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1 /* Fundamental definitions for XEmacs Lisp interpreter -- non-union objects.
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2 Copyright (C) 1985, 1986, 1987, 1992, 1993 Free Software Foundation, Inc.
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3
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4 This file is part of XEmacs.
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5
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6 XEmacs is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by the
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8 Free Software Foundation; either version 2, or (at your option) any
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9 later version.
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10
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11 XEmacs is distributed in the hope that it will be useful, but WITHOUT
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12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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14 for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with XEmacs; see the file COPYING. If not, write to
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18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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19 Boston, MA 02111-1307, USA. */
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20
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21 /* Synched up with: FSF 19.30. Split out from lisp.h. */
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22 /* This file has diverged greatly from FSF Emacs. Syncing is no
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23 longer desirable or possible */
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24
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25 /*
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26 Format of a non-union-type Lisp Object
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27
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28 3 2 1 0
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29 bit 10987654321098765432109876543210
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30 --------------------------------
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31 VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVTT
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32
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33 Integers are treated specially, and look like this:
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34
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35 3 2 1 0
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36 bit 10987654321098765432109876543210
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37 --------------------------------
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38 VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVT
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39
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40 For integral Lisp types, i.e. integers and characters, the value
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41 bits are the Lisp object. Some people call such Lisp_Objects "immediate".
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42
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43 The object is obtained by masking off the type bits.
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44 Bit 1 is used as a value bit by splitting the Lisp integer type
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45 into two subtypes, Lisp_Type_Int_Even and Lisp_Type_Int_Odd.
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46 By this trickery we get 31 bits for integers instead of 30.
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47
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48 For non-integral types, the value bits of a Lisp_Object contain
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49 a pointer to a structure containing the object. The pointer is
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50 obtained by masking off the type and mark bits.
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51
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52 All pointer-based types are coalesced under a single type called
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53 Lisp_Type_Record. The type bits for this type are required by the
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54 implementation to be 00, just like the least significant bits of
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55 word-aligned struct pointers on 32-bit hardware. This requires that
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56 all structs implementing Lisp_Objects have an alignment of at least 4
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57 bytes. Because of this, Lisp_Object pointers don't have to be masked
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58 and are full-sized.
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59
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60 There are no mark bits in the Lisp_Object itself (there used to be).
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61
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62 Integers and characters don't need to be marked. All other types are
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63 lrecord-based, which means they get marked by setting the mark bit in
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64 the struct lrecord_header.
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65
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66 Here is a brief description of the following macros:
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67
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68 XTYPE The type bits of a Lisp_Object
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69 XPNTRVAL The value bits of a Lisp_Object storing a pointer
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70 XCHARVAL The value bits of a Lisp_Object storing a Emchar
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71 XREALINT The value bits of a Lisp_Object storing an integer, signed
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72 XUINT The value bits of a Lisp_Object storing an integer, unsigned
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73 INTP Non-zero if this Lisp_Object is an integer
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74 Qzero Lisp Integer 0
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75 EQ Non-zero if two Lisp_Objects are identical, not merely equal. */
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76
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77
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78 typedef EMACS_INT Lisp_Object;
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79
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80 #define Lisp_Type_Int_Bit (Lisp_Type_Int_Even & Lisp_Type_Int_Odd)
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81 #define wrap_object(ptr) ((Lisp_Object) (ptr))
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82 #define make_int(x) ((Lisp_Object) (((x) << INT_GCBITS) | Lisp_Type_Int_Bit))
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83 #define make_char(x) ((Lisp_Object) (((x) << GCBITS) | Lisp_Type_Char))
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84 #define VALMASK (((1UL << VALBITS) - 1UL) << GCTYPEBITS)
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85 #define XTYPE(x) ((enum Lisp_Type) (((EMACS_UINT)(x)) & ~VALMASK))
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86 #define XPNTRVAL(x) (x) /* This depends on Lisp_Type_Record == 0 */
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87 #define XCHARVAL(x) ((x) >> GCBITS)
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88 #define XREALINT(x) ((x) >> INT_GCBITS)
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89 #define XUINT(x) ((EMACS_UINT)(x) >> INT_GCBITS)
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90 #define INTP(x) ((EMACS_UINT)(x) & Lisp_Type_Int_Bit)
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91 #define INT_PLUS(x,y) ((x)+(y)-Lisp_Type_Int_Bit)
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92 #define INT_MINUS(x,y) ((x)-(y)+Lisp_Type_Int_Bit)
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93 #define INT_PLUS1(x) INT_PLUS (x, make_int (1))
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94 #define INT_MINUS1(x) INT_MINUS (x, make_int (1))
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95
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96 #define Qzero make_int (0)
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97 #define Qnull_pointer ((Lisp_Object) 0)
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98 #define EQ(x,y) ((x) == (y))
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99 #define XSETINT(var, value) ((void) ((var) = make_int (value)))
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100 #define XSETCHAR(var, value) ((void) ((var) = make_char (value)))
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101 #define XSETOBJ(var, value) ((void) ((var) = wrap_object (value)))
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102
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103 /* Convert between a (void *) and a Lisp_Object, as when the
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104 Lisp_Object is passed to a toolkit callback function */
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105 #define VOID_TO_LISP(larg,varg) ((void) ((larg) = ((Lisp_Object) (varg))))
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106 #define CVOID_TO_LISP VOID_TO_LISP
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107 #define LISP_TO_VOID(larg) ((void *) (larg))
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108 #define LISP_TO_CVOID(larg) ((const void *) (larg))
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109
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110 /* Convert a Lisp_Object into something that can't be used as an
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111 lvalue. Useful for type-checking. */
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112 #define NON_LVALUE(larg) ((larg) + 0)
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