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/* classes: h_files */
#ifndef SCM_TAGS_H
#define SCM_TAGS_H
/* Copyright (C) 1995,1996,1997,1998,1999,2000,2001 Free Software Foundation, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this software; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307 USA
*
* As a special exception, the Free Software Foundation gives permission
* for additional uses of the text contained in its release of GUILE.
*
* The exception is that, if you link the GUILE library with other files
* to produce an executable, this does not by itself cause the
* resulting executable to be covered by the GNU General Public License.
* Your use of that executable is in no way restricted on account of
* linking the GUILE library code into it.
*
* This exception does not however invalidate any other reasons why
* the executable file might be covered by the GNU General Public License.
*
* This exception applies only to the code released by the
* Free Software Foundation under the name GUILE. If you copy
* code from other Free Software Foundation releases into a copy of
* GUILE, as the General Public License permits, the exception does
* not apply to the code that you add in this way. To avoid misleading
* anyone as to the status of such modified files, you must delete
* this exception notice from them.
*
* If you write modifications of your own for GUILE, it is your choice
* whether to permit this exception to apply to your modifications.
* If you do not wish that, delete this exception notice. */
/** This file defines the format of SCM values and cons pairs.
** It is here that tag bits are assigned for various purposes.
**/
#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif
#ifdef HAVE_INTTYPES_H
#include <inttypes.h>
#endif
/* In the beginning was the Word:
*/
#ifdef HAVE_UINTPTR_T
typedef uintptr_t scm_t_bits;
typedef intptr_t scm_t_signed_bits;
#else
typedef unsigned long scm_t_bits;
typedef signed long scm_t_signed_bits;
#endif
/* But as external interface, we use SCM, which may, according to the desired
* level of type checking, be defined in several ways:
*/
#if (SCM_DEBUG_TYPING_STRICTNESS == 2)
typedef union { struct { scm_t_bits n; } n; } SCM;
static SCM scm_pack(scm_t_bits b) { SCM s; s.n.n = b; return s; }
# define SCM_UNPACK(x) ((x).n.n)
# define SCM_PACK(x) (scm_pack ((scm_t_bits) (x)))
#elif (SCM_DEBUG_TYPING_STRICTNESS == 1)
/* This is the default, which provides an intermediate level of compile time
* type checking while still resulting in very efficient code.
*/
typedef struct scm_unused_struct * SCM;
# define SCM_UNPACK(x) ((scm_t_bits) (x))
# define SCM_PACK(x) ((SCM) (x))
#else
/* This should be used as a fall back solution for machines on which casting
* to a pointer may lead to loss of bit information, e. g. in the three least
* significant bits.
*/
typedef scm_t_bits SCM;
# define SCM_UNPACK(x) (x)
# define SCM_PACK(x) ((scm_t_bits) (x))
#endif
/* SCM values can not be compared by using the operator ==. Use the following
* macro instead, which is the equivalent of the scheme predicate 'eq?'.
*/
#define SCM_EQ_P(x, y) (SCM_UNPACK (x) == SCM_UNPACK (y))
/* SCM variables can contain:
*
* Non-objects -- meaning that the tag-related macros don't apply to them
* in the usual way.
*
* Immediates -- meaning that the variable contains an entire Scheme object.
*
* Non-immediates -- meaning that the variable holds a (possibly
* tagged) pointer into the cons pair heap.
*
* Non-objects are distinguished from other values by careful coding
* only (i.e., programmers must keep track of any SCM variables they
* create that don't contain ordinary scheme values).
*
* All immediates and non-immediates must have a 0 in bit 0. Only
* non-object values can have a 1 in bit 0. In some cases, bit 0 of a
* word in the heap is used for the GC tag so during garbage
* collection, that bit might be 1 even in an immediate or
* non-immediate value. In other cases, bit 0 of a word in the heap
* is used to tag a pointer to a GLOC (VM global variable address) or
* the header of a struct. But whenever an SCM variable holds a
* normal Scheme value, bit 0 is 0.
*
* Immediates and non-immediates are distinguished by bits two and four.
* Immediate values must have a 1 in at least one of those bits. Does
* this (or any other detail of tagging) seem arbitrary? Try changing it!
