# Copyright (c) 2005 Reece H. Dunn.
#
# Use, modification and distribution is subject to the Boost Software
# License Version 1.0. (See accompanying file LICENSE_1_0.txt or
# http://www.boost.org/LICENSE_1_0.txt)

import type ;
import feature : feature ;
import generators ;

##### Using Pre-compiled Headers (Quick Guide) #####
#
# Make mypch.hpp a pre-compiled header (PCH) using mypch.cpp as the source file:
#    import cast ;
#    pch mypch : [ cast _ pcheader : pch.hpp ] pch.cpp ;
#
# Enable PCHs in a target:
#    exe hello : mypch main.cpp hello.cpp ;
#                ^^^^^ -- mypch.hpp is a PCH
#
# Don't use PCHs for a specific source:
#    obj nopch : nopch.cpp : <pch>off ;
#

type.register PCH : pch ;
type.register PCHEADER : pcheader ;

feature pch : # control precompiled header (PCH) generation
    on  # this file has support for using PCHs (if available)
    off # this file doesn't use PCHs
  ;

feature pch-source : : free dependency ; # mypch.cpp
feature pch-header : : free dependency ; # mypch.h[pp]
feature pch-file   : : free dependency ; # mypch.pch

class pch-generator : generator
{
    import property-set ;

    rule __init__ ( * : * )
    {
        generator.__init__ $(1) : $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) : $(9) ;
    }

    rule action-class ( )
    {
        return compile-action ;
    }

    rule run ( project name ? : property-set : sources * )
    {
        # The two sources are cpp file and PCHEADER, but they
        # can be passed in any order. Figure out which source
        # is what.
        local cpp = $(sources[2]) ;
        local h   = $(sources[1]) ;
        if [ $(sources[2]).type ] = PCHEADER
        {
            cpp = $(sources[1]) ;
            h   = $(sources[2]) ;
        }

        local r =
          [ generator.run $(project) $(name) :
            [
              property-set.create
                <pch-source>$(cpp)      # mypch.cpp
                [ $(property-set).raw ]
            ] : $(sources)
          ] ;

        return
          [ property-set.create
              <pch-header>$(h)          # mypch.h[pp]
              <pch-file>$(r[2])         # mypch.pch
          ] $(r) ;
    }
}