I have a problem with allocating memory...

[toktam]

Hi guys!
I defined a type like this:

typedef struct {
char *key;
int freq;
float pr;
} TableEntry;

and then I have an array of pointers to this struct:
TableEntry* hash_table[hash_table_size];

But it gives an error when I want to allocate memory for this array:

assert((hash_ta ble = malloc((hash_ta ble_size)*sizeo f(TableEntry))) !=NULL);


Do I need to allocate some memory for key before allocating memory for struct???and how I can allocate memory for a string without knowing its length???

Cheers

[JosAH]

Hi guys!
I defined a type like this:

typedef struct {
char *key;
int freq;
float pr;
} TableEntry;

and then I have an array of pointers to this struct:
TableEntry* hash_table[hash_table_size];

But it gives an error when I want to allocate memory for this array:

assert((hash_ta ble = malloc((hash_ta ble_size)*sizeo f(TableEntry))) !=NULL);


Do I need to allocate some memory for key before allocating memory for struct???and how I can allocate memory for a string without knowing its length???

Cheers

Variable 'hash_table' is an array, i.e. you cannot assign to it. Make it a pointer
to a pointer of your struct instead:

TableEntry** hash_table;

kind regards,

Jos

[toktam]

Variable 'hash_table' is an array, i.e. you cannot assign to it. Make it a pointer
to a pointer of your struct instead:

TableEntry** hash_table;

kind regards,

Jos

Thanks for that Jos,
Can I use this type as an array,I mean an array of TableEntry* elements?Can I assign some value to for example hash_table[0] ???

[toktam]

Thanks for that Jos,
Can I use this type as an array,I mean an array of TableEntry* elements?Can I assign some value to for example hash_table[0] ???

Actually I tried to assign a string to it :

assert((hash_ta ble[h]->key=malloc(siz eof(strlen(inpu t)+1)))!=NULL);
strcpy(hash_tab le[h]->key,input);

it gave me a segmentation fault...

[JosAH]

Actually I tried to assign a string to it :

assert((hash_ta ble[h]->key=malloc(siz eof(strlen(inpu t)+1)))!=NULL);
strcpy(hash_tab le[h]->key,input);

it gave me a segmentation fault...

Sure, you have just allocated room for a bunch of pointers to those structures,
but you don't have the structures yet. Maybe you want to allocate room for
a bunch (read: array) of structs (but that is entirely different from what you
wrote in your original posting).

kind regards,

Jos

[toktam]

Sure, you have just allocated room for a bunch of pointers to those structures,
but you don't have the structures yet. Maybe you want to allocate room for
a bunch (read: array) of structs (but that is entirely different from what you
wrote in your original posting).

kind regards,

Jos

Actually I did this:

typedef struct {
char *key;
int freq;
float pr;
} TableEntry;

TableEntry** hash_table;

assert((hash_ta ble = malloc((hash_ta ble_size)*sizeo f(TableEntry))) !=NULL);
assert((hash_ta ble[h]->key=malloc(siz eof(strlen(inpu t)+1)))!=NULL);
strcpy(hash_tab le[h]->key,input);

But I gave segmentation fault for this lines...
I have another guestion:
when we declare hash_table's type as TableEntry** ,can we pass hash_table as an array to a function?

Thanks alot,

[JosAH]

Actually I did this:

typedef struct {
char *key;
int freq;
float pr;
} TableEntry;

TableEntry** hash_table;

assert((hash_ta ble = malloc((hash_ta ble_size)*sizeo f(TableEntry))) !=NULL);
assert((hash_ta ble[h]->key=malloc(siz eof(strlen(inpu t)+1)))!=NULL);
strcpy(hash_tab le[h]->key,input);

But I gave segmentation fault for this lines...
I have another guestion:
when we declare hash_table's type as TableEntry** ,can we pass hash_table as an array to a function?

Thanks alot,

That's not correct for two reasons:

1) you're allocating room for 'hash_table_siz e' structures

2) you're treating that memory as an array of pointers. Of course those pointers
don't point to sensible values. I guess you want this:

TableEntry* hash_table;

assert((hash_table = malloc((hash_table_size)*sizeof(TableEntry)))!=NULL);
assert((hash_table[h].key=malloc(sizeof(strlen(input)+1)))!=NULL);
strcpy(hash_table[h].key,input);

Now you can consider 'hash_table' and array of structures (not pointers).

kind regards,

Jos