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328 lines
16 KiB
328 lines
16 KiB
/*************************************************************************/ |
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/* */ |
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/* Language Technologies Institute */ |
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/* Carnegie Mellon University */ |
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/* Copyright (c) 2001 */ |
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/* All Rights Reserved. */ |
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/* */ |
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/* Permission is hereby granted, free of charge, to use and distribute */ |
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/* this software and its documentation without restriction, including */ |
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/* without limitation the rights to use, copy, modify, merge, publish, */ |
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/* distribute, sublicense, and/or sell copies of this work, and to */ |
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/* permit persons to whom this work is furnished to do so, subject to */ |
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/* the following conditions: */ |
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/* 1. The code must retain the above copyright notice, this list of */ |
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/* conditions and the following disclaimer. */ |
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/* 2. Any modifications must be clearly marked as such. */ |
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/* 3. Original authors' names are not deleted. */ |
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/* 4. The authors' names are not used to endorse or promote products */ |
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/* derived from this software without specific prior written */ |
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/* permission. */ |
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/* */ |
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/* CARNEGIE MELLON UNIVERSITY AND THE CONTRIBUTORS TO THIS WORK */ |
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/* DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING */ |
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/* ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT */ |
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/* SHALL CARNEGIE MELLON UNIVERSITY NOR THE CONTRIBUTORS BE LIABLE */ |
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/* FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES */ |
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/* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN */ |
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/* AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, */ |
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/* ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF */ |
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/* THIS SOFTWARE. */ |
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/* */ |
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/*************************************************************************/ |
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/* Author: Alan W Black (awb@cs.cmu.edu) */ |
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/* Date: January 2001 */ |
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/*************************************************************************/ |
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/* */ |
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/* Const Vals, and macros to define them */ |
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/* */ |
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/* Before you give up in disgust bear with me on this. Every single */ |
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/* line in this file has been *very* carefully decided on after much */ |
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/* thought, experimentation and reading more specs of the C language */ |
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/* than most people even thought existed. However inspite of that, the */ |
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/* result is still unsatisfying from an elegance point of view but the */ |
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/* given all the constraints this is probably the best compromise. */ |
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/* */ |
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/* This file offers macros for defining const cst_vals. I know many */ |
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/* are already laughing at me for wanting runtime types on objects and */ |
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/* will use this code as exemplars of why this should be done in C++, I */ |
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/* say good luck to them with their 4M footprint while I go for my */ |
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/* 50K footprint. But I *will* do cst_vals in 8 bytes and I *will* */ |
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/* have them defined const so they are in the text segment */ |
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/* */ |
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/* The problem here is that there is not yet a standard way to do */ |
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/* initialization of unions. There is one in the C99 standard and GCC */ |
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/* already supports it, but other compilers do not so I can't use that */ |
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/* */ |
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/* So I need a way to make an object that will have the right 8 bytes */ |
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/* for ints, floats, strings and cons cells that will work on any C */ |
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/* compiler and will be of type const cst_val. That unfortunately */ |
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/* isn't trivial. */ |
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/* */ |
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/* For the time being ignoring byte order, and address size, which */ |
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/* will be ignored in the particular discuss (though dealt with below) */ |
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/* I'd like to do something like */ |
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/* */ |
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/* const cst_val fredi = { CST_VAL_TYPE_INT,-1, 42 }; */ |
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/* const cst_val fredf = { CST_VAL_TYPE_FLOAT,-1, 4.2 }; */ |
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/* const cst_val freds = { CST_VAL_TYPE_STRING,-1, "42" }; */ |
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/* */ |
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/* Even if you accept warnings this isn't going to work, if you add */ |
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/* extra {} you can get rid of some warnings but the fval/ival/ *vval */ |
