/* 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 #endif #ifdef HAVE_INTTYPES_H #include #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: */