#include<stdio.h>
#include<string.h>
#include<stdlib.h>

typedef struct {
    int i1;
    int i2;
    char c[20];
} easystruct;

typedef struct {
    int i1;
    int i2;
    int ssl;
    char* c;
} hardstruct;
    

int writer()
{
    FILE* f = fopen("wb.bin", "w");
    char a = 'w';
    int r = fwrite(&a, 1, 1, f);
    if (r!=1)
	fprintf(stderr, "writing issue");

    char c[20];
    for (int i=0; i<20; i++)
	c[i]='a'+i;
    r = fwrite(c, 20, sizeof(char), f);
    if (r!=20*sizeof(char))
	fprintf(stderr, "writing issue");

    easystruct es[10];
    for (int i=0; i<10; i++)
    {
	es[i].i1=i+1;
	es[i].i2=i*i+2;
	for (int ch=0; ch<19; ch++)
	    es[i].c[ch]='a'+ch;
	es[i].c[19]='\0';
    }
    fwrite(es, 10, sizeof(easystruct), f);

    hardstruct hs[10];
    for (int i=0; i<10; i++)
    {
	hs[i].i1=i+1;
	hs[i].i2=i*i+2;
	hs[i].c = malloc(21*sizeof(char));
	for (int ch=0; ch<(8+i); ch++)
	    hs[i].c[ch]='B'+ch;
	hs[i].ssl = 9+i;
	hs[i].c[8+i]='\0';
    }
    
    // fwrite(es, 10, sizeof(hardstruct), f); // does not work because of pointer
    //you have to wriet out the structure parts individually 
    for (int i=0; i<10; i++)
    {
	fwrite(&hs[i].i1, sizeof(int),1, f);
	fwrite(&hs[i].i2, sizeof(int),1, f);
	// for the malloc'd string, need to write the length of the string
	// then the string -- in both cases leaving room for the null term
	fwrite(&hs[i].ssl, sizeof(int), 1, f);
	fwrite(hs[i].c, sizeof(char), hs[i].ssl, f);
    }
    
    fclose(f);
}


void reader()
{
    FILE* f = fopen("wb.bin", "r");
    char a;
    int r = fread(&a, 1, 1, f);
    if (r!=1)
	fprintf(stderr, "reading issue");
    printf("%d\n", a);
    
    char c[20];
    r = fread(c, 20, sizeof(char), f);
    if (r!=20*sizeof(char))
	fprintf(stderr, "reading issue");
    for (int i=0; i<20; i++)
	printf("%c", c[i]);
    printf("\n");
    
    easystruct es[10];
    r = fread(es, sizeof(easystruct), 10, f);
    if (r!=(10*sizeof(easystruct)))
	fprintf(stderr, "Reading issue %d  %d\n", 10*sizeof(easystruct), r);
    for (int i=0; i<10; i++)
    {
	printf("ES %d:  %d  %d  %s\n", i, es[i].i1, es[i].i2, es[i].c); 
    }

    hardstruct hs[10];
    for (int i=0; i<10; i++)
    {
	fread(&hs[i].i1, sizeof(hs[i].i1),1, f);
	fread(&hs[i].i2, sizeof(hs[i].i2),1, f);
	fread(&hs[i].ssl, sizeof(hs[i].ssl),1, f);
	hs[i].c  = malloc(hs[i].ssl*sizeof(char));
	fread(hs[i].c, sizeof(char),hs[i].ssl, f);
    }

    for (int i=0; i<10; i++)
    {
	printf("HS %d:  %d  %d  %s\n", i, hs[i].i1, hs[i].i2, hs[i].c); 
    }
    fclose(f);
}


int main()
{
    writer();
    reader();
}