rlSpawn Class Reference

#include <rlspawn.h>

Public Member Functions
	rlSpawn ()
virtual	~rlSpawn ()
int	spawn (const char *command)
const char *	readLine ()
int	getchar ()
int	select (int timeout=50)
int	writeString (const char *buf)
int	write (const char *buf, int len)
int	printf (const char *format,...)
void	printAll ()
FILE *	getFilepointer ()
int	sigkill ()
int	readJpegBuffer (unsigned char *buffer, int maxbuffer)

Public Attributes
int	pid

Private Attributes
HANDLE	toChildRD
HANDLE	toChildWR
HANDLE	fromChildRD
HANDLE	fromChildWR
HANDLE	hThread
HANDLE	hProcess
char	line [4096]

Detailed Description

Spawn an external program.
Redirect <stdin> <stdout> <stderr> of external program to this class

Now you can communicate with this external program over a pipe.
Attention: This class is only available on unix like systems.

Definition at line 40 of file rlspawn.h.

Constructor & Destructor Documentation

rlSpawn()

rlSpawn::rlSpawn

(

)

Definition at line 137 of file rlspawn.cpp.

{
#ifdef RLWIN32 
  fromChildRD = NULL;
  fromChildRD = NULL;
  toChildRD = NULL;
  toChildWR = NULL;
  hThread = NULL;
  hProcess = NULL;
  pid = 0;
#else  
  toChild = fromChild = NULL;
  pid = 0;
#endif  
}

~rlSpawn()

rlSpawn::~rlSpawn ( )

virtual

Definition at line 153 of file rlspawn.cpp.

{
#ifdef RLWIN32 
  if(fromChildRD != NULL) CloseHandle(fromChildRD);
  if(fromChildWR != NULL) CloseHandle(fromChildWR);
  if(toChildRD   != NULL) CloseHandle(toChildRD);
  if(toChildWR   != NULL) CloseHandle(toChildWR);
  if(hThread     != NULL) CloseHandle(hThread);
  if(hProcess    != NULL) CloseHandle(hProcess);
#else  
  if(toChild   != NULL) ::fclose((FILE*) toChild);
  if(fromChild != NULL) ::fclose((FILE*) fromChild);
#endif
}

Member Function Documentation

getchar()

int rlSpawn::getchar

(

)

Read a char from the spawned command.
When the command terminates EOF is returned.

Definition at line 355 of file rlspawn.cpp.

{
#ifdef RLWIN32
  if(fromChildRD == NULL) return EOF;
  DWORD readed = 0;
  unsigned char buf[4];
  int ret = (int) ReadFile(fromChildRD, buf, 1, &readed, NULL);
  if(ret)
  { // success
    if(readed == 1) return buf[0];
  }
  if(fromChildRD != NULL) CloseHandle(fromChildRD);
  if(fromChildWR != NULL) CloseHandle(fromChildWR);
  if(toChildRD   != NULL) CloseHandle(toChildRD);
  if(toChildWR   != NULL) CloseHandle(toChildWR);
  if(hThread     != NULL) CloseHandle(hThread);
  if(hProcess    != NULL) CloseHandle(hProcess);
  fromChildRD = NULL;
  fromChildWR = NULL;
  toChildRD   = NULL;
  toChildWR   = NULL;
  hThread     = NULL;
  hProcess    = NULL;
  return EOF;
#else
  if(fromChild == NULL) return EOF;
  return ::fgetc((FILE*) fromChild);
#endif  
}

getFilepointer()

FILE * rlSpawn::getFilepointer

(

)

Get FILE pointer fromChild

Definition at line 488 of file rlspawn.cpp.

{
#ifdef RLWIN32
  return NULL;
#else
  return (FILE *) fromChild;
#endif  
}

printAll()

void rlSpawn::printAll

(

)

Print all outputs from spawned command to <stdout>

Definition at line 450 of file rlspawn.cpp.

{
  const char *cptr;
  while((cptr=readLine()) != NULL) ::printf("%s",cptr);
}

printf()

int rlSpawn::printf	(	const char *	format,
			...
	)

similar to printf
Return: number of bytes written
        -1 error

Definition at line 402 of file rlspawn.cpp.

