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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
//
//===----------------------------------------------------------------------===//
// -----------------------------------------------------------------------------
// **** WARNING ****
// This file is shared with libc++. You should also be careful when adding
// dependencies to this file, since it needs to build for all libc++ targets.
// -----------------------------------------------------------------------------
#ifndef LLVM_LIBC_SRC___SUPPORT_STR_TO_INTEGER_H
#define LLVM_LIBC_SRC___SUPPORT_STR_TO_INTEGER_H
#include "hdr/errno_macros.h" // For ERANGE
#include "src/__support/CPP/limits.h"
#include "src/__support/CPP/type_traits.h"
#include "src/__support/CPP/type_traits/make_unsigned.h"
#include "src/__support/big_int.h"
#include "src/__support/common.h"
#include "src/__support/ctype_utils.h"
#include "src/__support/macros/config.h"
#include "src/__support/str_to_num_result.h"
#include "src/__support/uint128.h"
namespace LIBC_NAMESPACE_DECL {
namespace internal {
// Returns the idx to the first character in src that is not a whitespace
// character (as determined by isspace())
LIBC_INLINE size_t
first_non_whitespace(const char *__restrict src,
size_t src_len = cpp::numeric_limits<size_t>::max()) {
size_t src_cur = 0;
while (src_cur < src_len && internal::isspace(src[src_cur])) {
++src_cur;
}
return src_cur;
}
// 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,
size_t src_len = cpp::numeric_limits<size_t>::max()) {
if (src_len < 3)
return false;
return *src == '0' && tolower(*(src + 1)) == '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.
LIBC_INLINE int infer_base(const char *__restrict src, size_t src_len) {
// A hexadecimal number is defined as "the prefix 0x or 0X followed by a
// sequence of the decimal 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_len))
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.
if (src_len > 0 && src[0] == '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)
return 10;
}
// -----------------------------------------------------------------------------
// **** WARNING ****
// This interface is shared with libc++, if you change this interface you need
// to update it in both libc and libc++.
// -----------------------------------------------------------------------------
// 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,
const size_t src_len = cpp::numeric_limits<size_t>::max()) {
using ResultType = make_integral_or_big_int_unsigned_t<T>;
ResultType result = 0;
bool is_number = false;
size_t src_cur = 0;
int error_val = 0;
if (src_len == 0)
return {0, 0, 0};
if (base < 0 || base == 1 || base > 36)
return {0, 0, EINVAL};
src_cur = first_non_whitespace(src, src_len);
char result_sign = '+';
if (src[src_cur] == '+' || src[src_cur] == '-') {
result_sign = src[src_cur];
++src_cur;
}
if (base == 0)
base = infer_base(src + src_cur, src_len - src_cur);
if (base == 16 && is_hex_start(src + src_cur, src_len - src_cur))
src_cur = src_cur + 2;
constexpr bool IS_UNSIGNED = cpp::is_unsigned_v<T>;
const bool is_positive = (result_sign == '+');
ResultType constexpr NEGATIVE_MAX =
!IS_UNSIGNED ? static_cast<ResultType>(cpp::numeric_limits<T>::max()) + 1
: cpp::numeric_limits<T>::max();
ResultType const abs_max =
(is_positive ? cpp::numeric_limits<T>::max() : NEGATIVE_MAX);
ResultType const abs_max_div_by_base =
abs_max / static_cast<ResultType>(base);
while (src_cur < src_len && isalnum(src[src_cur])) {
int cur_digit = b36_char_to_int(src[src_cur]);
if (cur_digit >= base)
break;
is_number = true;
++src_cur;
// 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 * static_cast<ResultType>(base);
}
if (result > abs_max - static_cast<ResultType>(cur_digit)) {
result = abs_max;
error_val = ERANGE;
} else {
result = result + static_cast<ResultType>(cur_digit);
}
}
ptrdiff_t str_len = is_number ? static_cast<ptrdiff_t>(src_cur) : 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 {static_cast<T>(is_positive ? result : -result), str_len, error_val};
}
} // namespace internal
} // namespace LIBC_NAMESPACE_DECL
#endif // LLVM_LIBC_SRC___SUPPORT_STR_TO_INTEGER_H
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