ref: 397265f5791291defa76487c2388e1898e2e433c
dir: /include/cst_val_const.h/
/*************************************************************************/
/* */
/* Language Technologies Institute */
/* Carnegie Mellon University */
/* Copyright (c) 2001 */
/* All Rights Reserved. */
/* */
/* Permission is hereby granted, free of charge, to use and distribute */
/* this software and its documentation without restriction, including */
/* without limitation the rights to use, copy, modify, merge, publish, */
/* distribute, sublicense, and/or sell copies of this work, and to */
/* permit persons to whom this work is furnished to do so, subject to */
/* the following conditions: */
/* 1. The code must retain the above copyright notice, this list of */
/* conditions and the following disclaimer. */
/* 2. Any modifications must be clearly marked as such. */
/* 3. Original authors' names are not deleted. */
/* 4. The authors' names are not used to endorse or promote products */
/* derived from this software without specific prior written */
/* permission. */
/* */
/* CARNEGIE MELLON UNIVERSITY AND THE CONTRIBUTORS TO THIS WORK */
/* DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING */
/* ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT */
/* SHALL CARNEGIE MELLON UNIVERSITY NOR THE CONTRIBUTORS BE LIABLE */
/* FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES */
/* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN */
/* AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, */
/* ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF */
/* THIS SOFTWARE. */
/* */
/*************************************************************************/
/* Author: Alan W Black (awb@cs.cmu.edu) */
/* Date: January 2001 */
/*************************************************************************/
/* */
/* Const Vals, and macros to define them */
/* */
/* Before you give up in disgust bear with me on this. Every single */
/* line in this file has been *very* carefully decided on after much */
/* thought, experimentation and reading more specs of the C language */
/* than most people even thought existed. However inspite of that, the */
/* result is still unsatisfying from an elegance point of view but the */
/* given all the constraints this is probably the best compromise. */
/* */
/* This file offers macros for defining const cst_vals. I know many */
/* are already laughing at me for wanting runtime types on objects and */
/* will use this code as exemplars of why this should be done in C++, I */
/* say good luck to them with their 4M footprint while I go for my */
/* 50K footprint. But I *will* do cst_vals in 8 bytes and I *will* */
/* have them defined const so they are in the text segment */
/* */
/* The problem here is that there is not yet a standard way to do */
/* initialization of unions. There is one in the C99 standard and GCC */
/* already supports it, but other compilers do not so I can't use that */
/* */
/* So I need a way to make an object that will have the right 8 bytes */
/* for ints, floats, strings and cons cells that will work on any C */
/* compiler and will be of type const cst_val. That unfortunately */
/* isn't trivial. */
/* */
/* For the time being ignoring byte order, and address size, which */
/* will be ignored in the particular discuss (though dealt with below) */
/* I'd like to do something like */
/* */
/* const cst_val fredi = { CST_VAL_TYPE_INT,-1, 42 }; */
/* const cst_val fredf = { CST_VAL_TYPE_FLOAT,-1, 4.2 }; */
/* const cst_val freds = { CST_VAL_TYPE_STRING,-1, "42" }; */
/* */
/* Even if you accept warnings this isn't going to work, if you add */
/* extra {} you can get rid of some warnings but the fval/ival/ *vval */
/* part isn't going to work, the compiler *may* try to take the value */
/* and assign it using the type of the first field defined in the */
/* union. This could be made to work for ints and void* as pointers */
