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shell/math.c: small code shrink; fixed incomprehensible comments
function old new delta arith_apply 1334 1304 -30 Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This commit is contained in:
Denys Vlasenko
parent
51850c818c
commit
bd14770b0c
225
shell/math.c
225
shell/math.c
@ -52,17 +52,18 @@
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* than a comparable parser written in yacc. The supported operators are
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* listed in #defines below. Parens, order of operations, and error handling
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* are supported. This code is thread safe. The exact expression format should
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* be that which POSIX specifies for shells. */
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/* The code uses a simple two-stack algorithm. See
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* be that which POSIX specifies for shells.
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*
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* The code uses a simple two-stack algorithm. See
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* http://www.onthenet.com.au/~grahamis/int2008/week02/lect02.html
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* for a detailed explanation of the infix-to-postfix algorithm on which
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* this is based (this code differs in that it applies operators immediately
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* to the stack instead of adding them to a queue to end up with an
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* expression). */
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/* To use the routine, call it with an expression string and error return
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* pointer */
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* expression).
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*
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* To use the routine, call it with an expression string and error return
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* pointer
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*/
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/*
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* Aug 24, 2001 Manuel Novoa III
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@ -104,22 +105,21 @@
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* (C) 2003 Vladimir Oleynik <dzo@simtreas.ru>
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*
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* - allow access to variable,
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* used recursive find value indirection (c=2*2; a="c"; $((a+=2)) produce 6)
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* - realize assign syntax (VAR=expr, +=, *= etc)
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* - realize exponentiation (** operator)
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* - realize comma separated - expr, expr
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* - realise ++expr --expr expr++ expr--
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* - realise expr ? expr : expr (but, second expr calculate always)
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* use recursive value indirection: c="2*2"; a="c"; echo $((a+=2)) produce 6
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* - implement assign syntax (VAR=expr, +=, *= etc)
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* - implement exponentiation (** operator)
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* - implement comma separated - expr, expr
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* - implement ++expr --expr expr++ expr--
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* - implement expr ? expr : expr (but second expr is always calculated)
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* - allow hexadecimal and octal numbers
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* - was restored loses XOR operator
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* - remove one goto label, added three ;-)
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* - protect $((num num)) as true zero expr (Manuel`s error)
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* - restore lost XOR operator
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* - protect $((num num)) as true zero expr (Manuel's error)
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* - always use special isspace(), see comment from bash ;-)
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*/
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#include "libbb.h"
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#include "math.h"
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#define a_e_h_t arith_eval_hooks_t
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#define a_e_h_t arith_eval_hooks_t
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#define lookupvar (math_hooks->lookupvar)
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#define setvar (math_hooks->setvar )
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//#define endofname (math_hooks->endofname)
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@ -130,103 +130,104 @@ typedef unsigned char operator;
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* precedence, and 3 high bits are an ID unique across operators of that
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* precedence. The ID portion is so that multiple operators can have the
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* same precedence, ensuring that the leftmost one is evaluated first.
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* Consider * and /. */
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* Consider * and /
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*/
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#define tok_decl(prec,id) (((id)<<5) | (prec))
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#define PREC(op) ((op) & 0x1F)
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#define tok_decl(prec,id) (((id)<<5)|(prec))
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#define PREC(op) ((op) & 0x1F)
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#define TOK_LPAREN tok_decl(0,0)
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#define TOK_LPAREN tok_decl(0,0)
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#define TOK_COMMA tok_decl(1,0)
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#define TOK_COMMA tok_decl(1,0)
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/* All assignments are right associative and have the same precedence,
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* but there are 11 of them, which doesn't fit into 3 bits for unique id.
