[PATCH 1/3] ios: Introduce ios_flush and ios_dev_<...>_flush.

[Egeyar Bagcioglu]

Those functions are currently ineffective. This is a preparation patch
for stream IO implementation.

2020-07-11  Egeyar Bagcioglu  <egeyar@gmail.com>

        * libpoke/ios.h (ios_flush): New.
        * libpoke/ios.c (ios_flush): New.
        * libpoke/ios-dev.h (struct ios_dev_if): Add new member "flush".
        * libpoke/ios-dev-file.c (ios_dev_file_flush): New.
        * libpoke/ios-dev-mem.c (ios_dev_mem_flush): New.
        * libpoke/ios-dev-nbd.c (ios_dev_nbd_flush): New.
---
 libpoke/ios-dev-file.c | 7 +++++++
 libpoke/ios-dev-mem.c  | 7 +++++++
 libpoke/ios-dev-nbd.c  | 7 +++++++
 libpoke/ios-dev.h      | 5 +++++
 libpoke/ios.c          | 6 ++++++
 libpoke/ios.h          | 8 ++++++++
 6 files changed, 40 insertions(+)

diff --git a/libpoke/ios-dev-file.c b/libpoke/ios-dev-file.c
index fb42ed4f..4e4f3e63 100644
--- a/libpoke/ios-dev-file.c
+++ b/libpoke/ios-dev-file.c
@@ -203,6 +203,12 @@ ios_dev_file_size (void *iod)
   return st.st_size;
 }
 
+static int
+ios_dev_file_flush (void *iod, ios_dev_off offset)
+{
+  return IOS_OK;
+}
+
 struct ios_dev_if ios_dev_file
   __attribute__ ((visibility ("hidden"))) =
   {
@@ -213,4 +219,5 @@ struct ios_dev_if ios_dev_file
    .pwrite = ios_dev_file_pwrite,
    .get_flags = ios_dev_file_get_flags,
    .size = ios_dev_file_size,
+   .flush = ios_dev_file_flush
   };
diff --git a/libpoke/ios-dev-mem.c b/libpoke/ios-dev-mem.c
index fba99d41..56c3d42b 100644
--- a/libpoke/ios-dev-mem.c
+++ b/libpoke/ios-dev-mem.c
@@ -131,6 +131,12 @@ ios_dev_mem_size (void *iod)
   return mio->size;
 }
 
+static int
+ios_dev_mem_flush (void *iod, ios_dev_off offset)
+{
+  return IOS_OK;
+}
+
 struct ios_dev_if ios_dev_mem
   __attribute__ ((visibility ("hidden"))) =
   {
@@ -141,4 +147,5 @@ struct ios_dev_if ios_dev_mem
    .pwrite = ios_dev_mem_pwrite,
    .get_flags = ios_dev_mem_get_flags,
    .size = ios_dev_mem_size,
+   .flush = ios_dev_mem_flush,
   };
diff --git a/libpoke/ios-dev-nbd.c b/libpoke/ios-dev-nbd.c
index cfc68d48..9ed1834e 100644
--- a/libpoke/ios-dev-nbd.c
+++ b/libpoke/ios-dev-nbd.c
@@ -169,6 +169,12 @@ ios_dev_nbd_size (void *iod)
   return nio->size;
 }
 
+static int
+ios_dev_nbd_flush (void *iod, ios_dev_off offset)
+{
+  return IOS_OK;
+}
+
 struct ios_dev_if ios_dev_nbd
   __attribute__ ((visibility ("hidden"))) =
   {
@@ -179,4 +185,5 @@ struct ios_dev_if ios_dev_nbd
    .pwrite = ios_dev_nbd_pwrite,
    .get_flags = ios_dev_nbd_get_flags,
    .size = ios_dev_nbd_size,
+   .flush = ios_dev_nbd_flush,
   };
diff --git a/libpoke/ios-dev.h b/libpoke/ios-dev.h
index fa5f6a06..8461bb35 100644
--- a/libpoke/ios-dev.h
+++ b/libpoke/ios-dev.h
@@ -79,4 +79,9 @@ struct ios_dev_if
   /* Return the size of the device, in bytes.  */
 
   ios_dev_off (*size) (void *dev);
+
+  /* If called on a in-stream, free the buffer before OFFSET.  If called on
+     an out-stream, flush the data till OFFSET and free the buffer before
+     OFFSET.  Otherwise, do not do anything.  */
+  int (*flush) (void *dev, ios_dev_off offset);
 };
diff --git a/libpoke/ios.c b/libpoke/ios.c
index 217e96c6..36fc88e4 100644
--- a/libpoke/ios.c
+++ b/libpoke/ios.c
@@ -1517,3 +1517,9 @@ ios_size (ios io)
 {
   return io->dev_if->size (io->dev) * 8;
 }
+
+int
+ios_flush (ios io, ios_off offset)
+{
+  return io->dev_if->flush (io->dev, offset);
+}
diff --git a/libpoke/ios.h b/libpoke/ios.h
index 5c1f59ef..ab44ac68 100644
--- a/libpoke/ios.h
+++ b/libpoke/ios.h
@@ -352,6 +352,14 @@ int ios_write_string (ios io, ios_off offset, int flags,
                       const char *value)
   __attribute__ ((visibility ("hidden")));
 
+/* If the current IOD is a write stream, write out the data in the buffer
+   till OFFSET.  If the current IOD is a stream IOD, free (if allowed by the
+   embedded buffering strategy) bytes up to OFFSET.  This function has no
+   impact when called on other IO devices.  */
+
+int ios_flush (ios io, ios_off offset)
+  __attribute__ ((visibility ("hidden")));
+
 /* **************** Update API **************** */
 
 /* XXX: writeme.  */
-- 
2.25.4