I've been working on creating my own GUI library for MS-DOS on my free time and I got stuck on how I can implement an array that would contain structures of GUI elements.
So far I was able to make it draw the window itself, but I needed a way to draw the elements inside the window such as text boxes, text labels, buttons, ect.
Here's my current code:
#include <stdio.h>
#include <conio.h>
#include <malloc.h>
#include <string.h>
#include "graph.h" //Watcom graphics library
#define false 0
#define true 1
#define border_none 0
#define border_out 1
#define border_in 2
struct text_button {
char text[128];
int pos_x;
int pos_y;
int size_x;
int size_y;
int text_color;
int button_color;
};
struct window_structure {
char title[128];
int pos_x;
int pos_y;
int pre_pos_x;
int pre_pos_y;
int size_x;
int size_y;
int min_size_x;
int min_size_y;
int max_size_x;
int max_size_y;
int show_tab;
int border_type;
int focused;
//Right here is where I would add the array containing the elements.
};
void draw_border(int type,int pos_x,int pos_y,int size_x,int size_y) {
int c_1,c_2;
if (type==1) {
c_1=15;
c_2=0;
} else if (type==2) {
c_1=0;
c_2=15;
}
if (type!=0) {
_setcolor(c_1);
_moveto(pos_x,pos_y);
_lineto(pos_x+size_x,pos_y);
_moveto(pos_x,pos_y);
_lineto(pos_x,pos_y+size_y);
_setcolor(c_2);
_moveto(pos_x+size_x,pos_y+size_y);
_lineto(pos_x+size_x,pos_y);
_moveto(pos_x+size_x,pos_y+size_y);
_lineto(pos_x,pos_y+size_y);
}
}
void draw_box(int type,int color,int pos_x,int pos_y,int size_x,int size_y) {
_setcolor(color);
_rectangle(_GFILLINTERIOR,pos_x,pos_y,pos_x+size_x,pos_y+size_y);
draw_border(type,pos_x-1,pos_y-1,size_x+2,size_y+2);
}
struct window_structure create_window(
char title[],
int pos_x,
int pos_y,
int size_x,
int size_y,
int min_size_x,
int min_size_y,
int max_size_x,
int max_size_y,
int show_tab,
int border_type
) {
struct window_structure window;
strcpy(window.title,title);
window.pos_x=pos_x;
window.pos_y=pos_y;
window.pre_pos_x=pos_x;
window.pre_pos_y=pos_y;
window.size_x=size_x;
window.size_y=size_y;
window.min_size_x=min_size_x;
window.min_size_y=min_size_y;
window.max_size_x=max_size_x;
window.max_size_y=max_size_y;
window.show_tab=show_tab;
window.border_type=border_type;
window.focused=true;
return window;
}
void draw_window(struct window_structure window) {
int offset_x,offset_y;
if (window.size_x<window.min_size_x) {
window.size_x=window.min_size_x;
} else if (window.size_x>window.max_size_x) {
window.size_x=window.max_size_x;
}
if (window.size_y<window.min_size_y) {
window.size_y=window.min_size_y;
} else if (window.size_y>window.max_size_y) {
window.size_y=window.max_size_y;
}
if (window.show_tab==true) {
int tab_color;
if (window.focused==true) {
tab_color=9;
} else {
tab_color=8;
}
draw_box(
window.border_type,
tab_color,
window.pos_x,
window.pos_y-1,
window.size_x-1,
18
);
offset_x=0;
offset_y=20;
}
draw_box(
window.border_type,
7,
window.pos_x+offset_x,
window.pos_y+offset_y,
window.size_x-1,
window.size_y-1
);
//Once the window has been drawn, the next part it would do here is draw the elements
window.pre_pos_x=window.pos_x;
window.pre_pos_y=window.pos_y;
}
I know MS-DOS is quite outdated, this is just for my hobby. I'm currently using Open Watcom as my compiler.
//Right here is where I would add the array containing the elements.
You know, since you'll have a variable number of elements, you can't declare a fixed-size array here, so you can just declare a pointer and allocate the array as needed. You'll also need to store the number of elements allocated.
struct window_structure
{
…
int nelem; // how many elements are there
struct element *elements; // pointer to allocated elements
};
Both shall be initialized to 0.
struct window_structure create_window(…)
{
…
window.nelem = 0;
window.elements = NULL;
return window;
}
The struct element type could be defined as
struct element
{ enum elemtype { text_button, /* add other types here */ } elemtype;
union
{ struct text_button tb;
/* add other types here */
} u;
};
An element, e. g. a text_button, could then be added to the window with
struct element *new;
new = realloc(window.elements, (window.nelem+1) * sizeof *new);
if (!new) exit(1); // or some better error handling
window.elements = new;
window.elements[window.nelem].elemtype = text_button;
window.elements[window.nelem].u.tb = your_text_button_to_add;
++window.nelem;
//Once the window has been drawn, the next part it would do here is draw the elements
This would then be done like
int i;
for (i = 0; i < window.nelem; ++i)
switch (window.elements[i].elemtype)
{
case text_button:
/* draw the text_button window.elements[i].u.tb here */
break;
/* add cases for other element types here */
}
Related
so I've got a buggy C file in which i need to find an exploit. I have found a bug when accessing the following struct:
#define BOARD_SIZE 10
typedef int (*turn_function_t)(struct board *);
typedef void (*win_function_t)(struct board *);
struct board {
uint8_t f1[BOARD_SIZE][BOARD_SIZE];
uint8_t f2[BOARD_SIZE][BOARD_SIZE];
win_function_t win;
turn_function_t turn;
int avail;
};
int do_shot(struct board *board, int strength, int x, int y) {
if(!(x >= 0 && x <= BOARD_SIZE && y >= 0 && y <= BOARD_SIZE)) {
return SHOT_ERR_EINVAL;
}
/* If there was already a sunken ship, return error */
if(board->f1[x][y] && !board->f2[x][y])
return SHOT_ERR_SUNKEN;
/* Now perform shot */
if(!board->f2[x][y])
return SHOT_WATER;
board->f2[x][y] -= strength;
if(!board->f2[x][y])
return SHOT_SUNKEN;
return SHOT_HIT;
}
The bug I found is a wrong index check when accessing array f2. I can chose the index as input (index can be anything from 0 to 10 inclusive). I need to find a way to call the function win (doesn't matter which parameter). My question now is is there any way I can use that out of bounds access to call the function win since the function pointer is stored directly after the array f2 inside the struct?
of cause it can be done easily.