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* Abusing another precedence level:
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*/
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#define TOK_ASSIGN tok_decl(2,0)
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#define TOK_AND_ASSIGN tok_decl(2,1)
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#define TOK_OR_ASSIGN tok_decl(2,2)
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#define TOK_XOR_ASSIGN tok_decl(2,3)
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#define TOK_PLUS_ASSIGN tok_decl(2,4)
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#define TOK_MINUS_ASSIGN tok_decl(2,5)
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#define TOK_LSHIFT_ASSIGN tok_decl(2,6)
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#define TOK_RSHIFT_ASSIGN tok_decl(2,7)
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#define TOK_ASSIGN tok_decl(2,0)
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#define TOK_AND_ASSIGN tok_decl(2,1)
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#define TOK_OR_ASSIGN tok_decl(2,2)
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#define TOK_XOR_ASSIGN tok_decl(2,3)
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#define TOK_PLUS_ASSIGN tok_decl(2,4)
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#define TOK_MINUS_ASSIGN tok_decl(2,5)
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#define TOK_LSHIFT_ASSIGN tok_decl(2,6)
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#define TOK_RSHIFT_ASSIGN tok_decl(2,7)
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#define TOK_MUL_ASSIGN tok_decl(3,0)
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#define TOK_DIV_ASSIGN tok_decl(3,1)
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#define TOK_REM_ASSIGN tok_decl(3,2)
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#define TOK_MUL_ASSIGN tok_decl(3,0)
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#define TOK_DIV_ASSIGN tok_decl(3,1)
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#define TOK_REM_ASSIGN tok_decl(3,2)
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#define fix_assignment_prec(prec) do { if (prec == 3) prec = 2; } while (0)
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/* all assign is right associativity and precedence eq, but (7+3)<<5 > 256 */
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#define convert_prec_is_assign(prec) do { if (prec == 3) prec = 2; } while (0)
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/* ternary conditional operator is right associative too */
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#define TOK_CONDITIONAL tok_decl(4,0)
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#define TOK_CONDITIONAL_SEP tok_decl(4,1)
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/* conditional is right associativity too */
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#define TOK_CONDITIONAL tok_decl(4,0)
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#define TOK_CONDITIONAL_SEP tok_decl(4,1)
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#define TOK_OR tok_decl(5,0)
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#define TOK_OR tok_decl(5,0)
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#define TOK_AND tok_decl(6,0)
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#define TOK_AND tok_decl(6,0)
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#define TOK_BOR tok_decl(7,0)
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#define TOK_BOR tok_decl(7,0)
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#define TOK_BXOR tok_decl(8,0)
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#define TOK_BXOR tok_decl(8,0)
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#define TOK_BAND tok_decl(9,0)
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#define TOK_BAND tok_decl(9,0)
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#define TOK_EQ tok_decl(10,0)
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#define TOK_NE tok_decl(10,1)
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#define TOK_EQ tok_decl(10,0)
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#define TOK_NE tok_decl(10,1)
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#define TOK_LT tok_decl(11,0)
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#define TOK_GT tok_decl(11,1)
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#define TOK_GE tok_decl(11,2)
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#define TOK_LE tok_decl(11,3)
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#define TOK_LT tok_decl(11,0)
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#define TOK_GT tok_decl(11,1)
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#define TOK_GE tok_decl(11,2)
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#define TOK_LE tok_decl(11,3)
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#define TOK_LSHIFT tok_decl(12,0)
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#define TOK_RSHIFT tok_decl(12,1)
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#define TOK_LSHIFT tok_decl(12,0)
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#define TOK_RSHIFT tok_decl(12,1)
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#define TOK_ADD tok_decl(13,0)
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#define TOK_SUB tok_decl(13,1)
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#define TOK_ADD tok_decl(13,0)
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#define TOK_SUB tok_decl(13,1)
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#define TOK_MUL tok_decl(14,0)
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#define TOK_DIV tok_decl(14,1)
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#define TOK_REM tok_decl(14,2)
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#define TOK_MUL tok_decl(14,0)
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#define TOK_DIV tok_decl(14,1)
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#define TOK_REM tok_decl(14,2)
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/* exponent is right associative */
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#define TOK_EXPONENT tok_decl(15,1)
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/* exponent is right associativity */
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#define TOK_EXPONENT tok_decl(15,1)
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/* unary operators */
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#define UNARYPREC 16
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#define TOK_BNOT tok_decl(UNARYPREC,0)
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#define TOK_NOT tok_decl(UNARYPREC,1)
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/* For now unary operators. */
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#define UNARYPREC 16
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#define TOK_BNOT tok_decl(UNARYPREC,0)
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#define TOK_NOT tok_decl(UNARYPREC,1)
