fmtof(x) returns the format character of x:
  acid: +fmtof(33)
  W

fmtsize(x) returns the size in bytes of a single element of result's format:
  acid: +fmtsize(0\eX)
  4

Reference: /n/sources/patch/applied/acid.fmt-inspection
Date: Tue Jan 16 12:40:53 CET 2007
Signed-off-by: philip.dye@cs.cmu.edu

--- /sys/doc/acid.ms	Tue Jan 16 12:40:40 2007
+++ /sys/doc/acid.ms	Tue Jan 16 12:40:38 2007
@@ -1202,6 +1202,38 @@
 .\"
 .\"
 .\"
+.Ip fmt fmtof item "Get format
+.CW fmtof
+evaluates the expression
+.I item
+and returns the format of the result.
+.Ex
+acid: +fmtof(33)
+W
+acid: +fmtof("string")
+s
+.Ee
+.\"
+.\"
+.\"
+.Ip integer fmtsize item "Get format size
+.CW fmtsize
+evaluates the expression
+.I item
+and returns the size in bytes of a single element of result's format.
+.Ex
+acid: +fmtsize('c')
+8
+acid: +fmtsize('c'\ec)
+1
+acid: +fmtsize(0\eX)
+4
+acid: +fmtsize('c'\e3)
+10
+.Ee
+.\"
+.\"
+.\"
 .Ip list fnbound integer "Find start and end address of a function
 .CW fnbound
 interprets its
--- /sys/src/cmd/acid/builtin.c	Tue Jan 16 12:40:44 2007
+++ /sys/src/cmd/acid/builtin.c	Wed Jan 17 06:05:05 2007
@@ -40,6 +40,8 @@
 void	include(Node*, Node*);
 void	regexp(Node*, Node*);
 void	dosysr1(Node*, Node*);
+void	fmtof(Node*, Node*) ;
+void	dofmtsize(Node*, Node*) ;
 
 typedef struct Btab Btab;
 struct Btab
@@ -80,6 +82,8 @@
 	"interpret",	interpret,
 	"include",	include,
 	"regexp",	regexp,
+	"fmtof",	fmtof,
+	"fmtsize",	dofmtsize,
 	0
 };
 
@@ -1264,4 +1268,48 @@
 	if(p == 0)
 		error("pcline(addr): funny file %s", buf);
 	r->ival = strtol(p+1, 0, 0);	
+}
+
+void fmtof(Node *r, Node *args)
+{
+	Node *av[Maxarg];
+	Node res;
+
+	na = 0;
+	flatten(av, args);
+	if(na < 1)
+		error("fmtof(obj): no argument");
+	if(na > 1)
+		error("fmtof(obj): too many arguments") ;
+	expr(av[0], &res);
+
+	r->op = OCONST;
+	r->type = TINT ;
+	r->ival = res.fmt ;
+	r->fmt = 'c';
+}
+
+void dofmtsize(Node *r, Node *args)
+{
+	Node *av[Maxarg];
+	Node res;
+	Store * s ;
+	Value v ;
+
+	na = 0;
+	flatten(av, args);
+	if(na < 1)
+		error("fmtsize(obj): no argument");
+	if(na > 1)
+		error("fmtsize(obj): too many arguments") ;
+	expr(av[0], &res);
+
+	v.type = res.type ;
+	s = &v.Store ;
+	*s = res ;
+
+	r->op = OCONST;
+	r->type = TINT ;
+	r->ival = fmtsize(&v) ;
+	r->fmt = 'D';
 }
--- /sys/src/cmd/acid/acid.h	Tue Jan 16 12:40:49 2007
+++ /sys/src/cmd/acid/acid.h	Tue Jan 16 12:40:49 2007
@@ -53,8 +53,10 @@
 Extern List*	tracelist;
 Extern int	initialising;
 Extern int	quiet;
+
 extern void	(*expop[])(Node*, Node*);
 #define expr(n, r) (r)->comt=0; (*expop[(n)->op])(n, r);
+extern int	fmtsize(Value *v) ;
 
 enum
 {