329 lines
16 KiB
C
329 lines
16 KiB
C
/*************************************************************************/
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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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