pg_waldump: Allow hexadecimal values for -t/--timeline option

This makes it easier to specify values taken directly from WAL file
names.

The option parsing is arranged in the style of option_parse_int() (but
we need to parse unsigned int), to allow future refactoring in the
same manner.

Reviewed-by: Sébastien Lardière <sebastien@lardiere.net>
Discussion: https://www.postgresql.org/message-id/flat/8fef346e-2541-76c3-d768-6536ae052993@lardiere.net

doc/src/sgml/ref/pg_waldump.sgml

@@ -215,7 +215,8 @@ PostgreSQL documentation
        <para>
         Timeline from which to read WAL records. The default is to use the
         value in <replaceable>startseg</replaceable>, if that is specified; otherwise, the
-        default is 1.
+        default is 1.  The value can be specified in decimal or hexadecimal,
+        for example <literal>17</literal> or <literal>0x11</literal>.
        </para>
       </listitem>
      </varlistentry>

src/bin/pg_waldump/pg_waldump.c

@@ -13,6 +13,7 @@
 #include "postgres.h"
 
 #include <dirent.h>
+#include <limits.h>
 #include <signal.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ -1007,12 +1008,40 @@ main(int argc, char **argv)
 					private.startptr = (uint64) xlogid << 32 | xrecoff;
 				break;
 			case 't':
-				if (sscanf(optarg, "%u", &private.timeline) != 1)
+
+				/*
+				 * This is like option_parse_int() but needs to handle
+				 * unsigned 32-bit int.  Also, we accept both decimal and
+				 * hexadecimal specifications here.
+				 */
 				{
-					pg_log_error("invalid timeline specification: \"%s\"", optarg);
-					goto bad_argument;
+					char	   *endptr;
+					unsigned long val;
+
+					errno = 0;
+					val = strtoul(optarg, &endptr, 0);
+
+					while (*endptr != '\0' && isspace((unsigned char) *endptr))
+						endptr++;
+
+					if (*endptr != '\0')
+					{
+						pg_log_error("invalid value \"%s\" for option %s",
+									 optarg, "-t/--timeline");
+						goto bad_argument;
+					}
+
+					if (errno == ERANGE || val < 1 || val > UINT_MAX)
+					{
+						pg_log_error("%s must be in range %u..%u",
+									 "-t/--timeline", 1, UINT_MAX);
+						goto bad_argument;
+					}
+
+					private.timeline = val;
+
+					break;
 				}
-				break;
 			case 'w':
 				config.filter_by_fpw = true;
 				break;