I want to find size or length of an unsigned char pointer in a function where that pointer is an argument to that function.Near the pointers declaration size is coming correctly.
But when i am trying to find size in function it is giving 4.
How can i do this ?
#include <stdio.h>
//void writeFile(unsigned char *da);
void writeFile(char *da);
int main(int arc,char **argv)
{
unsigned char block_bmp[]=
{
0x0,0xff,0xff,0xff,0x0,0x0,0x0,0xff,0xff,0xff,0x0,0x0,0x0,0xff,0xff,0xff,//*16bytes*
};
printf("size::%d\n",sizeof(block_bmp));
writeFile(block_bmp);
}
//void writeFile(unsigned char *da)
void writeFile(char *da)
{
printf("%d\n",__LINE__);
printf("size::%d\n",sizeof(da));
printf("length::%d\n",strlen(da));
FILE *fp;
int i;
fp=fopen("/tmp/hexfile","wb");
for(i=0;i<3780;i++)
fprintf(fp,"%c",da[i]);
// fwrite(da,sizeof(unsigned char),sizeof(da),fp);
fclose(fp);
}
If it points to a NULL-terminated string, use strlen
. If not, the pointer is just some memory address for the called function, without any additional information about the size of the array (I assume, you try to pass an array). I suggest passing the number of array elements as additional parameter to the function.