[pacman-dev] [PATCH] Enable Perl regular expressions in NoExtract.

[Patrick Steinhardt]

Until now it was not easily possible to remove all files but some
in a given directory. By enabling Perl regular expressions for
NoExtract this is now made possible through negative lookahead.

Fixes FS#31749.
---

This patch is work in progress. I want to check if there is
interest in having this feature available in pacman and how the
extra dependency on libpcre is received. If it is well received I
might still do some rework for the actual matching of NoExtract
items, as currently I'm always recompiling the pattern for each
match.

 configure.ac            | 13 ++++++++++++-
 lib/libalpm/Makefile.am |  6 ++++--
 lib/libalpm/add.c       |  2 +-
 lib/libalpm/util.c      | 22 ++++++++++++++++++++++
 lib/libalpm/util.h      |  1 +
 5 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/configure.ac b/configure.ac
index 1ea0fce..29ea101 100644
--- a/configure.ac
+++ b/configure.ac
@@ -230,6 +230,17 @@ if test "x$with_libcurl" != "xno"; then
 fi
 AM_CONDITIONAL(HAVE_LIBCURL, [test "$have_libcurl" = "yes"])
 
+# Check for PCRE
+have_libpcre=no
+if test "x$with_libpcre" != "xno"; then
+	PKG_CHECK_MODULES(LIBPCRE, [libpcre],
+		[AC_DEFINE(HAVE_LIBPCRE, 1, [Define if libpcre is available]) have_libpcre=yes], have_libpcre=no)
+	if test "x$have_libpcre" = xno -a "x$with_libpcre" = xyes; then
+		AC_MSG_ERROR([*** libpcre is required for file matching support])
+	fi
+fi
+AM_CONDITIONAL(HAVE_LIBPCRE, [test "$have_libpcre" = "yes"])
+
 # Check for gpgme
 AC_MSG_CHECKING(whether to link with libgpgme)
 AS_IF([test "x$with_gpgme" != "xno"],
@@ -523,7 +534,7 @@ ${PACKAGE_NAME}:
     compiler               : ${CC}
     preprocessor flags     : ${CPPFLAGS}
     compiler flags         : ${WARNING_CFLAGS} ${CFLAGS}
-    library flags          : ${LIBS} ${LIBSSL_LIBS} ${LIBARCHIVE_LIBS} ${LIBCURL_LIBS} ${GPGME_LIBS}
+    library flags          : ${LIBS} ${LIBSSL_LIBS} ${LIBPCRE_LIBS} ${LIBARCHIVE_LIBS} ${LIBCURL_LIBS} ${GPGME_LIBS}
     linker flags           : ${LDFLAGS}
 
     Architecture           : ${CARCH}
diff --git a/lib/libalpm/Makefile.am b/lib/libalpm/Makefile.am
index 171bc46..0f71aed 100644
--- a/lib/libalpm/Makefile.am
+++ b/lib/libalpm/Makefile.am
@@ -75,13 +75,15 @@ libalpm_la_CFLAGS = \
 	$(GPGME_CFLAGS) \
 	$(LIBARCHIVE_CFLAGS) \
 	$(LIBCURL_CFLAGS) \
-	$(LIBSSL_CFLAGS)
+	$(LIBSSL_CFLAGS) \
+	$(LIBPCRE_CFLAGS)
 
 libalpm_la_LIBADD = \
 	$(LTLIBINTL) \
 	$(GPGME_LIBS) \
 	$(LIBARCHIVE_LIBS) \
 	$(LIBCURL_LIBS) \
-	$(LIBSSL_LIBS)
+	$(LIBSSL_LIBS) \
+	$(LIBPCRE_LIBS)
 
 # vim:set ts=2 sw=2 noet:
diff --git a/lib/libalpm/add.c b/lib/libalpm/add.c
index c20e7c6..d80dbe4 100644
--- a/lib/libalpm/add.c
+++ b/lib/libalpm/add.c
@@ -183,7 +183,7 @@ static int extract_single_file(alpm_handle_t *handle, struct archive *archive,
 	}
 
 	/* if a file is in NoExtract then we never extract it */
-	if(alpm_list_find(handle->noextract, entryname, _alpm_fnmatch)) {
+	if(alpm_list_find(handle->noextract, entryname, _alpm_regex)) {
 		_alpm_log(handle, ALPM_LOG_DEBUG, "%s is in NoExtract,"
 				" skipping extraction of %s\n",
 				entryname, filename);
diff --git a/lib/libalpm/util.c b/lib/libalpm/util.c
index f84fb66..5858d28 100644
--- a/lib/libalpm/util.c
+++ b/lib/libalpm/util.c
@@ -33,6 +33,7 @@
 #include <sys/wait.h>
 #include <locale.h> /* setlocale */
 #include <fnmatch.h>
+#include <pcre.h>
 
 /* libarchive */
 #include <archive.h>
@@ -1261,6 +1262,27 @@ int _alpm_fnmatch(const void *pattern, const void *string)
 	return fnmatch(pattern, string, 0);
 }
 
+/** Checks whether a string matches an extended Perl regular expression.
+ * @param pattern string to match against
+ * @param string string to check against pattern
+ * @return 0 if string matches pattern, non-zero if they don't match and on
+ * error
+ */
+int _alpm_regex(const void *pattern, const void *string)
+{
+	const char *error;
+	int erroroff;
+
+	pcre *pcre = pcre_compile(pattern, PCRE_EXTENDED | PCRE_ANCHORED, &error, &erroroff, NULL);
+	if (error != NULL) {
+		return -1;
+	}
+
+	int ret = pcre_exec(pcre, NULL, string, strlen(string), 0, 0, NULL, 0);
+	pcre_free(pcre);
+	return ret < 0;
+}
+
 void _alpm_alloc_fail(size_t size)
 {
 	fprintf(stderr, "alloc failure: could not allocate %zd bytes\n", size);
diff --git a/lib/libalpm/util.h b/lib/libalpm/util.h
index 56031f3..5ec36b6 100644
--- a/lib/libalpm/util.h
+++ b/lib/libalpm/util.h
@@ -141,6 +141,7 @@ int _alpm_raw_cmp(const char *first, const char *second);
 int _alpm_raw_ncmp(const char *first, const char *second, size_t max);
 int _alpm_access(alpm_handle_t *handle, const char *dir, const char *file, int amode);
 int _alpm_fnmatch(const void *pattern, const void *string);
+int _alpm_regex(const void *pattern, const void *string);
 
 #ifndef HAVE_STRSEP
 char *strsep(char **, const char *);
-- 
1.8.3

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