From f2f3868e0d69c586d395dc9187e0ca99d5e47880 Mon Sep 17 00:00:00 2001
From: Denis Vlasenko <vda.linux@googlemail.com>
Date: Sat, 29 Mar 2008 17:26:10 +0000
Subject: [PATCH] mdev: optional support for regex pattern group substitution.
 +142 bytes.

---
 testsuite/mdev.tests | 17 +++++++++++++++++
 util-linux/Config.in |  7 +++++++
 util-linux/mdev.c    | 44 +++++++++++++++++++++++++++++++++++++++++---
 3 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/testsuite/mdev.tests b/testsuite/mdev.tests
index 777c5c540..81c440d1f 100755
--- a/testsuite/mdev.tests
+++ b/testsuite/mdev.tests
@@ -76,6 +76,23 @@ br--r--r-- 1 0 0 sda
 " \
 	"" ""
 
+# continuing to use directory structure from prev test
+rm -rf mdev.testdir/dev/*
+# here we complicate things by having non-matching group 1 and using %0
+echo "s([0-9])*d([a-z]+) 0:0 644 >sd/%2_%0" >mdev.testdir/etc/mdev.conf
+testing "mdev regexp substring match + replace" \
+	"env - ACTION=add DEVPATH=/block/sda chroot mdev.testdir /mdev 2>&1;
+	ls -lnR mdev.testdir/dev | $FILTER_LS2" \
+"\
+mdev.testdir/dev:
+drwxr-xr-x 2 0 0 sd
+lrwxrwxrwx 1 0 0 sda -> sd/a_sda
+
+mdev.testdir/dev/sd:
+brw-r--r-- 1 0 0 a_sda
+" \
+	"" ""
+
 # clean up
 rm -rf mdev.testdir
 
diff --git a/util-linux/Config.in b/util-linux/Config.in
index 1f4322bec..869ec61d5 100644
--- a/util-linux/Config.in
+++ b/util-linux/Config.in
@@ -321,6 +321,13 @@ config FEATURE_MDEV_RENAME
 
 	  For more information, please see docs/mdev.txt
 
+config FEATURE_MDEV_RENAME_REGEXP
+	bool "Support regular expressions substitutions when renaming device"
+	default n
+	depends on FEATURE_MDEV_RENAME
+	help
+	  Add support for regular expressions substitutions when renaming device.
+
 config FEATURE_MDEV_EXEC
 	bool "Support command execution at device addition/removal"
 	default n
diff --git a/util-linux/mdev.c b/util-linux/mdev.c
index c8d603bcf..9d77f6a1f 100644
--- a/util-linux/mdev.c
+++ b/util-linux/mdev.c
@@ -84,6 +84,8 @@ static void make_device(char *path, int delete)
 			goto end_parse;
 
 		while ((line = xmalloc_fgetline(fp)) != NULL) {
+			regmatch_t off[1+9*ENABLE_FEATURE_MDEV_RENAME_REGEXP];
+
 			++lineno;
 			trim(line);
 			if (!line[0])
@@ -95,16 +97,24 @@ static void make_device(char *path, int delete)
 			next = next_field(line);
 			{
 				regex_t match;
-				regmatch_t off;
 				int result;
 
 				/* Is this it? */
 				xregcomp(&match, line, REG_EXTENDED);
-				result = regexec(&match, device_name, 1, &off, 0);
+				result = regexec(&match, device_name, ARRAY_SIZE(off), off, 0);
 				regfree(&match);
 
+				//bb_error_msg("matches:");
+				//for (int i = 0; i < ARRAY_SIZE(off); i++) {
+				//	if (off[i].rm_so < 0) continue;
+				//	bb_error_msg("match %d: '%.*s'\n", i,
+				//		(int)(off[i].rm_eo - off[i].rm_so),
+				//		device_name + off[i].rm_so);
+				//}
+
 				/* If not this device, skip rest of line */
-				if (result || off.rm_so || off.rm_eo != strlen(device_name))
+				/* (regexec returns whole pattern as "range" 0) */
+				if (result || off[0].rm_so || off[0].rm_eo != strlen(device_name))
 					goto next_line;
 			}
 
@@ -152,7 +162,35 @@ static void make_device(char *path, int delete)
 				val = next;
 				next = next_field(val);
 				if (*val == '>') {
+#if ENABLE_FEATURE_MDEV_RENAME_REGEXP
+					/* substitute %1..9 with off[1..9], if any */
+					char *s, *p;
+					unsigned i, n;
+
+					n = 0;
+					s = val;
+					while (*s && *s++ == '%')
+						n++;
+					
+					p = alias = xzalloc(strlen(val) + n * strlen(device_name));
+					s = val + 1;
+					while (*s) {
+						*p = *s;
+						if ('%' == *s) {
+							i = (s[1] - '0');
+							if (i <= 9 && off[i].rm_so >= 0) {
+								n = off[i].rm_eo - off[i].rm_so;
+								strncpy(p, device_name + off[i].rm_so, n);
+								p += n - 1;
+								s++;
+							}
+						}
+						p++;
+						s++;
+					}
+#else
 					alias = xstrdup(val + 1);
+#endif
 				}
 			}