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/* part isn't going to work, the compiler *may* try to take the value */ |
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/* and assign it using the type of the first field defined in the */ |
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/* union. This could be made to work for ints and void* as pointers */ |
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/* can be used as ints (even of 64 bit architectures) but the float */ |
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/* isn't going to work. Casting will cause the float to be changed to */ |
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/* an int by CPP which isn't what you want, what you want is that the */ |
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/* four byte region gets filled with the four bytes that represent the */ |
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/* float itself. Now you could get the four byte represention of the */ |
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/* float and pretend that is an int (0xbfff9a4 for 4.2 on intel), that */ |
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/* would work but that doesn't seem satifying and I'd need to have a */ |
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/* preprocessor that could convert that. You could make atoms always */ |
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/* have a pointer to another piece of memory, but that would take up */ |
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/* another 4 bytes not just for these constants but all other cst_vals */ |
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/* create */ |
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/* */ |
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/* So you could do */ |
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/* */ |
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/* const cst_val_int fredi = { CST_VAL_TYPE_INT,-1, 42 }; */ |
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/* const cst_val_float fredf = { CST_VAL_TYPE_FLOAT,-1, 4.2 }; */ |
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/* const cst_val_string freds = { CST_VAL_TYPE_STRING,-1, "42" }; */ |
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/* */ |
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/* Though that's a slippery slope I don't want to have these explicit */ |
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/* new types, the first short defines the type perfectly adequately */ |
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/* and the whole point of runtime types is that there is one object */ |
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/* type. */ |
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/* */ |
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/* Well just initialize them at runtime, but, that isn't thread safe, */ |
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/* slows down startup, requires a instance implicitly in the code and */ |
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/* on the heap. As these are const, they should go in ROM. */ |
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/* */ |
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/* At this moment, I think the second version is the least problematic */ |
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/* though it makes defining val_consts more unpleasant than they should */ |
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/* be and forces changes elsewhere in the code even when the compiler */ |
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/* does support initialization of unions */ |
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/* */ |
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/* */ |
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/*************************************************************************/ |
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#ifndef _CST_VAL_CONSTS_H__ |
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#define _CST_VAL_CONSTS_H__ |
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#include "cst_val_defs.h" |
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/* There is built-in int to string conversions here for numbers */ |
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/* up to 20, note if you make this bigger you have to hand change */ |
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/* other things too */ |
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#define CST_CONST_INT_MAX 19 |
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#ifndef NO_UNION_INITIALIZATION |
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/* This is the simple way when initialization of unions is supported */ |
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#define DEF_CONST_VAL_INT(N,V) const cst_val N = {{.a={.type=CST_VAL_TYPE_INT,.ref_count=-1,.v={.ival=V}}}} |
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#define DEF_CONST_VAL_STRING(N,S) const cst_val N = {{.a={.type=CST_VAL_TYPE_STRING,.ref_count=-1,.v={.vval= (void *)S}}}} |
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#define DEF_CONST_VAL_FLOAT(N,F) const cst_val N = {{.a={.type=CST_VAL_TYPE_FLOAT,.ref_count=-1,.v={.fval=F}}}} |
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#define DEF_CONST_VAL_CONS(N,A,D) const cst_val N = {{.cc={.car=A,.cdr=D }}} |
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extern const cst_val val_int_0; |
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extern const cst_val val_int_1; |
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extern const cst_val val_int_2; |
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extern const cst_val val_int_3; |
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extern const cst_val val_int_4; |
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extern const cst_val val_int_5; |
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extern const cst_val val_int_6; |
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extern const cst_val val_int_7; |
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extern const cst_val val_int_8; |
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extern const cst_val val_int_9; |
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extern const cst_val val_int_10; |
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extern const cst_val val_int_11; |
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extern const cst_val val_int_12; |
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extern const cst_val val_int_13; |
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extern const cst_val val_int_14; |
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extern const cst_val val_int_15; |
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extern const cst_val val_int_16; |
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extern const cst_val val_int_17; |
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extern const cst_val val_int_18; |
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extern const cst_val val_int_19; |
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extern const cst_val val_string_0; |
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extern const cst_val val_string_1; |
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extern const cst_val val_string_2; |
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extern const cst_val val_string_3; |
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extern const cst_val val_string_4; |
