libfdisk: add fdisk_script_set_table()

This small change improves possibility to modify by script described
PT and use script API in another tools as primary way to create
partitions.

All you need is to compose script by fdisk_script_set_header() and
fdisk_script_set_table() and than apply by fdisk_apply_script().

Requested-by: Lennart Poettering <lennart@poettering.net>
Signed-off-by: Karel Zak <kzak@redhat.com>

4 files changed, 69 insertions, 13 deletions

diff --git a/libfdisk/docs/libfdisk-sections.txt b/libfdisk/docs/libfdisk-sections.txt
index f6675fe46..d0d362f60 100644
--- a/libfdisk/docs/libfdisk-sections.txt
+++ b/libfdisk/docs/libfdisk-sections.txt
@@ -132,6 +132,7 @@ fdisk_ref_script
 fdisk_script_enable_json
 fdisk_script_get_header
 fdisk_script_get_nlines
+fdisk_script_set_table
 fdisk_script_get_table
 fdisk_script_has_force_label
 fdisk_script_read_context
diff --git a/libfdisk/src/libfdisk.h.in b/libfdisk/src/libfdisk.h.in
index 47e778a67..69c6fd820 100644
--- a/libfdisk/src/libfdisk.h.in
+++ b/libfdisk/src/libfdisk.h.in
@@ -757,6 +757,7 @@ void fdisk_unref_script(struct fdisk_script *dp);
 const char *fdisk_script_get_header(struct fdisk_script *dp, const char *name);
 int fdisk_script_set_header(struct fdisk_script *dp, const char *name, const char *data);
 struct fdisk_table *fdisk_script_get_table(struct fdisk_script *dp);
+int fdisk_script_set_table(struct fdisk_script *dp, struct fdisk_table *tb);
 int fdisk_script_get_nlines(struct fdisk_script *dp);
 int fdisk_script_has_force_label(struct fdisk_script *dp);
 
diff --git a/libfdisk/src/libfdisk.sym b/libfdisk/src/libfdisk.sym
index 8f80d7964..8ce943acc 100644
--- a/libfdisk/src/libfdisk.sym
+++ b/libfdisk/src/libfdisk.sym
@@ -303,3 +303,7 @@ FDISK_2.33 {
 	fdisk_get_devmodel;
 	fdisk_get_devno;
 } FDISK_2.32;
+
+FDISK_2.35 {
+	fdisk_script_set_table;
+} FDISK_2.33;
diff --git a/libfdisk/src/script.c b/libfdisk/src/script.c
index 66be4f08c..0a165aad4 100644
--- a/libfdisk/src/script.c
+++ b/libfdisk/src/script.c
@@ -7,13 +7,33 @@
 /**
  * SECTION: script
  * @title: Script
- * @short_description: text based sfdisk compatible description of partition table
+ * @short_description: complex way to create and dump partition table
  *
- * The libfdisk scripts are based on original sfdisk script (dumps).  Each
+ * This interface allows to compose in-memory partition table with all details,
+ * write all partition table description to human readable text file, read it
+ * from the file, and apply the script to on-disk label.
+ *
+ * The libfdisk scripts are based on original sfdisk script (dumps). Each
  * script has two parts: script headers and partition table entries
- * (partitions).
+ * (partitions). The script is possible to dump in JSON too (read JSON is not
+ * implemented yet).
  *
  * For more details about script format see sfdisk man page.
+ *
+ * There are four ways how to build the script:
+ *
+ * - read the current on-disk partition table by fdisk_script_read_context())
+ * - read it from text file by fdisk_script_read_file()
+ * - read it interactively from user by fdisk_script_read_line() and fdisk_script_set_fgets()
+ * - manually in code by fdisk_script_set_header() and fdisk_script_set_table()
+ *
+ * The read functions fdisk_script_read_context() and fdisk_script_read_file()
+ * creates always a new script partition table. The table (see
+ * fdisk_script_get_table()) is possible to modify by standard
+ * fdisk_table_...() functions and than apply by fdisk_apply_script().
+ *
+ * Note that script API is fully non-interactive and forces libfdisk to not use
+ * standard dialog driven partitioning as we have in fdisk(8).
  */
 
 /* script header (e.g. unit: sectors) */
@@ -76,12 +96,6 @@ struct fdisk_script *fdisk_new_script(struct fdisk_context *cxt)
 	dp->cxt = cxt;
 	fdisk_ref_context(cxt);
 
-	dp->table = fdisk_new_table();
-	if (!dp->table) {
-		fdisk_unref_script(dp);
-		return NULL;
-	}
-
 	INIT_LIST_HEAD(&dp->headers);
 	return dp;
 }
@@ -317,11 +331,11 @@ int fdisk_script_set_header(struct fdisk_script *dp,
  * fdisk_script_get_table:
  * @dp: script
  *
- * The table (container with partitions) is possible to create by
- * fdisk_script_read_context() or fdisk_script_read_file(), otherwise
- * this function returns NULL.
+ * The table represents partitions holded by the script. The table is possible to
+ * fill by fdisk_script_read_context() or fdisk_script_read_file(). All the "read"
+ * functions reset the table. See also fdisk_script_set_table().
  *
- * Returns: NULL or script.
+ * Returns: NULL or script table.
  */
 struct fdisk_table *fdisk_script_get_table(struct fdisk_script *dp)
 {
@@ -329,6 +343,40 @@ struct fdisk_table *fdisk_script_get_table(struct fdisk_script *dp)
 	return dp ? dp->table : NULL;
 }
 
+/**
+ * fdisk_script_set_table:
+ * @dp: script
+ * @tb: table
+ *
+ * Replaces table used by script and creates a new reference to @tb. This
+ * function allows to generate a new script table independently on the current
+ * context and without any file reading.
+ *
+ * This is useful for example to create partition table with the same basic
+ * settings (e.g. label-id, ...) but with different partitions -- just call
+ * fdisk_script_read_context() to get current settings and than
+ * fdisk_script_set_table() to set a different layout.
+ *
+ * If @tb is NULL than the current script table is unreferenced.
+ *
+ * Note that script read_ functions (e.g. fdisk_script_read_context()) create
+ * always a new script table.
+ *
+ * Returns: 0 on success, <0 on error
+ */
+int fdisk_script_set_table(struct fdisk_script *dp, struct fdisk_table *tb)
+{
+	if (!dp)
+		return -EINVAL;
+
+	fdisk_ref_table(tb);
+	fdisk_unref_table(dp->table);
+	dp->table = tb;
+
+	DBG(SCRIPT, ul_debugobj(dp, "table replaced"));
+	return 0;
+}
+
 static struct fdisk_label *script_get_label(struct fdisk_script *dp)
 {
 	assert(dp);
@@ -911,6 +959,7 @@ static int parse_line_nameval(struct fdisk_script *dp, char *s)
 
 	assert(dp);
 	assert(s);
+	assert(dp->table);
 
 	DBG(SCRIPT, ul_debugobj(dp, "   parse script line: '%s'", s));
 
@@ -1106,6 +1155,7 @@ static int parse_line_valcommas(struct fdisk_script *dp, char *s)
 
 	assert(dp);
 	assert(s);
+	assert(dp->table);
 
 	pa = fdisk_new_partition();
 	if (!pa)