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From 331328223912b66dd25d5cb6ed250d67419d54de Mon Sep 17 00:00:00 2001
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From: Michal Schmidt <mschmidt@redhat.com>
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Date: Mon, 16 Mar 2015 21:58:35 +0100
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Subject: [PATCH] shared: add path_compare(), an ordering path comparison
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... and make path_equal() a simple wrapper around it.
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(cherry picked from commit 2230852bd9755e1b7bfd1260082471f559b0a005)
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---
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 src/shared/path-util.c    | 37 +++++++++++++++++++++++++++----------
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 src/shared/path-util.h    |  1 +
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 src/test/test-path-util.c | 36 +++++++++++++++++++++++++-----------
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 3 files changed, 53 insertions(+), 21 deletions(-)
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diff --git a/src/shared/path-util.c b/src/shared/path-util.c
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index 70bc1ca..d5510bf 100644
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--- a/src/shared/path-util.c
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+++ b/src/shared/path-util.c
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@@ -403,12 +403,18 @@ char* path_startswith(const char *path, const char *prefix) {
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         }
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 }
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-bool path_equal(const char *a, const char *b) {
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+int path_compare(const char *a, const char *b) {
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+        int d;
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+
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         assert(a);
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         assert(b);
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-        if ((a[0] == '/') != (b[0] == '/'))
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-                return false;
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+        /* A relative path and an abolute path must not compare as equal.
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+         * Which one is sorted before the other does not really matter.
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+         * Here a relative path is ordered before an absolute path. */
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+        d = (a[0] == '/') - (b[0] == '/');
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+        if (d)
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+                return d;
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         for (;;) {
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                 size_t j, k;
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@@ -417,25 +423,36 @@ bool path_equal(const char *a, const char *b) {
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                 b += strspn(b, "/");
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                 if (*a == 0 && *b == 0)
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-                        return true;
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+                        return 0;
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-                if (*a == 0 || *b == 0)
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-                        return false;
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+                /* Order prefixes first: "/foo" before "/foo/bar" */
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+                if (*a == 0)
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+                        return -1;
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+                if (*b == 0)
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+                        return 1;
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                 j = strcspn(a, "/");
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                 k = strcspn(b, "/");
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-                if (j != k)
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-                        return false;
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+                /* Alphabetical sort: "/foo/aaa" before "/foo/b" */
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+                d = memcmp(a, b, MIN(j, k));
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+                if (d)
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+                        return (d > 0) - (d < 0); /* sign of d */
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-                if (memcmp(a, b, j) != 0)
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-                        return false;
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+                /* Sort "/foo/a" before "/foo/aaa" */
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+                d = (j > k) - (j < k);  /* sign of (j - k) */
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+                if (d)
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+                        return d;
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                 a += j;
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                 b += k;
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         }
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 }
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+bool path_equal(const char *a, const char *b) {
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+        return path_compare(a, b) == 0;
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+}
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+
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 bool path_equal_or_files_same(const char *a, const char *b) {
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         return path_equal(a, b) || files_same(a, b) > 0;
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 }
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diff --git a/src/shared/path-util.h b/src/shared/path-util.h
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index bcf116e..ca81b49 100644
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--- a/src/shared/path-util.h
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+++ b/src/shared/path-util.h
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@@ -44,6 +44,7 @@ char* path_make_absolute_cwd(const char *p);
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 int path_make_relative(const char *from_dir, const char *to_path, char **_r);
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 char* path_kill_slashes(char *path);
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 char* path_startswith(const char *path, const char *prefix) _pure_;
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+int path_compare(const char *a, const char *b) _pure_;
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 bool path_equal(const char *a, const char *b) _pure_;
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 bool path_equal_or_files_same(const char *a, const char *b);
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 char* path_join(const char *root, const char *path, const char *rest);
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diff --git a/src/test/test-path-util.c b/src/test/test-path-util.c
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index 11aa52a..6396fcb 100644
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--- a/src/test/test-path-util.c
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+++ b/src/test/test-path-util.c
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@@ -27,23 +27,37 @@
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 #include "macro.h"
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 #include "strv.h"
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+#define test_path_compare(a, b, result) {                 \
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+                assert_se(path_compare(a, b) == result);  \
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+                assert_se(path_compare(b, a) == -result); \
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+                assert_se(path_equal(a, b) == !result);   \
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+                assert_se(path_equal(b, a) == !result);   \
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+        }
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 static void test_path(void) {
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-        assert_se(path_equal("/goo", "/goo"));
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-        assert_se(path_equal("//goo", "/goo"));
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-        assert_se(path_equal("//goo/////", "/goo"));
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-        assert_se(path_equal("goo/////", "goo"));
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+        test_path_compare("/goo", "/goo", 0);
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+        test_path_compare("/goo", "/goo", 0);
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+        test_path_compare("//goo", "/goo", 0);
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+        test_path_compare("//goo/////", "/goo", 0);
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+        test_path_compare("goo/////", "goo", 0);
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+
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+        test_path_compare("/goo/boo", "/goo//boo", 0);
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+        test_path_compare("//goo/boo", "/goo/boo//", 0);
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-        assert_se(path_equal("/goo/boo", "/goo//boo"));
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-        assert_se(path_equal("//goo/boo", "/goo/boo//"));
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+        test_path_compare("/", "///", 0);
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-        assert_se(path_equal("/", "///"));
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+        test_path_compare("/x", "x/", 1);
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+        test_path_compare("x/", "/", -1);
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-        assert_se(!path_equal("/x", "x/"));
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-        assert_se(!path_equal("x/", "/"));
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+        test_path_compare("/x/./y", "x/y", 1);
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+        test_path_compare("x/.y", "x/y", -1);
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-        assert_se(!path_equal("/x/./y", "x/y"));
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-        assert_se(!path_equal("x/.y", "x/y"));
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+        test_path_compare("foo", "/foo", -1);
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+        test_path_compare("/foo", "/foo/bar", -1);
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+        test_path_compare("/foo/aaa", "/foo/b", -1);
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+        test_path_compare("/foo/aaa", "/foo/b/a", -1);
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+        test_path_compare("/foo/a", "/foo/aaa", -1);
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+        test_path_compare("/foo/a/b", "/foo/aaa", -1);
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         assert_se(path_is_absolute("/"));
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         assert_se(!path_is_absolute("./"));