I show you an example code below.
I use pragma pack(1) for byte align and use print to find the address of the function, and finally I got it.
the code may can not be run on your computer.
but your can find the address by print to make bounds address equal to function address.
it may be f[0][-1] on your computer
#include <stdio.h>
typedef int (*turn_function_t)(struct board *);
#pragma pack(1)
struct board
{
turn_function_t win;
int f[10][10];
};
#pragma pack(0)
int win(struct board *b)
{
printf("Win!\n");
return 0;
}
int main()
{
struct board b;
b.win = win;
// printf("%p\n", &b.f[0][-2]);
// printf("%p\n", &b.win);
(*(turn_function_t *)(&b.f[0][-2]))(&b);
return 0;
}
I'm trying to optimize access to some jump tables I have made, they are as follows:
int (*const usart_ctrl_table[USART_READ_WRITE_CLEAR])() =
{zg_usartCtrlRead, zg_usartCtrlWrite, zg_usartCtrlClr};
int (*const usart_frame_table[USART_READ_WRITE_CLEAR])() =
{zg_usartFrameRead, zg_usartFrameWrite, zg_usartFrameClr};
int (*const usart_trig_ctrl_table[USART_READ_WRITE_CLEAR])() =
{zg_usartTrigctrlRead, zg_usartTrigctrlWrite, zg_usartTrigctrlClr};
As you can see, the functions are for accessing a usart peripheral on a hardware level and are arranged in the table in the order of read/write/clear.
What I am attempting to do is have another jump table of jump tables, this way I can either run through initializing all the usart's registers in startup or simply change a single register later if desired.
i.e.
<datatype> (*usart_peripheral_table[<number of jump tables>])() =
{usart_ctrl_table, usart_frame_table, usart_trig_ctrl_table};
This way I can expose that table to my middleware layer, which will help maintain a standard across changing HALs, and also I can use a define to index this table i.e.
fn_ptr = usart_peripheral_table[CTRL_TABLE]
fn_ptr[WRITE](bitmask);
fn_ptr[READ](buffer);
As you may have already guessed, I am struggling to figure out how to construct this table. I figured it is one of two things:
Another simple array of pointers, as even a jump table itself is just an array of pointers. Hence my initialization would be:
const int* (*usart_peripheral_table[<number of jump tables])() =
{usart_ctrl_table, usart_frame_table, usart_trig_ctrl_table};
However this doesn't seem to be working. Then I thought:
An array of pointers to pointers. So I tried all kinds of combos:
const int**(*usart_perip...
const int**(usart_perip...
const int** (*usart_peripheral_table[<number of jump tables])() =
{&usart_ctrl_table, &usart_frame_table[0], usart_trig_ctrl_table};
Nothing seems to work. Do I need to store the address of the lower jump tables in yet another pointer before assigning that variable to a pointer-to-pointer array? i.e.
int* fn_ptr = usart_ctrl_table;
<dataytype>(*const usart_periph[<number>])() = {fn_ptr};
Thanks in advance, any help would be greatly appreciated.
MM25
EDIT:
const int** (*const peripheral_table[1])() =
{&usart_ctrl_table[0]};
const int** (*const peripheral_table[1])() =
{usart_ctrl_table};
The above both give the error "initialization from incomaptible pointer type", as do all other combinations I have tried
You might find that defining a typedef for your function pointers makes your code easier to read and maintain (although I’ve seen people recommend against it too):
#include <stdio.h>
#include <stdlib.h>
#define UART_RWC 3U
typedef int (*uart_ctl_func)(void);
int uart_read(void)
{
printf("Read.\n");
fflush(stdout);
return 0;
}
int uart_write(void)
{
printf("Write.\n");
fflush(stdout);
return(0);
}
int uart_clear(void)
{
printf("Clear.\n");
fflush(stdout);
return 0;
}
uart_ctl_func uart_ctl_jump_table[][UART_RWC] = {
{ uart_read, uart_write, uart_clear },
{ uart_read, uart_write, uart_clear }
};
int main(void)
{
uart_ctl_jump_table[0][1](); // Write.
uart_ctl_jump_table[1][0](); // Read.
uart_ctl_jump_table[1][2](); // Clear.
return EXIT_SUCCESS;
}
The next step might be to make the jump table a struct so you end up writing Uart_ctl_table.frame.read(), or to at least define an enum for the constants.
