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[PATCH v14 02/16] path.c: refactor relative_path(), not only strip prefix

From
Jiang Xin <worldhello.net@gmail.com>
Date
Jun 24, 2013, 15:21 UTC
Message-ID
<28a573cdde51da2f83a8692229fd360fec0e3783.1372087065.git.worldhello.net@gmail.com>
In-Reply-To
<cover.1372087065.git.worldhello.net@gmail.com>

Original design of relative_path() is simple, just strip the prefix (*base) from the absolute path (*abs). In most cases, we need a real relative path, such as: ../foo, ../../bar. That's why there is another reimplementation (path_relative()) in quote.c.

Borrowed some codes from path_relative() in quote.c to refactor relative_path() in path.c, so that it could return real relative path, and user can reuse this function without reimplement his/her own. The function path_relative() in quote.c will be substituted, and I would use the new relative_path() function when implement the interactive git-clean later.

Different results for relative_path() before and after this refactor:
    abs path  base path  relative (original)  relative (refactor)
    ========  =========  ===================  ===================
    /a/b/c/   /a/b       c/                   c/
    /a/b//c/  //a///b/   c/                   c/
    /a/b      /a/b       .                    ./
    /a/b/     /a/b       .                    ./
    /a        /a/b/      /a                   ../
    /         /a/b/      /                    ../../
    /a/c      /a/b/      /a/c                 ../c
    /a/b      (empty)    /a/b                 /a/b
    /a/b      (null)     /a/b                 /a/b
    (empty)   /a/b       (empty)              ./
    (null)    (empty)    (null)               ./
    (null)    /a/b       (segfault)           ./

You may notice that return value "." has been changed to "./". It is because:

 * Function quote_path_relative() in quote.c will show the relative
   path as "./" if abs(in) and base(prefix) are the same.
 * Function relative_path() is called only once (in setup.c), and
   it will be OK for the return value as "./" instead of ".".
Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 cache.h               |   2 +-
 path.c                | 112 +++++++++++++++++++++++++++++++++++++++-----------
 setup.c               |   5 ++-
 t/t0060-path-utils.sh |  27 ++++++------
 test-path-utils.c     |   4 +-
 5 files changed, 107 insertions(+), 43 deletions(-)
diff --git a/cache.h b/cache.h
index dd0fb..2f10c 100644
--- a/cache.h
+++ b/cache.h
@@ -758,7 +758,7 @@ int is_directory(const char *);
 const char *real_path(const char *path);
 const char *real_path_if_valid(const char *path);
 const char *absolute_path(const char *path);
-const char *relative_path(const char *abs, const char *base);
+const char *relative_path(const char *abs, const char *base, struct strbuf *sb);
 int normalize_path_copy(char *dst, const char *src);
 int longest_ancestor_length(const char *path, struct string_list *prefixes);
 char *strip_path_suffix(const char *path, const char *suffix);
diff --git a/path.c b/path.c
index 04ff..8ff16 100644
--- a/path.c
+++ b/path.c
@@ -441,42 +441,104 @@ int adjust_shared_perm(const char *path)
 	return 0;
 }
 
