[core,v2] prebake: allow packages to be fetched from web instead of local dirs only

diff --git a/conf/oe-lite.conf b/conf/oe-lite.conf
index b1e23b2..4468b37 100644
--- a/conf/oe-lite.conf
+++ b/conf/oe-lite.conf
@@ -41,6 +41,7 @@  DEFAULT_RELAX[nohash] = "1"
 PREBAKE_PATH[nohash] = "1"
 
 PARALLEL_MAKE[nohash] = True
+PREBAKE_URL[nohash] = True
 export PATH
 
 export LD_LIBRARY_PATH
diff --git a/conf/oelayout.conf b/conf/oelayout.conf
index 535cb6f..405e4a2 100644
--- a/conf/oelayout.conf
+++ b/conf/oelayout.conf
@@ -57,6 +57,9 @@  IMAGE_DEPLOY_DIR[nohash] = True
 PACKAGE_DEPLOY_DIR 	 = "${TMPDIR}/packages"
 PACKAGE_DEPLOY_DIR[nohash] = True
 
+PREBAKE_CACHE_DIR 	      = "${TMPDIR}/prebake"
+PREBAKE_CACHE_DIR[nohash] = True
+
 # Recipe directory layout
 FILESPATHBASE	= "${FILE_DIRNAME}"
 FILESPATHBASE[emit] = ""
diff --git a/doc/manual.txt b/doc/manual.txt
index 2bcd230..e0fe093 100644
--- a/doc/manual.txt
+++ b/doc/manual.txt
@@ -40,6 +40,8 @@  include::quickstart.txt[]
 // Overview
 //include::overview.txt[]
 
+include::prebake.txt[]
+
 // Build Configuration
 //include::buildcfg.txt[]
 
diff --git a/doc/prebake.txt b/doc/prebake.txt
new file mode 100644
index 0000000..b821e3d
--- /dev/null
+++ b/doc/prebake.txt
@@ -0,0 +1,29 @@ 
+Using prebaked packages
+=======================
+
+This section describes how to use packages build on another machine
+available via http.
+
+
+First you need to setup a http server that serves the prebaked packages 
+from another machine. The baked prebakes will be in `${TMPDIR}/packages` 
+so setup the  server to make files available online as you prefer.
+
+Secondly, you need to set PREBAKE_URL to point to your prebaked packages url 
+prefix e.g: PREBAKE_CACHE_DIR can be set to pin point where the fetched 
+prebaked packages are located
+
+----
+#cat conf/site.conf
+PREBAKE_URL="http://myserver.com/packages/"
+PREBAKE_CACHE_DIR="<path-to-temp-storage>"
+----
+
+Note, that the directory structure under "packages" should match the 
+structure under `${TMPDIR}/packages`.
+
+Presently, 32-bit machines should bake prebaked packages that should be 
+used on 32-bit machines as well (and likewise for 64-bit).
+
+The feature has been tested on Ubuntu 12.04 so please report a bug if you find 
+problems using this feature.
diff --git a/lib/oelite/baker.py b/lib/oelite/baker.py
index 20cf146..476b22a 100644
--- a/lib/oelite/baker.py
+++ b/lib/oelite/baker.py
@@ -12,6 +12,10 @@  import oelite.item
 from oelite.parse import *
 from oelite.cookbook import CookBook
 
+import oelite.fetch
+
+import bb.utils
+
 import sys
 import os
 import glob
@@ -437,6 +441,9 @@  class OEliteBaker:
         # check for availability of prebaked packages, and set package
         # filename for all packages.
         depend_packages = self.runq.get_depend_packages()
+        url_prefix = self.config.get("PREBAKE_URL")
+        if url_prefix is not None:
+            info("Trying to use prebakes from url: %s"%(url_prefix))
         for package in depend_packages:
             # FIXME: skip this package if it is to be rebuild
             prebake = self.find_prebaked_package(package)
@@ -608,6 +615,7 @@  class OEliteBaker:
     def find_prebaked_package(self, package):
         """return full-path filename string or None"""
         package_deploy_dir = self.config.get("PACKAGE_DEPLOY_DIR")
+        prebake_url_cache_dir = self.config.get("PREBAKE_CACHE_DIR")
         if not package_deploy_dir:
             die("PACKAGE_DEPLOY_DIR not defined")
         if self.options.prebake:
@@ -615,6 +623,7 @@  class OEliteBaker:
             if prebake_path:
                 prebake_path = prebake_path.split(":")
             prebake_path.insert(0, package_deploy_dir)
+            prebake_path.insert(0, prebake_url_cache_dir)
         else:
             prebake_path = [package_deploy_dir]
         debug("package=%s"%(repr(package)))
@@ -628,6 +637,7 @@  class OEliteBaker:
             raise NoSuchPackage()
         filename = "%s_%s_%s.tar"%(package.name, recipe.version, metahash)
         debug("prebake_path=%s"%(prebake_path))
+        #test local paths first
         for base_dir in prebake_path:
             path = os.path.join(
                 base_dir,
@@ -638,6 +648,23 @@  class OEliteBaker:
             if os.path.exists(path):
                 debug("found prebake: %s"%(path))
                 return path
+        #then test URLs from PREBAKE_URL
+        url_prefix = self.config.get("PREBAKE_URL")
+        if url_prefix is not None:
+            package_path =os.path.join(
+                    package.type,
+                    package.arch + (package.recipe.meta.get("EXTRA_ARCH") or ""),
+                    filename)
+            downloaded_file =os.path.join(
+                    prebake_url_cache_dir,
+                    package_path)
+            url = os.path.join(url_prefix, package_path)
+            if oelite.fetch.url.grab(url, downloaded_file, timeout=1, retry=1):
+                if os.path.exists(downloaded_file) and os.path.getsize(downloaded_file) > 0:
+                    debug("using prebake from web: %s"%(url))
+                    return downloaded_file
+                else:
+                    os.unlink(downloaded_file)
         return None