#include <stdio.h>
#include <stdlib.h>
#define UART_RWC 3U
typedef int (*uart_ctl_func)(void);
int uart_read(void)
{
printf("Read.\n");
fflush(stdout);
return 0;
}
int uart_write(void)
{
printf("Write.\n");
fflush(stdout);
return(0);
}
int uart_clear(void)
{
printf("Clear.\n");
fflush(stdout);
return 0;
}
typedef struct {
uart_ctl_func read;
uart_ctl_func write;
uart_ctl_func clear;
} uart_ctl_set_t;
typedef struct {
uart_ctl_set_t ctrl;
uart_ctl_set_t frame;
uart_ctl_set_t trig;
} uart_ctl_table_t;
const uart_ctl_table_t uart_ctl_table = {
.ctrl = { uart_read, uart_write, uart_clear },
.frame = { uart_read, uart_write, uart_clear },
.trig = { uart_read, uart_write, uart_clear }
};
int main(void)
{
uart_ctl_table.ctrl.write(); // Write.
uart_ctl_table.frame.read(); // Read.
uart_ctl_table.trig.clear(); // Clear.
return EXIT_SUCCESS;
}
Just add a * like you added [] when defining an array.
int zg_usartCtrlRead();
int zg_usartCtrlWrite();
int zg_usartCtrlClr();
int zg_usartFrameRead();
int zg_usartFrameWrite();
int zg_usartFrameClr();
int zg_usartTrigctrlRead();
int zg_usartTrigctrlWrite();
int zg_usartTrigctrlClr();
int (*const usart_ctrl_table[])() =
{zg_usartCtrlRead, zg_usartCtrlWrite, zg_usartCtrlClr};
int (*const usart_frame_table[])() =
{zg_usartFrameRead, zg_usartFrameWrite, zg_usartFrameClr};
int (*const usart_trig_ctrl_table[])() =
{zg_usartTrigctrlRead, zg_usartTrigctrlWrite, zg_usartTrigctrlClr};
int (* const * const usart_peripheral_table[])() =
{usart_ctrl_table, usart_frame_table, usart_trig_ctrl_table};
Usage:
usart_peripheral_table[1][2](5, 1, 3, 5, 6);
Btw, an empty parameter list on function declaration () means unspecified number and type of arguments. Do (void) if you want no arguments passed to your function.
This:
const int* (*usart_peripheral_table[<number of jump tables])();
Is an array of functions pointers that take unspecified number of arguments and return a pointer to constant integer.
This:
const int** (*usart_peripheral_table[<number of jump tables])()
Is an array of function pointers that take unspecified number of arguments and return a pointer to a pointer to a constant integer.
You can also go with a 2D array:
int (* const usart_peripheral_table_2d[][3])() = {
{
zg_usartCtrlRead, zg_usartCtrlWrite, zg_usartCtrlClr,
}, {
zg_usartFrameRead, zg_usartFrameWrite, zg_usartFrameClr,
}, {
zg_usartTrigctrlRead, zg_usartTrigctrlWrite, zg_usartTrigctrlClr,
},
};
But maybe you want to write accessor functions that will return a pointer to an array of functions. Nothing simpler!
#include <stddef.h>
int (*usart_ctrl_table_get(size_t idx))() {
return usart_ctrl_table[idx];
}
int (*usart_frame_table_get(size_t idx))() {
return usart_frame_table[idx];
}
int (*usart_trig_ctrl_table_get(size_t idx))() {
return usart_trig_ctrl_table[idx];
}
int (* const (* const usart_peripheral_table_indirect[])(size_t))() = {
usart_ctrl_table_get,
usart_frame_table_get,
usart_trig_ctrl_table_get,
};
Usage sample:
int main() {
usart_peripheral_table_indirect[2](1)();
}
int main()
{
enum Days{Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday};
Days TheDay;
int j = 0;
printf("Please enter the day of the week (0 to 6)\n");
scanf("%d",&j);
TheDay = Days(j);
//how to PRINT THE VALUES stored in TheDay
printf("%s",TheDay); // isnt working
return 0;
}
Enumerations in C are numbers that have convenient names inside your code. They are not strings, and the names assigned to them in the source code are not compiled into your program, and so they are not accessible at runtime.
The only way to get what you want is to write a function yourself that translates the enumeration value into a string. E.g. (assuming here that you move the declaration of enum Days outside of main):
const char* getDayName(enum Days day)
{
switch (day)
{
case Sunday: return "Sunday";
case Monday: return "Monday";
/* etc... */
}
}
/* Then, later in main: */
printf("%s", getDayName(TheDay));
Alternatively, you could use an array as a map, e.g.
const char* dayNames[] = {"Sunday", "Monday", "Tuesday", /* ... etc ... */ };
/* ... */
printf("%s", dayNames[TheDay]);
But here you would probably want to assign Sunday = 0 in the enumeration to be safe... I'm not sure if the C standard requires compilers to begin enumerations from 0, although most do (I'm sure someone will comment to confirm or deny this).
