eError << std::endl;
    }
}

static void read_from_file_as_string (const char * file_name)  /* do not use binary mode - else you might see even '\n' chars! */
{
    FILE * hFile;

std::cout << "====" << __FUNCTION__ << "====" << std::endl;

errno_t eError = fopen_s (&hFile, file_name, "r");
    if (eError == 0)
    {
        int iResult = 0;

{
            char ac[bufsize] = "0";
            std::cout << "_countof(ac) = " << _countof(ac) << std::endl; /* bufsize */
            std::cout << "  sizeof(ac) = " <<   sizeof(ac) << std::endl; /* bufsize */

/* char */
            std::cout << "char:\n";

for (size_t n = 0; n < 6; n++)
            {
                strcpy_s (ac, "0");
                iResult = fscanf_s (hFile, "%s", ac, _countof(ac));
                std::cout << "Read from file. fscanf_s result = " << iResult << "; retrived value: " << ac << std::endl;
            }
        }

{
            wchar_t aw[bufsize] = L"0";
            std::cout << "_countof(aw) = " << _countof(aw) << std::endl; /* bufsize */
            std::cout << "  sizeof(aw) = " <<   sizeof(aw) << std::endl; /* 128 */

/* wchar */

std::cout << "wchar:\n";

for (size_t n = 0; n < 6; n++)
            {
                wcscpy_s (aw, L"0");
                iResult = fwscanf_s (hFile, L"%s", aw, _countof(aw));
                std::wcout << L"Read from file. fwscanf_s result = " << iResult << L"; retrived value: " << aw << std::endl;  /* wchars must be printed using wcout */
            }
        }

fclose (hFile);
    }
    else
    {
        std::cout << "fopen_s for read from file: FAILED!!! error = " << eError << std::endl;
    }
}

static void read_from_file_native (const char * file_name)
{
    FILE * hFile;

std::cout << "====" << __FUNCTION__ << "====" << std::endl;

errno_t eError = fopen_s (&hFile, file_name, "r");  /* do not use binary mode - else you might see even '\n' chars! */
    if (eError == 0)
    {
        unsigned int u = 0u;
        signed int s = 0;
        char c = '0';
        wchar_t d = L'0';

char ac[bufsize] = "0";
        wchar_t aw[bufsize] = L"0";
            
        int iResult = 0;
            
        std::cout << "_countof(ac) = " << _countof(ac) << std::endl; /* bufsize */
        std::cout << "  sizeof(ac) = " <<   sizeof(ac) << std::endl; /* bufsize */
        std::cout << "_countof(aw) = " << _countof(aw) << std::endl; /* bufsize */
        std::cout << "  sizeof(aw) = " <<   sizeof(aw) << std::endl; /* 128 */

/* char */
        std::cout << "char:\n";

iResult = fscanf_s (hFile, "%u", &u);
        std::cout << "Read from file. fscanf_s result = " << iResult << "; retrived value: " << u << std::endl;

iResult = fscanf_s (hFile, "%d", &s);
        std::cout << "Read from file. fscanf_s result = " << iResult << "; retrived value: " << s << std::endl;

iResult = fscanf_s (hFile, " %c", &c);  /* please note the leading space in the format string */
        std::cout << "Read from file. fscanf_s result = " << iResult << "; retrived value: " << c << std::endl;

iResult = fscanf_s (hFile, " %C", &d);  /* please note the leading space in the format string */
        std::wcout << L"Read from file. fscanf_s result = " << iResult << L"; retrived value: " << d << std::endl;  /* wchars must be printed using wcout */

iResult = fscanf_s (hFile, "%s", ac, _countof(ac)); /* without the count we will likely see a segementation fault inside the function call */
        std::cout << "Read from file. fscanf_s result = " << iResult << "; retrived value: " << ac << std::endl;

iResult = fscanf_s (hFile, "%S", aw, _countof(aw)); /* without the count we will likely see a segementation fault inside the function call */   /* the value in the file is stored using only char width! */
        std::wcout << L"Read from file. fscanf_s result = " << iResult << L"; retrived value: " << aw << std::endl;  /* wchars must be printed using wcout */

