-void syscall_error(const char *err);
-void internal_error(const char *err);
-char *read_string(int fd, size_t bufsiz);
-char *address_string(struct sockaddr_in6 *addr);
-v3f html_to_v3f(const char *html);
+void syscall_error(const char *err); // print system call related error message and exit
+void internal_error(const char *err); // print general error message and exit
+char *read_string(int fd, size_t bufsiz); // read from fd until \0 or EOF terminator
+char *address_string(struct sockaddr_in6 *addr); // convert IPv6 address to human readable, return allocated buffer
+v3f32 html_to_v3f32(const char *html); // convert #RRGGBB color to v3f32
+void my_compress(const void *uncompressed, size_t uncompressed_size, char **compressed, size_t *compressed_size); // compress data using ZLib and store result(buffer allocated by malloc) in compressed
+bool my_decompress(const char *compressed, size_t compressed_size, void *decompressed, size_t expected_decompressed_size); // decompress data and put result into decompressed, return false if decompressed size does not match expected_decompressed_size
+bool within_simulation_distance(v3f64 player_pos, v3s32 block_pos, u32 simulation_distance); // return true if a player is close enough to a block to access it