I use something like this:
in a file "EnumToString.h":
#undef DECL_ENUM_ELEMENT
#undef DECL_ENUM_ELEMENT_VAL
#undef DECL_ENUM_ELEMENT_STR
#undef DECL_ENUM_ELEMENT_VAL_STR
#undef BEGIN_ENUM
#undef END_ENUM
#ifndef GENERATE_ENUM_STRINGS
#define DECL_ENUM_ELEMENT( element ) element,
#define DECL_ENUM_ELEMENT_VAL( element, value ) element = value,
#define DECL_ENUM_ELEMENT_STR( element, descr ) DECL_ENUM_ELEMENT( element )
#define DECL_ENUM_ELEMENT_VAL_STR( element, value, descr ) DECL_ENUM_ELEMENT_VAL( element, value )
#define BEGIN_ENUM( ENUM_NAME ) typedef enum tag##ENUM_NAME
#define END_ENUM( ENUM_NAME ) ENUM_NAME; \
const char* GetString##ENUM_NAME(enum tag##ENUM_NAME index);
#else
#define BEGIN_ENUM( ENUM_NAME) const char * GetString##ENUM_NAME( enum tag##ENUM_NAME index ) {\
switch( index ) {
#define DECL_ENUM_ELEMENT( element ) case element: return #element; break;
#define DECL_ENUM_ELEMENT_VAL( element, value ) DECL_ENUM_ELEMENT( element )
#define DECL_ENUM_ELEMENT_STR( element, descr ) case element: return descr; break;
#define DECL_ENUM_ELEMENT_VAL_STR( element, value, descr ) DECL_ENUM_ELEMENT_STR( element, descr )
#define END_ENUM( ENUM_NAME ) default: return "Unknown value"; } } ;
#endif
then in any header file you make the enum declaration, day enum.h
#include "EnumToString.h"
BEGIN_ENUM(Days)
{
DECL_ENUM_ELEMENT(Sunday) //will render "Sunday"
DECL_ENUM_ELEMENT(Monday) //will render "Monday"
DECL_ENUM_ELEMENT_STR(Tuesday, "Tuesday string") //will render "Tuesday string"
DECL_ENUM_ELEMENT(Wednesday) //will render "Wednesday"
DECL_ENUM_ELEMENT_VAL_STR(Thursday, 500, "Thursday string") // will render "Thursday string" and the enum will have 500 as value
/* ... and so on */
}
END_ENUM(MyEnum)
then in a file called EnumToString.c:
#include "enum.h"
#define GENERATE_ENUM_STRINGS // Start string generation
#include "enum.h"
#undef GENERATE_ENUM_STRINGS // Stop string generation
then in main.c:
int main(int argc, char* argv[])
{
Days TheDay = Monday;
printf( "%d - %s\n", TheDay, GetStringDay(TheDay) ); //will print "1 - Monday"
TheDay = Thursday;
printf( "%d - %s\n", TheDay, GetStringDay(TheDay) ); //will print "500 - Thursday string"
return 0;
}
this will generate "automatically" the strings for any enums declared this way and included in "EnumToString.c"
The way I usually do this is by storing the string representations in a separate array in the same order, then indexing the array with the enum value:
const char *DayNames[] = { "Sunday", "Monday", "Tuesday", /* etc */ };
printf("%s", DayNames[Sunday]); // prints "Sunday"
enums in C don't really work the way you're expecting them to. You can think of them kind of like glorified constants (with a few additional benefits relating to being a collection of such constants), and the text you've written in for "Sunday" really gets resolved to a number during compilation, the text is ultimately discarded.
In short: to do what you really want you'll need to keep an array of the strings or create a function to map from the enum's value to the text you'd like to print.
Enumerations in C are basically syntactical sugar for named lists of automatically-sequenced integer values. That is, when you have this code:
int main()
{
enum Days{Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday};
Days TheDay = Monday;
}
Your compiler actually spits out this:
int main()
{
int TheDay = 1; // Monday is the second enumeration, hence 1. Sunday would be 0.
}
Therefore, outputting a C enumeration as a string is not an operation that makes sense to the compiler. If you want to have human-readable strings for these, you will need to define functions to convert from enumerations to strings.
Here's a cleaner way to do it with macros:
#include <stdio.h>
#include <stdlib.h>
#define DOW(X, S) \
X(Sunday) S X(Monday) S X(Tuesday) S X(Wednesday) S X(Thursday) S X(Friday) S X(Saturday)
#define COMMA ,
/* declare the enum */
#define DOW_ENUM(DOW) DOW
enum dow {
DOW(DOW_ENUM, COMMA)
};
/* create an array of strings with the enum names... */
#define DOW_ARR(DOW ) [DOW] = #DOW
const char * const dow_str[] = {
DOW(DOW_ARR, COMMA)
};
/* ...or create a switchy function. */
static const char * dowstr(int i)
{
#define DOW_CASE(D) case D: return #D
switch(i) {
DOW(DOW_CASE, ;);
default: return NULL;
}
}
int main(void)
{
for(int i = 0; i < 7; i++)
printf("[%d] = «%s»\n", i, dow_str[i]);
printf("\n");
for(int i = 0; i < 7; i++)
printf("[%d] = «%s»\n", i, dowstr(i));
return 0;
}
I'm not sure that this is totally portable b/w preprocessors, but it works with gcc.
This is c99 btw, so use c99 strict if you plug it into (the online compiler) ideone.
I know I am late to the party, but how about this?
const char* dayNames[] = { [Sunday] = "Sunday", [Monday] = "Monday", /*and so on*/ };
printf("%s", dayNames[Sunday]); // prints "Sunday"
This way, you do not have to manually keep the enum and the char* array in sync. If you are like me, chances are that you will later change the enum, and the char* array will print invalid strings.
This may not be a feature universally supported. But afaik, most of the mordern day C compilers support this designated initialier style.
You can read more about designated initializers here.
I like this to have enum in the dayNames.
To reduce typing, we can do the following:
#define EP(x) [x] = #x /* ENUM PRINT */
const char* dayNames[] = { EP(Sunday), EP(Monday)};
The question is you want write the name just one times.
I have an ider like this:
#define __ENUM(situation,num) \
int situation = num; const char * __##situation##_name = #situation;
const struct {
__ENUM(get_other_string, -203);//using a __ENUM Mirco make it ease to write,
__ENUM(get_negative_to_unsigned, -204);
__ENUM(overflow,-205);
//The following two line showing the expanding for __ENUM
int get_no_num = -201; const char * __get_no_num_name = "get_no_num";
int get_float_to_int = -202; const char * get_float_to_int_name = "float_to_int_name";
}eRevJson;
#undef __ENUM
struct sIntCharPtr { int value; const char * p_name; };
//This function transform it to string.
inline const char * enumRevJsonGetString(int num) {
sIntCharPtr * ptr = (sIntCharPtr *)(&eRevJson);
for (int i = 0;i < sizeof(eRevJson) / sizeof(sIntCharPtr);i++) {
if (ptr[i].value == num) {
return ptr[i].p_name;
}
}
return "bad_enum_value";
}
it uses a struct to insert enum, so that a printer to string could follows each enum value define.
int main(int argc, char *argv[]) {
int enum_test = eRevJson.get_other_string;
printf("error is %s, number is %d\n", enumRevJsonGetString(enum_test), enum_test);
>error is get_other_string, number is -203
The difference to enum is builder can not report error if the numbers are repeated.
