source: downloads/boost_1_33_1/tools/build/v2/util/indirect.jam @ 13

# Copyright David Abrahams 2003. Permission to copy, use,
# modify, sell and distribute this software is granted provided this
# copyright notice appears in all copies. This software is provided
# "as is" without express or implied warranty, and with no claim as
# to its suitability for any purpose.
import modules ;
import numbers ;

# The pattern that indirect rules must match: module$rule
.pattern = ^([^%]*)%([^%]+)$ ;
  
#
# Type checking rules.
#
local rule indirect-rule ( x )
{
    if ! [ MATCH $(.pattern) : $(x) ]
    {
        return "expected a string of the form module$rule, but got \""$(x)"\" for argument" ;
    }
}

# make an indirect rule which calls the given rule; if context is
# supplied it is expected to be the module in which to invoke the rule
# by the 'call' rule below.  Otherwise, the rule will be invoked in
# the module of this rule's caller.
rule make ( rulename bound-args * : context ? )
{
    context ?= [ CALLER_MODULE ] ;
    context ?= "" ;
    return $(context)%$(rulename) $(bound-args) ;
}

# make an indirect rule which calls the given rule.  rulename may be a
# qualified rule; if so it is returned unchanged.  Otherwise, if
# frames is not supplied, the result will be invoked (by 'call',
# below) in the module of the caller.  Otherwise, frames > 1
# specifies additional call frames to back up in order to find the
# module context.
rule make-qualified ( rulename bound-args * : frames ? )
{
    if [ MATCH $(.pattern) : $(rulename) ]
    {
        return $(rulename) $(bound-args) ;
    }
    else
    {
        frames ?= 1 ;
        # Take the first dot-separated element as module name.
        # This disallows module names with dots, but allows rule names
        # with dots.
        local module-context = [ MATCH ^([^.]*)\\..* : $(rulename) ] ;
        module-context ?= [ CALLER_MODULE $(frames) ] ;
        return [ make $(rulename) $(bound-args) : $(module-context) ] ;
    }
}

# return the module name in which the given indirect rule will be
# invoked.
rule get-module ( [indirect-rule] x )
{
    local m = [ MATCH $(.pattern) : $(x) ] ;
    if ! $(m[1])
    {
        m = ;
    }
    return $(m[1]) ;
}

# return the rulename that will be called when x is invoked
rule get-rule ( [indirect-rule] x )
{
    local m = [ MATCH $(.pattern) : $(x) ] ;
    return $(m[2]) ;
}

# Invoke the given indirect-rule.
rule call ( [indirect-rule] r args * : * )
{
    return [
      modules.call-in [ get-module $(r) ]
        : [ get-rule $(r) ] $(args) : $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) : $(9) 
    ] ;
}

rule __test__
{
    import assert ;
    
    rule foo-barr! ( x )
    {
        assert.equal $(x) : x ;
    }
    
    assert.equal [ get-rule [ make foo-barr! ] ] : foo-barr! ;
    assert.equal [ get-module [ make foo-barr! ] ] : [ CALLER_MODULE ] ;
    
    call [ make foo-barr! ] x ;
    call [ make foo-barr! x ] ;
    
    
    call [ make foo-barr! : [ CALLER_MODULE ] ] x ;
}