Re: USE of CA lib: problem using ca_array_put_callback with strings

[haquin <haquin@ganil.fr>]

Sorry for the bad link,
here is the working one: 
http://lansce.lanl.gov/EPICSdata/ca/client/caX5Ftutor-1.html

You will find attached the C file we are using, it was reconstructed 
from the above link, Section 3 Writing to PVs and Using Connection Handlers.
the function call that doesn't work correctly is the "ca_put_callback" 
and the callback function is "an_event_handler"

We tryied with the command line, and we can reproduce the problem, here 
is the result:
[haquin@accep1 haquin]$ caput -c LB-DIA-ALB-TST2:Read_16bits_Reg.DESC 
"abcdefg"
Old : LB-DIA-ALB-TST2:Read_16bits_Reg.DESC It's 14-NOV-2008 16:52:23.04
New : LB-DIA-ALB-TST2:Read_16bits_Reg.DESC a
[haquin@accep1 haquin]$ caput LB-DIA-ALB-TST2:Read_16bits_Reg.DESC "abcdefg"
Old : LB-DIA-ALB-TST2:Read_16bits_Reg.DESC a
New : LB-DIA-ALB-TST2:Read_16bits_Reg.DESC abcdefg

Thanx

Andrew Johnson a Ãcrit :
> Hi Christophe,
>
> On Friday 14 November 2008 08:01:43 haquin wrote:
>   
> > I have some problems with the Channel Access library use,
> > more precisely the use of /*ca_array_put_callback*/ with STRINGS !
> >
> > We are using a peace of exemple C code, picked-up at :
> > *http://lansce.lanl.gov/EPICSdata/ca/client*, that uses this CA API.
> > We have some problems with the ca_array_put_callback when we want to
> > write strings.
> >     
>
> That URL doesn't work any more, can you post at least an extract of the code 
> that you're using, showing both the call to ca_array_put_callback() and your 
> callback routine.
>
>   
> > We use this code to put a string in the DESC field of a record,
> > The problem is that only the first caracter of the string is written to
> > the PV,
> > The callback is called, everything seem to bee correct except that there
> > is only the first caracter in the destination.
> >     
>
> I'm not able to recreate the problem on R3.14.10, so it may be a bug in the 
> code you're using (I'm not suggesting that you need to upgrade though, since 
> I'm not aware of any bug fixes in that area of the code).  The caput program 
> that comes with base has a -c option that means 'use put callback' and can 
> deal with arrays.  Here's how I tested it:
>
> tux% bin/linux-x86_64/caput -c anjHost:aiExample.DESC "New string"
> Old : anjHost:aiExample.DESC         Analog input
> New : anjHost:aiExample.DESC         New string
> tux% bin/linux-x86_64/caput -c -s -a anjHost:aiExample.DESC 1 "Array string"
> Old : anjHost:aiExample.DESC         New string
> New : anjHost:aiExample.DESC         Array string
>
> Note that the DESC field will only accept a 1-item array; if you try to send 
> more it will fail, demonstrating that caput is doing an array put:
>
> tux% bin/linux-x86_64/caput -c -s -a anjHost:aiExample.DESC 2 String array
> Old : anjHost:aiExample.DESC         Array string
> Write callback operation timed out
> New : anjHost:aiExample.DESC         Array string
>
> - Andrew
>   

#include <cadef.h>
#include <stdio.h>

#define MAXLEN  20
#define POLL 1.0e-9
#define SHRT_DLY 0.1
#define LNG_DLY 0.25

struct Channel{
  dbr_string_t name;
  chid chan;
  struct Channel *next;
  struct Channel *prev;} *pFirst = NULL, *pLast;

void connect_handler1(struct connection_handler_args);
void connect_handler2(struct connection_handler_args);
void an_event_handler(struct event_handler_args);
struct Channel *search(char *Name);
struct Channel *search(char *Name)
{
  struct Channel *pCurrent;
  int flag = 0;
  if(pFirst != NULL){
    for(pCurrent = pFirst; pCurrent != NULL; pCurrent = pCurrent->next){
      if(strcmp(pCurrent->name, Name) == 0){
	flag = 1;
	break;
      }
    }
  }
  if(flag)
    return (pCurrent);
  else
    return (NULL);
}
void an_event_handler(struct event_handler_args handler_args)
{
  
  if (handler_args.status != ECA_NORMAL){
    printf("channel %s: put operation not sucessful.\n",
	   ca_name(handler_args.chid));
    SEVCHK(handler_args.status, NULL);
  }
  else
    printf("channel %s: put operation completed.\n",
    ca_name(handler_args.chid)); 
  return;
}

void connect_handler1(struct connection_handler_args connect_args)
{
  struct Channel *pCurrent;

  /* set point to user-supplied address */
  pCurrent = ca_puser(connect_args.chid);

  /* if connection up, intialize list or add node */
  if(connect_args.op == CA_OP_CONN_UP){
    if(pFirst == NULL){
      pFirst = pCurrent;
      pFirst->prev = NULL;
      pLast = pCurrent;
    }
    pLast->next = pCurrent;
    pCurrent->prev = pLast;
    pCurrent->next = NULL;
    pLast = pCurrent;
    printf("%s is connected.\n", pCurrent->name);
  }
  /* if connection down, print message. This block */
  /*  is unlikely to ever be used.											        */
  else
    printf("%s is not connected.\n", pCurrent->name);
  return;
}
void connect_handler2(struct connection_handler_args connect_args)
{
  struct Channel *pCurrent;
  struct Channel *pPrevious, *pNext;