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#define TOK_UMINUS tok_decl(UNARYPREC+1,0)
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#define TOK_UPLUS tok_decl(UNARYPREC+1,1)
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#define TOK_UMINUS tok_decl(UNARYPREC+1,0)
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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 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 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 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 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 SPEC_PREC (UNARYPREC+4)
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#define TOK_NUM tok_decl(SPEC_PREC, 0)
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#define TOK_RPAREN tok_decl(SPEC_PREC, 1)
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#define NUMPTR (*numstackptr)
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#define TOK_NUM tok_decl(SPEC_PREC, 0)
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#define TOK_RPAREN tok_decl(SPEC_PREC, 1)
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static int
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tok_have_assign(operator op)
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{
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operator prec = PREC(op);
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convert_prec_is_assign(prec);
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fix_assignment_prec(prec);
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return (prec == PREC(TOK_ASSIGN) ||
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prec == PREC_PRE || prec == PREC_POST);
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}
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static int
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is_right_associativity(operator prec)
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is_right_associative(operator prec)
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{
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return (prec == PREC(TOK_ASSIGN) || prec == PREC(TOK_EXPONENT)
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|| prec == PREC(TOK_CONDITIONAL));
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@ -255,25 +256,25 @@ arith_lookup_val(v_n_t *t, a_e_h_t *math_hooks)
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if (p) {
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int errcode;
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/* recursive try as expression */
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chk_var_recursive_looped_t *cur;
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chk_var_recursive_looped_t cur_save;
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/* recursively try p as expression */
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for (cur = prev_chk_var_recursive; cur; cur = cur->next) {
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if (strcmp(cur->var, t->var) == 0) {
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/* expression recursion loop detected */
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return -5;
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}
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}
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/* save current lookuped var name */
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/* save current var name */
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cur = prev_chk_var_recursive;
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cur_save.var = t->var;
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cur_save.next = cur;
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prev_chk_var_recursive = &cur_save;
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t->val = arith (p, &errcode, math_hooks);
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/* restore previous ptr after recursiving */
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t->val = arith(p, &errcode, math_hooks);
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/* restore previous ptr after recursion */
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prev_chk_var_recursive = cur;
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return errcode;
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}
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@ -283,21 +284,24 @@ arith_lookup_val(v_n_t *t, a_e_h_t *math_hooks)
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return 0;
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}
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/* "applying" a token means performing it on the top elements on the integer
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* stack. For a unary operator it will only change the top element, but a
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* binary operator will pop two arguments and push a result */
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/* "Applying" a token means performing it on the top elements on the integer
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* stack. For an unary operator it will only change the top element, but a
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* binary operator will pop two arguments and push the result */
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static NOINLINE int
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arith_apply(operator op, v_n_t *numstack, v_n_t **numstackptr, a_e_h_t *math_hooks)
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{
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#define NUMPTR (*numstackptr)
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v_n_t *numptr_m1;
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arith_t numptr_val, rez;
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int ret_arith_lookup_val;
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/* There is no operator that can work without arguments */
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if (NUMPTR == numstack) goto err;
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if (NUMPTR == numstack)
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goto err;
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numptr_m1 = NUMPTR - 1;
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/* check operand is var with noninteger value */
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/* Check operand is var with noninteger value */
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ret_arith_lookup_val = arith_lookup_val(numptr_m1, math_hooks);
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if (ret_arith_lookup_val)
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return ret_arith_lookup_val;
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@ -388,16 +392,13 @@ arith_apply(operator op, v_n_t *numstack, v_n_t **numstackptr, a_e_h_t *math_hoo
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rez = rez ?