if you don't like write number, __LINE__ could replace it:
#define ____LINE__ __LINE__
#define __ENUM(situation) \
int situation = (____LINE__ - __BASELINE -2); const char * __##situation##_name = #situation;
constexpr int __BASELINE = __LINE__;
constexpr struct {
__ENUM(Sunday);
__ENUM(Monday);
__ENUM(Tuesday);
__ENUM(Wednesday);
__ENUM(Thursday);
__ENUM(Friday);
__ENUM(Saturday);
}eDays;
#undef __ENUM
inline const char * enumDaysGetString(int num) {
sIntCharPtr * ptr = (sIntCharPtr *)(&eDays);
for (int i = 0;i < sizeof(eDays) / sizeof(sIntCharPtr);i++) {
if (ptr[i].value == num) {
return ptr[i].p_name;
}
}
return "bad_enum_value";
}
int main(int argc, char *argv[]) {
int d = eDays.Wednesday;
printf("day %s, number is %d\n", enumDaysGetString(d), d);
d = 1;
printf("day %s, number is %d\n", enumDaysGetString(d), d);
}
>day Wednesday, number is 3 >day Monday, number is 1
There is another solution: Create your own dynamic enumeration class. Means you have a struct and some function to create a new enumeration, which stores the elements in a struct and each element has a string for the name. You also need some type to store a individual elements, functions to compare them and so on.
Here is an example:
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct Enumeration_element_T
{
size_t index;
struct Enumeration_T *parent;
char *name;
};
struct Enumeration_T
{
size_t len;
struct Enumeration_element_T elements[];
};
void enumeration_delete(struct Enumeration_T *self)
{
if(self)
{
while(self->len--)
{
free(self->elements[self->len].name);
}
free(self);
}
}
struct Enumeration_T *enumeration_create(size_t len,...)
{
//We do not check for size_t overflows, but we should.
struct Enumeration_T *self=malloc(sizeof(self)+sizeof(self->elements[0])*len);
if(!self)
{
return NULL;
}
self->len=0;
va_list l;
va_start(l,len);
for(size_t i=0;i<len;i++)
{
const char *name=va_arg(l,const char *);
self->elements[i].name=malloc(strlen(name)+1);
if(!self->elements[i].name)
{
enumeration_delete(self);
return NULL;
}
strcpy(self->elements[i].name,name);
self->len++;
}
return self;
}
bool enumeration_isEqual(struct Enumeration_element_T *a,struct Enumeration_element_T *b)
{
return a->parent==b->parent && a->index==b->index;
}
bool enumeration_isName(struct Enumeration_element_T *a, const char *name)
{
return !strcmp(a->name,name);
}
const char *enumeration_getName(struct Enumeration_element_T *a)
{
return a->name;
}
struct Enumeration_element_T *enumeration_getFromName(struct Enumeration_T *self, const char *name)
{
for(size_t i=0;i<self->len;i++)
{
if(enumeration_isName(&self->elements[i],name))
{
return &self->elements[i];
}
}
return NULL;
}
struct Enumeration_element_T *enumeration_get(struct Enumeration_T *self, size_t index)
{
return &self->elements[index];
}
size_t enumeration_getCount(struct Enumeration_T *self)
{
return self->len;
}
bool enumeration_isInRange(struct Enumeration_T *self, size_t index)
{
return index<self->len;
}
int main(void)
{
struct Enumeration_T *weekdays=enumeration_create(7,"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday");
if(!weekdays)
{
return 1;
}
printf("Please enter the day of the week (0 to 6)\n");
size_t j = 0;
if(scanf("%zu",&j)!=1)
{
enumeration_delete(weekdays);
return 1;
}
// j=j%enumeration_getCount(weekdays); //alternative way to make sure j is in range
if(!enumeration_isInRange(weekdays,j))
{
enumeration_delete(weekdays);
return 1;
}
struct Enumeration_element_T *day=enumeration_get(weekdays,j);
printf("%s\n",enumeration_getName(day));
enumeration_delete(weekdays);
return 0;
}
The functions of enumeration should be in their own translation unit, but i combined them here to make it simpler.
The advantage is that this solution is flexible, follows the DRY principle, you can store information along with each element, you can create new enumerations during runtime and you can add new elements during runtime.
The disadvantage is that this is complex, needs dynamic memory allocation, can't be used in switch-case, needs more memory and is slower. The question is if you should not use a higher level language in cases where you need this.
Using a Macro and stringize operator(#) we can achieve this....
#include <stdio.h>
typedef enum
{
MON=0,
TUE
}week;
int main()
{
#define printt(data) printf("%s",#data);
printt(MON);
return 0;
}
i'm new to this but a switch statement will defenitely work
#include <stdio.h>
enum mycolor;
int main(int argc, const char * argv[])
{
enum Days{Sunday=1,Monday=2,Tuesday=3,Wednesday=4,Thursday=5,Friday=6,Saturday=7};
enum Days TheDay;
printf("Please enter the day of the week (0 to 6)\n");
scanf("%d",&TheDay);
switch (TheDay)
{
case Sunday:
printf("the selected day is sunday");
break;
case Monday:
printf("the selected day is monday");
break;
case Tuesday:
printf("the selected day is Tuesday");
break;
case Wednesday:
printf("the selected day is Wednesday");
break;
case Thursday:
printf("the selected day is thursday");
break;
case Friday:
printf("the selected day is friday");
break;
case Saturday:
printf("the selected day is Saturaday");
break;
default:
break;
}
return 0;
}
TheDay maps back to some integer type. So:
printf("%s", TheDay);
Attempts to parse TheDay as a string, and will either print out garbage or crash.
printf is not typesafe and trusts you to pass the right value to it. To print out the name of the value, you'd need to create some method for mapping the enum value to a string - either a lookup table, giant switch statement, etc.