{
  int ret;
  char message[rl_PRINTF_LENGTH]; // should be big enough

  va_list ap;
  va_start(ap,format);
  ret = rlvsnprintf(message, rl_PRINTF_LENGTH - 1, format, ap);
  va_end(ap);
  if(ret < 0) return ret;
  return write(message,strlen(message));
}

readJpegBuffer()

int rlSpawn::readJpegBuffer	(	unsigned char *	buffer,
		int	maxbuffer
	)

Read JPEG buffer fromChild
return: length of buffer | -1 as error

Example: A thread continiously reads the mjpeg output of ffmpeg and stores it in jpegBuffer

rlThread mythread;
unsigned char jpegBuffer[256*256*16];

void *myThread(void *arg) // define your thread function
{
  rlSpawn spawn;

  restart:  
  if(arg == NULL) return NULL;

  THREAD_PARAM  *p = (THREAD_PARAM *) arg;
  //myThreadsData *d = (myThreadsData *) p->user;
  spawn.spawn("ffmpeg -f video4linux2 -i /dev/v4l/by-id/usb-046d_0825_A867B3D0-video-index0 -vf \"transpose, hflip" -r 10 -f mjpeg pipe:1");  
  while(p->running)
  {
    int ret = spawn.readJpegBuffer(jpegBuffer,sizeof(jpegBuffer));
    printf("ret=%d\n",ret);
    if(ret < 0) goto restart;
  }
  return arg;
}

Example: The jpegBuffer can now be Send to a Image Widget on the pvbrowser client

extern rlThread mythread;
extern unsigned char jpegBuffer[];

static int slotNullEvent(PARAM *p, DATA *d)
{
  if(p == NULL || d == NULL) return -1;
  pvSendJpegFrame(p,imgWebcam,jpegBuffer);
  return 0;
}

Definition at line 526 of file rlspawn.cpp.

{
  int c1, c2;

  // search for startOfImage ff d8
  while(1)
  {
    if((c1 = getchar()) < 0) return -1;
    if(c1 == 0x0ff)
    {
      if((c2 = getchar()) < 0) return -2;
      if(c2 == 0x0d8)
      {
        break;
      }
    }
  }

  int ind = 0;
  buffer[ind++] = (unsigned char) c1;
  buffer[ind++] = (unsigned char) c2;
  while(1) // read until endOfImage ff d9
  {
    if(ind >= maxbuffer) return -3;
    if((c1 = getchar()) < 0) return -4;
    buffer[ind++] = (unsigned char) c1;
    if(c1 == 0x0ff)
    {
      if((c2 = getchar()) < 0) return -5;
      buffer[ind++] = (unsigned char) c2;
      if(c2 == 0x0d9)
      {
        return ind;;
      }
    }
  }  
}

readLine()

const char * rlSpawn::readLine

(

)

Read a line from the spawned command.
When the command terminates NULL is returned.

Definition at line 307 of file rlspawn.cpp.

{
#ifdef RLWIN32
  char *cptr;
  if(fromChildRD == NULL) return NULL;
  int i,c;
  for(i=0; i < (int) sizeof(line) - 1; i++)
  {
    if((c = getchar()) < 0)
    {
      if(i==0) return NULL;
      line[i] = '\0';
      return line;
    }  
    line[i] = (char) c;
    if(c == '\n')
    {
      cptr = strchr(line,0x0d);
      if(cptr != NULL)
      {
        cptr[0] = '\n';
        cptr[1] = '\0';
        return line;
      }
      line[i+1] = '\0';
      return line;
    }
  }
  line[i] = '\0';
  return line;
#else
  if(fromChild == NULL) return NULL;
  if(::fgets(line,sizeof(line)-1,(FILE*) fromChild) == NULL)
  {
#ifdef RLUNIX
    if(pid != 0)
    {
      int status;
      waitpid(pid, &status, 0);
      kill(pid,SIGHUP);
    }
#endif
    return NULL;
  }
  return line;
#endif  
}

select()

int rlSpawn::select

(

int

timeout = 50

)

Wait for characters.
return = 0 // timeout
return = 1 // characters available

Definition at line 456 of file rlspawn.cpp.

{
#ifdef RLWIN32
  // windows does not support select on ReadFile
  // ReadFile will return if there are no more bytes available
  //if( _kbhit() ) return 1;
  if(1) return 1;
  if(timeout > 0)         return 0;
  if(fromChildRD == NULL) return 0;
  return 0;
#else
  struct timeval timout;
  fd_set wset,rset,eset;
  int    ret,maxfdp1,s;

  if(fromChild == NULL) return -1;
  s = fileno((FILE *) fromChild);
  /* setup sockets to read */
  maxfdp1 = s+1;
  FD_ZERO(&rset);
  FD_SET (s,&rset);
  FD_ZERO(&wset);
  FD_ZERO(&eset);
  timout.tv_sec  =  timeout / 1000;
  timout.tv_usec = (timeout % 1000) * 1000;

  ret = ::select(maxfdp1,&rset,&wset,&eset,&timout);
  if(ret == 0) return 0; /* timeout */
  return 1;
#endif  
}

sigkill()

int rlSpawn::sigkill

(

)

Kill process on other side of pipe

Definition at line 497 of file rlspawn.cpp.