/* can be used as ints (even of 64 bit architectures) but the float */
/* isn't going to work. Casting will cause the float to be changed to */
/* an int by CPP which isn't what you want, what you want is that the */
/* four byte region gets filled with the four bytes that represent the */
/* float itself. Now you could get the four byte represention of the */
/* float and pretend that is an int (0xbfff9a4 for 4.2 on intel), that */
/* would work but that doesn't seem satifying and I'd need to have a */
/* preprocessor that could convert that. You could make atoms always */
/* have a pointer to another piece of memory, but that would take up */
/* another 4 bytes not just for these constants but all other cst_vals */
/* create */
/* */
/* So you could do */
/* */
/* const cst_val_int fredi = { CST_VAL_TYPE_INT,-1, 42 }; */
/* const cst_val_float fredf = { CST_VAL_TYPE_FLOAT,-1, 4.2 }; */
/* const cst_val_string freds = { CST_VAL_TYPE_STRING,-1, "42" }; */
/* */
/* Though that's a slippery slope I don't want to have these explicit */
/* new types, the first short defines the type perfectly adequately */
/* and the whole point of runtime types is that there is one object */
/* type. */
/* */
/* Well just initialize them at runtime, but, that isn't thread safe, */
/* slows down startup, requires a instance implicitly in the code and */
/* on the heap. As these are const, they should go in ROM. */
/* */
/* At this moment, I think the second version is the least problematic */
/* though it makes defining val_consts more unpleasant than they should */
/* be and forces changes elsewhere in the code even when the compiler */
/* does support initialization of unions */
/* */
/* */
/*************************************************************************/
#ifndef _CST_VAL_CONSTS_H__
#define _CST_VAL_CONSTS_H__
#include "cst_val_defs.h"
#include <stdint.h>
/* There is built-in int to string conversions here for numbers */
/* up to 20, note if you make this bigger you have to hand change */
/* other things too */
#define CST_CONST_INT_MAX 19
#ifndef NO_UNION_INITIALIZATION
/* This is the simple way when initialization of unions is supported */
#define DEF_CONST_VAL_INT(N,V) const cst_val N = {{.a={.type=CST_VAL_TYPE_INT,.ref_count=-1,.v={.ival=V}}}}
#define DEF_CONST_VAL_STRING(N,S) const cst_val N = {{.a={.type=CST_VAL_TYPE_STRING,.ref_count=-1,.v={.vval= (void *)S}}}}
#define DEF_CONST_VAL_FLOAT(N,F) const cst_val N = {{.a={.type=CST_VAL_TYPE_FLOAT,.ref_count=-1,.v={.fval=F}}}}
#define DEF_CONST_VAL_CONS(N,A,D) const cst_val N = {{.cc={.car=(cst_val *)A,.cdr=(cst_val *)D }}}
extern const cst_val val_int_0;
extern const cst_val val_int_1;
extern const cst_val val_int_2;
extern const cst_val val_int_3;
extern const cst_val val_int_4;
extern const cst_val val_int_5;
extern const cst_val val_int_6;
extern const cst_val val_int_7;
extern const cst_val val_int_8;
extern const cst_val val_int_9;
extern const cst_val val_int_10;
extern const cst_val val_int_11;
extern const cst_val val_int_12;
extern const cst_val val_int_13;
extern const cst_val val_int_14;
extern const cst_val val_int_15;
extern const cst_val val_int_16;
extern const cst_val val_int_17;
extern const cst_val val_int_18;
extern const cst_val val_int_19;
extern const cst_val val_int_20;
extern const cst_val val_int_21;
extern const cst_val val_int_22;
extern const cst_val val_int_23;
extern const cst_val val_int_24;
extern const cst_val val_string_0;
extern const cst_val val_string_1;
extern const cst_val val_string_2;
extern const cst_val val_string_3;
extern const cst_val val_string_4;
extern const cst_val val_string_5;
extern const cst_val val_string_6;
extern const cst_val val_string_7;
extern const cst_val val_string_8;
extern const cst_val val_string_9;
extern const cst_val val_string_10;
extern const cst_val val_string_11;
extern const cst_val val_string_12;
extern const cst_val val_string_13;