* (Not always impossible but it is fair to say that many details of tags
* are mutually dependent). */
#define SCM_IMP(x) (6 & SCM_UNPACK (x))
#define SCM_NIMP(x) (!SCM_IMP (x))
/* Here is a summary of tagging in SCM values as they might occur in
* SCM variables or in the heap.
*
* low bits meaning
*
*
* 0 Most objects except...
* 1 ...glocs and structs (this tag valid only in a SCM_CAR or
* in the header of a struct's data).
*
* 00 heap addresses and many immediates (not integers)
* 01 glocs/structs, some tc7_ codes
* 10 immediate integers
* 11 various tc7_ codes including, tc16_ codes.
*
*
* 000 heap address
* 001 glocs/structs
* 010 integer
* 011 closure
* 100 immediates
* 101 tc7_
* 110 integer
* 111 tc7_
*
*
* 100 --- IMMEDIATES
*
* Looking at the seven final bits of an immediate:
*
* 0000-100 short instruction
* 0001-100 short instruction
* 0010-100 short instruction
* 0011-100 short instruction
* 0100-100 short instruction
* 0101-100 short instruction
* 0110-100 various immediates and long instructions
* 0111-100 short instruction
* 1000-100 short instruction
* 1001-100 short instruction
* 1010-100 short instruction
* 1011-100 short instruction
* 1100-100 short instruction
* 1101-100 short instruction
* 1110-100 immediate characters
* 1111-100 ilocs
*
* Some of the 0110100 immediates are long instructions (they dispatch
* in two steps compared to one step for a short instruction).
* The two steps are, (1) dispatch on 7 bits to the long instruction
* handler, (2) dispatch on 7 additional bits.
*
* One way to think of it is that there are 128 short instructions,
* with the 13 immediates above being some of the most interesting.
*
* Also noteworthy are the groups of 16 7-bit instructions implied by
* some of the 3-bit tags. For example, closure references consist
* of an 8-bit aligned address tagged with 011. There are 16 identical 7-bit
* instructions, all ending 011, which are invoked by evaluating closures.
*
* In other words, if you hand the evaluator a closure, the evaluator
* treats the closure as a graph of virtual machine instructions.
* A closure is a pair with a pointer to the body of the procedure
* in the CDR and a pointer to the environment of the closure in the CAR.
* The environment pointer is tagged 011 which implies that the least
* significant 7 bits of the environment pointer also happen to be
* a virtual machine instruction we could call "SELF" (for self-evaluating
* object).
*
* A less trivial example are the 16 instructions ending 000. If those
* bits tag the CAR of a pair, then evidently the pair is an ordinary
* cons pair and should be evaluated as a procedure application. The sixteen,
* 7-bit 000 instructions are all "NORMAL-APPLY" (Things get trickier.
* For example, if the CAR of a procedure application is a symbol, the NORMAL-APPLY
* instruction will, as a side effect, overwrite that CAR with a new instruction
* that contains a cached address for the variable named by the symbol.)
*
* Here is a summary of tags in the CAR of a non-immediate:
*
* HEAP CELL: G=gc_mark; 1 during mark, 0 other times.
*
* cons ..........SCM car..............0 ...........SCM cdr.............G
* gloc ..........SCM vcell..........001 ...........SCM cdr.............G
* struct ..........void * type........001 ...........void * data.........G
* closure ..........SCM code...........011 ...........SCM env.............G
* tc7 ......24.bits of data...Gxxxx1S1 ..........void *data............
*
*
*
* 101 & 111 --- tc7_ types
*
* tc7_tags are 7 bit tags ending in 1x1. These tags
* occur only in the CAR of heap cells, and have the
* handy property that all bits of the CAR above the
* bottom eight can be used to store some data, thus
* saving a word in the body itself. Thus, we use them
* for strings and vectors (among other things).
*
* TYP7(X) returns bits 0...6 of CELL_TYPE (X)
*
* Sometimes we choose the bottom seven bits carefully,
* so that the 2-valued bit (called S bit) can be masked
* off to reveal a common type.
*
* TYP7S(X) returns TYP7, but masking out the option bit S.
*
* For example, all strings have 0010 in the 'xxxx' bits
* in the diagram above, the S bit says whether it's a
* substring.
