Re: [pacman-dev] [PATCH v4 5/5] be_package: Build the file list from MTREE if possible

2 Feb 2014

On 02.02.2014 12:13, Allan McRae wrote:
...
On 02/02/14 04:12, Florian Pritz wrote:
...
This greatly speeds up file list generation times by avoiding
uncompressing the whole package.
pacman -S base with a deliberate file conflict:
before: 9.1 seconds
after:  2.2 seconds
Signed-off-by: Florian Pritz 
---
v4:
- fix mem leak when cleaning up pkg->files
- make mtree_*size names a little more descriptive
- switch comments to c style
- break some long lines, there are still a few left..
- files starting with . are handled by handle_simple_path now
- pass the path directly to add_entry_to_files_list
- consolidate early breaking in main loop
NOT changed:
- ret for archive_read_next_header: copied from original code in
  _alpm_pkg_load_internal, if anyone cares feel free to change it later
- I didn't break all lines > 80 chars, that should probably be done in a
  line break cleanup only commit
lib/libalpm/be_package.c | 150 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 146 insertions(+), 4 deletions(-)

diff --git a/lib/libalpm/be_package.c b/lib/libalpm/be_package.c
index 393f436..ac52ae1 100644
--- a/lib/libalpm/be_package.c
+++ b/lib/libalpm/be_package.c
@@ -386,13 +386,36 @@ static int add_entry_to_files_list(alpm_pkg_t *pkg, size_t *files_size,
 {
  const size_t files_count = pkg->files.count;
  alpm_file_t *current_file;
+	mode_t type;
+	size_t pathlen;
if(!_alpm_realloc((void **)&pkg->files.files, files_size, (files_count + 1) * sizeof(alpm_file_t))) {
      return -1;
  }
+	type = archive_entry_filetype(entry);
+
+	pathlen = strlen(path);
+
  current_file = pkg->files.files + files_count;
-	STRDUP(current_file->name, path, return -1);
+
+	/* mtree paths don't contain a tailing slash, those we get from
+	 * the archive directly do (expensive way)
+	 * Other code relies on it to detect directories so add it here.*/
+	if(type == AE_IFDIR && path[pathlen - 1] != '/') {
+		/* 2 = 1 for / + 1 for \0 */
+		char *newpath = malloc(pathlen + 2);
+		if (!newpath) {
+			_alpm_alloc_fail(pathlen + 2);
+			return -1;
+		}
+		strcpy(newpath, path);
+		newpath[pathlen] = '/';
+		newpath[pathlen + 1] = '\0';
+		current_file->name = newpath;
+	} else {
+		STRDUP(current_file->name, path, return -1);
+	}
  current_file->size = archive_entry_size(entry);
  current_file->mode = archive_entry_mode(entry);
  pkg->files.count++;
@@ -400,6 +423,115 @@ static int add_entry_to_files_list(alpm_pkg_t *pkg, size_t *files_size,
 }
/**
+ * Generate a new file list from an mtree file and add it to the package.
+ * An existing file list will be free()d first.
+ *
+ * archive should point to an archive struct which is already at the
+ * position of the mtree's header.
+ *
+ * @param handle
+ * @param pkg package to add the file list to
+ * @param archive archive containing the mtree
+ * @return 0 on success, <0 on error
+ */
+static int build_filelist_from_mtree(alpm_handle_t *handle, alpm_pkg_t *pkg, struct archive *archive)
+{
+	int ret = 0;
+	size_t mtree_maxsize = 0;
+	size_t mtree_cursize = 0;
+	size_t files_size = 0; /* we clean up the existing array so this is fine */
+	char *mtree_data = NULL;
+	struct archive *mtree;
+	struct archive_entry *mtree_entry = NULL;
+
+	_alpm_log(handle, ALPM_LOG_DEBUG,
+			"found mtree for package %s, getting file list\n", pkg->filename);
+
+	/* throw away any files we might have already found */
+	for (size_t i = 0; i < pkg->files.count; i++) {
+		free(pkg->files.files[i].name);
+	}
+	free(pkg->files.files);
+	pkg->files.files = NULL;
+	pkg->files.count = 0;
+
+	/* create a new archive to parse the mtree and load it from archive into memory */
+	/* TODO: split this into a function */
+	if((mtree = archive_read_new()) == NULL) {
+		handle->pm_errno = ALPM_ERR_LIBARCHIVE;
+		goto error;
+	}
+
+	_alpm_archive_read_support_filter_all(mtree);
+	archive_read_support_format_mtree(mtree);
+
