Experimental Physics and
Industrial Control System

On Thu, 2010-08-19 at 21:03 -0700, Eric Norum wrote:
> Have a look at 'postfix()' and 'calcPerform()' in the appDevGuide.
> 

Perfect! Here's a new version of the patch, bit less trivial, that uses
postfix() and calcPerform(). Now you can use any CALC-compatible
expression for the mask, provided that it doesn't contain whitespace,
commas, or parentheses.

I normally try not to commit code on Friday afternoons, but this patch
is pretty simple so I think I'm safe. ;)

- Angus

Slightly O/T: Having now encountered various pieces of parser code in
EPICS, it seems to me that many places in the framework would benefit
from using a tokenizer/parser framework. It seems like a few standard
syntaxes could be applied to most of the parsing done around the place.
Of course I know that's quite a big job. I wish I had time to volunteer
to try and implement it, but I thought I'd mention it as a talking point
anyway because it's been bothering me. :).

Index: asyn/devEpics/asynEpicsUtils.c
===================================================================
--- asyn/devEpics/asynEpicsUtils.c	(revision 21)
+++ asyn/devEpics/asynEpicsUtils.c	(working copy)
@@ -26,6 +26,7 @@
 #include <shareLib.h>
 #include "asynEpicsUtils.h"
 #include <epicsExport.h>
+#include <postfix.h>
 
 static asynStatus parseLink(asynUser *pasynUser, DBLINK *plink, 
                    char **port, int *addr, char **userParam);
@@ -155,7 +156,42 @@
     }
     return(asynSuccess);
 }
-
+
+
+// Scan a value for a bitmask, which can be any CALC-compatible value
+// that does not contain whitespace, commas or parentheses
+epicsUInt32 scanMaskValue(char *start, char **end)
+{
+	// find the end of this expression
+	*end = start;
+	while(!isspace(**end) && **end != 0 && **end != ')' && **end != ',') (*end)++;	
+
+	// Make a temporary complete infix string from start to end
+	char endChar = **end;
+	**end = 0;
+
+	// Build the postfix expression
+	char pfix[INFIX_TO_POSTFIX_SIZE(strlen(start)+1)];
+	short error;
+	long res = postfix(start, pfix, &error);
+
+	**end = endChar; // fix the source string back up
+	if(res) {
+		errno = EINVAL;
+		return 0;
+	}
+	
+	double result;
+	res = calcPerform(NULL, &result, pfix);
+	if(res) {
+		errno = EINVAL;
+		return 0;
+	}
+
+	errno=0;
+	return (epicsUInt32) result;
+}
+
 static asynStatus parseLinkMask(asynUser *pasynUser, DBLINK *plink, 
                    char **port, int *addr, epicsUInt32 *mask,char **userParam)
 {
@@ -196,7 +232,7 @@
     pnext = skipWhite(pnext,1);
     if(*pnext==0 || *pnext==')') goto error;
     errno = 0;
-    *mask = strtoul(pnext,&endp,0);
+    *mask = scanMaskValue(pnext, &endp);
     if(errno) goto error;
     /*next is timeout*/
     pnext = endp;
Index: documentation/asynDriver.html
===================================================================
--- documentation/asynDriver.html	(revision 21)
+++ documentation/asynDriver.html	(working copy)
@@ -3933,7 +3933,11 @@
     interface asynUInt32Digital. The INP or OUT field must define asynMask. The mask
     specified in the argument to asynMask is used in the calls to asynUInt32Digital
     methods. In addition it is used to set the mask fields in bi and bo records and
-    the mask and shft fields in mbbi, mbbo, mbbiDirect, and mbboDirect records.</p>
+    the mask and shft fields in mbbi, mbbo, mbbiDirect, and mbboDirect records. Mask
+    values can be specified as decimal or hexadecimal integers, or simple mathematical
+    expressions like 1<<9, 1+2, or ~0x3. Acceptable mask expressions are any that 
+    would be accepted by the CALC record, provided they contain no whitespace, commas 
+    or parentheses.)</p>
   <ul>
     <li>biRecord
       <p>
@@ -3992,7 +3996,7 @@
     Binary Output Example Record</p>
   <pre>record(bo,"boUInt32Bit2") {
     field(DTYP,"asynUInt32Digital")
-    field(OUT,"@asynMask( $(port) , 0, 0x4 , 1.0) ")
+    field(OUT,"@asynMask( $(port) , 0, 1<<2 , 1.0) ")
     field(ZNAM,"zero")
     field(ONAM,"one")
 }</pre>

References:

Small patch for asynMask bitmask values Angus Gratton

Re: Small patch for asynMask bitmask values Eric Norum

Re: Small patch for asynMask bitmask values Angus Gratton

Re: Small patch for asynMask bitmask values Eric Norum

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