btrfs-progs: add sorting API

Signed-off-by: David Sterba <dsterba@suse.com>

Makefile

@@ -211,6 +211,7 @@ objects = \
 	common/rbtree-utils.o	\
 	common/send-stream.o	\
 	common/send-utils.o	\
+	common/sort-utils.o	\
 	common/string-table.o	\
 	common/string-utils.o	\
 	common/task-utils.o \

common/sort-utils.c

@@ -0,0 +1,57 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <strings.h>
+#include <string.h>
+#include "common/sort-utils.h"
+
+int compare_init(struct compare *comp, const struct sortdef *sortdef)
+{
+	memset(comp, 0, sizeof(struct compare));
+	comp->sortdef = sortdef;
+	return 0;
+}
+
+int compare_cmp_multi(const void *a, const void *b, const struct compare *comp)
+{
+	for (int i = 0; i < comp->count; i++) {
+		int ret;
+
+		ret = comp->comp[i](a,b);
+		if (ret != 0)
+			return (comp->invert_map & (1U << i)) ? -ret : ret;
+	}
+	return 0;
+}
+
+int compare_add_sort_key(struct compare *comp, const char *key)
+{
+	int i;
+
+	if (!comp->sortdef)
+		return -1;
+
+	for (i = 0; i < 32; i++) {
+		if (comp->sortdef[i].name == NULL)
+			return -1;
+		if (strcasecmp(key, comp->sortdef[i].name) == 0) {
+			comp->comp[comp->count] = comp->sortdef[i].comp;
+			comp->count++;
+			break;
+		}
+	}
+	return 0;
+}

common/sort-utils.h

@@ -0,0 +1,89 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#ifndef __COMMON_SORT_UTILS_H__
+#define __COMMON_SORT_UTILS_H__
+
+/*
+ * Example:
+
+struct entry {
+	int id;
+	long size;
+};
+
+static int cmp_entry_id(const struct entry *a, const struct entry *b)
+{
+	return (a->id < b->id ? -1 :
+		a->id > b->id ?  1 : 0);
+}
+
+static int cmp_entry_size(const struct entry *a, const struct entry *b)
+{
+	return (a->size < b->size ? -1 :
+		a->size > b->size ?  1 : 0);
+}
+
+void test() {
+	// User data
+	struct entry entries[SIZE];
+	// Comparator structure
+	struct compare comp = { 0 };
+	// Keys, item comparators, help text defitions
+	struct sortdef sortit[] = {
+		{ .name = "id",   .comp = (sort_cmp_t)cmp_entry_id,
+		  .desc = "sort by id" },
+		{ .name = "size", .comp = (sort_cmp_t)cmp_entry_size,
+		  .desc = "sort by entry size" },
+		{ .name = NULL,   .comp = NULL }
+	};
+	// List of keys to use for sort (e.g. from command line options)
+	const char *sortby[] = { "size", "id" };
+
+	compare_init(&comp, sortit);
+	for (i = 0; i < sizeof(sortby) / sizeof(sortby[0]); i++) {
+		ret = compare_add_sort_key(&comp, sortby[i]);
+		if (ret < 0) {
+			printf("ERROR adding sort key %s\n", sortby[i]);
+			break;
+		}
+	}
+	qsort_r(entries, SIZE, sizeof(struct entry), (sort_r_cmp_t)compare_cmp_multi,
+		&comp);
+}
+ */
+
+typedef int (*sort_cmp_t)(const void *a, const void *b);
+typedef int (*sort_r_cmp_t)(const void *a, const void *b, void *data);
+
+struct sortdef {
+	const char *name;
+	const char *desc;
+	sort_cmp_t comp;
+};
+
+struct compare {
+	sort_cmp_t comp[32];
+	unsigned long invert_map;
+	int count;
+	const struct sortdef *sortdef;
+};
+
+int compare_init(struct compare *comp, const struct sortdef *sortdef);
+int compare_cmp_multi(const void *a, const void *b, const struct compare *comp);
+int compare_add_sort_key(struct compare *comp, const char *key);
+
+#endif