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shell/math: rename TOK_NUM to TOK_VALUE, improve comments
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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parent
c1c267fd36
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49
shell/math.c
49
shell/math.c
@ -94,7 +94,6 @@
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*
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* Merge in Aaron's comments previously posted to the busybox list,
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* modified slightly to take account of my changes to the code.
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*
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*/
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/*
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* (C) 2003 Vladimir Oleynik <dzo@simtreas.ru>
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@ -212,18 +211,18 @@ typedef unsigned char operator;
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#define TOK_UPLUS tok_decl(UNARYPREC+1,1)
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#define PREC_PRE (UNARYPREC+2)
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#define TOK_PRE_INC tok_decl(PREC_PRE, 0)
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#define TOK_PRE_DEC tok_decl(PREC_PRE, 1)
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#define PREC_POST (UNARYPREC+3)
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#define TOK_POST_INC tok_decl(PREC_POST, 0)
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#define TOK_POST_DEC tok_decl(PREC_POST, 1)
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#define SPEC_PREC (UNARYPREC+4)
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#define TOK_NUM tok_decl(SPEC_PREC, 0)
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/* TOK_VALUE marks a number, name, name++/name--, or (EXPR):
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* IOW: something which can be used as the left side of a binary op.
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* Since it's never pushed to opstack, its precedence does not matter.
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*/
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#define TOK_VALUE tok_decl(PREC_POST, 2)
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static int
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is_assign_op(operator op)
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@ -625,7 +624,9 @@ evaluate_string(arith_state_t *math_state, const char *expr)
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var_or_num_t *numstack, *numstackptr;
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/* Stack of operator tokens */
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operator *opstack, *opstackptr;
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/* To detect whether we are after a "value": */
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operator lasttok;
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/* To insert implicit () in ?: ternary op: */
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operator insert_op = 0xff;
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unsigned ternary_level = 0;
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const char *errmsg;
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@ -720,12 +721,12 @@ evaluate_string(arith_state_t *math_state, const char *expr)
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} else {
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dbg("[%d] var:IGNORED", (int)(numstackptr - numstack));
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expr = p;
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numstackptr->var_name = NULL;
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numstackptr->val = 0;
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numstackptr->var_name = NULL; /* not needed, paranoia */
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numstackptr->val = 0; /* not needed, paranoia */
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}
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push_num:
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push_value:
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numstackptr++;
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lasttok = TOK_NUM;
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lasttok = TOK_VALUE;
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continue;
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}
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@ -747,7 +748,7 @@ evaluate_string(arith_state_t *math_state, const char *expr)
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*/
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if (isalnum(*expr) || *expr == '_')
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goto syntax_err;
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goto push_num;
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goto push_value;
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}
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/* Should be an operator */
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@ -818,15 +819,14 @@ evaluate_string(arith_state_t *math_state, const char *expr)
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dbg("insert_op=%02x op=%02x", insert_op, op);
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}
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tok_found1:
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/* post grammar: a++ reduce to num */
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if (lasttok == TOK_POST_INC || lasttok == TOK_POST_DEC)
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lasttok = TOK_NUM;
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/* NAME++ is a "value" (something suitable for a binop) */
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if (PREC(lasttok) == PREC_POST)
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lasttok = TOK_VALUE;
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/* Plus and minus are binary (not unary) _only_ if the last
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* token was a number, or a right paren (which pretends to be
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* a number, since it evaluates to one). Think about it.
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* It makes sense. */
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if (lasttok != TOK_NUM) {
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* token was a "value". Think about it. It makes sense.
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*/
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if (lasttok != TOK_VALUE) {
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switch (op) {
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case TOK_ADD:
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//op = TOK_UPLUS;
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@ -857,8 +857,8 @@ evaluate_string(arith_state_t *math_state, const char *expr)
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prec = PREC(op);
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if (prec != PREC_LPAREN && prec < UNARYPREC) {
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/* binary, ternary or RPAREN */
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if (lasttok != TOK_NUM) {
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/* must be preceded by a num */
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if (lasttok != TOK_VALUE) {
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/* must be preceded by a num (example?) */
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goto syntax_err;
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}
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/* if op is RPAREN:
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@ -883,11 +883,12 @@ evaluate_string(arith_state_t *math_state, const char *expr)
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operator prev_op = *--opstackptr;
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if (op == TOK_RPAREN) {
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if (prev_op == TOK_LPAREN) {
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/* Erase var name: (var) is just a number, for example, (var) = 1 is not valid */
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/* Erase var name: for example, (VAR) = 1 is not valid */
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numstackptr[-1].var_name = NULL;
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/* Any operator directly after a
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* close paren should consider itself binary */
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lasttok = TOK_NUM;
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/* (EXPR) is a "value": next operator directly after
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* close paren should be considered binary
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*/
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lasttok = TOK_VALUE;
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goto next;
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}
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/* Not (y), but ...x~y). Fall through to evaluate x~y */
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