scripts: west_commands: blobs: support ZEPHYR_BLOBS_CACHE

In environment variable `ZEPHYR_BLOBS_CACHE` one or more directories
(separated by `;`) can be specified. `west blobs fetch` will search in
these folders for according file and copy it if it exists. If only one
directory was given, it will automatically fill the cache by fetching
the blob to this cache dir (with prefixed sha256 hashsum) and
subsequently copy the file to the blobs path. Otherwise it fetches the
blob as usual directly to the blobs path.

Signed-off-by: Thorsten Klein <[email protected]>

Author: thorsten-klein

scripts/west_commands/blobs.py

@@ -5,6 +5,7 @@
 import argparse
 import os
 import re
+import shutil
 import sys
 import textwrap
 from pathlib import Path
@@ -121,16 +122,47 @@ def list(self, args):
     def ensure_folder(self, path):
         path.parent.mkdir(parents=True, exist_ok=True)
 
-    def fetch_blob(self, url, path):
+    def fetch_blob(self, blob):
+        url = blob['url']
+        path = Path(blob['path'])
+
+
+        cached_blob = None
+        sha256 = blob['sha256']
+        cached_filenames = [f'{sha256}-{path.name}', path.name]
+
+        # check if the blob is already cached
+        cache_dirs = os.getenv('ZEPHYR_BLOBS_CACHE', '')
+        for cache in cache_dirs.split(';'):
+            for cached_filename in cached_filenames:
+                cached_path = Pathcache) / cached_filename
+                status = zephyr_module.get_blob_status(cached_path.resolve(), sha256)
+                if status == zephyr_module.BLOB_PRESENT:
+                    cached_blob = cached_path
+                    break
+            if cached_blob:
+                break
+
         scheme = urlparse(url).scheme
         self.dbg(f'Fetching {path} with {scheme}')
         import fetchers
         fetcher = fetchers.get_fetcher_cls(scheme)
 
         self.dbg(f'Found fetcher: {fetcher}')
         inst = fetcher()
+
+        # Fill the cache if only one cache dir is used.
+        if not cached_blob and len(cache_dirs) == 1:
+            cached_path = cache_dirs[0] / cached_filenames[0]
+            if not cached_path.exists(): # do not overwrite existing files
+                inst.fetch(url, cached_path)
+                cached_blob = cached_path
+
         self.ensure_folder(path)
-        inst.fetch(url, path)
+        if cached_blob:
+            shutil.copy(cached_path, path)
+        else:
+            inst.fetch(url, path)
 
     # Compare the checksum of a file we've just downloaded
     # to the digest in blob metadata, warn user if they differ.
@@ -200,7 +232,7 @@ def fetch(self, args):
                     self.wrn('Skip fetching this blob.')
                     continue
 
-            self.fetch_blob(blob['url'], blob['abspath'])
+            self.fetch_blob(blob)
             if not self.verify_blob(blob):
                 bad_checksum_count += 1