#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <strings.h>

#include "stdio-util.h"

typedef struct allocblk ALLOCBLK;
typedef struct rstrblk RSTRBLK;

struct allocblk {
  char **bufp;
  int *lenp;
  char *buf;
  int len;
  } ;

struct rstrblk {
  const char *buf;
  int len;
  off_t ptr;
  };

static int alloc_w(void *av, const char *b, int l)
{
 ALLOCBLK *a;

 a = av;
 a->buf = realloc(a->buf,a->len+l);
 bcopy(b,a->buf+a->len,l);
 a->len += l;
 return(l);
}

static int alloc_c(void *av)
{
 ALLOCBLK *a;

 a = av;
 *a->bufp = a->buf;
 *a->lenp = a->len;
 free(a);
 return(0);
}

FILE *fopen_alloc(char **bufp, int *lenp)
{
 FILE *f;
 ALLOCBLK *a;

 a = malloc(sizeof(ALLOCBLK));
 if (a == 0) return(0);
 a->bufp = bufp;
 a->lenp = lenp;
 a->buf = 0;
 a->len = 0;
 f = funopen(a,0,&alloc_w,0,&alloc_c);
 if (f == 0) free(a);
 return(f);
}

static int rstr_r(void *bv, char *buf, int len)
{
 RSTRBLK *b;
 int n;

 b = bv;
 if (b->ptr < 0)
  { errno = EINVAL;
    return(-1);
  }
 else if (b->ptr >= b->len)
  { return(0);
  }
 n = b->len - b->ptr;
 if (n > len) n = len;
 bcopy(b->buf+b->ptr,buf,n);
 b->ptr += n;
 return(n);
}

static fpos_t rstr_s(void *bv, fpos_t loc, int whence)
{
 RSTRBLK *b;

 b = bv;
 switch (whence)
  { case SEEK_SET:
       b->ptr = loc;
       break;
    case SEEK_CUR:
       b->ptr += loc;
       break;
    case SEEK_END:
       b->ptr = b->len + loc;
       break;
    default:
       errno = EINVAL;
       return(-1);
       break;
  }
 return(b->ptr);
}

static int rstr_c(void *bv)
{
 free(bv);
 return(0);
}

FILE *fopen_rstr(const char *s, int l)
{
 RSTRBLK *b;
 FILE *f;

 b = malloc(sizeof(RSTRBLK));
 if (b == 0) return(0);
 if (l < 0) l = strlen(s);
 b->buf = s;
 b->len = l;
 b->ptr = 0;
 f = funopen(b,&rstr_r,0,&rstr_s,&rstr_c);
 if (f == 0) free(b);
 return(f);
}