#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <netdb.h>#include <unistd.h>#include <errno.h>#include <stdlib.h>#include <string.h>#include "sfsource.h"uint32_t platform;int saferead(int fd, void *buffer, int count){  int actual = 0;  while (count > 0)    {      int n = read(fd, buffer, count);      if (n == -1 && errno == EINTR)	continue;      if (n == -1)	return -1;      if (n == 0)	return actual;      count -= n;      actual += n;      buffer += n;    }  return actual;}int safewrite(int fd, const void *buffer, int count){  int actual = 0;  while (count > 0)    {      int n = write(fd, buffer, count);      if (n == -1 && errno == EINTR)	continue;      if (n == -1)	return -1;      count -= n;      actual += n;      buffer += n;    }  return actual;}int open_sf_source(const char *host, int port)/* Returns: file descriptor for serial forwarder at host:port */{  int fd = socket(AF_INET, SOCK_STREAM, 0);  struct hostent *entry;  struct sockaddr_in addr;  if (fd < 0)    return fd;  entry = gethostbyname(host);  if (!entry)    {      close(fd);      return -1;    }        addr.sin_family = entry->h_addrtype;  memcpy(&addr.sin_addr, entry->h_addr, entry->h_length);  addr.sin_port = htons(port);  if (connect(fd, (struct sockaddr *)&addr, sizeof addr) < 0)    {      close(fd);      return -1;    }  if (init_sf_source(fd) < 0)    {      close(fd);      return -1;    }  return fd;}extern uint32_t platform; int init_sf_source(int fd)/* Effects: Checks that fd is following the serial forwarder protocol     Sends 'platform' for protocol version '!', and sets 'platform' to     the received platform value.   Modifies: platform   Returns: 0 if it is, -1 otherwise */{  char check[2], us[2];  int version;  unsigned char nonce[4];  /* Indicate version and check if serial forwarder on the other end */  us[0] = 'T'; us[1] = '!';  if (safewrite(fd, us, 2) != 2 ||      saferead(fd, check, 2) != 2 ||      check[0] != 'T' || check[1] < ' ')    return -1;  version = check[1];  if (us[1] < version)    version = us[1];  switch (version)    {    case ' ': break;    case '!':       nonce[0] = platform;      nonce[1] = platform >>  8;      nonce[2] = platform >> 16;      nonce[3] = platform >> 24;      if (safewrite(fd, nonce, 4) != 4)	return -1;      if (saferead(fd, nonce, 4) != 4)	return -1;      //Unlike the more general SFProtocol.java this piece of code always knows what platform it is connected to; just   drop the preferred platform from the client//platform = nonce[0] | nonce[1] << 8 | nonce[2] << 16 | nonce[3] << 24;      break;    }  return 0;}void *read_sf_packet(int fd, int *len)/* Effects: reads packet from serial forwarder on file descriptor fd   Returns: the packet read (in newly allocated memory), and *len is     set to the packet length, or NULL for failure*/{  unsigned char l;  void *packet;  if (saferead(fd, &l, 1) != 1)    return NULL;  packet = malloc(l);  if (!packet)    return NULL;  if (saferead(fd, packet, l) != l)    {      free(packet);      return NULL;    }  *len = l;    return packet;}int write_sf_packet(int fd, const void *packet, int len)/* Effects: writes len byte packet to serial forwarder on file descriptor     fd   Returns: 0 if packet successfully written, -1 otherwise*/{  unsigned char l = len;  if (safewrite(fd, &l, 1) != 1 ||      safewrite(fd, packet, l) != l)    return -1;  return 0;}