options.awk

#!/bin/awk -f
# scripts/options.awk - library build configuration control
#
# libpng version 1.5.0beta17 - April 2, 2010
#
# Copyright (c) 1998-2010 Glenn Randers-Pehrson
#
# This code is released under the libpng license.
# For conditions of distribution and use, see the disclaimer
# and license in png.h

# The output of this script is written to the file given by
# the variable 'out'.  The script is run twice, once with
# an intermediate output file, 'options.tmp' then again on
# that file to produce the final output.  Each time the
# output files and whether or not to pre-prrocess must be
# specified:
#
#  awk -f scripts/options.awk pre=1 out=options.tmp scripts/options.dat 1>&2
#  awk -f scripts/options.awk pre=0 out=options.dfn options.tmp 1>&2

BEGIN{
    out="/dev/null"                      # intermediate, preprocessed, file
    pre=-1                               # preprocess
    start="PNG_DEFN_MAGIC-"              # Arbitrary start
    end="-PNG_DEFN_END"                  # Arbitrary end
    cx= "/@@@*"                          # Open C comment for output file
    comment=start cx                     # Comment start
    cend="*/" end                        # Comment end
    def=start "#define PNG_@@@"          # Arbitrary define
    sup="@@@_SUPPORTED" end              # end supported option
    und=comment "#undef PNG_@@@"         # Unsupported option
    une="@@@_SUPPORTED" cend             # end unsupported option
    error=start "ERROR:"                 # error message
    deb=0                                # debug - set on command line
    logunsupported=0                     # write unsupported options too
    
    # Precreate arrays
    option[""] = ""      # list of all options: default on/off/""
    done[""] = 1         # marks option as having been output
    requires[""] = ""    # requires by option
    iffs[""] = ""        # if by option
    enabledby[""] = ""   # options that enable it by option
    setting[""] = ""     # requires by setting
    defaults[""] = ""    # used for a defaulted value
    doneset[""] = 1      # marks setting as having been output
    r[""] = ""           # Temporary array

    # For decorating the output file
    protect = ""
}

# Preprocessing - this just copies the input file with lines
# that need preprocessing (just chunk at present) expanded
pre && $1 != "chunk"{
    print >out
    next
}

# The first characters of the line determine how it is processed,
# leading spaces are ignored.  In general tokens that are not
# keywords are the names of options.  An option 'name' is
# controlled by the definition of the corresponding macros:
#
#   PNG_name_SUPPORTED    The option is turned on
#   PNG_NO_name
#   PNG_NO_name_SUPPORTED If the first macro is not defined
#                         either of these will turn the option off
#
# If none of these macros are defined the option is turned on, unless
# the keyword 'off' is given in a line relating to the option.  The
# keyword 'on' can also be given, but it will be ignored (since it is
# the default.)
#
# In the syntax below a 'name' is indicated by "NAME", other macro
# values are indicated by "MACRO", as with "NAME" the leading "PNG_"
# is omitted, but in this case the "NO_" prefix and the "_SUPPORTED"
# suffix are never used.
#
# Each line is introduced by a keyword - the first non-space characters
# on the line.  A line starting with a '#' is a comment - it is totally
# ignored.  Keywords are as follows, a NAME, is simply a macro name
# without the leading PNG_, PNG_NO_ or the trailing _SUPPORTED.

$1 ~ /^#/ || $0 ~ /^[ 	]*$/{
    next
}

# com <comment>
#   The whole line is placed in the output file as a comment with
#   the preceding 'com' removed
$1 == "com"{
    if (NF > 1) {
	sub(/^[ 	]*com[ 	]*/, "")
	print comment, $0, cend >out
    } else
    	print start end >out
    next
}

# file output input protect
#   Informational: the official name of the input file (without
#   make generated local directories), the official name of the
#   output file and, if required, a name to use in a protection
#   macro for the contents.
$1 == "file" && NF >= 2{
    print comment, $2, cend >out
    print comment, "Machine generated file: DO NOT EDIT", cend >out
    if (NF >= 3)
    	print comment, "Derived from:", $3, cend >out
    protect = $4
    if (protect != "") {
    	print start "#ifndef", protect end >out
    	print start "#define", protect end >out
    }
    next
}

# option NAME ( (requires|enables|if) NAME* | on | off )*
#   Declares an option 'NAME' and describes its default setting (on|off)
#   and its relationship to other options.  The option is disabled
#   unless *all* the options listed after 'requires' are set and at
#   least one of the options listed after 'if' is set.  If the
#   option is set then it turns on all the options listed after 'enables'.

