[pacman-dev] [PATCH 2/5] Add _alpm_filelist_resolve

[Allan McRae]

From: Andrew Gregory <andrew.gregory.8 at gmail.com>

The _alpm_filelist_resolve function takes a filelist and creates
a list with any symlinks in directory paths resolved.

Signed-off-by: Allan McRae <allan at archlinux.org>
---
 lib/libalpm/filelist.c | 156 +++++++++++++++++++++++++++++++++++++++++++++++++
 lib/libalpm/filelist.h |   2 +
 2 files changed, 158 insertions(+)

diff --git a/lib/libalpm/filelist.c b/lib/libalpm/filelist.c
index 1928056..d32a3e5 100644
--- a/lib/libalpm/filelist.c
+++ b/lib/libalpm/filelist.c
@@ -17,10 +17,166 @@
  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <limits.h>
 #include <string.h>
+#include <sys/stat.h>
 
 /* libalpm */
 #include "filelist.h"
+#include "util.h"
+
+/** Helper function for comparing strings when sorting */
+static int _strcmp(const void *s1, const void *s2)
+{
+	return strcmp(*(char **)s1, *(char **)s2);
+}
+
+/**
+ * @brief Resolves a symlink and its children.
+ *
+ * @attention Pre-condition: files must be sorted!
+ *
+ * @param files filelist to resolve
+ * @param i index in files to start processing
+ * @param path absolute path for the symlink being resolved
+ * @param root_len length of the root portion of path
+ * @param resolving is file \i in \files a symlink that needs to be resolved
+ *
+ * @return the index of the last file resolved
+ */
+size_t _alpm_filelist_resolve_link(
+		alpm_filelist_t *files, size_t i, char *path, size_t root_len, int resolving)
+{
+	struct stat sbuf;
+	const char *causal_dir; /* symlink being resolved */
+	char *filename_r; /* resolved filename */
+	size_t causal_dir_len = 0, causal_dir_r_len = 0;
+
+	if(resolving) {
+		/* deal with the symlink being resolved */
+		filename_r = malloc(PATH_MAX);
+		causal_dir = files->files[i].name;
+		causal_dir_len = strlen(causal_dir);
+		if(realpath(path, filename_r) == NULL) {
+			files->resolved_path[i] = strdup(causal_dir);
+			return i;
+		}
+		causal_dir_r_len = strlen(filename_r + root_len) + 1;
+		if(causal_dir_r_len >= PATH_MAX) {
+			files->resolved_path[i] = strdup(causal_dir);
+			return i;
+		}
+		/* remove root_r from filename_r */
+		memmove(filename_r, filename_r + root_len, causal_dir_r_len + 1);
+		strcpy(filename_r + causal_dir_r_len - 1, "/");
+		files->resolved_path[i] = strdup(filename_r);
+		i++;
+	}
+
+	for(; i < files->count && (!resolving ||
+				strncmp(files->files[i].name, causal_dir, causal_dir_len) == 0); i++) {
+		char *filename = files->files[i].name;
+		size_t f_len = strlen(filename);
+
+		if(resolving) {
+			if(f_len + causal_dir_r_len - causal_dir_len > PATH_MAX) {
+				files->resolved_path[i] = strdup(filename);
+				continue;
+			}
+
+			strcpy(filename_r + causal_dir_r_len, filename + causal_dir_len);
+
+			if(root_len + causal_dir_r_len + f_len - causal_dir_len > PATH_MAX) {
+				/* absolute path is too long */
+				files->resolved_path[i] = strdup(filename_r);
+				continue;
+			}
+		} else {
+			filename_r = filename;
+		}
+
+		/* deal with files and paths too long to resolve*/
+		if(filename[f_len-1] != '/') {
+			files->resolved_path[i] = strdup(filename_r);
+			continue;
+		}
+
+		/* construct absolute path and stat() */
+		strcpy(path + root_len, filename_r);
+		int exists = !_alpm_lstat(path, &sbuf);
+
+		/* deal with symlinks */
+		if(exists && S_ISLNK(sbuf.st_mode)) {
+			i = _alpm_filelist_resolve_link(files, i, path, root_len, 1);
+			continue;
+		}
+
+		/* deal with normal directories */
+		files->resolved_path[i] = strdup(filename_r);
+
+		/* deal with children of non-existent directories to reduce lstat() calls */
+		if (!exists) {
+			char *f;
+			i++;
+			while(i < files->count && strncmp(files->files[i].name, filename, f_len) == 0) {
+				f = files->files[i].name;
+				if(resolving && strlen(f + causal_dir_len) + causal_dir_r_len <= PATH_MAX) {
+					strcpy(filename_r + causal_dir_r_len, f + causal_dir_len);
+					files->resolved_path[i] = strdup(filename_r);
+				} else {
+					files->resolved_path[i] = strdup(f);
+				}
+				i++;
+			}
+			i--;
+		}
+	}
+
+	if(resolving) {
+		free(filename_r);
+	}
+
+	return i-1;
+}
+
+/**
+ * @brief Takes a file list and resolves all directory paths according to filesystem
+ *
+ * @attention Pre-condition: files must be sorted!
+ *
+ * @note A symlink and directory at the same path in two difference packages
+ * causes a conflict so the filepath can not change as packages get installed
+ *
+ * @param handle the context handle
+ * @param files list of files to resolve
+ */
+void _alpm_filelist_resolve(alpm_handle_t *handle, alpm_filelist_t *files)
+{
+	char path[PATH_MAX];
+	size_t root_len;
+
+	if(!files || files->resolved_path) {
+		return;
+	}
+
+	MALLOC(files->resolved_path, files->count * sizeof(char*), return);
+	memset(files->resolved_path, 0, files->count);
+
+	/* not much point in going on if we can't even resolve root */
+	if(realpath(handle->root, path) == NULL){
+		return;
+	}
+	root_len = strlen(path) + 1;
+	if(root_len >= PATH_MAX) {
+		return;
+	}
+	strcpy(path + root_len - 1, "/");
+
+	_alpm_filelist_resolve_link(files, 0, path, root_len, 0);
+
+	qsort(files->resolved_path, files->count, sizeof(char *), _strcmp);
+}
+
 
 /* Returns the difference of the provided two lists of files.
  * Pre-condition: both lists are sorted!
diff --git a/lib/libalpm/filelist.h b/lib/libalpm/filelist.h
index 2d5cbc0..3152b9d 100644
--- a/lib/libalpm/filelist.h
+++ b/lib/libalpm/filelist.h
@@ -21,6 +21,8 @@
 
 #include "alpm.h"
 
+size_t _alpm_filelist_resolve_link(alpm_filelist_t *files, size_t i, char *path, size_t root_len, int resolving);
+void _alpm_filelist_resolve(alpm_handle_t *handle, alpm_filelist_t *files);
 
 alpm_list_t *_alpm_filelist_difference(alpm_filelist_t *filesA,
 		alpm_filelist_t *filesB);
-- 
1.7.11.3