projects.py: Add cache_func()

Add a generic cache for function calls, and use it on functions doing file I/O.
This speeds the build process up considerably.

Signed-off-by: Jan Lindemann <jan@janware.com>

scripts/projects.py

@@ -27,6 +27,27 @@ def debug(*objs):
 def err(*objs):
         print("ERR: ", *objs, file=sys.stderr)
 
+def cache_func(func, args):
+    d = cache
+    depth = 0
+    for a in [ func.__name__ ] + args:
+        if a is None:
+            a = 'None'
+        depth += 1
+        #debug('depth = ', depth, 'arg = ', a, 'd = ', str(d))
+        if a in d:
+            if len(args) == depth:
+                return d[a]
+            d = d[a]
+            continue
+        if len(args) == depth:
+            r = func(*args)
+            d[a] = r
+            return r
+        d[a] = {}
+        d = d[a]
+    raise Exception("cache algorithm failed for function", func.__name__, "in depth", depth)
+
 def proj_dir(name):
     if name == top_name:
         return topdir
@@ -59,6 +80,11 @@ def get_os(args = ""):
             return out
     return "linux"
 
+def get_os_cached(args = ""):
+    if 'os' in cache:
+        return cache['os']
+    return get_os(args)
+
 # TODO: add support for customizing this in project.conf
 def htdocs_dir(name):
     pd = proj_dir(name)
@@ -69,7 +95,7 @@ def htdocs_dir(name):
     return None
 
 def os_cascade():
-    os = get_os()
+    os = get_os_cached()
     name = re.sub('-.*', '', os)
     # e.g. os, linux, suse, suse-tumbleweed
     return [ 'os', platform.system().lower(), name, os ]
@@ -92,7 +118,10 @@ def get_section(path, section):
             r = r + line
     file.close()
     return r.rstrip()
- 
+
+def get_section_cached(path, section):
+    return cache_func(get_section, [ path, section ])
+
 def read_value(path, section, key):
     debug("opening ", path)
     try:
@@ -131,6 +160,9 @@ def read_value(path, section, key):
         return r[0]
     return None
 
+def read_value_cached(path, section, key):
+    return cache_func(read_value, [path, section, key])
+
 def get_value(name, section, key):
     debug("getting value [%s].%s for project %s (%s)" %(section, key, name, top_name))
     if top_name and name == top_name:
@@ -147,7 +179,7 @@ def get_value(name, section, key):
 
     path = proj_root + '/make/project.conf'
     #print('path = ', path, 'top_name = ', top_name, 'name = ', name)
-    return read_value(path, section, key)
+    return read_value_cached(path, section, key)
 
 def collect_values(names, section, key):
     r = ""
@@ -557,6 +589,8 @@ def cmd_getval(args_):
 # -------------------------------------------------------------------- here we go
 
 global_args = []
+cache = {}
+
 skip = 0
 for a in sys.argv[1::]:
     global_args.append(a)
@@ -587,7 +621,7 @@ debug("----------------------------------------- running ", ' '.join(sys.argv))
 projs_root = args.prefix
 if args.topdir:
     topdir = args.topdir
-    top_name = read_value(topdir + '/make/project.conf', 'build', 'name')
+    top_name = read_value_cached(topdir + '/make/project.conf', 'build', 'name')
     if not top_name:
         top_name = re.sub('-[0-9.-]*$', '', basename(realpath(topdir)))