Combining two files of floats into a single file in C - c

Question

My task is to read from two files both containing floats. Then I have to put them in a new file in an ascending order. The code is as follows:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int numLines(const char * fileName){
FILE *file=fopen(fileName,"r");
int lines=0;
char c;
while((c=fgetc(file))!=EOF){
if(c==10){
lines++;
}
}
fclose(file);
return lines;
}
float * fileToArray(const char * fileName){
FILE *file=fopen(fileName,"r");
int numOfLines= numLines(fileName);
float * arr= (float*)malloc(numOfLines*sizeof(float));
int i;
for(i=0;i<numOfLines;i++){
fscanf(file,"%f\n",&arr[i]);
}
fclose(file);
return arr;
}
int cmpfunc(const void *a, const void *b){
float fa= *(const float*) a;
float fb= *(const float*) b;
return (fa>fb)-(fa<fb);
}
int isSorted(FILE *fp){
float prev;
float o;
do{
fscanf(fp,"%f\n",&prev);
fscanf(fp,"%f\n",&o);
if(prev>o){
fclose(fp);
return 1;
}
}while(fscanf(fp,"%f\n",&o)==1);
fclose(fp);
return 0;
}
int main(int argc, const char * argv[]){
const char *fileName1;
const char *fileName2;
const char *fileOut;
FILE *fp1;
FILE *fp2;
FILE *fp3;
float *arr1;
float *arr2;
int size1;
int size2;
if(argc!=4){
printf("Usage: fileSort.exe FILENAME1 FILENAME2 FILEOUT");
return 0;
}
else{
fileName1= argv[1];
fileName2= argv[2];
fileOut= argv[3];
fp1= fopen(fileName1,"r");
fp2= fopen(fileName2, "r");
fp3= fopen(fileOut, "w");
if(fp1!=NULL && fp2!=NULL){
arr1=fileToArray(fileName1);
arr2=fileToArray(fileName2);
size1=sizeof(arr1)/sizeof(float);
size2=sizeof(arr2)/sizeof(float);
if(!isSorted(fp1) || !isSorted(fp2)){
printf("The files are not sorted in increasing order. Please sort them.");
}
else{
float * arr3= malloc((size1+size2)*sizeof(float));
int k;
memcpy(arr3,arr1,size1*sizeof(float));
memcpy(arr3+size1,arr2,size2*sizeof(float));
qsort(arr3,size1+size2,sizeof(float),cmpfunc);
for(k=0;k<(size1+size2);k++){
fprintf(fp3,"%f\n",arr3[k]);
}
}
fclose(fp1);
fclose(fp2);
fclose(fp3);
}
else{
printf("Files could not be opened\n");
}
return EXIT_SUCCESS;
}
Two sample files for testing this code would be:
data1.txt:
0.586399
0.769484
0.864755
6.229683
data2.txt:
0.279828
0.309235
0.591884
0.962811
1.361349
10.203892
12.158343
The result should be their ordered combination. However, I get this as a result:
0.279828
0.309235
0.586399
0.769484
No matter what I change, it always writes four numbers into the resulting file. The helper functions seem to be doing their jobs just fine. It looks like the problem comes up when I'm trying to create the third array and fill it up (or at least I assume that's the source). I have no idea where this problem is coming from though. I would really appreciate some help on this issue.

Answer 1

The variable arr1 is not an array, it is a pointer to a float even though you are using it as pointer to the first float element in the array.
This means that sizeof will return to you the size of the pointer which is either 4 bytes or 8 bytes depending whether you are compiler 32-bit or 64-bit.
One way to fix this is to pull out the calculation of the number of lines like this:
int size1 = numLines(fileName1);
int size2 = numLines(fileName2);
arr1=fileToArray(fileName1, size1);
arr2=fileToArray(fileName2, size2);