I'm trying to make a game that requires dynamically sized arrays in C but my code isn't working even though identical code works in another one of my programs.
Here are my #includes
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "SwinGame.h" //API for graphics, physics etc
#include <math.h>
Here are my typedefs for the relevant structs used:
typedef struct position_data
{
double x;
double y;
} position_data;
typedef enum enemy_type_data {CIRCLE, TRIANGLE, SQUARE} enemy_type_data;
typedef struct enemy_data
{
position_data location;
enemy_type_data type;
bitmap bmp;
double health;
double speed;
int path_to;
} enemy_data;
typedef struct enemy_data_array
{
int size;
enemy_data *data;
} enemy_data_array;
Here is the function to add an element to the array:
void add_enemy(enemy_data_array *enemies)
{
enemy_data *new_array;
enemies->size++;
new_array = (enemy_data *)realloc(enemies->data, sizeof(enemy_data) * enemies->size);
if (new_array) //if realloc fails (ie out of memory) it will return null
{
enemies->data = new_array;
// enemies->data[enemies->size - 1] = read_enemy_data();
printf("Enemy added successfully!\n");
}
else
{
printf("FAILED. Out of Memory!\n");
enemies->size--;
}
}
And here is my function call and variable declaration in the main procedure:
int main()
{
path_data my_path[41];
enemy_data_array enemies;
enemies.size = 0;
add_enemy(&enemies);
}
Why isn't this working?
You invoked undefined behavior by passing indeterminate value enemies->data in uninitialized variable having automatic storage duration. Initialize it before using add_enemy().
int main()
{
path_data my_path[41];
enemy_data_array enemies;
enemies.size = 0;
enemies.data = 0; /* add this line */
add_enemy(&enemies);
}
0 is a null pointer constant and can safely be converted to pointer NULL. Unlike NULL, 0 will work without including any headers. Of course you can use enemies.data = NULL; with proper header included.
#2501's explanation is completely correct. Another solution is to change your implementation of add_enemy() to something like this:
void add_enemy(enemy_data_array *enemies)
{
enemy_data *new_array;
// check if size was non-zero
if (enemies->size++)
{
new_array = (enemy_data *)realloc(enemies->data, sizeof(enemy_data) * enemies->size);
}
// start new allocation
else
{
new_array = (enemy_data *)alloc(sizeof(enemy_data) * enemies->size);
}
if (new_array) //if (re)alloc fails (ie out of memory) it will return null
{
enemies->data = new_array;
// enemies->data[enemies->size - 1] = read_enemy_data();
printf("Enemy added successfully!\n");
}
else
{
printf("FAILED. Out of Memory!\n");
enemies->size--;
}
}
If fails because you haven't cleared the content of "enemies". Since it is a stack variable, it will contain whatever garbage data is on the stack.
set enemies.data to NULL in the main function and try it again.
int main()
{
enum Days{Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday};
Days TheDay;
int j = 0;
printf("Please enter the day of the week (0 to 6)\n");
scanf("%d",&j);
TheDay = Days(j);
//how to PRINT THE VALUES stored in TheDay
printf("%s",TheDay); // isnt working
return 0;
}
Enumerations in C are numbers that have convenient names inside your code. They are not strings, and the names assigned to them in the source code are not compiled into your program, and so they are not accessible at runtime.
The only way to get what you want is to write a function yourself that translates the enumeration value into a string. E.g. (assuming here that you move the declaration of enum Days outside of main):
const char* getDayName(enum Days day)
{
switch (day)
{
case Sunday: return "Sunday";
case Monday: return "Monday";
/* etc... */
}
}
/* Then, later in main: */
printf("%s", getDayName(TheDay));
Alternatively, you could use an array as a map, e.g.
const char* dayNames[] = {"Sunday", "Monday", "Tuesday", /* ... etc ... */ };
/* ... */
printf("%s", dayNames[TheDay]);
But here you would probably want to assign Sunday = 0 in the enumeration to be safe... I'm not sure if the C standard requires compilers to begin enumerations from 0, although most do (I'm sure someone will comment to confirm or deny this).
