New 'configuration' class, for storing all auto-detected configuration of

tools.

Patch from Alexey Pakhunov.


[SVN r31078]

src/tools/common.jam

@@ -18,6 +18,109 @@ import sequence ;
 import toolset ;
 
 
+# Configurations
+#
+# The following class helps to manage toolset configurations. Each configuration 
+# has unique ID and one or more parameters. A typical example of unique ID is 
+# a condition generated by 'common.check-init-parameters' rule. Other kinds of 
+# ID can be used. Parameters may include any details about the configuration like 
+# 'command', 'path', etc. 
+#
+# A configuration may be in one of two states: 
+# 
+#   - registered - a toolset configuration is registered (by autodetection code 
+#       for instance) but is not used. I.e. 'toolset.using' wasn't yet been called 
+#       for this configuration.
+#   - used - once called 'toolset.using' marks the configuration as 'used'.
+#
+# The main difference between the states is that while a configuration is 
+# 'registered' its options can be freely changed. This is useful in particular 
+# for autodetection code - all detected configurations may be safely overwritten 
+# by a user.
+
+class configurations
+{
+    import errors : error ;
+
+    rule __init__ ( )
+    {
+    }
+    
+    # Registers a configuration. 
+    #
+    # Returns 'true' if the configuration has been added and an empty value if 
+    # it already exists. Reports an error if the configuration is 'used'.
+    rule register ( id )
+    {
+        if $(id) in $(self.used) 
+        {
+            error "common: the configuration '$(id)' is in use" ;
+        }
+
+        local retval ;
+
+        if ! $(id) in $(self.all)
+        {
+            self.all += $(id) ;
+
+            # indicate that a new configuration has been added
+            retval = true ;
+        }
+
+        return $(retval) ;
+    }
+
+    # Mark a configuration as 'used'. 
+    #
+    # Returns 'true' if the state of the configuration has been changed to 
+    # 'used' and an empty value if it the state wasn't changed. Reports an error
+    # if the configuration isn't known.
+    rule use ( id )
+    {
+        if ! $(id) in $(self.all)
+        {
+            error "common: the configuration '$(id)' is not known" ;
+        }
+
+        local retval ;
+
+        if ! $(id) in $(self.used) 
+        {
+            self.used += $(id) ;
+
+            # indicate that the configuration has been marked as 'used'
+            retval = true ;
+        }
+
+        return $(retval) ;
+    }
+
+    # Return all registered configurations.
+    rule all ( )
+    {
+        return $(self.all) ;
+    }
+
+    # Return all used configurations.
+    rule used ( )
+    {
+        return $(self.used) ;
+    }
+    
+    # Returns the value of a configuration parameter.
+    rule get ( id : param )
+    {
+        return $(self.$(param).$(id)) ; 
+    }
+
+    # Sets the value of a configuration parameter.
+    rule set ( id : param : value * )
+    {
+        self.$(param).$(id) = $(value) ; 
+    }
+}
+
+
 # The rule checks toolset parameters. Each trailing parameter 
 # should be a pair of parameter name and parameter value.
 # The rule will check that each parameter either has value in