  /* if connection down, free memory of user       */
  /* supplied address, and delete nodes from list. */
  if (connect_args.op == CA_OP_CONN_DOWN){
    pCurrent = ca_puser(connect_args.chid);
    if(pCurrent != pLast && pCurrent != pFirst){
      pPrevious = pCurrent->prev;
      pNext = pCurrent->next;
      pPrevious->next = pNext;
      pNext->prev = pPrevious;
      free(pCurrent);
    }
    else if (pCurrent == pLast && pCurrent != pFirst){
      pLast = pCurrent->prev;
      pLast->next = NULL;
      free(pCurrent);
    }
    else if (pCurrent == pFirst && pCurrent != pLast){
      pFirst = pCurrent->next;
      pFirst->prev = NULL;
      free(pCurrent);
    }
    else if(pCurrent == pFirst && pCurrent == pLast){
      pFirst = NULL;
      pLast = NULL;
      free(pCurrent);
    }
    printf("%s: channel disconnected.\n", ca_name(connect_args.chid));
  }
  /* if re-connected, re-allocate memory */
  else if(connect_args.op == CA_OP_CONN_UP){
 strcpy(pCurrent->name, ca_name(connect_args.chid));
    pCurrent->chan = connect_args.chid;
    if (pFirst == NULL){
      pFirst = pCurrent;
      pFirst->prev = NULL;
      pLast = pCurrent;
      pCurrent->next = NULL;
    }
    else{
      pLast->next = pCurrent;
      pCurrent->prev = pLast;
      pCurrent->next = NULL;
      pLast = pCurrent;
    }
    printf("%s: channel re-connected.\n", pCurrent->name);
  }
  return;
}
int main()
{
  int status, i, j, k;
  dbr_float_t *pValue;
  dbr_string_t Value;
  dbr_string_t Name[MAXLEN];
  struct Channel *pCurrent;
  unsigned long Nelem; 

  /* initialize Channel Access task */
  SEVCHK(ca_task_initialize(), "Unable to initialize");

  /* Get channel names and establish connection for each.*/
  /* Allocate memory for first node, and then for each       */
  /* addtional node after connection is established. Loop   */
  /* until user enters"quit".											                     */
  for (printf("Enter a channel name.\n"),
	 pCurrent=(struct Channel *)calloc(1, sizeof(struct Channel));
       gets(pCurrent->name) != NULL && strcmp(pCurrent->name, "quit") != 0;
       printf("Enter a channel name or \"quit\" to stop.\n")){

    status = ca_search_and_connect(pCurrent->name, /* name string */
				   &(pCurrent->chan),/* chid */
				   connect_handler1, /* connection handler */
				   pCurrent      /* user-supplied address */ );
    SEVCHK(status, NULL);
    ca_pend_event(LNG_DLY);
    if (ca_state(pCurrent->chan) != cs_conn)
      printf("couldn't establish connection to %s; ignoring\n", pCurrent->name);
    else 
      pCurrent =(struct Channel *) calloc(1,sizeof(struct Channel));
  }

  /* Install a different connection handler on each channel. */
  if(pFirst != NULL){
    for (pCurrent = pFirst; pCurrent != NULL; pCurrent = pCurrent->next){
      status=ca_change_connection_event(pCurrent->chan, connect_handler2);
      SEVCHK(status, "ca_change_connection_event: couldn't change handler");
    }
	
    ca_flush_io();

    /* Loop until "quit" is entered. Get Channel name. If */
    /* found, prompt for values; else skip rest of loop.    */
    /* Call ca_put_callback().                                          */
    for (i = 0, printf("%s\n%s\n", "Enter the PV's name", "Enter \"quit\" to stop");
	 gets(Name) != NULL && strcmp(Name, "quit") !=0;
	 printf("%s\n", "Enter PV name or \"quit\" to stop")){

      ca_pend_event(POLL);
      pCurrent = search(Name);
      if(pCurrent == NULL){
	printf("Cannot find channel name in list. Disconnected?\n");
	continue;
      }
      Nelem = ca_element_count(pCurrent->chan);
      if(Nelem == 1){
	printf("Enter value.\n");
	if(gets(Value) != NULL){
	  status = ca_put_callback(DBR_STRING,   /* external type */
				   pCurrent->chan,                 /* chid */
				   Value,                  /* string of value */
				   an_event_handler,         /* callback */
				   pCurrent   /* user supplied address */);
	  SEVCHK(status, NULL);
	}
      }
      else if (Nelem > 1){
	printf("Enter up to %u values or q to quit.\n", Nelem);
	pValue = (float *) calloc(Nelem, sizeof(*pValue));
	for(k = 0; (j = scanf("%f", pValue+k)) == 1&& j != EOF && k < Nelem; k++)
	  ;
	j = getchar();
	status = ca_array_put_callback(DBR_FLOAT,      /* external type */
				       Nelem,  /* no. of elements to be sent */
				       pCurrent->chan,                       /* chid */
				       pValue,                    /* array of values */
				       an_event_handler,             /* callback */
				       pCurrent       /* user supplied address */ );
	SEVCHK(status, NULL);
      }
      ca_pend_event(SHRT_DLY);
    }
    return(0);
  }
}

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email;internet:haquin@ganil.fr
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