From: grembo <freebsd@grem.de>
Date: Mon, 11 Dec 2023 05:51:13 +0000 (+0100)
Subject: Add trailing letter b to bsdtar substitute pattern (#2012)
X-Git-Tag: v3.7.3~33
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0f410f8cfb512f1c7e36f01bd141f2e929281c26;p=thirdparty%2Flibarchive.git

Add trailing letter b to bsdtar substitute pattern (#2012)

The letter b stands for "from (b)eginning" and specifies that a
substitute expression should be matched from the beginning of the
string, regardless if and where a previous substitute expression
matched.

Example:
Transform filename from B-A to A-B and remove all underscores.

Attempt without option b:

    bsdtar -cft -s '/\(.*\)-\(.*\)/\2-\1/gp' -s "/_//g" ab_c-d_ef
    ab_c-d_ef >> d_ef-ab_c

With option b:

    bsdtar -cft -s '/\(.*\)-\(.*\)/\2-\1/gp' -s "/_//gb" ab_c-d_ef
    ab_c-d_ef >> def-abc
---

diff --git a/tar/bsdtar.1 b/tar/bsdtar.1
index c80952600..9a94bf761 100644
--- a/tar/bsdtar.1
+++ b/tar/bsdtar.1
@@ -23,7 +23,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd December 1, 2022
+.Dd December 10, 2023
 .Dt TAR 1
 .Os
 .Sh NAME
@@ -772,7 +772,7 @@ This works similar to the conv=sparse option of dd.
 Modify file or archive member names according to
 .Pa pattern .
 The pattern has the format
-.Ar /old/new/ Ns Op ghHprRsS
+.Ar /old/new/ Ns Op bghHprRsS
 where
 .Ar old
 is a basic regular expression,
@@ -794,6 +794,9 @@ of symbolic links.
 The optional trailing p specifies that after a successful substitution
 the original path name and the new path name should be printed to
 standard error.
+The optional trailing b specifies that the substitution should be
+matched from the beginning of the string rather than from right after the
+position at which the previous matching substitution ended.
 Optional trailing H, R, or S characters suppress substitutions
 for hardlink targets, regular filenames, or symlink targets,
 respectively.
diff --git a/tar/subst.c b/tar/subst.c
index 659c0b88f..9747abb90 100644
--- a/tar/subst.c
+++ b/tar/subst.c
@@ -49,7 +49,7 @@ struct subst_rule {
 	struct subst_rule *next;
 	regex_t re;
 	char *result;
-	unsigned int global:1, print:1, regular:1, symlink:1, hardlink:1;
+	unsigned int global:1, print:1, regular:1, symlink:1, hardlink:1, from_begin:1;
 };
 
 struct substitution {
@@ -129,9 +129,14 @@ add_substitution(struct bsdtar *bsdtar, const char *rule_text)
 	rule->regular = 1; /* Rewrite regular filenames. */
 	rule->symlink = 1; /* Rewrite symlink targets. */
 	rule->hardlink = 1; /* Rewrite hardlink targets. */
+	rule->from_begin = 0; /* Don't match from start. */
 
 	while (*++end_pattern) {
 		switch (*end_pattern) {
+		case 'b':
+		case 'B':
+			rule->from_begin = 1;
+			break;
 		case 'g':
 		case 'G':
 			rule->global = 1;
@@ -214,6 +219,7 @@ apply_substitution(struct bsdtar *bsdtar, const char *name, char **result,
 {
 	const char *path = name;
 	regmatch_t matches[10];
+	char* buffer = NULL;
 	size_t i, j;
 	struct subst_rule *rule;
 	struct substitution *subst;
@@ -239,6 +245,13 @@ apply_substitution(struct bsdtar *bsdtar, const char *name, char **result,
 				continue;
 		}
 
+		if (rule->from_begin && *result) {
+			realloc_strcat(result, name);
+			realloc_strcat(&buffer, *result);
+			name = buffer;
+			(*result)[0] = 0;
+		}
+
 		while (1) {
 			if (regexec(&rule->re, name, 10, matches, 0))
 				break;
@@ -278,6 +291,7 @@ apply_substitution(struct bsdtar *bsdtar, const char *name, char **result,
 				case '9':
 					realloc_strncat(result, rule->result + j, i - j - 1);
 					if ((size_t)(c - '0') > (size_t)(rule->re.re_nsub)) {
+						free(buffer);
 						free(*result);
 						*result = NULL;
 						return -1;
@@ -304,6 +318,8 @@ apply_substitution(struct bsdtar *bsdtar, const char *name, char **result,
 	if (got_match)
 		realloc_strcat(result, name);
 
+	free(buffer);
+
 	if (print_match)
 		fprintf(stderr, "%s >> %s\n", path, *result);
 
diff --git a/tar/test/test_option_s.c b/tar/test/test_option_s.c
index ed68ebf72..564793b97 100644
--- a/tar/test/test_option_s.c
+++ b/tar/test/test_option_s.c
@@ -87,6 +87,17 @@ DEFINE_TEST(test_option_s)
 	assertFileContents("foo", 3, "test4/in/d1/bar");
 	assertFileContents("bar", 3, "test4/in/d1/baz");
 
+	/*
+	 * Test 4b: Multiple substitutions behavior with option b).
+	 */
+	assertMakeDir("test4b", 0755);
+	systemf("%s -cf test4b.tar in/d1/foo in/d1/bar",
+	    testprog);
+	systemf("%s -xf test4b.tar -s /oo/ar/ -s }ar}az}b -C test4b",
+	    testprog);
+	assertFileContents("foo", 3, "test4b/in/d1/faz");
+	assertFileContents("bar", 3, "test4b/in/d1/baz");
+
 	/*
 	 * Test 5: Name-switching substitutions when extracting archive.
 	 */