acrn-hypervisor/hypervisor/debug/string.c

88 lines
2.0 KiB
C
Raw Normal View History

/*
* Copyright (C) 2018 Intel Corporation. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <types.h>
#include <rtl.h>
/*
* Convert a string to a long integer - decimal support only.
*/
int64_t strtol_deci(const char *nptr)
{
const char *s = nptr;
char c;
uint64_t acc, cutoff, cutlim;
int32_t neg = 0, any;
uint64_t base = 10UL;
/*
* Skip white space and pick up leading +/- sign if any.
*/
do {
c = *s;
s++;
} while (is_space(c));
if (c == '-') {
neg = 1;
c = *s;
s++;
} else if (c == '+') {
c = *s;
s++;
} else {
/* No sign character. */
}
/*
* Compute the cutoff value between legal numbers and illegal
* numbers. That is the largest legal value, divided by the
* base. An input number that is greater than this value, if
* followed by a legal input character, is too big. One that
* is equal to this value may be valid or not; the limit
* between valid and invalid numbers is then based on the last
* digit. For instance, if the range for longs is
* [-2147483648..2147483647] and the input base is 10,
* cutoff will be set to 214748364 and cutlim to either
* 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
* a value > 214748364, or equal but the next digit is > 7 (or 8),
* the number is too big, and we will return a range error.
*
* Set any if any `digits' consumed; make it negative to indicate
* overflow.
*/
cutoff = (neg != 0) ? LONG_MIN : LONG_MAX;
cutlim = cutoff % base;
cutoff /= base;
acc = 0UL;
any = 0;
while ((c >= '0') && (c <= '9')) {
c -= '0';
if ((acc > cutoff) ||
((acc == cutoff) && ((uint64_t)c > cutlim))) {
any = -1;
break;
} else {
acc *= base;
acc += (uint64_t)c;
}
c = *s;
s++;
}
if (any < 0) {
acc = (neg != 0) ? LONG_MIN : LONG_MAX;
} else if (neg != 0) {
acc = ~acc + 1UL;
} else {
/* There is no overflow and no leading '-' exists. In such case
* acc already holds the right number. No action required. */
}
return (long)acc;
}