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extern const cst_val val_string_5; |
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extern const cst_val val_string_6; |
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extern const cst_val val_string_7; |
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extern const cst_val val_string_8; |
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extern const cst_val val_string_9; |
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extern const cst_val val_string_10; |
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extern const cst_val val_string_11; |
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extern const cst_val val_string_12; |
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extern const cst_val val_string_13; |
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extern const cst_val val_string_14; |
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extern const cst_val val_string_15; |
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extern const cst_val val_string_16; |
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extern const cst_val val_string_17; |
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extern const cst_val val_string_18; |
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extern const cst_val val_string_19; |
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#else |
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/* Only GCC seems to currently support the C99 standard for giving */ |
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/* explicit names for fields for initializing unions, because we want */ |
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/* things to be const, and to be small structures this is really useful */ |
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/* thus for compilers not supporting no_union_initization we use other */ |
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/* structure that we know (hope ?) are the same size and use agressive */ |
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/* casting. The goal here is wholly justified by the method here isn't */ |
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/* pretty */ |
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/* These structures are defined *solely* to get round initialization */ |
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/* problems if you need to use these in any code you are using your are */ |
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/* unquestionably doing the wrong thing */ |
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typedef struct cst_val_atom_struct_float { |
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#ifdef WORDS_BIGENDIAN |
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short ref_count; |
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short type; /* order is here important */ |
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#else |
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short type; /* order is here important */ |
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short ref_count; |
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#endif |
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float fval; |
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} cst_val_float; |
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typedef struct cst_val_atom_struct_int { |
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#ifdef WORDS_BIGENDIAN |
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short ref_count; |
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short type; /* order is here important (and unintuitive) */ |
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#else |
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short type; /* order is here important */ |
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short ref_count; |
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#endif |
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int ival; |
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} cst_val_int; |
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typedef struct cst_val_atom_struct_void { |
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#ifdef WORDS_BIGENDIAN |
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short ref_count; |
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short type; /* order is here important */ |
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#else |
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short type; /* order is here important */ |
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short ref_count; |
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#endif |
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void *vval; |
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} cst_val_void; |
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#ifdef WORDS_BIGENDIAN |
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#define DEF_CONST_VAL_INT(N,V) const cst_val_int N={-1, CST_VAL_TYPE_INT, V} |
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#define DEF_CONST_VAL_STRING(N,S) const cst_val_void N={-1,CST_VAL_TYPE_STRING,(void *)S} |
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#define DEF_CONST_VAL_FLOAT(N,F) const cst_val_float N={-1,CST_VAL_TYPE_FLOAT,(float)F} |
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#else |
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#define DEF_CONST_VAL_INT(N,V) const cst_val_int N={CST_VAL_TYPE_INT,-1,V} |
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#define DEF_CONST_VAL_STRING(N,S) const cst_val_void N={CST_VAL_TYPE_STRING,-1,(void *)S} |
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#define DEF_CONST_VAL_FLOAT(N,F) const cst_val_float N={CST_VAL_TYPE_FLOAT,-1,(float)F} |
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#endif |
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#define DEF_CONST_VAL_CONS(N,A,D) const cst_val_cons N={A,D} |
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/* in the non-union intialization version we these consts have to be */ |
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/* more typed than need, we'll cast the back later */ |
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extern const cst_val_int val_int_0; |
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extern const cst_val_int val_int_1; |
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extern const cst_val_int val_int_2; |
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extern const cst_val_int val_int_3; |
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extern const cst_val_int val_int_4; |
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extern const cst_val_int val_int_5; |
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extern const cst_val_int val_int_6; |
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extern const cst_val_int val_int_7; |
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extern const cst_val_int val_int_8; |
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extern const cst_val_int val_int_9; |
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extern const cst_val_int val_int_10; |
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extern const cst_val_int val_int_11; |
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extern const cst_val_int val_int_12; |
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extern const cst_val_int val_int_13; |