{
#ifdef RLUNIX
  if(pid == -1) return -1;
  if(pid ==  0) return -1;
  kill(pid,SIGKILL);
  //printf("kill pid=%ld\n",m_pid);
#endif

#ifdef __VMS
  if(pid == -1) return -1;
  if(pid ==  0) return -1;
  kill(pid,SIGKILL);
#endif

#ifdef RLWIN32
  if(hProcess ==  0) return -1;
  TerminateProcess((HANDLE) hProcess, 0);
  WaitForSingleObject((HANDLE) hProcess, 60000);
  CloseHandle((HANDLE) hProcess);
  CloseHandle((HANDLE) hThread);
  hThread = 0;
  hProcess = 0;
#endif

  pid = 0;
  return 0;
}

spawn()

int rlSpawn::spawn

(

const char *

command

)

Start an operating system command.
The output from the command can be read with readLine()
You can write to the program with writeString() or write()
Return: 0=success -1=error

Definition at line 168 of file rlspawn.cpp.

{
#ifdef RLWIN32 
  if(fromChildRD != NULL) CloseHandle(fromChildRD);
  if(fromChildWR != NULL) CloseHandle(fromChildWR);
  if(toChildRD   != NULL) CloseHandle(toChildRD);
  if(toChildWR   != NULL) CloseHandle(toChildWR);
  if(hThread     != NULL) CloseHandle(hThread);
  if(hProcess    != NULL) CloseHandle(hProcess);
  fromChildRD = NULL;
  fromChildWR = NULL;
  toChildRD   = NULL;
  toChildWR   = NULL;
  hThread     = NULL;
  hProcess    = 0;

  SECURITY_ATTRIBUTES saAttr;
  saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
  saAttr.bInheritHandle = TRUE;
  saAttr.lpSecurityDescriptor = NULL;

  char cmd[strlen(command)+1];
  strcpy(cmd,command);

  if(!CreatePipe(&fromChildRD, &fromChildWR, &saAttr, 0))
  {
    printf("CreatePipe() - pipe for child process STDOUT failed\n");
    return -1;
  }
  if(!SetHandleInformation(fromChildRD, HANDLE_FLAG_INHERIT, 0)) // Ensure the read handle to the pipe for STDOUT is not inherited
  {
    printf("SetHandleInformation() - pipe STDOUT read handle failed for inheritance\n");
    CloseHandle(fromChildRD);
    fromChildRD = NULL;
    CloseHandle(fromChildWR);
    fromChildWR = NULL;
    return -2;
  }
  if(!CreatePipe(&toChildRD, &toChildWR, &saAttr, 0))
  {
    printf("CreatePipe() - pipe for child process STDIN failed\n");
    CloseHandle(fromChildRD);
    fromChildRD = NULL;
    CloseHandle(fromChildWR);
    fromChildWR = NULL;
    return -3;
  }
  if(!SetHandleInformation(toChildWR, HANDLE_FLAG_INHERIT, 0)) // Ensure the write handle to the pipe for STDIN is not inherited
  {
    printf("SetHandleInformation() - pipe STDIN write handle failed for inheritance\n");
    CloseHandle(fromChildRD);
    fromChildRD = NULL;
    CloseHandle(fromChildWR);
    fromChildWR = NULL;
    CloseHandle(toChildRD);
    toChildRD = NULL;
    CloseHandle(toChildWR);
    toChildWR = NULL;
    return -4;
  }  

  STARTUPINFO si; //  = { sizeof(si)};
  memset(&si,0,sizeof(si));
  si.cb = sizeof(si);
  si.hStdError  = fromChildWR;
  si.hStdOutput = fromChildWR;
  si.hStdInput  = toChildRD;
  si.dwFlags   |= STARTF_USESTDHANDLES;

  PROCESS_INFORMATION pi;
  memset(&pi,0,sizeof(pi));

