C String array problem

[16702]

I have no idea why this happen to me, plz help.
In a method i have:

char p[255] = "";
char* p2;
char** temp;

for (i = 0 ...){
...
p = "abc" // when i = 0
= "222" // when i = 1
p2 = (char*)p;
p2 = &p2[loc];
temp=p2;
}
however, when I try to print out temp it gives me
abc222
222
instead of
abc
222

thx in advance

 

[MOrac]

The code you've posted is not helpful for solving your problem. Either post it complete or don't post ;-)

 

[16702]

The program is about writing an API on top of NDBM.
Here is the method that I'm talking about.
dbID is an array stores a structure that has info. about a table.
char* key is the key value of the table.
char** outAttrs is where I should store the list of attributes correspond to the key.
since NDBM only support key,value pair, therefore when I get the record from NDBM, I need to parse it.
The format of the record is "020504AABBBBBCCCC", where the numbers are the lengh of each attribute.


int DBE_GetRecord(int tableID, char *key, char **outAttrs){
char *rec;
char* r;
char* t2 = "";
char** temp;
int i, j;
DBM *db;
if (!dbID[tableID].isOpened)
return 2;

db = dbID[tableID].dbm;
datum k = {key, strlen(key)+1};

rec = dbm_fetch(db, k).dptr; // getting the record.
// let rec = "030405abc2222kkkkk";
if (rec == NULL)
return 3; // key not found
for (i = 0; i < dbID[tableID].attrNum; i++){
int loc, len; // location and length of attribute
char p[255] = "";
char* p2;

loc = 2*dbID[tableID].attrNum;

// sums up the length of attribute before attrNumber to find location
for (j = 0; j < 2*i; j+=2){
// convert char to int
loc += 10*(rec[j] - 48);
loc += rec[j+1] - 48;
}
len = 10 * (rec[2*i] - 48);
len = rec[2*i+1] - 48;

strncpy (p,rec,loc+len);
p[len] = NULL;
p2 = (char*)p;
p2 = &p2[loc];
temp=p2;
printf("temp[%d]: %s\n", i, p2);
// this prints out
//abc
//2222
//kkkkk
}

for (i = 0; i < dbID[tableID].attrNum; i++){
printf("in get: %s, len: %d \n", temp,strlen(temp));
//this prints out
//abc2222kkkkk
//2222kkkkk
//kkkkk
}
return 0;
}

 

[marsd]

Wow. I'm amazed temp gives you anything but a segmentation fault. No memory has been assigned to it that I can see.

 

[Salem]

Please use the [tt][ignore]

[/ignore][/tt] tags when posting code.

--

 

[16702]

Thanx marsd, the code works now. (posted below)

But here comes another problem, the outAttrs doesn't return to caller.
In the caller method:

char** outAttrs; // have to defined like this
DBE_GEtRecord(2, "aaa", outAttrs);
for (i = 0; i < dbID[id].attrCount; i++)
	printf("%s     ",abc[i]); // seg fault

The callee:

int DBE_GetRecord(int tableID, char* key, char** outAttrs){
	datum recD;
	char* rec;
	int i, j, loc, len;
	if (dbID[tableID].tableName == NULL)
		return 2;
	outAttrs = (char**)malloc(dbID[tableID].attrCount);
	DBM *db = dbID[tableID].dbm;
	datum k = {key, strlen(key)+1};
	recD = dbm_fetch(db, k);
	if (NULL == (rec = recD.dptr)) return 3; 	// no key found
printf("GetRec:rec = %s\n", rec);	
	for (i = 0; i < dbID[tableID].attrCount; i++){
		loc = 2*dbID[tableID].attrCount;;
		for (j = 0; j < 2*i; j+=2){
			// convert char to int
			loc += 10*(rec[j] - 48);
			loc += rec[j+1] - 48;
		}
		len = 10 * (rec[2*i] - 48);
		len = rec[2*i+1] - 48;

		outAttrs[i] = (char*)malloc(len+1);
		for (j = 0; j < len; j++)
			outAttrs[i][j] = rec[loc+j];
		outAttrs[i][j] = '\0';
		printf("loc: %d    len: %d   \n",loc, len);
		printf("prev[%d] = %s\n", i, outAttrs[i]);
                // prints out correctly
	}
	
	for (i = 0; i < dbID[tableID].attrCount; i++)
		printf("attr[%d] = %s\n", i, outAttrs[i]);
                // prints out correctly too
	return 0;
}

Plz tell me what should i change to make it work.

Thx in advance