$1 == "option" && NF >= 2{
    onoff = option[$2]  # records default on or default off
    key = ""
    for (i=3; i<=NF; ++i) {
    	if ($(i) == "on" || $(i) == "off") {
	    key = ""
	    if (onoff != $(i)) {
	    	if (onoff == "")
		    onoff = $(i)
		else {
		    # Print a message, otherwise the error
		    # below is incomprehensible
		    print $2 ": currently", onoff ": attempt to turn", $(i)
		    break
		}
	    }
	} else if ($(i) == "requires" || $(i) == "if" || $(i) == "enables") {
	    key = $(i)
	} else if (key == "requires") {
	    requires[$2] = requires[$2] " " $(i)
	} else if (key == "if") {
	    iffs[$2] = iffs[$2] " " $(i)
	} else if (key == "enables") {
	    enabledby[$(i)] = enabledby[$(i)] " " $2
	} else
	    break # bad line format
    }

    if (i > NF) {
	# Set the option - this may explicitly set it to "", that's good
	# becaue we need to ensure it exists and we can't rely on some
	# actually quite sensible awk implementation not optimising the
	# read above away (gawk doesn't)
	option[$2] = onoff
	next
    }
    # Else fall through to the error handler
}

# chunk NAME [requires OPT] [off]
#   Expands to the 'option' settings appropriate to the reading and
#   writing of an ancilliary PNG chunk 'NAME':
#
#    option READ_NAME requires READ_ANCILLARY_CHUNKS [READ_OPT]
#    option READ_NAME enables NAME
#    [option READ_NAME off]
#    option WRITE_NAME requires WRITE_ANCILLARY_CHUNKS [WRITE_OPT]
#    option WRITE_NAME enables NAME
#    [option WRITE_NAME off]

pre && $1 == "chunk" && NF >= 2{
    # 'chunk' is handled on the first pass by writing appropriate
    # 'option' lines into the intermediate file.
    onoff = ""
    reqread = ""
    reqwrite = ""
    i = 3 # indicates format error
    if (NF > 2) {
	# read the keywords/additional OPTS
    	req = 0
	for (i=3; i<=NF; ++i) {
	    if ($(i) == "on" || $(i) == "off") {
	    	if (onoff != $(i)) {
		    if (onoff == "")
			onoff = $(i)
		    else
		    	break # on/off conflict
		}
	    } else if ($(i) == "requires")
	    	req = 1
	    else if (req != 1)
	    	break # bad line: handled below
	    else {
	    	reqread = reqread " READ_" $(i)
	    	reqwrite = reqwrite " WRITE_" $(i)
	    }
	}
    }
	    	
    if (i > NF) {
    	# Output new 'option' lines to the intermediate file (out)
	print "option READ_" $2,
		"requires READ_ANCILLARY_CHUNKS" reqread,
		"enables", $2, onoff >out
    	print "option WRITE_" $2,
		"requires WRITE_ANCILLARY_CHUNKS" reqwrite,
		"enables", $2, onoff >out
	next
    }
    # Else hit the error handler below - bad line format!
}

# setting MACRO ( requires MACRO* )* [ default VALUE ]
#    Behaves in a similar way to 'option' without looking for NO_ or
#    _SUPPORTED; the macro is enabled if it is defined so long as all
#    the 'requires' macros are also defined.  The definitions may be
#    empty, an error will be issued if the 'requires' macros are
#    *not* defined.  If given the 'default' value is used if the
#    macro is not defined.  The default value will be re-tokenised.
#    (BTW: this is somewhat restrictive, it mainly exists for the
#    support of non-standard configurations and numeric parameters,
#    see the uses in scripts/options.dat 

