[Libguestfs] [PATCH nbdkit 6/9] partition: Implement mapping of extents.

[Richard W.M. Jones]

---
 filters/partition/partition.c | 52 +++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/filters/partition/partition.c b/filters/partition/partition.c
index c1fe7a1..c8fcc7f 100644
--- a/filters/partition/partition.c
+++ b/filters/partition/partition.c
@@ -38,6 +38,7 @@
 #include <stdint.h>
 #include <string.h>
 #include <inttypes.h>
+#include <assert.h>
 
 #include <nbdkit-filter.h>
 
@@ -222,6 +223,56 @@ partition_zero (struct nbdkit_next_ops *next_ops, void *nxdata,
   return next_ops->zero (nxdata, count, offs + h->offset, flags, err);
 }
 
+/* Extents. */
+struct subtract_offset_data {
+  struct handle *h;
+  struct nbdkit_extents_map *extents_map;
+};
+
+static int
+subtract_offset (uint64_t offs, uint64_t length, uint32_t type,
+                 void *dv)
+{
+  struct subtract_offset_data *data = dv;
+
+  assert (offs >= data->h->offset);
+  offs -= data->h->offset;
+  return nbdkit_extent_add (data->extents_map, offs, length, type);
+}
+
+static int
+partition_extents (struct nbdkit_next_ops *next_ops, void *nxdata,
+                   void *handle, uint32_t count, uint64_t offs, uint32_t flags,
+                   struct nbdkit_extents_map *extents_map,
+                   int *err)
+{
+  struct handle *h = handle;
+  struct nbdkit_extents_map *map2;
+  struct subtract_offset_data data;
+
+  map2 = nbdkit_extents_new ();
+  if (map2 == NULL)
+    return -1;
+  if (next_ops->extents (nxdata, count, offs + h->offset,
+                         flags, map2, err) == -1) {
+    nbdkit_extents_free (map2);
+    return -1;
+  }
+
+  /* Transform offsets in map2, return result in extents_map. */
+  data.h = h;
+  data.extents_map = extents_map;
+  if (nbdkit_extents_foreach (map2, subtract_offset, &data,
+                              NBDKIT_EXTENTS_FOREACH_FLAG_RANGE,
+                              h->offset, h->range) == -1) {
+    nbdkit_extents_free (map2);
+    return -1;
+  }
+  nbdkit_extents_free (map2);
+
+  return 0;
+}
+
 static struct nbdkit_filter filter = {
   .name              = "partition",
   .longname          = "nbdkit partition filter",
@@ -237,6 +288,7 @@ static struct nbdkit_filter filter = {
   .pwrite            = partition_pwrite,
   .trim              = partition_trim,
   .zero              = partition_zero,
+  .extents           = partition_extents,
 };
 
 NBDKIT_REGISTER_FILTER(filter)
-- 
2.20.1