pcre2grep: correctly handle multiple passes (#35)

* tests: use a explicit filehandle to share in testing -m

The way stdin is shared to all participants of a subshell varies
per shell, and at least the standard /bin/sh in Solaris seem to
create a new copy for each command, defeating the purpose of the
test.

Use instead exec to create a filehandle that could then be used
explicitly in the test to confirm that the stream is set.

* pcre2grep: correctly handle multiple passes

When the -m option is used, pcre2grep is meant to exit after enough
matches are found but while leaving the stream pinned to the next position
after the last match.

Unfortunately, it wasn't tracking correctly the beginning of the stream
on subsequent passes, and therefore it will fail to use the right seek
value.

Grab the position of the stream at the beginning and while at it, make
sure that the stream passed hasn't been consumed already.

RunGrepTest

@@ -674,10 +674,14 @@ echo "---------------------------- Test 131 -----------------------------" >>tes
 echo "RC=$?" >>testtrygrep
 
 echo "---------------------------- Test 132 -----------------------------" >>testtrygrep
-(cd $srcdir; $valgrind $vjs $pcre2grep -m1 -A3 '^match'; echo '---'; head -1) <$srcdir/testdata/grepinput >>testtrygrep 2>&1
+(cd $srcdir; exec 3<$srcdir/testdata/grepinput; $valgrind $vjs $pcre2grep -m1 -A3 '^match' <&3; echo '---'; head -1 <&3; exec 3<&-) >>testtrygrep 2>&1
 echo "RC=$?" >>testtrygrep
 
 echo "---------------------------- Test 133 -----------------------------" >>testtrygrep
+(cd $srcdir; exec 3<$srcdir/testdata/grepinput; $valgrind $vjs $pcre2grep -m1 -A3 '^match' <&3; echo '---'; $valgrind $vjs $pcre2grep -m1 -A3 '^match' <&3; exec 3<&-) >>testtrygrep 2>&1
+echo "RC=$?" >>testtrygrep
+
+echo "---------------------------- Test 134 -----------------------------" >>testtrygrep
 (cd $srcdir; $valgrind $vjs $pcre2grep -m1 -O '=$x{41}$x423$o{103}$o1045=' 'fox') <$srcdir/testdata/grepinputv >>testtrygrep 2>&1
 echo "RC=$?" >>testtrygrep
 

src/pcre2grep.c

@@ -2538,6 +2538,7 @@ BOOL endhyphenpending = FALSE;
 BOOL lines_printed = FALSE;
 BOOL input_line_buffered = line_buffered;
 FILE *in = NULL;                    /* Ensure initialized */
+long stream_start = -1;             /* Only non-negative if relevant */
 
 /* Do the first read into the start of the buffer and set up the pointer to end
 of what we have. In the case of libz, a non-zipped .gz file will be read as a
@@ -2547,7 +2548,15 @@ fail. */
 if (frtype != FR_LIBZ && frtype != FR_LIBBZ2)
   {
   in = (FILE *)handle;
-  if (is_file_tty(in)) input_line_buffered = TRUE;
+  if (feof(in))
+    return 1;
+  if (is_file_tty(in))
+    input_line_buffered = TRUE;
+  else
+    {
+    if (count_limit >= 0  && filename == stdin_name)
+      stream_start = ftell(in);
+    }
   }
 else input_line_buffered = FALSE;
 
@@ -2594,8 +2603,8 @@ while (ptr < endptr)
 
   if (count_limit >= 0 && count_matched_lines >= count_limit)
     {
-    if (frtype == FR_PLAIN && filename == stdin_name && !is_file_tty(handle))
-      (void)fseek(handle, (long int)filepos, SEEK_SET);
+    if (stream_start >= 0)
+      (void)fseek(handle, stream_start + (long int)filepos, SEEK_SET);
     rc = (count_limit == 0)? 1 : 0;
     break;
     }

testdata/grepoutput

@@ -978,5 +978,16 @@ match 2:
  a
 RC=0
 ---------------------------- Test 133 -----------------------------
+match 1:
+ a
+match 2:
+ b
+---
+match 2:
+ b
+match 3:
+ c
+RC=0
+---------------------------- Test 134 -----------------------------
 =AB3CD5=
 RC=0