$1 == "setting" && (NF == 2 || NF >= 3 && ($3 == "requires" || $3 == "default")){
    reqs = ""
    deflt = ""
    isdef = 0
    key = ""
    for (i=3; i<=NF; ++i)
    	if ($(i) == "requires" || $(i) == "default") {
	    key = $(i)
	    if (key == "default") isdef = 1
	} else if (key == "requires")
	    reqs = reqs " " $(i)
	else if (key == "default")
	    deflt = deflt " " $(i)
	else
	    break # Format error, handled below

    setting[$2] = reqs
    if (isdef && deflt == "")
    	deflt = " " # as a flag to force output
    defaults[$2] = deflt
    next
}

# The order of the dependency lines (option, chunk, setting) is irrelevant
# - the 'enables', 'requires' and 'if' settings will be used to determine
# the correct order in the output and the final values in pnglconf.h are
# not order dependent.  'requires' and 'if' entries take precedence over
# 'enables' from other options; if an option requires another option it
# won't be set regardless of any options that enable it unless the other
# option is also enabled.
#
# Similarly 'enables' trumps a NO_ definition in CFLAGS or pngusr.h
#
# For simplicity cycles in the definitions are regarded as errors,
# even if they are not ambiguous.
# A given NAME can be specified in as many 'option' lines as required, the
# definitions are additive.

# For backwards compatibility equivalent macros may be listed thus:
#
# = [NO_]NAME MACRO
#   Makes -DMACRO equivalent to -DPNG_NO_NAME or -DPNG_NAME_SUPPORTED
#   as appropriate.
#
# The definition is injected into the C compiler input when encountered
# in the second pass (so all these definitions appear *after* the @
# lines!)
#
# 'NAME' is as above, but 'MACRO' is the full text of the equivalent
# old, deprecated, macro.

$1 == "=" && NF == 3{
    print "#ifdef PNG_" $3 >out
    if ($2 ~ /^NO_/)
	print "#   define PNG_" $2 >out
    else
	print "#   define PNG_" $2 "_SUPPORTED" >out
    print "#endif" >out
    next
}

# Lines may be injected into the C compiler input by preceding them
# with an "@" character.  The line is copied with just the leading
# @ removed.

$1 ~ /^@/{
    sub(/^[ 	]*@/, "")
    print >out
    next
}

# Check for unreognized lines, because of the preprocessing chunk
# format errors will be detected on the first pass independent of
# any other format errors.
{
    print "options.awk: bad line (" NR "):", $0
    exit 1
}

# For checking purposes names that start with "ok_" or "fail_" are
# not output to pnglconf.h and must be either enabled or disabled
# respectively for the build to succeed.  This allows interdependencies
# between options of the form "at least one of" or "at most one of"
# to be checked.  For example:
#
# option FLOATING_POINT enables ok_math
# option FIXED_POINT enables ok_math
#    This ensures that at least one of FLOATING_POINT and FIXED_POINT
#    must be set for the build to succeed.
#
# option fail_math requires FLOATING_POINT FIXED_POINT
#    This means the build will fail if *both* FLOATING_POINT and
#    FIXED_POINT are set (this is an example; in fact both are allowed.)
#
# If all these options were given the build would require exactly one
# of the names to be enabled.

