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Annotation of coherent/f/usr/include/common/_canon.h, revision 1.1

1.1     ! root        1: #ifndef        __COMMON__CANON_H__
        !             2: #define        __COMMON__CANON_H__
        !             3: 
        !             4: /*
        !             5:  * This file contains definitions related to canonicalization of numeric
        !             6:  * formats. Routines are provided for conversions between the native format
        !             7:  * and numerous other canonical forms, with varying argument patterns so that
        !             8:  * conversion can be done in a space- and/or time-efficient manner. In
        !             9:  * particular, separate versions for each routine exists that operate on an
        !            10:  * lvalue to return a converted value, on an rvalue to return a converted
        !            11:  * value, and to perform in-place conversion on an lvalue, so that the most
        !            12:  * efficient machine idioms can be used for particular target machines.
        !            13:  * The routines in this file are oriented towards systems with 32-bit long-
        !            14:  * integer arithmetic, but extensions should be trivial.
        !            15:  *
        !            16:  *     canonicalize    -> to make canonical
        !            17:  *     canonical       -> according to the canons
        !            18:  *     canons          -> the law
        !            19:  *     canonize        -> to bestow sainthood
        !            20:  */
        !            21: 
        !            22: #include <common/feature.h>
        !            23: #include <common/_limits.h>
        !            24: 
        !            25: #if    __CHAR_BIT != 8
        !            26: # error        The canonicalization system only applies to octet-oriented machines
        !            27: #endif
        !            28: 
        !            29: /*
        !            30:  * We begin by defining a basic type for the lvalue-oriented manipulations and
        !            31:  * some fundamental concepts and facilities that build on that to create a
        !            32:  * bottom layer to the system. We explain the operation of the system entirely
        !            33:  * in terms of manipulations of octets.
        !            34:  *
        !            35:  * We begin by defining the basic notation for describing formats; the basic
        !            36:  * parameter for a data format is how the octets in the numbers in that format
        !            37:  * are laid out, which we specify relative to the lowest machine address
        !            38:  * occupied by the datum (many canonical data formats are based on the notion
        !            39:  * of transmission order, and we typically expect that "is transmitted before"
        !            40:  * maps directly onto "has a lower address than" for a structure laid out in
        !            41:  * machine memory).
        !            42:  *
        !            43:  * So, for an M68K, the index of the most-significant byte of a native-format
        !            44:  * number is always zero, whereas for an Intel-format number the bytes (and
        !            45:  * thus their indexes) are reversed. If we encode the index of the byte in the
        !            46:  * canonical order as a (machine-independent) number with each index taking
        !            47:  * up a byte, then we get a value which when stored in that format will have
        !            48:  * the values 0, 1, 2, ... stored in consecutive octets of machine memory.
        !            49:  *
        !            50:  * The nice thing about this encoding is that is thus reflective; if we have
        !            51:  * a way of transforming abstract numbers according to this "map", we can
        !            52:  * apply the transformation to the maps themselves to generate new maps which
        !            53:  * can be used to encode other numbers or maps. This enables us to better deal
        !            54:  * with the potential n^2 nature of the conversions by dynamically composing
        !            55:  * the maps.
        !            56:  */
        !            57: 
        !            58: typedef unsigned char *        __canon_t;
        !            59: 
        !            60: #define        __IDENTITY_16_MAP       0x0100U
        !            61: #define __REVERSE_16_MAP       0x0001U
        !            62: #define        __I386_16_MAP           __IDENTITY_16_MAP
        !            63: #define        __M68K_16_MAP           __REVERSE_16_MAP
        !            64: #define        __OCOH_16_MAP           __IDENTITY_16_MAP
        !            65: 
        !            66: #define        __IDENTITY_32_MAP       0x03020100UL
        !            67: #define        __REVERSE_32_MAP        0x00010203UL
        !            68: #define        __SWAP16_32_MAP         0x01000302UL
        !            69: #define        __I386_32_MAP           __IDENTITY_32_MAP
        !            70: #define        __M68K_32_MAP           __REVERSE_32_MAP
        !            71: #define        __OCOH_32_MAP           __SWAP16_32_MAP
        !            72: 
        !            73: 
        !            74: /*
        !            75:  * The following primitive mapping functions use a map, and come in two
        !            76:  * flavours; r-value oriented, and l-value oriented. The r-value-oriented
        !            77:  * transformations have the special property of using only operations which
        !            78:  * are permitted in the restricted form of integral constant expression that
        !            79:  * can be used in #if-expressions. Applying the r-value transformations to
        !            80:  * constants yields other constants.
