diff options
| author | Denys Vlasenko <vda.linux@googlemail.com> | 2023-07-02 20:32:12 +0300 |
|---|---|---|
| committer | Denys Vlasenko <vda.linux@googlemail.com> | 2023-07-02 20:32:12 +0300 |
| commit | cc9543fed1f916f62a63cfbe9eaefba3df8e22cb (patch) | |
| tree | ca45333b5d738d2ccad7fb2ef65a3b8f423b4b6f | |
| parent | 045924ed7d3c887cce1c6a22a0b4e0b692719154 (diff) | |
shell/math: avoid $((3**999999999999999999)) to take years
function old new delta
arith_apply 991 1030 +39
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
| -rw-r--r-- | shell/math.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/shell/math.c b/shell/math.c index b06d1ae3c..e90a38f05 100644 --- a/shell/math.c +++ b/shell/math.c @@ -155,7 +155,7 @@ typedef unsigned char operator; #define PREC_ASSIGN2 3 #define TOK_MUL_ASSIGN tok_decl(3,0) /* "/" and "/=" ops have the same id bits */ -#define DIV_ID1 1 +#define DIV_ID1 1 #define TOK_DIV_ASSIGN tok_decl(3,DIV_ID1) #define TOK_REM_ASSIGN tok_decl(3,2) @@ -422,8 +422,19 @@ arith_apply(arith_state_t *math_state, operator op, var_or_num_t *numstack, var_ if (right_side_val < 0) return "exponent less than 0"; c = 1; - while (--right_side_val >= 0) + while (right_side_val != 0) { + if ((right_side_val & 1) == 0) { + /* this if() block is not necessary for correctness, + * but otherwise echo $((3**999999999999999999)) + * takes a VERY LONG time + * (and it's not interruptible by ^C) + */ + rez *= rez; + right_side_val >>= 1; + } c *= rez; + right_side_val--; + } rez = c; } else /*if (op == TOK_DIV || op == TOK_DIV_ASSIGN @@ -550,7 +561,7 @@ static arith_t parse_with_base(const char *nptr, char **endptr, unsigned base) /* current char is one of :;<=>?@A..Z[\]^_`a..z */ /* in bases up to 36, case does not matter for a-z, - * map A..Z and a..z to 10..35: */ + * map @A..Z and `a..z to 9..35: */ digit = (unsigned)(*nptr | 0x20) - ('a' - 10); if (base > 36 && *nptr <= '_') { /* base > 36: A-Z,@,_ are 36-61,62,63 */ |