-const char *relative_path(const char *abs, const char *base)
+/*
+ * Give relative path for abs to base.
+ *
+ * The strbuf may or may not be used, so do not assume it contains the
+ * returned path.
+ */
+const char *relative_path(const char *abs, const char *base,
+			  struct strbuf *sb)
 {
-	static char buf[PATH_MAX + 1];
-	int i = 0, j = 0;
-
-	if (!base || !base[0])
+	int abs_off, base_off, i, j;
+	int abs_len, base_len;
+
+	abs_len = abs ? strlen(abs) : 0;
+	base_len = base ? strlen(base) : 0;
+	abs_off = 0;
+	base_off = 0;
+	i = 0;
+	j = 0;
+
+	if (!abs_len)
+		return "./";
+	else if (!base_len)
 		return abs;
-	while (base[i]) {
+
+	while (i < base_len && j < abs_len && base[i] == abs[j]) {
 		if (is_dir_sep(base[i])) {
-			if (!is_dir_sep(abs[j]))
-				return abs;
 			while (is_dir_sep(base[i]))
 				i++;
 			while (is_dir_sep(abs[j]))
 				j++;
-			continue;
-		} else if (abs[j] != base[i]) {
+			base_off = i;
+			abs_off = j;
+		} else {
+			i++;
+			j++;
+		}
+	}
+
+	if (
+	    /* base seems like prefix of abs */
+	    i >= base_len &&
+	    /*
+	     * but "/foo" is not a prefix of "/foobar"
+	     * (i.e. base not end with '/')
+	     */
+	    base_off < base_len) {
+		if (j >= abs_len) {
+			/* abs="/a/b", base="/a/b" */
+			abs_off = abs_len;
+		} else if (is_dir_sep(abs[j])) {
+			/* abs="/a/b/c", base="/a/b" */
+			while (is_dir_sep(abs[j]))
+				j++;
+			abs_off = j;
+		} else {
+			/* abs="/a/bbb/c", base="/a/b" */
+			i = base_off;
+		}
+	} else if (
+		   /* abs is short than base (prefix of base) */
+		   j >= abs_len &&
+		   /* abs not end with '/' */
+		   abs_off < abs_len) {
+		if (is_dir_sep(base[i])) {
+			/* abs="/a/b", base="/a/b/c/" */
+			while (is_dir_sep(base[i]))
+				i++;
+			abs_off = abs_len;
+		}
+	}
+	abs += abs_off;
+	abs_len -= abs_off;
+
+	if (i >= base_len) {
+		if (!abs_len)
+			return "./";
+		else
 			return abs;
+	}
+
+	strbuf_reset(sb);
+	strbuf_grow(sb, abs_len);
+
+	while (i < base_len) {
+		if (is_dir_sep(base[i])) {
+			strbuf_addstr(sb, "../");
+			while (is_dir_sep(base[i]))
+				i++;
+			continue;
 		}
 		i++;
-		j++;
 	}
-	if (
-	    /* "/foo" is a prefix of "/foo" */
-	    abs[j] &&
-	    /* "/foo" is not a prefix of "/foobar" */
-	    !is_dir_sep(base[i-1]) && !is_dir_sep(abs[j])
-	   )
-		return abs;
-	while (is_dir_sep(abs[j]))
-		j++;
-	if (!abs[j])
-		strcpy(buf, ".");
-	else
-		strcpy(buf, abs + j);
-	return buf;
+	if (!is_dir_sep(base[base_len - 1]))
+		strbuf_addstr(sb, "../");
+
+	strbuf_addstr(sb, abs);
+
+	return sb->buf;
 }
 
 /*
diff --git a/setup.c b/setup.c
index 94c1e..0d9ea 100644
--- a/setup.c
+++ b/setup.c
@@ -360,6 +360,7 @@ int is_inside_work_tree(void)
 
 void setup_work_tree(void)
 {
+	struct strbuf sb = STRBUF_INIT;
 	const char *work_tree, *git_dir;
 	static int initialized = 0;
 
@@ -379,8 +380,10 @@ void setup_work_tree(void)
 	if (getenv(GIT_WORK_TREE_ENVIRONMENT))
 		setenv(GIT_WORK_TREE_ENVIRONMENT, ".", 1);
 
-	set_git_dir(relative_path(git_dir, work_tree));
+	set_git_dir(relative_path(git_dir, work_tree, &sb));
 	initialized = 1;
+
+	strbuf_release(&sb);
 }
 
 static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 7e258..4deec 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -191,22 +191,19 @@ test_expect_success SYMLINKS 'real path works on symlinks' '
 relative_path /a/b/c/	/a/b/		c/
 relative_path /a/b/c/	/a/b		c/
 relative_path /a//b//c/	//a/b//		c/	POSIX
-relative_path /a/b	/a/b		.
-relative_path /a/b/	/a/b		.
-relative_path /a	/a/b		/a	POSIX
-relative_path /		/a/b/		/	POSIX
-relative_path /a/c	/a/b/		/a/c	POSIX
-relative_path /a/c	/a/b		/a/c	POSIX
+relative_path /a/b	/a/b		./
+relative_path /a/b/	/a/b		./
+relative_path /a	/a/b		../
+relative_path /		/a/b/		../../
+relative_path /a/c	/a/b/		../c
+relative_path /a/c	/a/b		../c
 relative_path /a/b	"<empty>"	/a/b	POSIX
 relative_path /a/b 	"<null>"	/a/b	POSIX
-relative_path "<empty>"	/a/b		"(empty)"
-relative_path "<empty>"	"<empty>"	"(empty)"
-relative_path "<empty>"	"<null>"	"(empty)"
-relative_path "<null>"	"<empty>"	"(null)"
-relative_path "<null>"	"<null>"	"(null)"
-
-test_expect_failure 'relative path: <null> /a/b => segfault' '
-	test-path-utils relative_path "<null>" "/a/b"
-'
+relative_path "<empty>"	/a/b		./
+relative_path "<empty>"	"<empty>"	./
+relative_path "<empty>"	"<null>"	./
+relative_path "<null>"	"<empty>"	./
+relative_path "<null>"	"<null>"	./
+relative_path "<null>"	/a/b		./
 
