#include "streamfer.h"
#include <unistd.h>

static void vwarning(const char *msg,va_list ap) {
  int err=vfprintf(stderr,msg,ap);
  assert(err>0);
  fputc('\n',stderr);
}

void warning(const char *msg,...) {
  va_list ap;
  va_start(ap,msg);
  vwarning(msg,ap);
  va_end(ap);
}

void fatal(const char *msg,...) {
  va_list ap;
  va_start(ap,msg);
  vwarning(msg,ap);
  va_end(ap);
  exit(EXIT_FAILURE);
}

uint64_t transfer(int from_fd,const char *from_fn,int to_fd,const char *to_fn) {
  size_t total(0);
  uint8_t buffer[0x10000];
  size_t buffer_filled(0);
  for (;;) {
    if (buffer_filled==0) {
      ssize_t got(read(from_fd,buffer+buffer_filled,sizeof(buffer)-buffer_filled));
      if (got==-1)
	fatal("Error reading %s: %m",from_fn);
      if (got==0)
	return total;
      buffer_filled=got;
      assert(buffer_filled<=sizeof(buffer));
    }
    size_t buffer_written(0);
    while (buffer_written<buffer_filled) {
      ssize_t got(write(to_fd,buffer+buffer_written,buffer_filled-buffer_written));
      if (got==-1)
	fatal("Error writing %s: %m",to_fn);
      assert(got>0);
      buffer_written+=got;
      assert(buffer_written<=buffer_filled);
    }
    total+=buffer_filled;
    buffer_filled=0;
  }
}