END{
    if (out == "/dev/null") {
	print "out=output.file must be given on the command line"
	exit 1
    }
    if (pre) {
    	if (pre != 1) {
	    print "pre=0 or pre=1 must be given on command line"
	    exit 1
	}
	exit 0
    }

    # Do the 'setting' values first, the algorithm the standard
    # tree walk (O(1)) done in an O(2) while/for loop; interations
    # settings x depth, outputing the deepest required macros
    # first.
    print "" >out
    print "/* SETTINGS */" >out
    print comment, "settings", cend >out
    finished = 0
    while (!finished) {
    	finished = 1
	movement = 0 # done nothing
	for (i in setting) if (!doneset[i]) {
	    nreqs = split(setting[i], r)
	    if (nreqs > 0) {
		for (j=1; j<=nreqs; ++j) if (!doneset[r[j]])
		    break
	    	if (j<=nreqs) {
		    finished = 0
		    continue # try a different setting
		}
	    }

	    # All the requirements have been processed, output
	    # this setting.
	    if (deb) print "setting", i
	    print "" >out
	    print "/* setting: ", i >out
	    print " *   requires:" setting[i] >out
	    print " *   default: ", defaults[i], "*/" >out
	    if (defaults[i] == "") # no default, only check if defined
		print "#ifdef PNG_" i >out
	    for (j=1; j<=nreqs; ++j) {
	    	print "# ifndef PNG_" r[j] >out
		print error, i, "requires", r[j] end >out
		print "# endif" >out
	    }
	    if (defaults[i] != "") # default handling
		print "#ifdef PNG_" i >out
	    print def i, "PNG_" i end >out
	    if (defaults[i] != "") {
	    	print "#else /*default*/" >out
		print def i defaults[i] end >out
	    }
	    print "#endif" >out

	    doneset[i] = 1
	    ++movement
	}

	if (!finished && !movement) {
	    print "setting: loop or missing setting in 'requires', cannot process:"
	    for (i in setting) if (!doneset[i])
	    	print "  setting", i, "requires" setting[i]
	    exit 1
	}
    }
    print comment, "end of settings", cend >out

    # Now do the options - somewhat more complex.  The dependency
    # tree is thus:
    #
    #   name    >      name
    #	name requires  name
    #   name if        name
    #   name enabledby name
    #
    # First build a list 'tree' by option of all the things on which
    # it depends.
    print "" >out
    print "/* OPTIONS */" >out
    print comment, "options", cend >out
    for (opt in enabledby) tree[opt] = 1  # may not be explicit options
    for (opt in option) tree[opt] = ""    # so unlisted options marked
    for (opt in tree) {
    	if (tree[opt] == 1) {
	    tree[opt] = ""
	    if (option[opt] != "") {
	    	print "internal error (1)"
		exit 1
	    }
	    # Macros only listed in 'enables' remain off unless
	    # one of the enabling macros is on.
	    option[opt] = "off"
	}

    	split("", list) # clear 'list'
	# Now add every requires, iffs or enabledby entry to 'list'
	# so that we can add a unique list of requirements to tree[i]
    	split(requires[opt] iffs[opt] enabledby[opt], r)
	for (i in r) list[r[i]] = 1
	for (i in list) tree[opt] = tree[opt] " " i
    }

    # print the tree for extreme debugging
    if (deb > 2) for (i in tree) if (i != "") print i, "depends-on" tree[i]

    # option[i] is now the complete list of all the tokens we may
    # need to output, go through it as above, depth first.
    finished = 0
    while (!finished) {
    	finished = 1
	movement = 0 # done nothing
	for (i in option) if (!done[i]) {
	    nreqs = split(tree[i], r)
	    if (nreqs > 0) {
		for (j=1; j<=nreqs; ++j) if (!done[r[j]])
		    break
	    	if (j<=nreqs) {
		    finished = 0
		    continue  # next option
		}
	    }

	    # All the requirements have been processed, output
	    # this option.  An option is _SUPPORTED if:
	    #
	    # all 'requires' are _SUPPORTED AND
	    # at least one of the 'if' options are _SUPPORTED AND
	    # EITHER:
	    #   The name is _SUPPORTED (on the command line)
	    # OR:
	    #   an 'enabledby' is _SUPPORTED
	    # OR:
	    #   NO_name is not defined AND
	    #   the option is not marked "off"
	    if (deb) print "option", i
	    print "" >out
	    print "/* option:", i, option[i] >out
	    print " *   requires:  " requires[i] >out
	    print " *   if:        " iffs[i] >out
	    print " *   enabled-by:" enabledby[i], "*/" >out
	    print "#undef PNG_on" >out
	    print "#define PNG_on 1" >out

