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

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