[pacman-dev] [PATCH] filelist_intersection: manually compare paths

[Andrew Gregory]

Prevents the need to modify paths, removing strndup as an unchecked
point of failure, and lengths only need to be calculated if the paths
match.

Also removed an old comment regarding directory/symlink compatibility.

Signed-off-by: Andrew Gregory <andrew.gregory.8 at gmail.com>
---
 lib/libalpm/filelist.c | 56 ++++++++++++++++++++------------------------------
 1 file changed, 22 insertions(+), 34 deletions(-)

diff --git a/lib/libalpm/filelist.c b/lib/libalpm/filelist.c
index 2d2426c..c41989c 100644
--- a/lib/libalpm/filelist.c
+++ b/lib/libalpm/filelist.c
@@ -61,6 +61,23 @@ alpm_list_t *_alpm_filelist_difference(alpm_filelist_t *filesA,
 	return ret;
 }
 
+static int _alpm_filelist_pathcmp(const char *p1, const char *p2)
+{
+	while(*p1 && *p1 == *p2) {
+		p1++;
+		p2++;
+	}
+
+	/* skip trailing '/' */
+	if(*p1 == '\0' && *p2 == '/') {
+		p2++;
+	} else if(*p2 == '\0' && *p1 == '/') {
+		p1++;
+	}
+
+	return *p1 - *p2;
+}
+
 /* Returns the intersection of the provided two lists of files.
  * Pre-condition: both lists are sorted!
  * When done, free the list but NOT the contained data.
@@ -70,52 +87,23 @@ alpm_list_t *_alpm_filelist_intersection(alpm_filelist_t *filesA,
 {
 	alpm_list_t *ret = NULL;
 	size_t ctrA = 0, ctrB = 0;
+	alpm_file_t *arrA = filesA->files, *arrB = filesB->files;
 
 	while(ctrA < filesA->count && ctrB < filesB->count) {
-		int cmp, isdirA, isdirB;
-		char *strA, *strB;
-
-		isdirA = 0;
-		strA = filesA->files[ctrA].name;
-		if(strA[strlen(strA)-1] == '/') {
-			isdirA = 1;
-			strA = strndup(strA, strlen(strA)-1);
-		}
-
-		isdirB = 0;
-		strB = filesB->files[ctrB].name;
-		if(strB[strlen(strB)-1] == '/') {
-			isdirB = 1;
-			strB = strndup(strB, strlen(strB)-1);
-		}
-
-		cmp = strcmp(strA, strB);
+		const char *strA = arrA[ctrA].name, *strB = arrB[ctrB].name;
+		int cmp = _alpm_filelist_pathcmp(strA, strB);
 		if(cmp < 0) {
 			ctrA++;
 		} else if(cmp > 0) {
 			ctrB++;
 		} else {
-			/* TODO: this creates conflicts between a symlink to a directory in
-			 * one package and a real directory in the other. For example,
-			 * lib -> /usr/lib in pkg1 and /lib in pkg2. This would be allowed
-			 * when installing one package at a time _provided_ pkg1 is installed
-			 * first. This will need adjusted if the order of package install can
-			 * be guaranteed to install the symlink first */
-
 			/* when not directories, item in both qualifies as an intersect */
-			if(! (isdirA && isdirB)) {
-				ret = alpm_list_add(ret, filesA->files[ctrA].name);
+			if(strA[strlen(strA) - 1] != '/' || strB[strlen(strB) - 1] != '/') {
+				ret = alpm_list_add(ret, arrA[ctrA].name);
 			}
 			ctrA++;
 			ctrB++;
 		}
-
-		if(isdirA) {
-			free(strA);
-		}
-		if(isdirB) {
-			free(strB);
-		}
 	}
 
 	return ret;
-- 
2.0.1