From 48d60fa69c533fc094eac4adedf9e18cce3f4d3d Mon Sep 17 00:00:00 2001
From: Ingo Weinhold <ingo_weinhold@gmx.de>
Date: Sun, 4 Mar 2007 05:09:59 +0000
Subject: [PATCH] Introduced new build system features: The variable
 HAIKU_DONT_INCLUDE_SRC to turn off the inclusion of src/Jamfile, and the rule
 DeferredSubInclude to include a subdirectory in UserBuildConfig. Together
 they allow a developer working on a subproject to reduce jam's parsing time
 when only building the subproject. Relevant mostly on BeOS; on Linux jam is
 pretty fast anyway.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@20321 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
 Jamfile                          | 13 ++++++++++-
 build/jam/HeadersRules           | 39 ++++++++++++++++++++++++++++++++
 build/jam/UserBuildConfig.sample | 16 +++++++++++++
 3 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/Jamfile b/Jamfile
index c475ff3c8b..8cc1f32a4c 100644
--- a/Jamfile
+++ b/Jamfile
@@ -132,4 +132,15 @@ Depends ScreenSaverKit :
 	Haiku
 ;
 
-SubInclude HAIKU_TOP src ;
+# Optionally we allow not to include the "src" subdirectory.
+if $(HAIKU_DONT_INCLUDE_SRC) {
+	# Don't include "src", but at least include the stuff needed for the
+	# build.
+	SubInclude HAIKU_TOP src build ;
+	SubInclude HAIKU_TOP src tools ;
+} else {
+	SubInclude HAIKU_TOP src ;
+}
+
+# Perform deferred SubIncludes.
+ExecuteDeferredSubIncludes ;
diff --git a/build/jam/HeadersRules b/build/jam/HeadersRules
index e7490235d6..ac51b40903 100644
--- a/build/jam/HeadersRules
+++ b/build/jam/HeadersRules
@@ -397,5 +397,44 @@ rule FStandardHeaders
 	return $(headers) ;
 }
 
+rule DeferredSubInclude params
+{
+	# DeferredSubInclude <subdir tokens> ;
+	#
+	# Takes the same parameter as SubInclude. The the subdirectory referred to
+	# by <subdir tokens> will be included when ExecuteDeferredSubIncludes is
+	# invoked, i.e. at the end of the root Jamfile.
+
+	HAIKU_DEFERRED_SUB_INCLUDES += "/" $(params) ;
+}
+
+rule ExecuteDeferredSubIncludes
+{
+	# ExecuteDeferredSubIncludes ;
+	#
+	# Performs the deferred SubIncludes scheduled by DeferredSubInclude.
+
+	local tokensList = $(HAIKU_DEFERRED_SUB_INCLUDES) ;
+	while $(tokensList) {
+		# chop off leading "/"
+		tokensList = $(tokensList[2-]) ;
+
+		# get the tokens for the next include
+		local tokens ;
+		while $(tokensList) && $(tokensList[1]) != "/" {
+			tokens += $(tokensList[1]) ;
+			tokensList = $(tokensList[2-]) ;
+		}
+
+		# perform the include
+		if $(tokens) {
+			SubInclude $(tokens) ;
+		}
+	}
+}
+
+# The variable used to collect the deferred SubIncludes.
+HAIKU_DEFERRED_SUB_INCLUDES = ;
+
 # SUBDIRSYSHDRS shall be reset automatically for each subdir
 SUBDIRRESET += SYSHDRS ;
diff --git a/build/jam/UserBuildConfig.sample b/build/jam/UserBuildConfig.sample
index 9c99c2c5d8..9493d998d5 100644
--- a/build/jam/UserBuildConfig.sample
+++ b/build/jam/UserBuildConfig.sample
@@ -75,3 +75,19 @@ AddTargetVariableToScript test.inc : fs_shell_command : fsShellCommand ;
 # used, i.e. a variable "rc" referring to the rc command built for the host
 # platform is defined in the script.
 AddTargetVariableToScript test.inc : <build>rc ;
+
+
+# Optimizing Jamfile Parsing Times
+
+# Setting this variable will prevent the root Jamfile to include the Jamfile
+# in the src directory. Instead only the directories required for building the
+# build tools are included. Only useful in combination with DeferredSubInclude.
+HAIKU_DONT_INCLUDE_SRC = 1 ;
+
+# Schedule the given subdirectory for inclusion at the end of the root
+# Jamfile (directly using SubInclude here is not possible). Using this
+# feature together with HAIKU_DONT_INCLUDE_SRC allows developers working
+# only on a subproject to reduce Jamfile parsing times considerably.
+DeferredSubInclude HAIKU_TOP src tests add-ons kernel file_systems
+	userlandfs ;
+