extern const cst_val val_string_14;
extern const cst_val val_string_15;
extern const cst_val val_string_16;
extern const cst_val val_string_17;
extern const cst_val val_string_18;
extern const cst_val val_string_19;
extern const cst_val val_string_20;
extern const cst_val val_string_21;
extern const cst_val val_string_22;
extern const cst_val val_string_23;
extern const cst_val val_string_24;
#else
/* Only GCC seems to currently support the C99 standard for giving */
/* explicit names for fields for initializing unions, because we want */
/* things to be const, and to be small structures this is really useful */
/* thus for compilers not supporting no_union_initization we use other */
/* structure that we know (hope ?) are the same size and use agressive */
/* casting. The goal here is wholly justified but the method here isn't */
/* pretty */
/* These structures are defined *solely* to get round initialization */
/* problems if you need to use these in any code you are using, you are */
/* unquestionably doing the wrong thing */
typedef struct cst_val_atom_struct_float {
#ifdef WORDS_BIGENDIAN
#if UINTPTR_MAX > 0xfffffffful
int ref_count;
int type; /* order is here important */
#else
short ref_count;
short type; /* order is here important */
#endif
#else
#if UINTPTR_MAX > 0xfffffffful
int type; /* order is here important */
int ref_count;
#else
short type; /* order is here important */
short ref_count;
#endif
#endif
#if UINTPTR_MAX > 0xfffffffful
double fval;
#else
float fval;
#endif
} cst_val_float;
typedef struct cst_val_atom_struct_int {
#ifdef WORDS_BIGENDIAN
#if UINTPTR_MAX > 0xfffffffful
int ref_count;
int type; /* order is here important (and unintuitive) */
#else
short ref_count;
short type; /* order is here important (and unintuitive) */
#endif
#else
#if UINTPTR_MAX > 0xfffffffful
int type; /* order is here important */
int ref_count;
#else
short type; /* order is here important */
short ref_count;
#endif
#endif
#if UINTPTR_MAX > 0xfffffffful
long long ival;
#else
int ival;
#endif
} cst_val_int;
typedef struct cst_val_atom_struct_void {
#ifdef WORDS_BIGENDIAN
#if UINTPTR_MAX > 0xfffffffful
int ref_count;
int type; /* order is here important */
#else
short ref_count;
short type; /* order is here important */
#endif
#else
#if UINTPTR_MAX > 0xfffffffful
int type; /* order is here important */
int ref_count;
#else
short type; /* order is here important */
short ref_count;
#endif
#endif
void *vval;
} cst_val_void;
#ifdef WORDS_BIGENDIAN
#define DEF_CONST_VAL_INT(N,V) const cst_val_int N={-1, CST_VAL_TYPE_INT, V}
#define DEF_CONST_VAL_STRING(N,S) const cst_val_void N={-1,CST_VAL_TYPE_STRING,(void *)S}
#define DEF_CONST_VAL_FLOAT(N,F) const cst_val_float N={-1,CST_VAL_TYPE_FLOAT,(float)F}
#else
#define DEF_CONST_VAL_INT(N,V) const cst_val_int N={CST_VAL_TYPE_INT,-1,V}
#define DEF_CONST_VAL_STRING(N,S) const cst_val_void N={CST_VAL_TYPE_STRING,-1,(void *)S}
#define DEF_CONST_VAL_FLOAT(N,F) const cst_val_float N={CST_VAL_TYPE_FLOAT,-1,(float)F}
#endif
#define DEF_CONST_VAL_CONS(N,A,D) const cst_val_cons N={A,D}
/* in the non-union intialization version we these consts have to be */
/* more typed than need, we'll cast the back later */
extern const cst_val_int val_int_0;
extern const cst_val_int val_int_1;
extern const cst_val_int val_int_2;
extern const cst_val_int val_int_3;
extern const cst_val_int val_int_4;
extern const cst_val_int val_int_5;
extern const cst_val_int val_int_6;
extern const cst_val_int val_int_7;
extern const cst_val_int val_int_8;
extern const cst_val_int val_int_9;
extern const cst_val_int val_int_10;
extern const cst_val_int val_int_11;
extern const cst_val_int val_int_12;
extern const cst_val_int val_int_13;
extern const cst_val_int val_int_14;
extern const cst_val_int val_int_15;
extern const cst_val_int val_int_16;
extern const cst_val_int val_int_17;
extern const cst_val_int val_int_18;
extern const cst_val_int val_int_19;
