[PATCH v6 1/3] binman: Generate preload header and sign data only once

[Yan WANG <yan.wang@softathome.com>]

From: Paul HENRYS <paul.henrys_ext@softathome.com>

To optimize preload generation, generate the header and signatures only
after all data has been collected in ProcessContentsUpdate(). This
avoids signing the data multiple times.

Since header_size is known upfront (from __init__), create a placeholder
in `ObtainContents()` to avoid an extra packing pass when
ProcessContentsUpdate() detects a size change.

This reduces unnecessary repacking and signing operations.

Signed-off-by: Paul HENRYS <paul.henrys_ext@softathome.com>
---

Changes in v6:
- No changes

 tools/binman/etype/pre_load.py | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/tools/binman/etype/pre_load.py b/tools/binman/etype/pre_load.py
index 00f1a896767..0d953cb258e 100644
--- a/tools/binman/etype/pre_load.py
+++ b/tools/binman/etype/pre_load.py
@@ -152,14 +152,11 @@ class Entry_pre_load(Entry_collection):
         return data + pad
 
     def ObtainContents(self):
-        """Obtain a placeholder for the header contents"""
-        # wait that the image is available
-        self.image = self.GetContents(False)
-        if self.image is None:
-            return False
-        self.SetContents(self._CreateHeader())
+        """Create a placeholder for the header"""
+        self.SetContents(tools.get_bytes(0, self.header_size))
         return True
 
     def ProcessContents(self):
+        self.image = self.GetContents(True)
         data = self._CreateHeader()
         return self.ProcessContentsUpdate(data)
-- 
2.25.1