CODEWITHSUNDEEP
carraysstringstruct
krausl
krausl

Reputation: 3

Saving text out of a struct in a char array

I have a struct with letters inside and I want to give the letters to an array so i can use it afterwards. It works if i would just print the letters.

Top (struct):

 #include "stdafx.h"

typedef struct { char* code; char* letter;}morse_tabelle; 

morse_tabelle tabelle[] = {
    { ".-", "A" },
    { "-...", "B" },
    { " -.-. ", "C" },
    { "-..", "D" },
    { ".", "E" },
    { "..-.", "F" },
    { "--.", "G" },
    { "....", "H" },
    { "..", "I" },
    { ".---", "J" },
    { "-.-", "K" },
    { ".-..", "L" },
    { "--", "M" },
    { "-.", "N" },
    { "---", "O" },
    { ".--.", "P" },
    { "--.-", "Q" },
    { ".-.", "R" },
    { "...", "S" },
    { "-", "T" },
    { "..-", "U" },
    { "...-", "V" },
    { ".--", "W" },
    { "-..-", "X" },
    { "-.--", "Y" },
    { "--..", "Z" },
    { "-----", "0" },
    { ".----", "1" },
    { "..---", "2" },
    { "...--", "3" },
    { "....-", "4" },
    { ".....", "5" },
    { "-....", "6" },
    { "--...", "7" },
    { "---..", "8" },
    {"----.", "9" },
    { "/", " " },
    };

For the arraysize: 

#define ARR_SIZE(x) (sizeof(x)/sizeof((x)[0]))

Function: 

    void morse_to_text(void)
    {


    char input[100];
    char* morse_letter;

    int j = 0;
    char* translation[50];


    printf_s("\n\nput in Morsecode:\n\n");
    fgets(input, 100, stdin);                                             
    input[strlen(input)-1] = '\0';                                       

    morse_letter = strtok(input, " ");                               

    while (morse_letter)                                                      
    {
        for (int i = 0; i < ARR_SIZE(tabelle); i++)                            
        {

            if (!strcmp(morse_letter, tabelle[i].code))                  
            {
                translation[j] = tabelle[i].letter;                    
                j++;
                /*printf_s("%s", tabelle[i].letter);*/   //This works              
            }
        }
        morse_letter = strtok(NULL, " ");                            
    }

    /*output*/
    printf_s("\n\n---------------\n\n");
    for (int i = 0; i <= strlen(translation[50]); i++){
            printf("%s", translation[i]);
    }

};

It sort of works if i change the char* letter to char letter inside of the struct. but then i get a buffer overrun. The question again: how can i store strings inside an array.

Upvotes: 0

Views: 86

Answers (3)

AlastairG
AlastairG

Reputation: 4314

Instead of:

translation[j] = tabelle[i].letter;

do:

translation[j] = tabelle[i].letter[0];

Or instead, and even better, do:

typedef struct { char* code; char letter;} morse_tabelle; 

morse_tabelle tabelle[] = {
    { ".-", 'A' },
    { "-...", 'B' },
    { " -.-. ", 'C' },
    { "-..", 'D' },
    etc. etc.

char translation[50];
...
printf("%s\n", translation);

Or, if you want to print out the translation letter by letter:

for (int i = 0; i < strlen(translation); i++)
{
    printf("%c\n", translation[i]);
}

To add some basic C tuition:

char * is a pointer to an array of char types. "A" is a char array with two elements and can be written as { 'A', '\0' }. Hence assigning "A" to a char type is wrong.

If you define letter as a char * and populate the data with a one character string, then you can access the character by indexing the 0th element as letter[0]. However, rather than using character arrays all over the space and wasting memory and over-complicating your code, it is better just to use characters instead.

Upvotes: 1

Aconcagua
Aconcagua

Reputation: 25518

What you actually want is this:

char translation[50]; // no string array, char array!

Then have the letter as char as you intended:

typedef struct { char* code; char letter;} morse_tabelle;

With that, you now can simply do

translation[j] = tabelle[i].letter;

again, just as before. Only the data type changed...

However, you need to null-terminate your translated string, else you cannot use it with printf("%s", translation)

while(...) { ... }
translation[j] = 0;

// output:
// no for loop any more!

printf("%s", translation);

An alternative to terminating the null character would be giving the length to the printf format parameter:

while(...) { ... }
// no termination any more...

// output:
// no for loop any more!

printf("%.*s", j, translation);

See printf for details (OK, link actually is C++, but documentation is exactly true for C, too...).

Upvotes: 3

Jabberwocky
Jabberwocky

Reputation: 50778

Here:

for (int i = 0; i <= strlen(translation[50]); i++) {

strlen(translation[50] is wrong. translation is an array of 50 pointers to char*. So strlen(translation[50]) is the length of the 50th translated character (which BTW only exists if you have typed in 50 morse codes) and not the number of elements you've put into the translation array. You've put j char* pointers into the translation array, therefore the correct code is:

for (int i = 0; i < j); i++) {

Upvotes: 0

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