	    # requires
	    nreqs = split(requires[i], r)
	    for (j=1; j<=nreqs; ++j) {
	    	print "#ifndef PNG_" r[j] "_SUPPORTED" >out
		print "#   undef PNG_on /*!" r[j] "*/" >out
		print "#endif" >out
	    }

	    # if
	    nreqs = split(iffs[i], r)
	    print "#undef PNG_no_if" >out
	    if (nreqs > 0) {
		print "/* if" iffs[i], "*/" >out
	    	print "#define PNG_no_if 1" >out
		for (j=1; j<=nreqs; ++j) {
		    print "#ifdef PNG_" r[j] "_SUPPORTED" >out
		    print "#   undef PNG_no_if /*" r[j] "*/" >out
		    print "#endif" >out
		}
		print "#ifdef PNG_no_if /*missing if*/" >out
		print "#   undef PNG_on" >out
		print "#endif" >out
	    }

	    print "#ifdef PNG_on /*requires, if*/" >out
	    # enables
	    print "#   undef PNG_not_enabled" >out
	    print "#   define PNG_not_enabled 1" >out
	    print "   /* enabled by" enabledby[i], "*/" >out
	    nreqs = split(enabledby[i], r)
	    for (j=1; j<=nreqs; ++j) {
	    	print "#ifdef PNG_" r[j] "_SUPPORTED" >out
		print "#   undef PNG_not_enabled /*" r[j] "*/" >out
		print "#endif" >out
	    }

	    print "#   ifndef PNG_" i "_SUPPORTED /*!command line*/" >out
	    print "#     ifdef PNG_not_enabled /*!enabled*/" >out
	    if (option[i] == "off") {
		print "#       undef PNG_on /*default off*/" >out
	    } else {
		print "#       ifdef PNG_NO_" i >out
		print "#         undef PNG_on /*turned off*/" >out
		print "#       endif" >out
		print "#       ifdef PNG_NO_" i "_SUPPORTED" >out
		print "#         undef PNG_on /*turned off*/" >out
		print "#       endif" >out
	    }
	    print "#     endif /*!enabled*/" >out
	    print "#     ifdef PNG_on" >out
	    # The _SUPPORTED macro must be defined so that dependent
	    # options output later work.
	    print "#       define PNG_" i "_SUPPORTED" >out
	    print "#     endif" >out
	    print "#   endif /*!command line*/" >out
	    # If PNG_on is still set the option should be defined in
	    # pnglconf.h
	    print "#   ifdef PNG_on" >out
	    if (i ~ /^fail_/)
	        print error, i, "if" iffs[i], "requires" requires[i] end >out
	    else if (i !~ /^ok_/)
		print def i sup >out
	    print "#   endif /* definition */" >out
	    print "#endif /*requires, if*/" >out
	    if (logunsupported || i ~ /^ok_/) {
		print "#ifndef  PNG_on" >out
		if (logunsupported)
		    print und i une >out
		if (i ~ /^ok_/)
		    print error, i, "if" iffs[i], "requires" requires[i] end >out
		print "#endif" >out
	    }

	    done[i] = 1
	    ++movement
	}

	if (!finished && !movement) {
	    print "option: loop or missing option in dependency tree, cannot process:"
	    for (i in option) if (!done[i]) {
	    	print "  option", i, "depends on" tree[i], "needs:"
		nreqs = split(tree[i], r)
		if (nreqs > 0) for (j=1; j<=nreqs; ++j) if (!done[r[j]])
		    print "    " r[j]
	    }
	    exit 1
	}
    }
    print comment, "end of options", cend >out

    # Regular end - everything looks ok
    if (protect != "")
    	print start "#endif", cx, protect, "*/" end >out
}