 test_done
diff --git a/test-path-utils.c b/test-path-utils.c
index dcc530..95ef4 100644
--- a/test-path-utils.c
+++ b/test-path-utils.c
@@ -117,14 +117,16 @@ int main(int argc, char **argv)
 	}
 
 	if (argc == 4 && !strcmp(argv[1], "relative_path")) {
+		struct strbuf sb = STRBUF_INIT;
 		const char *abs, *base, *rel;
 		normalize_argv_string(&abs, argv[2]);
 		normalize_argv_string(&base, argv[3]);
-		rel = relative_path(abs, base);
+		rel = relative_path(abs, base, &sb);
 		if (!rel)
 			puts("(null)");
 		else
 			puts(strlen(rel) > 0 ? rel : "(empty)");
+		strbuf_release(&sb);
 		return 0;
 	}
 

-- 
1.8.3.1.756.g41beab0
Previous: Jiang XinNext: Jiang Xin
Message 9 of 33 in “t0060: skip a few relative_path tests on Windows”
  1. t0060: skip a few relative_path tests on WindowsJohannes Sixt, Jun 13, 2013
  2. Jiang XinJun 13, 2013
  3. 00/16 Interactive git-cleanJiang Xin, Jun 24, 2013
  4. 01/16 test: add test cases for relative_pathJiang Xin, Jun 24, 2013
  5. Junio C HamanoJun 24, 2013
  6. Jiang XinJun 25, 2013
  7. Junio C HamanoJun 25, 2013
  8. Jiang XinJun 25, 2013
  9. 02/16 path.c: refactor relative_path(), not only strip prefixJiang Xin, Jun 24, 2013
  10. 03/16 quote.c: remove path_relative, use relative_path insteadJiang Xin, Jun 24, 2013
  11. Junio C HamanoJun 24, 2013
  12. Jiang XinJun 25, 2013
  13. Junio C HamanoJun 25, 2013
  14. 04/16 Refactor quote_path_relative, remove unused paramsJiang Xin, Jun 24, 2013
  15. Junio C HamanoJun 24, 2013
  16. Jiang XinJun 25, 2013
  17. 05/16 Refactor write_name_quoted_relative, remove unused paramsJiang Xin, Jun 24, 2013
  18. Junio C HamanoJun 24, 2013
  19. Jiang XinJun 25, 2013
  20. 06/16 git-clean: refactor git-clean into two phasesJiang Xin, Jun 24, 2013
  21. Junio C HamanoJun 24, 2013
  22. 07/16 git-clean: add support for -i/--interactiveJiang Xin, Jun 24, 2013
  23. 08/16 git-clean: show items of del_list in columnsJiang Xin, Jun 24, 2013
  24. 09/16 git-clean: add colors to interactive git-cleanJiang Xin, Jun 24, 2013
  25. 10/16 git-clean: use a git-add-interactive compatible UIJiang Xin, Jun 24, 2013
  26. 11/16 git-clean: add filter by pattern interactive actionJiang Xin, Jun 24, 2013
  27. 12/16 git-clean: add select by numbers interactive actionJiang Xin, Jun 24, 2013
  28. 13/16 git-clean: add ask each interactive actionJiang Xin, Jun 24, 2013
  29. 14/16 git-clean: add documentation for interactive git-cleanJiang Xin, Jun 24, 2013
  30. 15/16 test: add t7301 for git-clean--interactiveJiang Xin, Jun 24, 2013
  31. 16/16 test: run testcases with POSIX absolute paths on WindowsJiang Xin, Jun 24, 2013
  32. Johannes SixtJun 24, 2013
  33. Jiang XinJun 25, 2013

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