*
* for example:
* S
* scm_tc7_string = G0010101
* scm_tc7_substring = G0010111
*
* TYP7S turns both string tags into tc7_string; thus,
* testing TYP7S against tc7_string is a quick way to
* test for any kind of string, shared or unshared.
*
* Some TC7 types are subdivided into 256 subtypes giving
* rise to the macros:
*
* TYP16
* TYP16S
*
* TYP16S functions similarly wrt to TYP16 as TYP7S to TYP7,
* but a different option bit is used (bit 2 for TYP7S,
* bit 8 for TYP16S).
* */
/* {Non-immediate values.}
*
* If X is non-immediate, it is necessary to look at SCM_CAR (X) to
* figure out Xs type. X may be a cons pair, in which case the value
* SCM_CAR (x) will be either an immediate or non-immediate value. X
* may be something other than a cons pair, in which case the value
* SCM_CAR (x) will be a non-object value.
*
* All immediates and non-immediates have a 0 in bit 0. We
* additionally preserve the invariant that all non-object values
* stored in the SCM_CAR of a non-immediate object have a 1 in bit 1:
*/
#define SCM_CONSP(x) (!SCM_IMP (x) && ((1 & SCM_CELL_TYPE (x)) == 0))
#define SCM_NCONSP(x) (!SCM_CONSP (x))
/* SCM_ECONSP should be used instead of SCM_CONSP at places where GLOCS
* can be expected to occur.
*/
#define SCM_ECONSP(x) \
(!SCM_IMP (x) \
&& (SCM_CONSP (x) \
|| (SCM_TYP3 (x) == 1 \
&& (SCM_STRUCT_VTABLE_DATA (x)[scm_vtable_index_vcell] != 0))))
#define SCM_NECONSP(x) (!SCM_ECONSP (x))
#define SCM_CELLP(x) (((sizeof (scm_t_cell) - 1) & SCM_UNPACK (x)) == 0)
#define SCM_NCELLP(x) (!SCM_CELLP (x))
/* See numbers.h for macros relating to immediate integers.
*/
#define SCM_ITAG3(x) (7 & SCM_UNPACK (x))
#define SCM_TYP3(x) (7 & SCM_CELL_TYPE (x))
#define scm_tc3_cons 0
#define scm_tc3_cons_gloc 1
#define scm_tc3_int_1 2
#define scm_tc3_closure 3
#define scm_tc3_imm24 4
#define scm_tc3_tc7_1 5
#define scm_tc3_int_2 6
#define scm_tc3_tc7_2 7
/*
* Do not change the three bit tags.
*/
#define SCM_ITAG7(x) (127 & SCM_UNPACK (x))
#define SCM_TYP7(x) (0x7f & SCM_CELL_TYPE (x))
#define SCM_TYP7S(x) ((0x7f & ~2) & SCM_CELL_TYPE (x))
#define SCM_TYP16(x) (0xffff & SCM_CELL_TYPE (x))
#define SCM_TYP16S(x) (0xfeff & SCM_CELL_TYPE (x))
#define SCM_TYP16_PREDICATE(tag,x) (SCM_NIMP (x) && SCM_TYP16 (x) == (tag))
#define scm_tc7_symbol 5
/* free 7 */
/* couple */
#define scm_tc7_vector 13
#define scm_tc7_wvect 15
/* couple */
#define scm_tc7_string 21
#define scm_tc7_substring 23
/* Many of the following should be turned
* into structs or smobs. We need back some
* of these 7 bit tags!
*/
#define scm_tc7_pws 31
#ifdef HAVE_ARRAYS
#define scm_tc7_llvect 29
#define scm_tc7_uvect 37
/* free 39 */
#define scm_tc7_fvect 45
#define scm_tc7_dvect 47
#define scm_tc7_cvect 53
#define scm_tc7_svect 55
#define scm_tc7_bvect 71
#define scm_tc7_byvect 77
#define scm_tc7_ivect 79
#endif
/* free 61 */
#define scm_tc7_cclo 63
#define scm_tc7_rpsubr 69
#define scm_tc7_subr_0 85
#define scm_tc7_subr_1 87
#define scm_tc7_cxr 93
#define scm_tc7_subr_3 95
#define scm_tc7_subr_2 101
#define scm_tc7_asubr 103
#define scm_tc7_subr_1o 109
#define scm_tc7_subr_2o 111
#define scm_tc7_lsubr_2 117
#define scm_tc7_lsubr 119
/* There are 256 port subtypes.