        !            81:  *
        !            82:  * Note that the fundamental transformations have two (nearly) equivalent
        !            83:  * forms, of which I find the recursive more aesthetically pleasing, so that
        !            84:  * is the default form. We leave both in here for your amusement.
        !            85:  */
        !            86: 
        !            87: #define        __OCTET_N_OF_R(r,n)     (((r) >> ((n) * 8)) & 0xFFU)
        !            88: #define        __OCTET_N_OF_L(l,n)     (((__canon_t) & (l)) [n])
        !            89: #define        __MAKE_OCTET_N(o,n)     ((o) << ((n) * 8))
        !            90: 
        !            91: #define        __CONVERT_OCTET_N_OF_R_VIA_MAP0(r,m,n) \
        !            92:                __MAKE_OCTET_N (__OCTET_N_OF_R (r, n), __OCTET_N_OF_R (m, n))
        !            93: 
        !            94: #define        __CONVERT_OCTET_N_OF_R_VIA_MAP1(r,m,n) \
        !            95:                __MAKE_OCTET_N (__OCTET_N_OF_R (r, __OCTET_N_OF_R (m, n)), n)
        !            96: 
        !            97: #define        __CONVERT_OCTET_N_OF_L_VIA_MAP0(l,m,n) \
        !            98:                __MAKE_OCTET_N (__OCTET_N_OF_L (l, n), __OCTET_N_OF_R (m, n))
        !            99: 
        !           100: #define        __CONVERT_OCTET_N_OF_L_VIA_MAP1(l,m,n) \
        !           101:                __MAKE_OCTET_N (__OCTET_N_OF_L (l, __OCTET_N_OF_R (m, n)), n)
        !           102: 
        !           103: #define        __CONVERT_R_16(r,m) \
        !           104:                (__CONVERT_OCTET_N_OF_R_VIA_MAP1 (r, m, 0) | \
        !           105:                 __CONVERT_OCTET_N_OF_R_VIA_MAP1 (r, m, 1))
        !           106: 
        !           107: #define        __CONVERT_L_16(l,m) \
        !           108:                (__CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 0) | \
        !           109:                 __CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 1))
        !           110: 
        !           111: #define        __CONVERT_R_32(r,m) \
        !           112:                (__CONVERT_OCTET_N_OF_R_VIA_MAP1 (r, m, 0) | \
        !           113:                 __CONVERT_OCTET_N_OF_R_VIA_MAP1 (r, m, 1) | \
        !           114:                 __CONVERT_OCTET_N_OF_R_VIA_MAP1 (r, m, 2) | \
        !           115:                 __CONVERT_OCTET_N_OF_R_VIA_MAP1 (r, m, 3))
        !           116: 
        !           117: #define        __CONVERT_L_32(l,m) \
        !           118:                (__CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 0) | \
        !           119:                 __CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 1) | \
        !           120:                 __CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 2) | \
        !           121:                 __CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 3))
        !           122: 
        !           123: /*
        !           124:  * Here, we use rather more specific feature-tests to see about escaping to
        !           125:  * special hand-coded routines or inlines, which is highly translator-specific
        !           126:  * in addition to being machine-specific.
        !           127:  */
        !           128: 
        !           129: #if    __GNUC__ && _I386
        !           130: 
        !           131: #if    __SHRT_BIT != 16 || __LONG_BIT != 32
        !           132: # error        For GCC on i386, short should be 16 bits and a long should be 32.
        !           133: #endif
        !           134: 
        !           135: #include <common/ccompat.h>
        !           136: #include <common/xdebug.h>
        !           137: 
        !           138: /*
        !           139:  * We supply two versions of some of the following depending on whether or not
        !           140:  * you care about not being able to use the %ebp, %esi, and %edi registers as
        !           141:  * operands or not.