+	/* TODO: split this into a function */
+	while(1) {
+		ssize_t size;
+
+		if(!_alpm_realloc((void **)&mtree_data, &mtree_maxsize, mtree_cursize + ALPM_BUFFER_SIZE)) {
+			goto error;
+		}
+
+		size = archive_read_data(archive, mtree_data + mtree_cursize, ALPM_BUFFER_SIZE);
+
+		if(size < 0) {
+			_alpm_log(handle, ALPM_LOG_ERROR, _("error while reading package %s: %s\n"),
+					pkg->filename, archive_error_string(archive));
+			handle->pm_errno = ALPM_ERR_LIBARCHIVE;
+			goto error;
+		}
+		if(size == 0) {
+			break;
+		}
+
+		mtree_cursize += size;
+	}
+
+	/* TODO: need wrapper function for archive_read_open_memory for old libarchive versions? */
When did support for that function get added?
Seems like it's been there from the beginning of the git repo (2007) so
I guess I can remove that comment.
...
...
+	if(archive_read_open_memory(mtree, mtree_data, mtree_cursize)) {
+		_alpm_log(handle, ALPM_LOG_ERROR,
+				_("error while reading mtree of package %s: %s\n"),
+				pkg->filename, archive_error_string(mtree));
+		handle->pm_errno = ALPM_ERR_LIBARCHIVE;
+		goto error;
+	}
+
+	while((ret = archive_read_next_header(mtree, &mtree_entry)) == ARCHIVE_OK) {
+		const char *path = archive_entry_pathname(mtree_entry);
+
+		/* strip leading "./" from path entries */
+		if(path[0] == '.' && path[1] == '/') {
+			path += 2;
+		}
+
+		if(handle_simple_path(pkg, path)) {
+			continue;
+		}
+
+		if(add_entry_to_files_list(pkg, &files_size, mtree_entry, path) < 0) {
+			goto error;
+		}
+	}
+
+	if(ret != ARCHIVE_EOF && ret != ARCHIVE_OK) { /* An error occurred */
+		_alpm_log(handle, ALPM_LOG_ERROR, _("error while reading mtree of package %s: %s\n"),
+				pkg->filename, archive_error_string(mtree));
+		handle->pm_errno = ALPM_ERR_LIBARCHIVE;
+		goto error;
+	}
+
+	free(mtree_data);
+	_alpm_archive_read_free(mtree);
+	_alpm_log(handle, ALPM_LOG_DEBUG, "finished mtree reading for %s\n", pkg->filename);
+	return 0;
+error:
+	free(mtree_data);
+	_alpm_archive_read_free(mtree);
+	return -1;
+}
+
+/**
  * Load a package and create the corresponding alpm_pkg_t struct.
  * @param handle the context handle
  * @param pkgfile path to the package file
@@ -409,7 +541,7 @@ static int add_entry_to_files_list(alpm_pkg_t *pkg, size_t *files_size,
 alpm_pkg_t *_alpm_pkg_load_internal(alpm_handle_t *handle,
      const char *pkgfile, int full)
 {
-	int ret, fd, config = 0;
+	int ret, fd, config, hit_mtree = 0;
  struct archive *archive;
  struct archive_entry *entry;
  alpm_pkg_t *newpkg;
@@ -472,7 +604,17 @@ alpm_pkg_t *_alpm_pkg_load_internal(alpm_handle_t *handle,
      	continue;
      } else if(handle_simple_path(newpkg, entry_name)) {
      	continue;
handle_simple_path will return 1 if the file starts with a ".".
".MTREE" starts with a ".", so....
...
-		} else if(full) {
+		} else if(full && strcmp(entry_name, ".MTREE") == 0) {
... this can never happen.
Thanks, messed that up when rebasing some other changes.
...
...
+			/* building the file list: cheap way
+			 * get the filelist from the mtree file rather than scanning
+			 * the whole archive  */
+			if(build_filelist_from_mtree(handle, newpkg, archive) < 0) {
+				goto error;
+			}
+			hit_mtree = 1;
+			continue;
+		} else if(full && !hit_mtree) {
+			/* building the file list: expensive way */
      	if(add_entry_to_files_list(newpkg, &files_size, entry, entry_name) < 0) {
      		goto error;
      	}
@@ -486,7 +628,7 @@ alpm_pkg_t *_alpm_pkg_load_internal(alpm_handle_t *handle,
      }
/* if we are not doing a full read, see if we have all we need */
-		if(!full && config) {
+		if((!full || hit_mtree) && config) {
Why does hit_mtree matter here?  if(!full) we should never read the
mtree file.
hit_mtree matters because we want to break the loop once we have a file
list (if we need one), but only if we also have read .PKGINFO.

Since .MTREE could be before .PKGINFO in the tarball I can't break just
after reading the mtree.

Does that make sense?
...
...
break;
      }
  }


    