/*
DESCRIPTION
  helpers.c provides C helper functions for interfacing with C code used for
  testing in this package.

AUTHORS
  Saxon A. Nelson-Milton <saxon@ausocean.org>

LICENSE
  Copyright (C) 2019 the Australian Ocean Lab (AusOcean).

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  for more details.

  You should have received a copy of the GNU General Public License
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

#include "helpers.h"

typedef struct BitReader BitReader;
typedef struct Reader Reader;

BitReader* new_BitReader(char* d, int l){
  Reader* r = (Reader*)malloc(sizeof(Reader));
  if(r == NULL){
    return NULL;
  }
  r->data = d;
  r->curr = 0;
  r->len = l;
  r->err = 0;

  BitReader* br = (BitReader*)malloc(sizeof(BitReader));
  if(br == NULL){
    return NULL;
  }
  br->r = r;
  br->n = 0;
  br->bits = 0;
  br->nRead = 0;
  br->err = 0;
  return br;
}

char next_byte(Reader *r) {
  if(r->curr >= r->len){
    r->err = 1;
  }
  char next = r->data[r->curr];
  r->curr++;
  return next;
}

uint64_t read_bits(BitReader *br, int n) {
  while( n > br->bits ){
    char b = next_byte(br->r);
    if(br->r->err != 0){
      br->err = 1;
      return 0;
    }
    br->nRead++;
    br->n <<= 8;
    br->n |= (uint64_t)b;
    br->bits += 8;
  }

  uint64_t r = (br->n >> (br->bits-n)) & ((1 << n) - 1);
  br->bits -= n;
  return r;
}