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Annotation of 40BSD/cmd/pc0/tree.c, revision 1.1

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

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