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extern const cst_val_int val_int_14; |
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extern const cst_val_int val_int_15; |
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extern const cst_val_int val_int_16; |
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extern const cst_val_int val_int_17; |
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extern const cst_val_int val_int_18; |
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extern const cst_val_int val_int_19; |
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extern const cst_val_void val_string_0; |
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extern const cst_val_void val_string_1; |
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extern const cst_val_void val_string_2; |
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extern const cst_val_void val_string_3; |
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extern const cst_val_void val_string_4; |
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extern const cst_val_void val_string_5; |
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extern const cst_val_void val_string_6; |
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extern const cst_val_void val_string_7; |
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extern const cst_val_void val_string_8; |
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extern const cst_val_void val_string_9; |
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extern const cst_val_void val_string_10; |
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extern const cst_val_void val_string_11; |
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extern const cst_val_void val_string_12; |
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extern const cst_val_void val_string_13; |
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extern const cst_val_void val_string_14; |
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extern const cst_val_void val_string_15; |
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extern const cst_val_void val_string_16; |
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extern const cst_val_void val_string_17; |
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extern const cst_val_void val_string_18; |
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extern const cst_val_void val_string_19; |
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#endif |
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#define DEF_STATIC_CONST_VAL_INT(N,V) static DEF_CONST_VAL_INT(N,V) |
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#define DEF_STATIC_CONST_VAL_STRING(N,S) static DEF_CONST_VAL_STRING(N,S) |
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#define DEF_STATIC_CONST_VAL_FLOAT(N,F) static DEF_CONST_VAL_FLOAT(N,F) |
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#define DEF_STATIC_CONST_VAL_CONS(N,A,D) static DEF_CONST_VAL_CONS(N,A,D) |
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/* Some actual val consts */ |
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/* The have casts as in the non-union intialize case the casts are necessary */ |
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/* but in the union initial case these casts are harmless */ |
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#define VAL_INT_0 (cst_val *)&val_int_0 |
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#define VAL_INT_1 (cst_val *)&val_int_1 |
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#define VAL_INT_2 (cst_val *)&val_int_2 |
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#define VAL_INT_3 (cst_val *)&val_int_3 |
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#define VAL_INT_4 (cst_val *)&val_int_4 |
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#define VAL_INT_5 (cst_val *)&val_int_5 |
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#define VAL_INT_6 (cst_val *)&val_int_6 |
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#define VAL_INT_7 (cst_val *)&val_int_7 |
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#define VAL_INT_8 (cst_val *)&val_int_8 |
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#define VAL_INT_9 (cst_val *)&val_int_9 |
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#define VAL_INT_10 (cst_val *)&val_int_10 |
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#define VAL_INT_11 (cst_val *)&val_int_11 |
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#define VAL_INT_12 (cst_val *)&val_int_12 |
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#define VAL_INT_13 (cst_val *)&val_int_13 |
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#define VAL_INT_14 (cst_val *)&val_int_14 |
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#define VAL_INT_15 (cst_val *)&val_int_15 |
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#define VAL_INT_16 (cst_val *)&val_int_16 |
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#define VAL_INT_17 (cst_val *)&val_int_17 |
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#define VAL_INT_18 (cst_val *)&val_int_18 |
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#define VAL_INT_19 (cst_val *)&val_int_19 |
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const cst_val *val_int_n(int n); |
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#define VAL_STRING_0 (cst_val *)&val_string_0 |
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#define VAL_STRING_1 (cst_val *)&val_string_1 |
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#define VAL_STRING_2 (cst_val *)&val_string_2 |
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#define VAL_STRING_3 (cst_val *)&val_string_3 |
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#define VAL_STRING_4 (cst_val *)&val_string_4 |
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#define VAL_STRING_5 (cst_val *)&val_string_5 |
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#define VAL_STRING_6 (cst_val *)&val_string_6 |
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#define VAL_STRING_7 (cst_val *)&val_string_7 |
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#define VAL_STRING_8 (cst_val *)&val_string_8 |
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#define VAL_STRING_9 (cst_val *)&val_string_9 |
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#define VAL_STRING_10 (cst_val *)&val_string_10 |
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#define VAL_STRING_11 (cst_val *)&val_string_11 |
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#define VAL_STRING_12 (cst_val *)&val_string_12 |
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#define VAL_STRING_13 (cst_val *)&val_string_13 |
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#define VAL_STRING_14 (cst_val *)&val_string_14 |
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#define VAL_STRING_15 (cst_val *)&val_string_15 |
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#define VAL_STRING_16 (cst_val *)&val_string_16 |
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#define VAL_STRING_17 (cst_val *)&val_string_17 |
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#define VAL_STRING_18 (cst_val *)&val_string_18 |
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#define VAL_STRING_19 (cst_val *)&val_string_19 |
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const cst_val *val_string_n(int n); |
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#endif
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