extern const cst_val_int val_int_20;
extern const cst_val_int val_int_21;
extern const cst_val_int val_int_22;
extern const cst_val_int val_int_23;
extern const cst_val_int val_int_24;
extern const cst_val_void val_string_0;
extern const cst_val_void val_string_1;
extern const cst_val_void val_string_2;
extern const cst_val_void val_string_3;
extern const cst_val_void val_string_4;
extern const cst_val_void val_string_5;
extern const cst_val_void val_string_6;
extern const cst_val_void val_string_7;
extern const cst_val_void val_string_8;
extern const cst_val_void val_string_9;
extern const cst_val_void val_string_10;
extern const cst_val_void val_string_11;
extern const cst_val_void val_string_12;
extern const cst_val_void val_string_13;
extern const cst_val_void val_string_14;
extern const cst_val_void val_string_15;
extern const cst_val_void val_string_16;
extern const cst_val_void val_string_17;
extern const cst_val_void val_string_18;
extern const cst_val_void val_string_19;
extern const cst_val_void val_string_20;
extern const cst_val_void val_string_21;
extern const cst_val_void val_string_22;
extern const cst_val_void val_string_23;
extern const cst_val_void val_string_24;
#endif
#define DEF_STATIC_CONST_VAL_INT(N,V) static DEF_CONST_VAL_INT(N,V)
#define DEF_STATIC_CONST_VAL_STRING(N,S) static DEF_CONST_VAL_STRING(N,S)
#define DEF_STATIC_CONST_VAL_FLOAT(N,F) static DEF_CONST_VAL_FLOAT(N,F)
#define DEF_STATIC_CONST_VAL_CONS(N,A,D) static DEF_CONST_VAL_CONS(N,A,D)
/* Some actual val consts */
/* The have casts as in the non-union intialize case the casts are necessary */
/* but in the union initial case these casts are harmless */
#define VAL_INT_0 (cst_val *)&val_int_0
#define VAL_INT_1 (cst_val *)&val_int_1
#define VAL_INT_2 (cst_val *)&val_int_2
#define VAL_INT_3 (cst_val *)&val_int_3
#define VAL_INT_4 (cst_val *)&val_int_4
#define VAL_INT_5 (cst_val *)&val_int_5
#define VAL_INT_6 (cst_val *)&val_int_6
#define VAL_INT_7 (cst_val *)&val_int_7
#define VAL_INT_8 (cst_val *)&val_int_8
#define VAL_INT_9 (cst_val *)&val_int_9
#define VAL_INT_10 (cst_val *)&val_int_10
#define VAL_INT_11 (cst_val *)&val_int_11
#define VAL_INT_12 (cst_val *)&val_int_12
#define VAL_INT_13 (cst_val *)&val_int_13
#define VAL_INT_14 (cst_val *)&val_int_14
#define VAL_INT_15 (cst_val *)&val_int_15
#define VAL_INT_16 (cst_val *)&val_int_16
#define VAL_INT_17 (cst_val *)&val_int_17
#define VAL_INT_18 (cst_val *)&val_int_18
#define VAL_INT_19 (cst_val *)&val_int_19
#define VAL_INT_20 (cst_val *)&val_int_20
#define VAL_INT_21 (cst_val *)&val_int_21
#define VAL_INT_22 (cst_val *)&val_int_22
#define VAL_INT_23 (cst_val *)&val_int_23
#define VAL_INT_24 (cst_val *)&val_int_24
const cst_val *val_int_n(int n);
#define VAL_STRING_0 (cst_val *)&val_string_0
#define VAL_STRING_1 (cst_val *)&val_string_1
#define VAL_STRING_2 (cst_val *)&val_string_2
#define VAL_STRING_3 (cst_val *)&val_string_3
#define VAL_STRING_4 (cst_val *)&val_string_4
#define VAL_STRING_5 (cst_val *)&val_string_5
#define VAL_STRING_6 (cst_val *)&val_string_6
#define VAL_STRING_7 (cst_val *)&val_string_7
#define VAL_STRING_8 (cst_val *)&val_string_8
#define VAL_STRING_9 (cst_val *)&val_string_9
#define VAL_STRING_10 (cst_val *)&val_string_10
#define VAL_STRING_11 (cst_val *)&val_string_11
#define VAL_STRING_12 (cst_val *)&val_string_12
#define VAL_STRING_13 (cst_val *)&val_string_13
#define VAL_STRING_14 (cst_val *)&val_string_14
#define VAL_STRING_15 (cst_val *)&val_string_15
#define VAL_STRING_16 (cst_val *)&val_string_16
#define VAL_STRING_17 (cst_val *)&val_string_17
#define VAL_STRING_18 (cst_val *)&val_string_18
#define VAL_STRING_19 (cst_val *)&val_string_19
#define VAL_STRING_20 (cst_val *)&val_string_20
#define VAL_STRING_21 (cst_val *)&val_string_21
#define VAL_STRING_22 (cst_val *)&val_string_22
#define VAL_STRING_23 (cst_val *)&val_string_23
#define VAL_STRING_24 (cst_val *)&val_string_24
const cst_val *val_string_n(int n);
#endif