/* wchar */
        u = 0u;
        s = 0;
        c = '0';
        d = L'0';

strcpy_s (ac, "0");
        wcscpy_s (aw, L"0");

std::cout << "wchar:\n";

iResult = fwscanf_s (hFile, L"%u", &u);
        std::cout << "Read from file. fwscanf_s result = " << iResult << "; retrived value: " << u << std::endl;

iResult = fwscanf_s (hFile, L"%d", &s);
        std::cout << "Read from file. fwscanf_s result = " << iResult << "; retrived value: " << s << std::endl;

iResult = fwscanf_s (hFile, L" %C", &c);  /* please note the leading space in the format string */
        std::cout << "Read from file. fwscanf_s result = " << iResult << "; retrived value: " << c << std::endl;

iResult = fwscanf_s (hFile, L" %c", &d);  /* please note the leading space in the format string */
        std::wcout << L"Read from file. fwscanf_s result = " << iResult << L"; retrived value: " << d << std::endl;     /* wchars must be printed using wcout */

iResult = fwscanf_s (hFile, L"%S", ac, _countof(ac)); /* without the count we will likely see a segementation fault inside the function call */ /* the value in the file is stored using the much wider wchars! */
        std::cout << "Read from file. fwscanf_s result = " << iResult << "; retrived value: " << ac << std::endl;

iResult = fwscanf_s (hFile, L"%s", aw, _countof(aw)); /* without the count we will likely see a segementation fault inside the function call */
        std::wcout << L"Read from file. fwscanf_s result = " << iResult << L"; retrived value: " << aw << std::endl;    /* wchars must be printed using wcout */

fclose (hFile);
    }
    else
    {
        std::cout << "fopen_s for read from file: FAILED!!! error = " << eError << std::endl;
    }
}

int main(int argc, char * argv[])
{
    (void)argc;
    (void)argv;

std::cout << "Hello, world!\n";

const char file_name[] = "helper.txt";

write_to_file (file_name);

read_from_file_as_string (file_name);
    read_from_file_native (file_name);

return 0;
}

/* sample outputs:

Hello, world!
====write_to_file====
writing this data: 123 -456 c d abcdefgh ijklmnop
as chars and as wchars
Write to file as char. chars written = 31
Write to file as wchar. chars written = 31
====read_from_file_as_string====
_countof(ac) = 16
  sizeof(ac) = 16
char:
Read from file. fscanf_s result = 1; retrived value: 123
Read from file. fscanf_s result = 1; retrived value: -456
Read from file. fscanf_s result = 1; retrived value: c
Read from file. fscanf_s result = 1; retrived value: d
Read from file. fscanf_s result = 1; retrived value: abcdefgh
Read from file. fscanf_s result = 1; retrived value: ijklmnop
_countof(aw) = 16
  sizeof(aw) = 32
wchar:
Read from file. fwscanf_s result = 1; retrived value: 123
Read from file. fwscanf_s result = 1; retrived value: -456
Read from file. fwscanf_s result = 1; retrived value: c
Read from file. fwscanf_s result = 1; retrived value: d
Read from file. fwscanf_s result = 1; retrived value: abcdefgh
Read from file. fwscanf_s result = 1; retrived value: ijklmnop
====read_from_file_native====
_countof(ac) = 16
  sizeof(ac) = 16
_countof(aw) = 16
  sizeof(aw) = 32
char:
Read from file. fscanf_s result = 1; retrived value: 123
Read from file. fscanf_s result = 1; retrived value: -456
Read from file. fscanf_s result = 1; retrived value: c
Read from file. fscanf_s result = 1; retrived value: d
Read from file. fscanf_s result = 1; retrived value: abcdefgh
Read from file. fscanf_s result = 1; retrived value: ijklmnop
wchar:
Read from file. fwscanf_s result = 1; retrived value: 123
Read from file. fwscanf_s result = 1; retrived value: -456
Read from file. fwscanf_s result = 1; retrived value: c
Read from file. fwscanf_s result = 1; retrived value: d
Read from file. fwscanf_s result = 1; retrived value: abcdefgh
Read from file. fwscanf_s result = 1; retrived value: ijklmnop

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Compilation time: 1,94 sec, absolute running time: 0,25 sec, absolute service time: 2,21 sec