zipl/src: Implement sorting bls entries by versions

This patch implements an additional method of sorting bls entries
by version field and uses it as default one. If sorting by version
fails, then it falls back to the most robust method of sorting by
file names

Signed-off-by: Eduard Shishkin <edward6@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zipl/src/scan.c

@@ -10,6 +10,7 @@
  *
  */
 
+static const char *VERSION_KEYWORD = "version";
 
 /* Need ISOC99 function isblank() in ctype.h */
 #ifndef __USE_ISOC99
@@ -645,7 +646,7 @@ scan_file(const char* filename, struct scan_token** token)
 
 
 static int
-bls_filter(const struct dirent *ent)
+bls_filter_by_names(const struct dirent *ent)
 {
 	int offset = strlen(ent->d_name) - strlen(".conf");
 
@@ -655,13 +656,111 @@ bls_filter(const struct dirent *ent)
 	return strncmp(ent->d_name + offset, ".conf", strlen(".conf")) == 0;
 }
 
+struct version {
+	char *line; /* pointer to a line with version keyword */
+	int offset; /* offset of version value in the line */
+};
+
+/*
+ * Locate version in bls file represented by ENT
+ */
+static void get_version(const struct dirent *ent, struct version *v)
+{
+	char *line = NULL;
+	size_t len = 0;
+	char *d_name;
+	FILE *stream;
+	ssize_t read;
+
+	memset(v, 0, sizeof(*v));
+	d_name = misc_make_path((char *)blsdir, (char *)ent->d_name);
+	if (!d_name)
+		return;
+
+	stream = fopen(d_name, "r");
+	free(d_name);
+	if (!stream)
+		return;
+
+	while ((read = getline(&line, &len, stream)) != -1) {
+		if (line[read - 1] == '\n') {
+			line[read - 1] = '\0';
+			read--;
+		}
+		if ((size_t)read <= strlen(VERSION_KEYWORD) + 1)
+			continue;
+		if (strcmp(VERSION_KEYWORD, line) > 0)
+			continue;
+		if (!isblank(line[strlen(VERSION_KEYWORD)]))
+			continue;
+		/* skip blanks */
+		v->offset = strlen(VERSION_KEYWORD) + 1;
+		while (v->offset < read - 1 && isblank(line[v->offset]))
+			v->offset++;
+		if (isblank(line[v->offset]))
+			/*
+			 * all characters after the keyword
+			 * are blanks. Invalid version
+			 */
+			continue;
+		v->line = line;
+		fclose(stream);
+		return;
+	}
+	free(line);
+	fclose(stream);
+}
+
+static void put_version(struct version *v)
+{
+	free(v->line);
+}
+
+/**
+ * Check version in bls file represented by ENT.
+ * Return 1 if version is valid. Otherwise return 0
+ */
+static int bls_filter_by_versions(const struct dirent *ent)
+{
+	struct version v;
+
+	if (bls_filter_by_names(ent) == 0)
+		return 0;
+
+	get_version(ent, &v);
+	if (v.line) {
+		put_version(&v);
+		return 1;
+	}
+	return 0;
+}
+
 
 static int
-bls_sort(const struct dirent **ent_a, const struct dirent **ent_b)
+bls_sort_by_names(const struct dirent **ent_a, const struct dirent **ent_b)
 {
 	return strverscmp((*ent_a)->d_name, (*ent_b)->d_name);
 }
 
+static int
+bls_sort_by_versions(const struct dirent **ent_a, const struct dirent **ent_b)
+{
+	struct version v1, v2;
+	int ret;
+
+	get_version(*ent_a, &v1);
+	get_version(*ent_b, &v2);
+	/*
+	 * Both versions are valid.
+	 * It is guaranteed by bls_filter_by_versions()
+	 */
+	ret = strverscmp(v1.line + v1.offset, v2.line + v2.offset);
+
+	put_version(&v1);
+	put_version(&v2);
+
+	return ret;
+}
 
 static int
 scan_append_section_heading(struct scan_token* scan, int* index, char* name);
@@ -1011,6 +1110,40 @@ scan_count_target_keywords(char* keyword[])
 	return num;
 }
 
+static int bls_scandir(struct dirent ***bls_entries)
+{
+	struct dirent **entries1;
+	struct dirent **entries2;
+	int n1, n2;
+
+	/* arrange by names */
+	n1 = scandir(blsdir, &entries1,
+		     bls_filter_by_names, bls_sort_by_names);
+	if (n1 <= 0)
+		return n1;
+	/* arrange by versions */
+	n2 = scandir(blsdir, &entries2,
+		     bls_filter_by_versions, bls_sort_by_versions);
+
+	if (n2 <= 0 || n2 < n1) {
+		/*
+		 * failed to sort by versions,
+		 * fall back to sorting by filenames
+		 */
+		*bls_entries = entries1;
+		while (n2--)
+			free(entries2[n2]);
+		free(entries2);
+		return n1;
+	}
+	/* use arrangement by versions */
+	*bls_entries = entries2;
+	while (n1--)
+		free(entries1[n1]);
+	free(entries1);
+	return n2;
+}
+
 int
 scan_check_target_data(char* keyword[], int* line)
 {
@@ -1331,7 +1464,7 @@ int scan_bls(struct scan_token **token, int scan_size)
 	if (!(stat(blsdir, &sb) == 0 && S_ISDIR(sb.st_mode)))
 		return 0;
 
-	n = scandir(blsdir, &bls_entries, bls_filter, bls_sort);
+	n = bls_scandir(&bls_entries);
 	if (n <= 0)
 		return n;