main.m

#import <sys/socket.h>
#import <sys/un.h>

#import <unistd.h>
#import <fcntl.h>
#import <poll.h>

#define SOCKET_PATH "/var/run/lockdown/syslog.sock"

#define COLOR_RESET         "\e[m"
#define COLOR_NORMAL        "\e[0m"
#define COLOR_DARK          "\e[2m"
#define COLOR_RED           "\e[0;31m"
#define COLOR_DARK_RED      "\e[2;31m"
#define COLOR_GREEN         "\e[0;32m"
#define COLOR_DARK_GREEN    "\e[2;32m"
#define COLOR_YELLOW        "\e[0;33m"
#define COLOR_DARK_YELLOW   "\e[2;33m"
#define COLOR_BLUE          "\e[0;34m"
#define COLOR_DARK_BLUE     "\e[2;34m"
#define COLOR_MAGENTA       "\e[0;35m"
#define COLOR_DARK_MAGENTA  "\e[2;35m"
#define COLOR_CYAN          "\e[0;36m"
#define COLOR_DARK_CYAN     "\e[2;36m"
#define COLOR_WHITE         "\e[0;37m"
#define COLOR_DARK_WHITE    "\e[0;37m"



size_t atomicio(ssize_t (*f) (int, void *, size_t), int fd, void *_s, size_t n)
{
  char *s = _s;
  size_t pos = 0;
  ssize_t res;
  struct pollfd pfd;

  pfd.fd = fd;
  pfd.events = f == read ? POLLIN : POLLOUT;
  while (n > pos) {
    res = (f) (fd, s + pos, n - pos);
    switch (res) {
    case -1:
      if (errno == EINTR)
        continue;
      if ((errno == EAGAIN) || (errno == ENOBUFS)) {
        (void)poll(&pfd, 1, -1);
        continue;
      }
      return 0;
    case 0:
      errno = EPIPE;
      return pos;
    default:
      pos += (size_t)res;
    }
  }
  return (pos);
}

int unix_connect(char* path) {
  struct sockaddr_un sun;
  int s;

  if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
    return (-1);
  (void)fcntl(s, F_SETFD, 1);

  memset(&sun, 0, sizeof(struct sockaddr_un));
  sun.sun_family = AF_UNIX;

  if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= sizeof(sun.sun_path)) {
    close(s);
    errno = ENAMETOOLONG;
    return (-1);
  }
  if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
    close(s);
    return (-1);
  }

  return (s);
}

#define LINE_REGEX "(\\w+\\s+\\d+\\s+\\d+:\\d+:\\d+)\\s(\\S+|)\\s(.+)\\[(\\d+)\\]\\s+(?:\\(\\S+\\)\\s+)*\\<(\\w+)\\>:\\s(.*)"

ssize_t write_colored(int fd, void* buffer, size_t len) {

  char *escapedBuffer = malloc(len + 1);
  memcpy(escapedBuffer, buffer, len);
  escapedBuffer[len] = '\0';

  NSString *str = [NSString stringWithUTF8String:escapedBuffer];
  free(escapedBuffer);

  NSError *error = nil;
  NSRegularExpression *regex = [NSRegularExpression
                                  regularExpressionWithPattern:@LINE_REGEX
                                  options:NSRegularExpressionCaseInsensitive
                                  error:&error];

  NSArray *matches = [regex matchesInString:str
                            options:0
                            range:NSMakeRange(0, [str length])];

  if ([matches count] == 0)
    return write(fd, buffer, len);

  for (NSTextCheckingResult *match in matches) {

    if ([match numberOfRanges] < 6) {
      write(fd, buffer, len); // if entry doesn't match regex, print uncolored
      continue;
    }

    NSRange dateRange    =  [match rangeAtIndex:1];
    NSRange deviceRange  =  [match rangeAtIndex:2];
    NSRange processRange =  [match rangeAtIndex:3];
    NSRange pidRange     =  [match rangeAtIndex:4];
    NSRange typeRange    =  [match rangeAtIndex:5];
    NSRange logRange     =  [match rangeAtIndex:6];

    NSString *date       =  [str substringWithRange:dateRange];
    NSString *device     =  [str substringWithRange:deviceRange];
    NSString *process    =  [str substringWithRange:processRange];
    NSString *pid        =  [str substringWithRange:pidRange];
    NSString *type       =  [str substringWithRange:typeRange];
    NSString *log        =  [str substringWithRange:
                                  NSMakeRange(logRange.location,
                                              [str length] - logRange.location)];

    log = [log stringByTrimmingCharactersInSet:
                [NSCharacterSet newlineCharacterSet]];

    NSMutableString *build = [NSMutableString new];

    [build appendString:@COLOR_DARK_WHITE];
    [build appendString:date];
    [build appendString:@" "];
    [build appendString:device];
    [build appendString:@" "];

    [build appendString:@COLOR_CYAN];
    [build appendString:process];
    [build appendString:@"["];
    [build appendString:pid];
    [build appendString:@"]"];

    char *typeColor = COLOR_DARK_WHITE;
    char *darkTypeColor = COLOR_DARK_WHITE;

    if ([type isEqualToString:@"Notice"]) {
      typeColor = COLOR_GREEN;
      darkTypeColor = COLOR_DARK_GREEN;
    } else if ([type isEqualToString:@"Warning"]) {
      typeColor = COLOR_YELLOW;
      darkTypeColor = COLOR_DARK_YELLOW;
    } else if ([type isEqualToString:@"Error"]) {
      typeColor = COLOR_RED;
      darkTypeColor = COLOR_DARK_RED;
    } else if ([type isEqualToString:@"Debug"]) {
      typeColor = COLOR_MAGENTA;
      darkTypeColor = COLOR_DARK_MAGENTA;
    }

    [build appendString:@(darkTypeColor)];
    [build appendString:@" <"];
    [build appendString:@(typeColor)];
    [build appendString:type];
    [build appendString:@(darkTypeColor)];
    [build appendString:@">"];
    [build appendString:@COLOR_RESET];
    [build appendString:@": "];
    [build appendString:log];

    printf("%s\n", [build UTF8String]);
    [build release];
  }

  return len;
}

int main(int argc, char **argv, char **envp) {

  int nfd = unix_connect(SOCKET_PATH);

  // write "watch" command to socket to begin receiving messages
  write(nfd, "watch\n", 6);

  struct pollfd pfd[2];
  unsigned char buf[16384];
  int n = fileno(stdin);
  int lfd = fileno(stdout);
  int plen = 16384;

  pfd[0].fd = nfd;
  pfd[0].events = POLLIN;

  while (pfd[0].fd != -1) {

    if ((n = poll(pfd, 1, -1)) < 0) {
      close(nfd);
      perror("polling error");
      exit(1);
    }

    if (pfd[0].revents & POLLIN) {
      if ((n = read(nfd, buf, plen)) < 0)
        perror("read error"), exit(1); /* possibly not an error, just disconnection */
      else if (n == 0) {
        shutdown(nfd, SHUT_RD);
        pfd[0].fd = -1;
        pfd[0].events = 0;
      } else {
        if (atomicio(write_colored, lfd, buf, n) != n)
          perror("atomicio failure"), exit(1);
      }
    }
  }

  return 0;
}