        !           142:  */
        !           143: 
        !           144: __LOCAL__ __INLINE__ unsigned short __swap_bytes (unsigned short _number) {
        !           145:        unsigned short  _result;
        !           146: #if    1
        !           147:        __NON_ISO (asm) ("rolw $8, %0" : "=r" (_result) : "0" (_number));
        !           148: #else
        !           149:        __NON_ISO (asm) ("xchg %h0, %b0" : "=q" (_result) : "0" (_number));
        !           150: #endif
        !           151:        return _result;
        !           152: }
        !           153: 
        !           154: __LOCAL__ __INLINE__ unsigned long __swap_words (unsigned long _number) {
        !           155:        unsigned long   _result;
        !           156:        __NON_ISO (asm) ("roll $16, %0" : "=r" (_result) : "0" (_number));
        !           157:        return _result;
        !           158: }
        !           159: 
        !           160: /*
        !           161:  * On the i486 processor we have the BSWAP instruction, but the following
        !           162:  * works on the i386 as well.
        !           163:  */
        !           164: 
        !           165: __LOCAL__ __INLINE__ unsigned long __reverse_long (unsigned long _number) {
        !           166:        unsigned long   _result;
        !           167: #if    1
        !           168:        __NON_ISO (asm) ("rolw $8, %0\n"
        !           169:                         "roll $16, %0\n",
        !           170:                         "rolw $8, %0\n" : "=r" (_result) : "0" (_number));
        !           171: #else
        !           172:        __NON_ISO (asm) ("xchg %h0, %b0\n"
        !           173:                         "rorl $16, %0\n"
        !           174:                         "xchg %h0, %b0\n" : "=q" (_result) : "0" (_number));
        !           175: #endif
        !           176:        return _result;
        !           177: }
        !           178: 
        !           179: #undef __CONVERT_L_16
        !           180: #define        __CONVERT_L_16(l,m) \
        !           181:                ((m) == __REVERSE_16_MAP ? __swap_bytes (l) : \
        !           182:                 __CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 0) | \
        !           183:                 __CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 1))
        !           184: 
        !           185: #undef __CONVERT_L_32
        !           186: #define        __CONVERT_L_32(l,m) \
        !           187:                ((m) == __SWAP16_32_MAP ? __swap_words (l) : \
        !           188:                 (m) == __REVERSE_32_MAP ? __reverse_long (l) : \
        !           189:                 __CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 0) | \
        !           190:                 __CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 1) | \
        !           191:                 __CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 2) | \
        !           192:                 __CONVERT_OCTET_N_OF_L_VIA_MAP1 (l, m, 3))
        !           193: 
        !           194: #endif /* __GNUC__ && _I386 */
        !           195: 
        !           196: 
        !           197: /*
        !           198:  * Now, use a variety of feature-tests to figure out the native format for the
        !           199:  * host we are compiling for.
        !           200:  */
        !           201: 
        !           202: #if    __MSDOS__ || _I386
        !           203: 
        !           204: # define       __NATIVE_16_MAP         __I386_16_MAP
        !           205: # define       __NATIVE_32_MAP         __I386_32_MAP
        !           206: 
        !           207: #else
        !           208: 
        !           209: # error        What is the native endianness of your system?
        !           210: 
        !           211: #endif
        !           212: 
        !           213: #define        __CANON_FOO(value,l_or_r,type, map,ident) \
        !           214:                ((map) == (ident) ? value : \
        !           215:                        __CONCAT4 (__CONVERT_, l_or_r, _, type) \
        !           216:                                (value, map))
        !           217: 
        !           218: #define        __CANONICALIZE(value,l_or_r,machine,type) \
        !           219:                __CANON_FOO (value, l_or_r, type, \
        !           220:                             __CONCAT (__CONVERT_R_, type) \
        !           221:                                (__CONCAT3 (__NATIVE_, type, _MAP), \
        !           222:                                 __CONCAT4 (machine, _, type, _MAP)), \
        !           223:                             __CONCAT3 (__IDENTITY_, type, _MAP))
        !           224: 
        !           225: 
        !           226: #endif /* ! defined (__COMMON__CANON_H__) */
        !           227: 

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