From 5d06d08e734fe734c4a9189071f394ad6e9ccaac Mon Sep 17 00:00:00 2001
From: Malcolm Beattie <mbeattie@sable.ox.ac.uk>
Date: Thu, 11 Dec 1997 11:54:41 +0000
Subject: Stop tr/// from writing to target when only counting.

p4raw-id: //depot/perl@359
---
 doop.c | 12 ++++++++++--
 op.c   |  5 ++++-
 op.h   |  1 +
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/doop.c b/doop.c
index 277f46ef7a..be3e674109 100644
--- a/doop.c
+++ b/doop.c
@@ -31,7 +31,7 @@ do_trans(SV *sv, OP *arg)
     register I32 squash = op->op_private & OPpTRANS_SQUASH;
     STRLEN len;
 
-    if (SvREADONLY(sv))
+    if (SvREADONLY(sv) && !(op->op_private & OPpTRANS_COUNTONLY))
 	croak(no_modify);
     tbl = (short*)cPVOP->op_pv;
     s = (U8*)SvPV(sv, len);
@@ -52,6 +52,14 @@ do_trans(SV *sv, OP *arg)
 	    }
 	    s++;
 	}
+	SvSETMAGIC(sv);
+    }
+    else if (op->op_private & OPpTRANS_COUNTONLY) {
+	while (s < send) {
+	    if (tbl[*s] >= 0)
+		matches++;
+	    s++;
+	}
     }
     else {
 	d = s;
@@ -74,8 +82,8 @@ do_trans(SV *sv, OP *arg)
 	matches += send - d;	/* account for disappeared chars */
 	*d = '\0';
 	SvCUR_set(sv, d - (U8*)SvPVX(sv));
+	SvSETMAGIC(sv);
     }
-    SvSETMAGIC(sv);
     return matches;
 }
 
diff --git a/op.c b/op.c
index a922a2bf86..c6e1cfe41d 100644
--- a/op.c
+++ b/op.c
@@ -1993,12 +1993,13 @@ pmtrans(OP *o, OP *expr, OP *repl)
     register I32 j;
     I32 Delete;
     I32 complement;
+    I32 squash;
     register short *tbl;
 
     tbl = (short*)cPVOPo->op_pv;
     complement	= o->op_private & OPpTRANS_COMPLEMENT;
     Delete	= o->op_private & OPpTRANS_DELETE;
-    /* squash	= o->op_private & OPpTRANS_SQUASH; */
+    squash	= o->op_private & OPpTRANS_SQUASH;
 
     if (complement) {
 	Zero(tbl, 256, short);
@@ -2022,6 +2023,8 @@ pmtrans(OP *o, OP *expr, OP *repl)
     else {
 	if (!rlen && !Delete) {
 	    r = t; rlen = tlen;
+	    if (!squash)
+		o->op_private |= OPpTRANS_COUNTONLY;
 	}
 	for (i = 0; i < 256; i++)
 	    tbl[i] = -1;
diff --git a/op.h b/op.h
index 471ace0760..a203c44639 100644
--- a/op.h
+++ b/op.h
@@ -95,6 +95,7 @@ typedef U32 PADOFFSET;
 #define OPpRUNTIME		64	/* Pattern coming in on the stack */
 
 /* Private for OP_TRANS */
+#define OPpTRANS_COUNTONLY	8
 #define OPpTRANS_SQUASH		16
 #define OPpTRANS_DELETE		32
 #define OPpTRANS_COMPLEMENT	64
-- 
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