*/
#define scm_tc7_port 125
/* There are 256 smob subtypes. Here are the first four.
*/
#define scm_tc7_smob 127 /* DO NOT CHANGE [**] */
/* [**] If you change scm_tc7_smob, you must also change
* the places it is hard coded in this file and possibly others.
*/
/* scm_tc_free_cell is also the 0th smob type. We place this
* in free cells to tell the conservative marker not to trace it.
*/
#define scm_tc_free_cell (scm_tc7_smob + 0 * 256L)
/* Smob type 1 to 3 (note the dependency on the predicate SCM_NUMP)
*/
#define scm_tc16_big (scm_tc7_smob + 1 * 256L)
#define scm_tc16_real (scm_tc7_smob + 2 * 256L)
#define scm_tc16_complex (scm_tc7_smob + 3 * 256L)
/* {Immediate Values}
*/
enum scm_tags
{
scm_tc8_char = 0xf4,
scm_tc8_iloc = 0xfc
};
#define SCM_ITAG8(X) (SCM_UNPACK (X) & 0xff)
#define SCM_MAKE_ITAG8(X, TAG) SCM_PACK (((X) << 8) + TAG)
#define SCM_ITAG8_DATA(X) (SCM_UNPACK (X) >> 8)
/* Immediate Symbols, Special Symbols, Flags (various constants).
*/
/* SCM_ISYMP tests for ISPCSYM and ISYM */
#define SCM_ISYMP(n) ((0x187 & SCM_UNPACK (n)) == 4)
/* SCM_IFLAGP tests for ISPCSYM, ISYM and IFLAG */
#define SCM_IFLAGP(n) ((0x87 & SCM_UNPACK (n)) == 4)
#define SCM_ISYMNUM(n) (SCM_UNPACK (n) >> 9)
#define SCM_ISYMCHARS(n) (scm_isymnames[SCM_ISYMNUM (n)])
#define SCM_MAKSPCSYM(n) SCM_PACK (((n) << 9) + ((n) << 3) + 4L)
#define SCM_MAKISYM(n) SCM_PACK (((n) << 9) + 0x74L)
#define SCM_MAKIFLAG(n) SCM_PACK (((n) << 9) + 0x174L)
extern char *scm_isymnames[]; /* defined in print.c */
/* This table must agree with the declarations
* in repl.c: {Names of immediate symbols}.
*
* These are used only in eval but their values
* have to be allocated here.
*
*/
#define SCM_IM_AND SCM_MAKSPCSYM (0)
#define SCM_IM_BEGIN SCM_MAKSPCSYM (1)
#define SCM_IM_CASE SCM_MAKSPCSYM (2)
#define SCM_IM_COND SCM_MAKSPCSYM (3)
#define SCM_IM_DO SCM_MAKSPCSYM (4)
#define SCM_IM_IF SCM_MAKSPCSYM (5)
#define SCM_IM_LAMBDA SCM_MAKSPCSYM (6)
#define SCM_IM_LET SCM_MAKSPCSYM (7)
#define SCM_IM_LETSTAR SCM_MAKSPCSYM (8)
#define SCM_IM_LETREC SCM_MAKSPCSYM (9)
#define SCM_IM_OR SCM_MAKSPCSYM (10)
#define SCM_IM_QUOTE SCM_MAKSPCSYM (11)
#define SCM_IM_SET_X SCM_MAKSPCSYM (12)
#define SCM_IM_DEFINE SCM_MAKSPCSYM (13)
#define SCM_IM_APPLY SCM_MAKISYM (14)
#define SCM_IM_CONT SCM_MAKISYM (15)
#define SCM_BOOL_F SCM_MAKIFLAG (16)
#define SCM_BOOL_T SCM_MAKIFLAG (17)
#define SCM_UNDEFINED SCM_MAKIFLAG (18)
#define SCM_EOF_VAL SCM_MAKIFLAG (19)
#define SCM_EOL SCM_MAKIFLAG (20)
#define SCM_UNSPECIFIED SCM_MAKIFLAG (21)
#define SCM_IM_DISPATCH SCM_MAKISYM (22)
#define SCM_IM_SLOT_REF SCM_MAKISYM (23)
#define SCM_IM_SLOT_SET_X SCM_MAKISYM (24)
/* Multi-language support */
#define SCM_IM_NIL_COND SCM_MAKISYM (25)
#define SCM_IM_NIL_IFY SCM_MAKISYM (26)