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numptr_val : numptr_m1->contidional_second_val;
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} else if (op == TOK_EXPONENT) {
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arith_t c;
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if (numptr_val < 0)
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return -3; /* exponent less than 0 */
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else {
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arith_t c = 1;
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if (numptr_val)
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while (numptr_val--)
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c *= rez;
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rez = c;
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}
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c = 1;
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while (--numptr_val >= 0)
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c *= rez;
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rez = c;
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} else if (numptr_val==0) /* zero divisor check */
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return -2;
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else if (op == TOK_DIV || op == TOK_DIV_ASSIGN)
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@ -422,11 +423,12 @@ arith_apply(operator op, v_n_t *numstack, v_n_t **numstackptr, a_e_h_t *math_hoo
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rez++;
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}
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numptr_m1->val = rez;
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/* protect geting var value, is number now */
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/* erase var name, it is just a number now */
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numptr_m1->var = NULL;
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return 0;
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err:
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return -1;
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#undef NUMPTR
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}
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/* longest must be first */
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@ -473,7 +475,6 @@ static const char op_tokens[] ALIGN1 = {
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'(', 0, TOK_LPAREN,
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0
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};
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/* ptr to ")" */
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#define ptr_to_rparen (&op_tokens[sizeof(op_tokens)-7])
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const char* FAST_FUNC
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@ -529,15 +530,15 @@ arith(const char *expr, int *perrcode, a_e_h_t *math_hooks)
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* result on the integer stack */
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if (expr != ptr_to_rparen + 1) {
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/* If we haven't done so already, */
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/* append a closing right paren */
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/* If we haven't done so already,
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* append a closing right paren
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* and let the loop process it */
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expr = ptr_to_rparen;
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/* and let the loop process it. */
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continue;
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}
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/* At this point, we're done with the expression. */
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/* At this point, we're done with the expression */
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if (numstackptr != numstack + 1) {
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/* ... but if there isn't, it's bad */
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/* ...but if there isn't, it's bad */
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goto err;
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}
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if (numstack->var) {
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@ -619,11 +620,11 @@ arith(const char *expr, int *perrcode, a_e_h_t *math_hooks)
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/* We don't want an unary operator to cause recursive descent on the
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* stack, because there can be many in a row and it could cause an
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* operator to be evaluated before its argument is pushed onto the
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* integer stack. */
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/* But for binary operators, "apply" everything on the operator
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* integer stack.
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* But for binary operators, "apply" everything on the operator
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* stack until we find an operator with a lesser priority than the
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* one we have just extracted. */
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/* Left paren is given the lowest priority so it will never be
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* one we have just extracted.
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* Left paren is given the lowest priority so it will never be
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* "applied" in this way.
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* if associativity is right and priority eq, applied also skip
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*/
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@ -641,17 +642,17 @@ arith(const char *expr, int *perrcode, a_e_h_t *math_hooks)
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* hit an open paren nor the bottom of the stack, pop
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* tokens and apply them */
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if (prev_op == TOK_LPAREN) {
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/* Any operator directly after a */
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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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/* close paren should consider itself binary */
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goto next;
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}
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} else {
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operator prev_prec = PREC(prev_op);
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convert_prec_is_assign(prec);
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convert_prec_is_assign(prev_prec);
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fix_assignment_prec(prec);
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fix_assignment_prec(prev_prec);
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if (prev_prec < prec
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|| (prev_prec == prec && is_right_associativity(prec))
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|| (prev_prec == prec && is_right_associative(prec))
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) {
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stackptr++;
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break;
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