I use something like this:
in a file "EnumToString.h":
#undef DECL_ENUM_ELEMENT
#undef DECL_ENUM_ELEMENT_VAL
#undef DECL_ENUM_ELEMENT_STR
#undef DECL_ENUM_ELEMENT_VAL_STR
#undef BEGIN_ENUM
#undef END_ENUM
#ifndef GENERATE_ENUM_STRINGS
#define DECL_ENUM_ELEMENT( element ) element,
#define DECL_ENUM_ELEMENT_VAL( element, value ) element = value,
#define DECL_ENUM_ELEMENT_STR( element, descr ) DECL_ENUM_ELEMENT( element )
#define DECL_ENUM_ELEMENT_VAL_STR( element, value, descr ) DECL_ENUM_ELEMENT_VAL( element, value )
#define BEGIN_ENUM( ENUM_NAME ) typedef enum tag##ENUM_NAME
#define END_ENUM( ENUM_NAME ) ENUM_NAME; \
const char* GetString##ENUM_NAME(enum tag##ENUM_NAME index);
#else
#define BEGIN_ENUM( ENUM_NAME) const char * GetString##ENUM_NAME( enum tag##ENUM_NAME index ) {\
switch( index ) {
#define DECL_ENUM_ELEMENT( element ) case element: return #element; break;
#define DECL_ENUM_ELEMENT_VAL( element, value ) DECL_ENUM_ELEMENT( element )
#define DECL_ENUM_ELEMENT_STR( element, descr ) case element: return descr; break;
#define DECL_ENUM_ELEMENT_VAL_STR( element, value, descr ) DECL_ENUM_ELEMENT_STR( element, descr )
#define END_ENUM( ENUM_NAME ) default: return "Unknown value"; } } ;
#endif
then in any header file you make the enum declaration, day enum.h
#include "EnumToString.h"
BEGIN_ENUM(Days)
{
DECL_ENUM_ELEMENT(Sunday) //will render "Sunday"
DECL_ENUM_ELEMENT(Monday) //will render "Monday"
DECL_ENUM_ELEMENT_STR(Tuesday, "Tuesday string") //will render "Tuesday string"
DECL_ENUM_ELEMENT(Wednesday) //will render "Wednesday"
DECL_ENUM_ELEMENT_VAL_STR(Thursday, 500, "Thursday string") // will render "Thursday string" and the enum will have 500 as value
/* ... and so on */
}
END_ENUM(MyEnum)
then in a file called EnumToString.c:
#include "enum.h"
#define GENERATE_ENUM_STRINGS // Start string generation
#include "enum.h"
#undef GENERATE_ENUM_STRINGS // Stop string generation
then in main.c:
int main(int argc, char* argv[])
{
Days TheDay = Monday;
printf( "%d - %s\n", TheDay, GetStringDay(TheDay) ); //will print "1 - Monday"
TheDay = Thursday;
printf( "%d - %s\n", TheDay, GetStringDay(TheDay) ); //will print "500 - Thursday string"
return 0;
}
this will generate "automatically" the strings for any enums declared this way and included in "EnumToString.c"
The way I usually do this is by storing the string representations in a separate array in the same order, then indexing the array with the enum value:
const char *DayNames[] = { "Sunday", "Monday", "Tuesday", /* etc */ };
printf("%s", DayNames[Sunday]); // prints "Sunday"
enums in C don't really work the way you're expecting them to. You can think of them kind of like glorified constants (with a few additional benefits relating to being a collection of such constants), and the text you've written in for "Sunday" really gets resolved to a number during compilation, the text is ultimately discarded.
In short: to do what you really want you'll need to keep an array of the strings or create a function to map from the enum's value to the text you'd like to print.
Enumerations in C are basically syntactical sugar for named lists of automatically-sequenced integer values. That is, when you have this code:
int main()
{
enum Days{Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday};
Days TheDay = Monday;
}
Your compiler actually spits out this:
int main()
{
int TheDay = 1; // Monday is the second enumeration, hence 1. Sunday would be 0.
}
Therefore, outputting a C enumeration as a string is not an operation that makes sense to the compiler. If you want to have human-readable strings for these, you will need to define functions to convert from enumerations to strings.
Here's a cleaner way to do it with macros:
#include <stdio.h>
#include <stdlib.h>
#define DOW(X, S) \
X(Sunday) S X(Monday) S X(Tuesday) S X(Wednesday) S X(Thursday) S X(Friday) S X(Saturday)
#define COMMA ,
/* declare the enum */
#define DOW_ENUM(DOW) DOW
enum dow {
DOW(DOW_ENUM, COMMA)
};
/* create an array of strings with the enum names... */
#define DOW_ARR(DOW ) [DOW] = #DOW
const char * const dow_str[] = {
DOW(DOW_ARR, COMMA)
};
/* ...or create a switchy function. */
static const char * dowstr(int i)
{
#define DOW_CASE(D) case D: return #D
switch(i) {
DOW(DOW_CASE, ;);
default: return NULL;
}
}
int main(void)
{
for(int i = 0; i < 7; i++)
printf("[%d] = «%s»\n", i, dow_str[i]);
printf("\n");
for(int i = 0; i < 7; i++)
printf("[%d] = «%s»\n", i, dowstr(i));
return 0;
}
I'm not sure that this is totally portable b/w preprocessors, but it works with gcc.
This is c99 btw, so use c99 strict if you plug it into (the online compiler) ideone.
I know I am late to the party, but how about this?
const char* dayNames[] = { [Sunday] = "Sunday", [Monday] = "Monday", /*and so on*/ };
printf("%s", dayNames[Sunday]); // prints "Sunday"
This way, you do not have to manually keep the enum and the char* array in sync. If you are like me, chances are that you will later change the enum, and the char* array will print invalid strings.
This may not be a feature universally supported. But afaik, most of the mordern day C compilers support this designated initialier style.
You can read more about designated initializers here.
I like this to have enum in the dayNames.
To reduce typing, we can do the following:
#define EP(x) [x] = #x /* ENUM PRINT */
const char* dayNames[] = { EP(Sunday), EP(Monday)};
The question is you want write the name just one times.
I have an ider like this:
#define __ENUM(situation,num) \
int situation = num; const char * __##situation##_name = #situation;
const struct {
__ENUM(get_other_string, -203);//using a __ENUM Mirco make it ease to write,
__ENUM(get_negative_to_unsigned, -204);
__ENUM(overflow,-205);
//The following two line showing the expanding for __ENUM
int get_no_num = -201; const char * __get_no_num_name = "get_no_num";
int get_float_to_int = -202; const char * get_float_to_int_name = "float_to_int_name";
}eRevJson;
#undef __ENUM
struct sIntCharPtr { int value; const char * p_name; };
//This function transform it to string.
inline const char * enumRevJsonGetString(int num) {
sIntCharPtr * ptr = (sIntCharPtr *)(&eRevJson);
for (int i = 0;i < sizeof(eRevJson) / sizeof(sIntCharPtr);i++) {
if (ptr[i].value == num) {
return ptr[i].p_name;
}
}
return "bad_enum_value";
}
it uses a struct to insert enum, so that a printer to string could follows each enum value define.
int main(int argc, char *argv[]) {
int enum_test = eRevJson.get_other_string;
printf("error is %s, number is %d\n", enumRevJsonGetString(enum_test), enum_test);
>error is get_other_string, number is -203
The difference to enum is builder can not report error if the numbers are repeated.
