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Diffstat (limited to 'ext/mysql/libmysql/str2int.c')
| -rw-r--r-- | ext/mysql/libmysql/str2int.c | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/ext/mysql/libmysql/str2int.c b/ext/mysql/libmysql/str2int.c new file mode 100644 index 0000000000..c6de1a436a --- /dev/null +++ b/ext/mysql/libmysql/str2int.c @@ -0,0 +1,185 @@ +/* + str2int(src, radix, lower, upper, &val) + converts the string pointed to by src to an integer and stores it in + val. It skips leading spaces and tabs (but not newlines, formfeeds, + backspaces), then it accepts an optional sign and a sequence of digits + in the specified radix. The result should satisfy lower <= *val <= upper. + The result is a pointer to the first character after the number; + trailing spaces will NOT be skipped. + + If an error is detected, the result will be NullS, the value put + in val will be 0, and errno will be set to + EDOM if there are no digits + ERANGE if the result would overflow or otherwise fail to lie + within the specified bounds. + Check that the bounds are right for your machine. + This looks amazingly complicated for what you probably thought was an + easy task. Coping with integer overflow and the asymmetric range of + twos complement machines is anything but easy. + + So that users of atoi and atol can check whether an error occured, + I have taken a wholly unprecedented step: errno is CLEARED if this + call has no problems. +*/ + +#include <global.h> +#include "m_string.h" +#include "m_ctype.h" +#include "my_sys.h" /* defines errno */ +#include <errno.h> + +#define char_val(X) (X >= '0' && X <= '9' ? X-'0' :\ + X >= 'A' && X <= 'Z' ? X-'A'+10 :\ + X >= 'a' && X <= 'z' ? X-'a'+10 :\ + '\177') + +char *str2int(register const char *src, register int radix, long int lower, long int upper, long int *val) +{ + int sign; /* is number negative (+1) or positive (-1) */ + int n; /* number of digits yet to be converted */ + long limit; /* "largest" possible valid input */ + long scale; /* the amount to multiply next digit by */ + long sofar; /* the running value */ + register int d; /* (negative of) next digit */ + char *start; + int digits[32]; /* Room for numbers */ + + /* Make sure *val is sensible in case of error */ + + *val = 0; + + /* Check that the radix is in the range 2..36 */ + +#ifndef DBUG_OFF + if (radix < 2 || radix > 36) { + errno=EDOM; + return NullS; + } +#endif + + /* The basic problem is: how do we handle the conversion of + a number without resorting to machine-specific code to + check for overflow? Obviously, we have to ensure that + no calculation can overflow. We are guaranteed that the + "lower" and "upper" arguments are valid machine integers. + On sign-and-magnitude, twos-complement, and ones-complement + machines all, if +|n| is representable, so is -|n|, but on + twos complement machines the converse is not true. So the + "maximum" representable number has a negative representative. + Limit is set to min(-|lower|,-|upper|); this is the "largest" + number we are concerned with. */ + + /* Calculate Limit using Scale as a scratch variable */ + + if ((limit = lower) > 0) limit = -limit; + if ((scale = upper) > 0) scale = -scale; + if (scale < limit) limit = scale; + + /* Skip leading spaces and check for a sign. + Note: because on a 2s complement machine MinLong is a valid + integer but |MinLong| is not, we have to keep the current + converted value (and the scale!) as *negative* numbers, + so the sign is the opposite of what you might expect. + */ + while (isspace(*src)) src++; + sign = -1; + if (*src == '+') src++; else + if (*src == '-') src++, sign = 1; + + /* Skip leading zeros so that we never compute a power of radix + in scale that we won't have a need for. Otherwise sticking + enough 0s in front of a number could cause the multiplication + to overflow when it neededn't. + */ + start=(char*) src; + while (*src == '0') src++; + + /* Move over the remaining digits. We have to convert from left + to left in order to avoid overflow. Answer is after last digit. + */ + + for (n = 0; (digits[n]=char_val(*src)) < radix && n < 20; n++,src++) ; + + /* Check that there is at least one digit */ + + if (start == src) { + errno=EDOM; + return NullS; + } + + /* The invariant we want to maintain is that src is just + to the right of n digits, we've converted k digits to + sofar, scale = -radix**k, and scale < sofar < 0. Now + if the final number is to be within the original + Limit, we must have (to the left)*scale+sofar >= Limit, + or (to the left)*scale >= Limit-sofar, i.e. the digits + to the left of src must form an integer <= (Limit-sofar)/(scale). + In particular, this is true of the next digit. In our + incremental calculation of Limit, + + IT IS VITAL that (-|N|)/(-|D|) = |N|/|D| + */ + + for (sofar = 0, scale = -1; --n >= 1;) + { + if ((long) -(d=digits[n]) < limit) { + errno=ERANGE; + return NullS; + } + limit = (limit+d)/radix, sofar += d*scale; scale *= radix; + } + if (n == 0) + { + if ((long) -(d=digits[n]) < limit) /* get last digit */ + { + errno=ERANGE; + return NullS; + } + sofar+=d*scale; + } + + /* Now it might still happen that sofar = -32768 or its equivalent, + so we can't just multiply by the sign and check that the result + is in the range lower..upper. All of this caution is a right + pain in the neck. If only there were a standard routine which + says generate thus and such a signal on integer overflow... + But not enough machines can do it *SIGH*. + */ + if (sign < 0) + { + if (sofar < -LONG_MAX || (sofar= -sofar) > upper) + { + errno=ERANGE; + return NullS; + } + } + else if (sofar < lower) + { + errno=ERANGE; + return NullS; + } + *val = sofar; + errno=0; /* indicate that all went well */ + return (char*) src; +} + + /* Theese are so slow compared with ordinary, optimized atoi */ + +#ifdef WANT_OUR_ATOI + +int atoi(const char *src) +{ + long val; + str2int(src, 10, (long) INT_MIN, (long) INT_MAX, &val); + return (int) val; +} + + +long atol(const char *src) +{ + long val; + str2int(src, 10, LONG_MIN, LONG_MAX, &val); + return val; +} + +#endif /* WANT_OUR_ATOI */ |