driver/usbloader: support synchronizing extra files used by uuu scripts

When using a non-builtin ``uuu`` script as image for the ``UUUDriver``,
that script can reference files relative to script file itself. To
support that case, the ``UUUDriver`` is expandend to take a list of
files to synchronize to the remote exporter before invoking ``uuu``.

However, the ``ManagedFile`` helper places the files in a per-file
directory based on the hash of the file being synchronized (when using
``rsync`` instead of ``nfs``). This breaks the files-relative-to-uuu-
script use case, so use a combined hash of all the configured files
instead.

Author: hundeboll

doc/configuration.rst

@@ -2541,6 +2541,8 @@ Implements:
          UUUDriver:
            image: 'mybootloaderkey'
            script: 'spl'
+           extra_files:
+             - 'fitImage'
 
    images:
      mybootloaderkey: 'path/to/mybootloader.img'
@@ -2549,6 +2551,7 @@ Arguments:
   - image (str): optional, key in :ref:`images <labgrid-device-config-images>` containing the path
     of an image to bootstrap onto the target
   - script (str): optional, run built-in script with ``uuu -b``, called with image as arg0
+  - extra_files (list): optional, paths to synchronize to exporter before invoking ``uuu``
 
 USBStorageDriver
 ~~~~~~~~~~~~~~~~

labgrid/driver/usbloader.py

@@ -1,3 +1,4 @@
+import hashlib
 import subprocess
 import attr
 
@@ -158,6 +159,7 @@ class UUUDriver(Driver, BootstrapProtocol):
 
     image = attr.ib(default=None)
     script = attr.ib(default='', validator=attr.validators.instance_of(str))
+    extra_files = attr.ib(default=[], validator=attr.validators.instance_of(list))
 
     def __attrs_post_init__(self):
         super().__attrs_post_init__()
@@ -167,6 +169,8 @@ def __attrs_post_init__(self):
         else:
             self.tool = 'uuu-loader'
 
+        self.hash = None
+
     def on_activate(self):
         pass
 
@@ -178,16 +182,46 @@ def on_deactivate(self):
     def load(self, filename=None):
         if filename is None and self.image is not None:
             filename = self.target.env.config.get_image_path(self.image)
+
         mf = ManagedFile(filename, self.loader)
+        mf.hash = self.get_hash(filename)
         mf.sync_to_resource()
 
+        for file in self.extra_files or []:
+            file_mf = ManagedFile(file, self.loader)
+            file_mf.hash = self.get_hash(filename)
+            file_mf.sync_to_resource()
+
         cmd = ['-b', self.script] if self.script else []
 
         processwrapper.check_output(
             self.loader.command_prefix + [self.tool] + cmd + [mf.get_remote_path()],
             print_on_silent_log=True
         )
 
+    def get_hash(self, image):
+        """Create a hash of all input files combined to use when synchronizing managed files."""
+        if self.hash is not None:
+            return self.hash
+
+        hasher = hashlib.sha256()
+
+        # Inspired by the implementation of hashlib.file_digest() from CPython, but adapted to read
+        # multiple files instead of a single one.
+        buf = bytearray(2**18)  # Reusable buffer to reduce allocations.
+        view = memoryview(buf)
+
+        for file in [image] + self.extra_files:
+            with open(file, 'rb') as fileobj:
+                while True:
+                    size = fileobj.readinto(buf)
+                    if size == 0:
+                        break  # EOF
+                    hasher.update(view[:size])
+
+        self.hash = hasher.hexdigest()
+        return self.hash
+
 
 @target_factory.reg_driver
 @attr.s(eq=False)