if you don't like write number, __LINE__ could replace it:
#define ____LINE__ __LINE__
#define __ENUM(situation) \
int situation = (____LINE__ - __BASELINE -2); const char * __##situation##_name = #situation;
constexpr int __BASELINE = __LINE__;
constexpr struct {
__ENUM(Sunday);
__ENUM(Monday);
__ENUM(Tuesday);
__ENUM(Wednesday);
__ENUM(Thursday);
__ENUM(Friday);
__ENUM(Saturday);
}eDays;
#undef __ENUM
inline const char * enumDaysGetString(int num) {
sIntCharPtr * ptr = (sIntCharPtr *)(&eDays);
for (int i = 0;i < sizeof(eDays) / sizeof(sIntCharPtr);i++) {
if (ptr[i].value == num) {
return ptr[i].p_name;
}
}
return "bad_enum_value";
}
int main(int argc, char *argv[]) {
int d = eDays.Wednesday;
printf("day %s, number is %d\n", enumDaysGetString(d), d);
d = 1;
printf("day %s, number is %d\n", enumDaysGetString(d), d);
}
>day Wednesday, number is 3 >day Monday, number is 1
There is another solution: Create your own dynamic enumeration class. Means you have a struct and some function to create a new enumeration, which stores the elements in a struct and each element has a string for the name. You also need some type to store a individual elements, functions to compare them and so on.
Here is an example:
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct Enumeration_element_T
{
size_t index;
struct Enumeration_T *parent;
char *name;
};
struct Enumeration_T
{
size_t len;
struct Enumeration_element_T elements[];
};
void enumeration_delete(struct Enumeration_T *self)
{
if(self)
{
while(self->len--)
{
free(self->elements[self->len].name);
}
free(self);
}
}
struct Enumeration_T *enumeration_create(size_t len,...)
{
//We do not check for size_t overflows, but we should.
struct Enumeration_T *self=malloc(sizeof(self)+sizeof(self->elements[0])*len);
if(!self)
{
return NULL;
}
self->len=0;
va_list l;
va_start(l,len);
for(size_t i=0;i<len;i++)
{
const char *name=va_arg(l,const char *);
self->elements[i].name=malloc(strlen(name)+1);
if(!self->elements[i].name)
{
enumeration_delete(self);
return NULL;
}
strcpy(self->elements[i].name,name);
self->len++;
}
return self;
}
bool enumeration_isEqual(struct Enumeration_element_T *a,struct Enumeration_element_T *b)
{
return a->parent==b->parent && a->index==b->index;
}
bool enumeration_isName(struct Enumeration_element_T *a, const char *name)
{
return !strcmp(a->name,name);
}
const char *enumeration_getName(struct Enumeration_element_T *a)
{
return a->name;
}
struct Enumeration_element_T *enumeration_getFromName(struct Enumeration_T *self, const char *name)
{
for(size_t i=0;i<self->len;i++)
{
if(enumeration_isName(&self->elements[i],name))
{
return &self->elements[i];
}
}
return NULL;
}
struct Enumeration_element_T *enumeration_get(struct Enumeration_T *self, size_t index)
{
return &self->elements[index];
}
size_t enumeration_getCount(struct Enumeration_T *self)
{
return self->len;
}
bool enumeration_isInRange(struct Enumeration_T *self, size_t index)
{
return index<self->len;
}
int main(void)
{
struct Enumeration_T *weekdays=enumeration_create(7,"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday");
if(!weekdays)
{
return 1;
}
printf("Please enter the day of the week (0 to 6)\n");
size_t j = 0;
if(scanf("%zu",&j)!=1)
{
enumeration_delete(weekdays);
return 1;
}
// j=j%enumeration_getCount(weekdays); //alternative way to make sure j is in range
if(!enumeration_isInRange(weekdays,j))
{
enumeration_delete(weekdays);
return 1;
}
struct Enumeration_element_T *day=enumeration_get(weekdays,j);
printf("%s\n",enumeration_getName(day));
enumeration_delete(weekdays);
return 0;
}
The functions of enumeration should be in their own translation unit, but i combined them here to make it simpler.
The advantage is that this solution is flexible, follows the DRY principle, you can store information along with each element, you can create new enumerations during runtime and you can add new elements during runtime.
The disadvantage is that this is complex, needs dynamic memory allocation, can't be used in switch-case, needs more memory and is slower. The question is if you should not use a higher level language in cases where you need this.
Using a Macro and stringize operator(#) we can achieve this....
#include <stdio.h>
typedef enum
{
MON=0,
TUE
}week;
int main()
{
#define printt(data) printf("%s",#data);
printt(MON);
return 0;
}
i'm new to this but a switch statement will defenitely work
#include <stdio.h>
enum mycolor;
int main(int argc, const char * argv[])
{
enum Days{Sunday=1,Monday=2,Tuesday=3,Wednesday=4,Thursday=5,Friday=6,Saturday=7};
enum Days TheDay;
printf("Please enter the day of the week (0 to 6)\n");
scanf("%d",&TheDay);
switch (TheDay)
{
case Sunday:
printf("the selected day is sunday");
break;
case Monday:
printf("the selected day is monday");
break;
case Tuesday:
printf("the selected day is Tuesday");
break;
case Wednesday:
printf("the selected day is Wednesday");
break;
case Thursday:
printf("the selected day is thursday");
break;
case Friday:
printf("the selected day is friday");
break;
case Saturday:
printf("the selected day is Saturaday");
break;
default:
break;
}
return 0;
}
TheDay maps back to some integer type. So:
printf("%s", TheDay);
Attempts to parse TheDay as a string, and will either print out garbage or crash.
printf is not typesafe and trusts you to pass the right value to it. To print out the name of the value, you'd need to create some method for mapping the enum value to a string - either a lookup table, giant switch statement, etc.