  DWORD dwCreationFlags = 0;

  int ret = (int) CreateProcess( NULL, cmd
                                , NULL, NULL
                                , TRUE, dwCreationFlags
                                , NULL, NULL
                                , &si, &pi);
  if(ret)
  { // success
    hProcess = pi.hProcess;
    hThread  = pi.hThread;
    return 1;
  }
  // fail
  CloseHandle(fromChildRD);
  fromChildRD = NULL;
  CloseHandle(fromChildWR);
  fromChildWR = NULL;
  CloseHandle(toChildRD);
  toChildRD = NULL;
  CloseHandle(toChildWR);
  toChildWR = NULL;
  return -1;
#else  
  int to_child[2],from_child[2],ret;

  if(toChild   != NULL) ::fclose((FILE*) toChild);
  if(fromChild != NULL) ::fclose((FILE*) fromChild);
  toChild = fromChild = NULL;

  ret = ::pipe(to_child);
  if(ret == -1) return -1;
  ret = ::pipe(from_child);
  if(ret == -1) return -1;

  if((pid = ::fork()) == 0)
  {
    if(to_child[0] != 0) // stdin
    {
      ::dup2(to_child[0],0);
      ::close(to_child[0]);
    }
    if(from_child[1] != 2) // stderr
    {
      ::dup2(from_child[1] ,2);
    }
    if(from_child[1] != 1) // stdout
    {
      ::dup2(from_child[1],1);
      ::close(from_child[1]);
    }
    ::close(to_child[1]);
    ::close(from_child[0]);
    ::rlexec(command);
    ::exit(0);
  }

  ::close(to_child[0]);
  ::close(from_child[1]);
  toChild   = (void*) ::fdopen(to_child[1],"w");
  if(toChild == NULL)   {                            return -1; }
  fromChild = (void*) ::fdopen(from_child[0],"r");
  if(fromChild == NULL) { ::fclose((FILE*) toChild); return -1; }
  return pid;
#endif
}

write()

int rlSpawn::write	(	const char *	buf,
		int	len
	)

Write buf to <stdin> of spawned command
Return: number of bytes written
        -1 error

Definition at line 385 of file rlspawn.cpp.

{
#ifdef RLWIN32
  if(toChildWR == NULL) return -1;
  DWORD written = 0;
  int ret = (int) WriteFile(toChildWR, buf, len, &written, NULL);
  if(ret)
  { // success
    return written;
  }
  return -1;
#else  
  if(toChild == NULL) return -1;
  return ::write(fileno((FILE*)toChild),buf,len);
#endif
}

writeString()

int rlSpawn::writeString

(

const char *

buf

)

Write buf to <stdin> of spawned command
buf must be 0 terminated
Return: number of bytes written
        -1 error

Definition at line 415 of file rlspawn.cpp.

{
  if(buf[0] == EOF && buf[1] == '\0')
  {
#ifdef RLWIN32 
    if(fromChildRD != NULL) CloseHandle(fromChildRD);
    if(fromChildWR != NULL) CloseHandle(fromChildWR);
    if(toChildRD   != NULL) CloseHandle(toChildRD);
    if(toChildWR   != NULL) CloseHandle(toChildWR);
    if(hThread     != NULL) CloseHandle(hThread);
    if(hProcess    != NULL) CloseHandle(hProcess);
    fromChildRD = NULL;
    fromChildWR = NULL;
    toChildRD   = NULL;
    toChildWR   = NULL;
    hThread     = NULL;
    hProcess    = NULL;
#else  
    if(toChild   != NULL) ::fclose((FILE*) toChild);
    if(fromChild != NULL) ::fclose((FILE*) fromChild);
    toChild   = NULL;
    fromChild = NULL;
#endif
    return 0;
  } 
#ifdef RLWIN32
  if(toChildWR == NULL) return -1;
  int len = strlen(buf);
  return write(buf,len+1);
#else
  if(toChild == NULL) return -1;
  return fprintf((FILE*)toChild,"%s",buf);
#endif  
}

Member Data Documentation

fromChildRD

HANDLE rlSpawn::fromChildRD

private

Definition at line 159 of file rlspawn.h.

fromChildWR

HANDLE rlSpawn::fromChildWR

private

Definition at line 160 of file rlspawn.h.

hProcess

HANDLE rlSpawn::hProcess

private

Definition at line 162 of file rlspawn.h.

hThread

HANDLE rlSpawn::hThread

private

Definition at line 161 of file rlspawn.h.

line

char rlSpawn::line[4096]

private

Definition at line 166 of file rlspawn.h.

pid

int rlSpawn::pid

Definition at line 153 of file rlspawn.h.

toChildRD

HANDLE rlSpawn::toChildRD

private

Definition at line 157 of file rlspawn.h.

toChildWR

HANDLE rlSpawn::toChildWR

private

Definition at line 158 of file rlspawn.h.

---

The documentation for this class was generated from the following files:

• rlspawn.h
• rlspawn.cpp