Why is sscanf Causing an Error When Reading Data from a Text File?

[nenyan]

the function for read data from a txt.file.

the data looks like:

2|name|3.444|...|..|
3|name|5.344|...|..|

I use debugging tools and find the error occurred in sscanf. But I can not find the specific point. please help me.

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define BUF 10240
#define pi 3.14159
#define SKYFILE "H1L1V1-LUMIN_cbc_trig-970399241-1.txt"
#define CATALOG "GWGCCatalog.txt"
#define ResultNumber 20


typedef struct catalogdata
{	char pgc[20];
	char name[100];
	double ra;
	double dec;
	double absmag;
	double dist;} cdata;

typedef struct catalogtemp
{	char pgc[20];
	char name[100];
	char ra[30];
	char dec[30];
	char absmag[20];
	char dist[20];} catatemp;






	/* This function is for readding catalog.*/
int
readevent( FILE *pFile, cdata **catalog)
{
	
	catatemp *ctemp, *ctemp1;  
	void *temp;
    int c, i=0, j, n=BUF;       /* n is the buffer. */
	
	if ( !(ctemp=(catatemp *)malloc(n*sizeof(catatemp))))  
		printf("memory error 1\n");                        //allocate memory.
	if ( !(temp=(char *)malloc(100)))  
		printf("memory error 1\n");                        //allocate memory for temp.

	do{
		c=getc(pFile);
	}while(c!='\n');                                   //skip the first line.

	while (!feof(pFile))
	{  
		/*read all data as a string*/
		fscanf(pFile, "%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|", &(ctemp->pgc), &(ctemp->name), &(ctemp->ra), &(ctemp->dec), temp, temp, temp, temp, temp, temp, temp, temp, temp, &(ctemp->absmag), &(ctemp->dist), temp, temp, temp);
		i++;
		
		if (i==(n-1))                              /*the number of lines is going to be longer than buffer. */
		{
			if(!(ctemp1=realloc(ctemp, 2*n*sizeof(cdata)))) {
				printf("memory error 2\n"); }
			ctemp=ctemp1;
			n*=2;   /*double the buffer*/
		}  

	}

	if ( !(*catalog=(cdata *)malloc(i*sizeof(cdata))))  
		printf("memory error 1\n");                        //allocate memory.

	/*convert string to data*/
	for(j=0;j<i;j++)
	{	
		sscanf((ctemp+j)->pgc, "%s", &((*catalog+j)->pgc));
		sscanf((ctemp+j)->name, "%s", &((*catalog+j)->name));
		sscanf((ctemp+j)->ra, "%lf", &((*catalog+j)->ra));
		sscanf((ctemp+j)->dec, "%lf", &((*catalog+j)->dec));
		if((ctemp+j)->absmag=="~")
			(*catalog+j)->absmag=10000.0;
		else
			sscanf((ctemp+j)->absmag, "%lf", &((*catalog+j)->absmag));
		if((ctemp+j)->dist=="~") 
			(*catalog+j)->dist=10000.0;
		else
			sscanf((ctemp+j)->dist, "%lf", &((*catalog+j)->dist));
	}

free(temp);
free(ctemp);
free(ctemp1);
return i;       
}

int
main()
{
	int i, n;
	cdata *catalog;
	FILE *pFile;
	
	if ( !( pFile=fopen(CATALOG, "r"))) {
		printf ("cannot open the cata_std.txt file\n");
		return 1;}
	n=readevent(pFile, &catalog);                         //catalog done.

	for(i=0; i<n; i++)
		printf("%s, %s, %e, %e, %e, %e\n", catalog[i].pgc, catalog[i].name, catalog[i].ra, catalog[i].dec, catalog[i].absmag, catalog[i].dist);

free(catalog);
fclose(pFile);

}

 

[rcgldr]

You only allocate one instance of catalog in main, but you treat it as an array in readevent() when you reference ( ... catalog + j ...). It might also help to add temporary code to print out the structure for each loop in readevent().

 

[nenyan]

I find something
&(ctemp->pgc), &(ctemp->name), should be (ctemp+i)->pgc
but still out of order

 

[Mark44]

When you are using the debugger and see a problem with sscanf, which line is causing the problem, and what is the error that is generated?

 

[nenyan]

i==14168 causing the problem
memory error...

 

[nenyan]

in fact, the error occur in fscanf()

 

[Mark44]

Here's my guess. The heap memory that temp points to consists of 100 bytes. One of the file reads (using fscanf) pulls in a string that's too big to fit in 100 bytes, which causes the problem you're seeing.

Instead of using fscanf to input to six variables you care about, and a slew of "don't care" variables, it might be better to have a loop. Each iteration of the loop could read one line of data from the file and store it in a string, and then parse the string.