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Diffstat (limited to 'libguile/tags.h')
| -rw-r--r-- | libguile/tags.h | 532 |
1 files changed, 532 insertions, 0 deletions
diff --git a/libguile/tags.h b/libguile/tags.h new file mode 100644 index 000000000..1469a90f6 --- /dev/null +++ b/libguile/tags.h @@ -0,0 +1,532 @@ +/* classes: h_files */ + +#ifndef TAGSH +#define TAGSH +/* Copyright (C) 1995,1996 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, 675 Mass Ave, Cambridge, MA 02139, 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. + **/ + + + +/* In the beginning was the Word: + */ +typedef long SCM; + + + +/* Cray machines have pointers that are incremented once for each word, + * rather than each byte, the 3 most significant bits encode the byte + * within the word. The following macros deal with this by storing the + * native Cray pointers like the ones that looks like scm expects. This + * is done for any pointers that might appear in the car of a scm_cell, pointers + * to scm_vector elts, functions, &c are not munged. + */ +#ifdef _UNICOS +# define SCM2PTR(x) ((int)(x) >> 3) +# define PTR2SCM(x) (((SCM)(x)) << 3) +# define SCM_POINTERS_MUNGED +#else +# define SCM2PTR(x) (x) +# define PTR2SCM(x) ((SCM)(x)) +#endif /* def _UNICOS */ + + +/* 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 chaning it! + * (Not always impossible but it is fair to say that many details of tags + * are mutually dependent). + */ + +#define SCM_IMP(x) (6 & (int)(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 .........long length....GxxxD1S1 ..........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. + * + * SCM_LENGTH returns the bits in "length" (see the diagram). + * SCM_CHARS returns the data cast to "char *" + * SCM_CDR returns the data cast to "SCM" + * TYP7(X) returns bits 0...6 of SCM_CAR (X) + * + * For the interpretation of SCM_LENGTH and SCM_CHARS + * that applies to a particular type, see the header file + * for that type. + * + * TYP7S(X) returns TYP7, but masking out the option bit S. + * TYP7D(X) returns TYP7, but masking out the option bit D. + * TYP7SD(X) masks out both option bits. + * + * for example: + * D S + * scm_tc7_string = Gxxx0101 + * scm_tc7_mb_string = Gxxx0111 + * scm_tc7_substring = Gxxx1101 + * scm_tc7_mb_substring = Gxxx1111 + * + * TYP7S turns tc7_mb_string into tc7_string and + * tc7_mb_substring into tc7_substring. + * + * TYP7D turns tc7_mb_substring into tc7_mb_string and + * tc7_substring into tc7_string. + * + * TYP7DS turns all string tags into tc7_string. + * + * Some TC7 types are subdivided into 256 subtypes giving + * rise to the macros: + * + * TYP16 + * TYP16S + * GCTYP16 + * + * 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_NCONSP(x) (1 & (int)SCM_CAR(x)) +#define SCM_CONSP(x) (!SCM_NCONSP(x)) + + +/* ECONSP is historical and, in fact, slightly buggy. + * There are two places to fix where structures and glocs can be confused. + * !!! + */ +#define SCM_ECONSP(x) (SCM_CONSP(x) || (1==SCM_TYP3(x))) +#define SCM_NECONSP(x) (SCM_NCONSP(x) && (1 != SCM_TYP3(x))) + + + +#define SCM_CELLP(x) (!SCM_NCELLP(x)) +#define SCM_NCELLP(x) ((sizeof(scm_cell)-1) & (int)(x)) + +/* See numbers.h for macros relating to immediate integers. + */ + +#define SCM_ITAG3(x) (7 & (int)x) +#define SCM_TYP3(x) (7 & (int)SCM_CAR(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_TYP7(x) (0x7f & (int)SCM_CAR(x)) +#define SCM_TYP7S(x) (0x7d & (int)SCM_CAR(x)) +#define SCM_TYP7SD(x) (0x75 & (int)SCM_CAR(x)) +#define SCM_TYP7D(x) (0x77 & (int)SCM_CAR(x)) + + +#define SCM_TYP16(x) (0xffff & (int)SCM_CAR(x)) +#define SCM_TYP16S(x) (0xfeff & (int)SCM_CAR(x)) +#define SCM_GCTYP16(x) (0xff7f & (int)SCM_CAR(x)) + + + +/* Testing and Changing GC Marks in Various Standard Positions + */ +#define SCM_GCMARKP(x) (1 & (int)SCM_CDR(x)) +#define SCM_GC8MARKP(x) (0x80 & (int)SCM_CAR(x)) +#define SCM_SETGCMARK(x) (SCM_CDR(x) |= 1) +#define SCM_CLRGCMARK(x) (SCM_CDR(x) &= ~1L) +#define SCM_SETGC8MARK(x) (SCM_CAR(x) |= 0x80) +#define SCM_CLRGC8MARK(x) (SCM_CAR(x) &= ~0x80L) + + + + +/* couple */ +#define scm_tc7_ssymbol 5 +#define scm_tc7_msymbol 7 + +/* couple */ +#define scm_tc7_vector 13 +#define scm_tc7_wvect 15 + +/* a quad, two couples, two trists */ +#define scm_tc7_string 21 +#define scm_tc7_mb_string 23 +#define scm_tc7_substring 29 +#define scm_tc7_mb_substring 31 + +/* Many of the following should be turned + * into structs or smobs. We need back some + * of these 7 bit tags! + */ +#define scm_tc7_uvect 37 +#define scm_tc7_lvector 39 +#define scm_tc7_fvect 45 +#define scm_tc7_dvect 47 +#define scm_tc7_cvect 53 +#define scm_tc7_svect 55 +#define scm_tc7_contin 61 +#define scm_tc7_cclo 63 +#define scm_tc7_rpsubr 69 +#define scm_tc7_bvect 71 +#define scm_tc7_byvect 77 +#define scm_tc7_ivect 79 +#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. Here are the first four. + * These must agree with the init function in ports.c + */ +#define scm_tc7_port 125 + +/* fports and pipes form an intended TYP16S equivelancy + * group (similar to a tc7 "couple". + */ +#define scm_tc16_fport (scm_tc7_port + 0*256L) +#define scm_tc16_pipe (scm_tc7_port + 1*256L) + +#define scm_tc16_strport (scm_tc7_port + 2*256L) +#define scm_tc16_sfport (scm_tc7_port + 3*256L) + + +/* 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. + */ +#define scm_tc_free_cell 127 + +/* The 1st smob type: + */ +#define scm_tc16_flo 0x017f +#define scm_tc_flo 0x017fL + +/* Some option bits begeinning at bit 16 of scm_tc16_flo: + */ +#define SCM_REAL_PART (1L<<16) +#define SCM_IMAG_PART (2L<<16) +#define scm_tc_dblr (scm_tc16_flo|SCM_REAL_PART) +#define scm_tc_dblc (scm_tc16_flo|SCM_REAL_PART|SCM_IMAG_PART) + + +/* Smob types 2 and 3: + */ +#define scm_tc16_bigpos 0x027f +#define scm_tc16_bigneg 0x037f + + + +/* {Immediate Values} + */ + +enum scm_tags +{ + scm_tc8_char = 0xf4, + scm_tc8_iloc = 0xfc, +}; + +#define SCM_ITAG8(X) ((int)(X) & 0xff) +#define SCM_MAKE_ITAG8(X, TAG) (((X)<<8) + TAG) +#define SCM_ITAG8_DATA(X) ((X)>>8) + + + +/* Immediate Symbols, Special Symbols, Flags (various constants). + */ + +/* SCM_ISYMP tests for ISPCSYM and ISYM */ +#define SCM_ISYMP(n) ((0x187 & (int)(n))==4) + +/* SCM_IFLAGP tests for ISPCSYM, ISYM and IFLAG */ +#define SCM_IFLAGP(n) ((0x87 & (int)(n))==4) +#define SCM_ISYMNUM(n) ((int)((n)>>9)) +#define SCM_ISYMSCM_CHARS(n) (scm_isymnames[SCM_ISYMNUM(n)]) +#define SCM_MAKSPCSYM(n) (((n)<<9)+((n)<<3)+4L) +#define SCM_MAKISYM(n) (((n)<<9)+0x74L) +#define SCM_MAKIFLAG(n) (((n)<<9)+0x174L) + +/* 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 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_UNUSED_NIL_VALUE SCM_MAKIFLAG(20) +#define SCM_UNSPECIFIED SCM_MAKIFLAG(21) + + +#define SCM_UNBNDP(x) (SCM_UNDEFINED==(x)) + + + +/* 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 + +#define scm_tcs_symbols scm_tc7_ssymbol:case scm_tc7_msymbol + +#define scm_tcs_bignums scm_tc16_bigpos:case scm_tc16_bigneg + + +#ifdef __STDC__ + +#else /* STDC */ + +#endif /* STDC */ + + +#endif /* TAGSH */ |