utils.py: add parallel make helpers

The code to extract the integer number of parallel build threads and
construct a new argument from them has started to be copied in multiple
locations, so create two new helper utilities to aid recipes.

The first helper (parallel_make()) extracts the integer number of
parallel build threads from PARALLEL_MAKE. The second
(parallel_make_argument()) does the same and then puts the result back
into a format string, optionally clamping it to some maximum value.

Additionally, rework the oe-core recipes that were manually doing this
to use the new helper utilities.

(From OE-Core rev: ccd1142d22b31ed85d8823b1bc9e11ccfd72b61f)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oe/utils.py

@@ -156,6 +156,49 @@ def any_distro_features(d, features, truevalue="1", falsevalue=""):
     """
     return bb.utils.contains_any("DISTRO_FEATURES", features, truevalue, falsevalue, d)
 
+def parallel_make(d):
+    """
+    Return the integer value for the number of parallel threads to use when
+    building, scraped out of PARALLEL_MAKE. If no parallelization option is
+    found, returns None
+
+    e.g. if PARALLEL_MAKE = "-j 10", this will return 10 as an integer.
+    """
+    pm = (d.getVar('PARALLEL_MAKE') or '').split()
+    # look for '-j' and throw other options (e.g. '-l') away
+    while pm:
+        opt = pm.pop(0)
+        if opt == '-j':
+            v = pm.pop(0)
+        elif opt.startswith('-j'):
+            v = opt[2:].strip()
+        else:
+            continue
+
+        return int(v)
+
+    return None
+
+def parallel_make_argument(d, fmt, limit=None):
+    """
+    Helper utility to construct a parallel make argument from the number of
+    parallel threads specified in PARALLEL_MAKE.
+
+    Returns the input format string `fmt` where a single '%d' will be expanded
+    with the number of parallel threads to use. If `limit` is specified, the
+    number of parallel threads will be no larger than it. If no parallelization
+    option is found in PARALLEL_MAKE, returns an empty string
+
+    e.g. if PARALLEL_MAKE = "-j 10", parallel_make_argument(d, "-n %d") will return
+    "-n 10"
+    """
+    v = parallel_make(d)
+    if v:
+        if limit:
+            v = max(limit, v)
+        return fmt % v
+    return ''
+
 def packages_filter_out_system(d):
     """
     Return a list of packages from PACKAGES with the "system" packages such as