#include <stdio.h>
#include <errno.h>
#include <unistd.h>

#include "util.h"


int xread(int sd, void *buf, size_t len) {
  char *p = (char *)buf;
  size_t nrecv = 0;
  size_t rv;
  
  while (nrecv < len) {
    rv = read(sd, p, len - nrecv);
    if (0 > rv && errno == EINTR)
      continue;
    if (0 > rv)
      return -1;
    if (0 == rv)
      return 0;
    nrecv += rv;
    p += rv;
  }
  return nrecv;
}

int xwrite(int sd, const void *buf, size_t len) {
  char *p = (char *)buf;
  size_t nsent = 0;
  ssize_t rv;

  while (nsent < len) {
    rv = write(sd, p, len - nsent);
    if (0 > rv && (errno == EINTR || errno == EAGAIN))
      continue;
    if (0 > rv)
      return -1;
    nsent += rv;
    p += rv;
  }
  return nsent;
}

int read_header(int fd, byte *compress_type) {
  int checkbit;

  assert(compress_type != NULL);

  if (xread(fd, &checkbit, sizeof(int)) < 0){
    return -1;
  }
  if (checkbit != CHECKBIT) {
    printf("format error!\n");
    return -1;
  }

  if (xread(fd, compress_type, sizeof(byte)) < 0){
    return -1;
  }

  return 0;
}

int write_header(int fd, byte compress_type) {
  int checkbit = CHECKBIT;
  if (xwrite(fd, &checkbit, sizeof(int)) < 0){
    return -1;
  }

  if (xwrite(fd, &compress_type, sizeof(byte)) < 0){
    return -1;
  }
  return 0;
}