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Annotation of 3BSD/cmd/pi/tree.c, revision 1.1

1.1     ! root        1: /* Copyright (c) 1979 Regents of the University of California */
        !             2: #
        !             3: /*
        !             4:  * pi - Pascal interpreter code translator
        !             5:  *
        !             6:  * Charles Haley, Bill Joy UCB
        !             7:  * Version 1.1 February 1978
        !             8:  *
        !             9:  *
        !            10:  * pxp - Pascal execution profiler
        !            11:  *
        !            12:  * Bill Joy UCB
        !            13:  * Version 1.1 February 1978
        !            14:  */
        !            15: 
        !            16: #include "whoami"
        !            17: #include "0.h"
        !            18: 
        !            19: /*
        !            20:  * TREE SPACE DECLARATIONS
        !            21:  */
        !            22: struct tr {
        !            23:        int     *tr_low;
        !            24:        int     *tr_high;
        !            25: } ttab[MAXTREE], *tract;
        !            26: 
        !            27: /*
        !            28:  * The variable space is the
        !            29:  * absolute base of the tree segments.
        !            30:  * (exactly the same as ttab[0].tr_low)
        !            31:  * Spacep is maintained to point at the
        !            32:  * beginning of the next tree slot to
        !            33:  * be allocated for use by the grammar.
        !            34:  * Spacep is used "extern" by the semantic
        !            35:  * actions in pas.y.
        !            36:  * The variable tract is maintained to point
        !            37:  * at the tree segment out of which we are
        !            38:  * allocating (the active segment).
        !            39:  */
        !            40: int    *space, *spacep;
        !            41: 
        !            42: /*
        !            43:  * TREENMAX is the maximum width
        !            44:  * in words that any tree node 
        !            45:  * due to the way in which the parser uses
        !            46:  * the pointer spacep.
        !            47:  */
        !            48: #define        TREENMAX        6
        !            49: 
        !            50: int    trspace[ITREE];
        !            51: int    *space  = trspace;
        !            52: int    *spacep = trspace;
        !            53: struct tr *tract       = ttab;
        !            54: 
        !            55: /*
        !            56:  * Inittree allocates the first tree slot
        !            57:  * and sets up the first segment descriptor.
        !            58:  * A lot of this work is actually done statically
        !            59:  * above.
        !            60:  */
        !            61: inittree()
        !            62: {
        !            63: 
        !            64:        ttab[0].tr_low = space;
        !            65:        ttab[0].tr_high = &space[ITREE];
        !            66: }
        !            67: 
        !            68: /*
        !            69:  * Tree builds the nodes in the
        !            70:  * parse tree. It is rarely called
        !            71:  * directly, rather calls are made
        !            72:  * to tree[12345] which supplies the
        !            73:  * first argument to save space in
        !            74:  * the code. Tree also guarantees
        !            75:  * that spacep points to the beginning
        !            76:  * of the next slot it will return,
        !            77:  * a property required by the parser
        !            78:  * which was always true before we
        !            79:  * segmented the tree space.
        !            80:  */
        !            81: int *tree(cnt, a)
        !            82:        int cnt;
        !            83: {
        !            84:        register int *p, *q;
        !            85:        register int i;
        !            86: 
        !            87:        i = cnt;
        !            88:        p = spacep;
        !            89:        q = &a;
        !            90:        do
        !            91:                *p++ = *q++;
        !            92:        while (--i);
        !            93:        q = spacep;
        !            94:        spacep = p;
        !            95:        if (p+TREENMAX >= tract->tr_high)
        !            96:                /*
        !            97:                 * this peek-ahead should
        !            98:                 * save a great number of calls
        !            99:                 * to tralloc.
        !           100:                 */
        !           101:                tralloc(TREENMAX);
        !           102:        return (q);
        !           103: }
        !           104: 
        !           105: /*
        !           106:  * Tralloc preallocates enough
        !           107:  * space in the tree to allow
        !           108:  * the grammar to use the variable
        !           109:  * spacep, as it did before the
        !           110:  * tree was segmented.
        !           111:  */
        !           112: tralloc(howmuch)
        !           113: {
        !           114:        register char *cp;
        !           115:        register i;
        !           116: 
        !           117:        if (spacep + howmuch >= tract->tr_high) {
        !           118:                i = TRINC;
        !           119:                cp = malloc(i * sizeof ( int ));
        !           120:                if (cp == -1) {
        !           121:                        yerror("Ran out of memory (tralloc)");
        !           122:                        pexit(DIED);
        !           123:                }
        !           124:                spacep = cp;
        !           125:                tract++;
        !           126:                if (tract >= &ttab[MAXTREE]) {
        !           127:                        yerror("Ran out of tree tables");
        !           128:                        pexit(DIED);
        !           129:                }
        !           130:                tract->tr_low = cp;
        !           131:                tract->tr_high = tract->tr_low+i;
        !           132:        }
        !           133: }
        !           134: 
        !           135: extern int yylacnt;
        !           136: extern bottled;
        !           137: #ifdef PXP
        !           138: #endif
        !           139: /*
        !           140:  * Free up the tree segments
        !           141:  * at the end of a block.
        !           142:  * If there is scanner lookahead,
        !           143:  * i.e. if yylacnt != 0 or there is bottled output, then we
        !           144:  * cannot free the tree space.
        !           145:  * This happens only when errors
        !           146:  * occur and the forward move extends
        !           147:  * across "units".
        !           148:  */
        !           149: trfree()
        !           150: {
        !           151: 
        !           152:        if (yylacnt != 0 || bottled != NIL)
        !           153:                return;
        !           154: #ifdef PXP
        !           155:        if (needtree())
        !           156:                return;
        !           157: #endif
        !           158:        spacep = space;
        !           159:        while (tract->tr_low > spacep || tract->tr_high <= spacep) {
        !           160:                free(tract->tr_low);
        !           161:                tract->tr_low = NIL;
        !           162:                tract->tr_high = NIL;
        !           163:                tract--;
        !           164:                if (tract < ttab)
        !           165:                        panic("ttab");
        !           166:        }
        !           167: #ifdef PXP
        !           168:        packtree();
        !           169: #endif
        !           170: }
        !           171: 
        !           172: /*
        !           173:  * Copystr copies a token from
        !           174:  * the "token" buffer into the
        !           175:  * tree space.
        !           176:  */
        !           177: copystr(token)
        !           178:        register char *token;
        !           179: {
        !           180:        register char *cp;
        !           181:        register int i;
        !           182: 
        !           183:        i = (strlen(token) + sizeof ( int )) & ~( ( sizeof ( int ) ) - 1 );
        !           184:        tralloc(i / sizeof ( int ));
        !           185:        strcpy(spacep, token);
        !           186:        cp = spacep;
        !           187:        spacep = cp + i;
        !           188:        tralloc(TREENMAX);
        !           189:        return (cp);
        !           190: }

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