//* how C-level operations are implemented *
// selected functions from <cstring> library

void strcpy(char dest[], const char src[]) {
    // note: the actual function is not void
    int i;
    for(i=0; src[i]!='\0'; i++)
        dest[i]=src[i];
    dest[i]=src[i]; // copy '\0' at the end
}

void strcat(char dest[], const char src[]) {
    // note: the actual function is not void
    int i, j;
    for(i=0; dest[i]!='\0'; i++)
        ;
    for(j=0; src[j]!='\0'; i++, j++)
        dest[i]=src[j];
    dest[i]=src[j]; // copy '\0' at the end
}

void strcatchr(char dest[], char chr) {
    int i;
    for(i=0; dest[i]!='\0'; i++)
        ;
    // now we are at the end of the original string
    dest[i]=chr;
    i++;
    // remember about terminating the string!
    dest[i]='\0';
}

int strlen(const char s[]) {
    int len;
    for(len=0; s[len]!='\0'; len++)
        ;
    return(len);
}

void strtrunc(char s[], int len) {
    // first LEN characters are from 0 to (len-1)
    // and the string needs to be terminated with '\0'
    s[len]='\0';
}

int strcmp(const char s1[], const char s2[]) {
    // s1<s2  -> -1
    // s1>s2  -> +1
    // s1==s2 ->  0
    int i;
    for(i=0; s1[i]!='\0' && s2[i]!='\0'; i++)
        if (s1[i]!=s2[i]) break; // stop comparison if different
    int r=s2[i]-s1[i];
    if (r>0) return(-1);       //s1[i]<s2[i], or s1 ended while s2 not
    else if (r<0) return(+1);  //s1[i]>s2[i], or s2 ended while s1 not
    else /* r==0 */ return(0); //s1[i]==s2[i]=='\0' => both are the same 
}

// Other important functions to remember:
// Searching functions
// strstr   ( string,   searchforstr)
// strchr   ( string,   searchforchr)