Task: File extension is in extensions list

C: 

#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <locale.h>
#include <string.h>

#ifdef _Bool
#include <stdbool.h>
#else
#define bool int
#define true  1
#define false 0
#endif


int checkFileExtension(char* fileName, char* fileExtensions)
{
    char* fileExtension = fileExtensions;

    if ( *fileName )
    {
        while ( *fileExtension )
        {
            int fileNameLength = strlen(fileName);
            int extensionLength = strlen(fileExtension);
            if ( fileNameLength >= extensionLength )
            {
                char* a = fileName + fileNameLength - extensionLength;
                char* b = fileExtension;
                while ( *a && toupper(*a++) == toupper(*b++) )
                    ;
                if ( !*a )
                    return true;
            }
            fileExtension += extensionLength + 1;
        }
    }
    return false;
}

void printExtensions(char* extensions)
{
    while( *extensions )
    {
        printf("%s\n", extensions);
        extensions += strlen(extensions) + 1;
    }
}

bool test(char* fileName, char* extension, bool expectedResult)
{
    bool result = checkFileExtension(fileName,extension);
    bool returnValue = result == expectedResult;
    printf("%20s  result: %-5s  expected: %-5s  test %s\n", 
        fileName,
        result         ? "true"   : "false",
        expectedResult ? "true"   : "false", 
        returnValue    ? "passed" : "failed" );
    return returnValue;
}

int main(void)
{
    static char extensions[] = ".zip\0.rar\0.7z\0.gz\0.archive\0.A##\0.tar.bz2\0";

    setlocale(LC_ALL,"");

    printExtensions(extensions);
    printf("\n");

    if ( test("MyData.a##",         extensions,true )
    &&   test("MyData.tar.Gz",      extensions,true )
    &&   test("MyData.gzip",        extensions,false)
    &&   test("MyData.7z.backup",   extensions,false)
    &&   test("MyData...",          extensions,false)
    &&   test("MyData",             extensions,false)
    &&   test("MyData_v1.0.tar.bz2",extensions,true )
    &&   test("MyData_v1.0.bz2",    extensions,false) 
    &&   test("filename",           extensions,false)
    )
        printf("\n%s\n", "All tests passed.");
    else
        printf("\n%s\n", "Last test failed.");

    printf("\n%s\n", "press enter");
    getchar();
    return 0;
}




Go: package main

import (
    "fmt"
    "strings"
)

var extensions = []string{"zip", "rar", "7z", "gz", "archive", "A##", "tar.bz2"}

func fileExtInList(filename string) (bool, string) {
    filename2 := strings.ToLower(filename)
    for _, ext := range extensions {
        ext2 := "." + strings.ToLower(ext)
        if strings.HasSuffix(filename2, ext2) {
            return true, ext
        }
    }
    s := strings.Split(filename, ".")
    if len(s) > 1 {
        t := s[len(s)-1]
        if t != "" {
            return false, t
        } else {
            return false, "<empty>"
        }
    } else {
        return false, "<none>"
    }
}

func main() {
    fmt.Println("The listed extensions are:")
    fmt.Println(extensions, "\n")
    tests := []string{
        "MyData.a##", "MyData.tar.Gz", "MyData.gzip",
        "MyData.7z.backup", "MyData...", "MyData",
        "MyData_v1.0.tar.bz2", "MyData_v1.0.bz2",
    }
    for _, test := range tests {
        ok, ext := fileExtInList(test)
        fmt.Printf("%-20s => %-5t  (extension = %s)\n", test, ok, ext)
    }
}