#define SCM_IM_T_IFY SCM_MAKISYM (27)
#define SCM_IM_0_COND SCM_MAKISYM (28)
#define SCM_IM_0_IFY SCM_MAKISYM (29)
#define SCM_IM_1_IFY SCM_MAKISYM (30)
#define SCM_IM_BIND SCM_MAKISYM (31)
#define SCM_IM_DELAY SCM_MAKISYM (32)
#define SCM_IM_CALL_WITH_VALUES SCM_MAKISYM (33)
/* When a variable is unbound this is marked by the SCM_UNDEFINED
* value. The following is an unbound value which can be handled on
* the Scheme level, i.e., it can be stored in and retrieved from a
* Scheme variable. This value is only intended to mark an unbound
* slot in GOOPS. It is needed now, but we should probably rewrite
* the code which handles this value in C so that SCM_UNDEFINED can be
* used instead. It is not ideal to let this kind of unique and
* strange values loose on the Scheme level.
*/
#define SCM_UNBOUND SCM_MAKIFLAG (34)
#define SCM_UNBNDP(x) (SCM_EQ_P ((x), SCM_UNDEFINED))
/* Dispatching aids: */
/* For cons pairs with immediate values in the CAR
*/
#define scm_tcs_cons_imcar 2:case 4:case 6:case 10:\
case 12:case 14:case 18:case 20:\
case 22:case 26:case 28:case 30:\
case 34:case 36:case 38:case 42:\
case 44:case 46:case 50:case 52:\
case 54:case 58:case 60:case 62:\
case 66:case 68:case 70:case 74:\
case 76:case 78:case 82:case 84:\
case 86:case 90:case 92:case 94:\
case 98:case 100:case 102:case 106:\
case 108:case 110:case 114:case 116:\
case 118:case 122:case 124:case 126
/* For cons pairs with non-immediate values in the SCM_CAR
*/
#define scm_tcs_cons_nimcar 0:case 8:case 16:case 24:\
case 32:case 40:case 48:case 56:\
case 64:case 72:case 80:case 88:\
case 96:case 104:case 112:case 120
/* A CONS_GLOC occurs in code. It's CAR is a pointer to the
* CDR of a variable. The low order bits of the CAR are 001.
* The CDR of the gloc is the code continuation.
*/
#define scm_tcs_cons_gloc 1:case 9:case 17:case 25:\
case 33:case 41:case 49:case 57:\
case 65:case 73:case 81:case 89:\
case 97:case 105:case 113:case 121
#define scm_tcs_closures 3:case 11:case 19:case 27:\
case 35:case 43:case 51:case 59:\
case 67:case 75:case 83:case 91:\
case 99:case 107:case 115:case 123
#define scm_tcs_subrs scm_tc7_asubr:case scm_tc7_subr_0:case scm_tc7_subr_1:case scm_tc7_cxr:\
case scm_tc7_subr_3:case scm_tc7_subr_2:case scm_tc7_rpsubr:case scm_tc7_subr_1o:\
case scm_tc7_subr_2o:case scm_tc7_lsubr_2:case scm_tc7_lsubr
#if (SCM_DEBUG_DEPRECATED == 0)
#define SCM_SLOPPY_CONSP(x) ((1 & SCM_CELL_TYPE (x)) == 0)
#define SCM_SLOPPY_NCONSP(x) (!SCM_SLOPPY_CONSP(x))
#define scm_tc7_ssymbol scm_tc7_symbol
#define scm_tc7_msymbol scm_tc7_symbol
#define scm_tcs_symbols scm_tc7_symbol
#endif /* SCM_DEBUG_DEPRECATED == 0 */
#endif /* SCM_TAGS_H */
/*
Local Variables:
c-file-style: "gnu"
End:
*/
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