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-rw-r--r--unpack/optimize_unpack_order.c119
1 files changed, 119 insertions, 0 deletions
diff --git a/unpack/optimize_unpack_order.c b/unpack/optimize_unpack_order.c
new file mode 100644
index 0000000..a76dd51
--- /dev/null
+++ b/unpack/optimize_unpack_order.c
@@ -0,0 +1,119 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * optimize_unpack_order.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+#include "rdsquashfs.h"
+
+static bool has_fragment(const fstree_t *fs, const file_info_t *file)
+{
+ if (file->size % fs->block_size == 0)
+ return false;
+
+ return file->fragment_offset < fs->block_size &&
+ (file->fragment != 0xFFFFFFFF);
+}
+
+static int compare_files(const fstree_t *fs, const file_info_t *lhs,
+ const file_info_t *rhs)
+{
+ /* NOOP < everything else */
+ if (lhs->input_file == NULL)
+ return rhs->input_file == NULL ? 0 : -1;
+
+ if (rhs->input_file == NULL)
+ return 1;
+
+ /* Files with fragments come first, ordered by ID.
+ In case of tie, files without data blocks come first,
+ and the others are ordered by start block. */
+ if (has_fragment(fs, lhs)) {
+ if (!(has_fragment(fs, rhs)))
+ return -1;
+
+ if (lhs->fragment < rhs->fragment)
+ return -1;
+ if (lhs->fragment > rhs->fragment)
+ return 1;
+
+ if (lhs->size < fs->block_size)
+ return (rhs->size < fs->block_size) ? 0 : -1;
+ if (rhs->size < fs->block_size)
+ return 1;
+ goto order_by_start;
+ }
+
+ if (has_fragment(fs, rhs))
+ return 1;
+
+ /* order the rest by start block */
+order_by_start:
+ return lhs->startblock < rhs->startblock ? -1 :
+ lhs->startblock > rhs->startblock ? 1 : 0;
+}
+
+/* TODO: unify ad-hoc merge sort with the one in fstree_sort */
+static file_info_t *merge(const fstree_t *fs, file_info_t *lhs,
+ file_info_t *rhs)
+{
+ file_info_t *it;
+ file_info_t *head = NULL;
+ file_info_t **next_ptr = &head;
+
+ while (lhs != NULL && rhs != NULL) {
+ if (compare_files(fs, lhs, rhs) <= 0) {
+ it = lhs;
+ lhs = lhs->next;
+ } else {
+ it = rhs;
+ rhs = rhs->next;
+ }
+
+ *next_ptr = it;
+ next_ptr = &it->next;
+ }
+
+ it = (lhs != NULL ? lhs : rhs);
+ *next_ptr = it;
+ return head;
+}
+
+static file_info_t *list_sort(const fstree_t *fs, file_info_t *head)
+{
+ file_info_t *it, *half, *prev;
+
+ it = half = prev = head;
+ while (it != NULL) {
+ prev = half;
+ half = half->next;
+ it = it->next;
+ if (it != NULL) {
+ it = it->next;
+ }
+ }
+
+ // half refers to the (count/2)'th element ROUNDED UP.
+ // It will be null therefore only in the empty and the
+ // single element list
+ if (half == NULL) {
+ return head;
+ }
+
+ prev->next = NULL;
+
+ return merge(fs, list_sort(fs, head), list_sort(fs, half));
+}
+
+file_info_t *optimize_unpack_order(fstree_t *fs)
+{
+ file_info_t *file_list;
+
+ file_list = list_sort(fs, fs->files);
+ while (file_list != NULL && file_list->input_file == NULL)
+ file_list = file_list->next;
+
+ fs->files = NULL;
+ return file_list;
+}