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//===-- String to integer conversion utils ----------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LIBC_SRC_SUPPORT_STR_TO_INTEGER_H
#define LIBC_SRC_SUPPORT_STR_TO_INTEGER_H
#include "src/__support/CPP/limits.h"
#include "src/__support/CPP/type_traits.h"
#include "src/__support/common.h"
#include "src/__support/ctype_utils.h"
#include "src/__support/str_to_num_result.h"
#include "src/errno/libc_errno.h" // For ERANGE
#include <limits.h>
namespace __llvm_libc {
namespace internal {
// Returns a pointer to the first character in src that is not a whitespace
// character (as determined by isspace())
LIBC_INLINE const char *first_non_whitespace(const char *__restrict src) {
while (internal::isspace(*src)) {
++src;
}
return src;
}
LIBC_INLINE int b36_char_to_int(char input) {
if (isdigit(input))
return input - '0';
if (isalpha(input))
return (input | 32) + 10 - 'a';
return 0;
}
// checks if the next 3 characters of the string pointer are the start of a
// hexadecimal number. Does not advance the string pointer.
LIBC_INLINE bool is_hex_start(const char *__restrict src) {
return *src == '0' && (*(src + 1) | 32) == 'x' && isalnum(*(src + 2)) &&
b36_char_to_int(*(src + 2)) < 16;
}
// Takes the address of the string pointer and parses the base from the start of
// it. This function will advance |src| to the first valid digit in the inferred
// base.
LIBC_INLINE int infer_base(const char *__restrict *__restrict src) {
// A hexadecimal number is defined as "the prefix 0x or 0X followed by a
// sequence of the deimal digits and the letters a (or A) through f (or F)
// with values 10 through 15 respectively." (C standard 6.4.4.1)
if (is_hex_start(*src)) {
(*src) += 2;
return 16;
} // An octal number is defined as "the prefix 0 optionally followed by a
// sequence of the digits 0 through 7 only" (C standard 6.4.4.1) and so any
// number that starts with 0, including just 0, is an octal number.
else if (**src == '0') {
return 8;
} // A decimal number is defined as beginning "with a nonzero digit and
// consist[ing] of a sequence of decimal digits." (C standard 6.4.4.1)
else {
return 10;
}
}
// Takes a pointer to a string and the base to convert to. This function is used
// as the backend for all of the string to int functions.
template <class T>
LIBC_INLINE StrToNumResult<T> strtointeger(const char *__restrict src,
int base) {
unsigned long long result = 0;
bool is_number = false;
const char *original_src = src;
int error_val = 0;
if (base < 0 || base == 1 || base > 36) {
error_val = EINVAL;
return {0, 0, error_val};
}
src = first_non_whitespace(src);
char result_sign = '+';
if (*src == '+' || *src == '-') {
result_sign = *src;
++src;
}
if (base == 0) {
base = infer_base(&src);
} else if (base == 16 && is_hex_start(src)) {
src = src + 2;
}
constexpr bool IS_UNSIGNED = (cpp::numeric_limits<T>::min() == 0);
const bool is_positive = (result_sign == '+');
unsigned long long constexpr NEGATIVE_MAX =
!IS_UNSIGNED
? static_cast<unsigned long long>(cpp::numeric_limits<T>::max()) + 1
: cpp::numeric_limits<T>::max();
unsigned long long const abs_max =
(is_positive ? cpp::numeric_limits<T>::max() : NEGATIVE_MAX);
unsigned long long const abs_max_div_by_base = abs_max / base;
while (isalnum(*src)) {
int cur_digit = b36_char_to_int(*src);
if (cur_digit >= base)
break;
is_number = true;
++src;
// If the number has already hit the maximum value for the current type then
// the result cannot change, but we still need to advance src to the end of
// the number.
if (result == abs_max) {
error_val = ERANGE;
continue;
}
if (result > abs_max_div_by_base) {
result = abs_max;
error_val = ERANGE;
} else {
result = result * base;
}
if (result > abs_max - cur_digit) {
result = abs_max;
error_val = ERANGE;
} else {
result = result + cur_digit;
}
}
ptrdiff_t str_len = is_number ? (src - original_src) : 0;
if (error_val == ERANGE) {
if (is_positive || IS_UNSIGNED)
return {cpp::numeric_limits<T>::max(), str_len, error_val};
else // T is signed and there is a negative overflow
return {cpp::numeric_limits<T>::min(), str_len, error_val};
}
return {is_positive
? static_cast<T>(result)
: static_cast<T>(-static_cast<cpp::make_unsigned_t<T>>(result)),
str_len, error_val};
}
} // namespace internal
} // namespace __llvm_libc
#endif // LIBC_SRC_SUPPORT_STR_TO_INTEGER_H
|
