#include <stddef.h>

void write_all(int fd, char const *buf, size_t len);
size_t read_all(int fd, unsigned char *buf, size_t len);
void write_str(int fd, char const *s);
void newline(int fd);
void write_line(int fd, char const *s);
#define assert(expr) ((void) ((expr) || (assert_fail(#expr), 0)))
void assert_fail(char const *expr);
void perr(char const *context);
int chkp(char const *context, int ret);