readBin(what="character", n=overcount)->extra "" in result (PR#9361)

When I use readBin() to read an unknown number
of null-terminated strings from a file by supplying
an overcount as the n= argument, it appends an empty
string to the result.

tf<-tempfile()
strings<-c("One","Two","Three")
writeBin(strings, con=tf)
readBin(con=tf,what="character",n=100) # expect "One","Two","Three" only

[1] "One"   "Two"   "Three" ""

On Mon, 13 Nov 2006 bill at insightful.com wrote:

When I use readBin() to read an unknown number
of null-terminated strings from a file by supplying
an overcount as the n= argument, it appends an empty
string to the result.

tf<-tempfile()
strings<-c("One","Two","Three")
writeBin(strings, con=tf)
readBin(con=tf,what="character",n=100) # expect "One","Two","Three" only

[1] "One"   "Two"   "Three" ""

I think the fix is to src/library/connections.c, where
m (the number of items read) is initialized to 1 instead
of 0.  It is later used to shorten the vector of read
objects:
   if(m < n) {
       PROTECT(ans = lengthgets(ans, m));
       UNPROTECT(1);
   }

*** connections.c-orig	2006-09-13 19:05:06.000000000 -0700
--- connections.c	2006-11-13 11:46:35.000000000 -0800
***************
*** 2740,2746 ****
     if(!strcmp(what, "character")) {
 	SEXP onechar;
 	PROTECT(ans = allocVector(STRSXP, n));
! 	for(i = 0, m = i+1; i < n; i++) {
 	    onechar = isRaw ? rawOneString(bytes, nbytes, &np)
 		: readOneString(con);
 	    if(onechar != R_NilValue) {
--- 2740,2746 ----
     if(!strcmp(what, "character")) {
 	SEXP onechar;
 	PROTECT(ans = allocVector(STRSXP, n));
! 	for(i = 0, m = 0; i < n; i++) {
 	    onechar = isRaw ? rawOneString(bytes, nbytes, &np)
 		: readOneString(con);
 	    if(onechar != R_NilValue) {