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cpython/Python/pystrtod.c

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/* -*- Mode: C; c-file-style: "python" -*- */
#include <Python.h>
#include <locale.h>
/* ascii character tests (as opposed to locale tests) */
#define ISSPACE(c) ((c) == ' ' || (c) == '\f' || (c) == '\n' || \
(c) == '\r' || (c) == '\t' || (c) == '\v')
#define ISDIGIT(c) ((c) >= '0' && (c) <= '9')
/**
* PyOS_ascii_strtod:
* @nptr: the string to convert to a numeric value.
* @endptr: if non-%NULL, it returns the character after
* the last character used in the conversion.
*
* Converts a string to a #gdouble value.
* This function behaves like the standard strtod() function
* does in the C locale. It does this without actually
* changing the current locale, since that would not be
* thread-safe.
*
* This function is typically used when reading configuration
* files or other non-user input that should be locale independent.
* To handle input from the user you should normally use the
* locale-sensitive system strtod() function.
*
* If the correct value would cause overflow, plus or minus %HUGE_VAL
* is returned (according to the sign of the value), and %ERANGE is
* stored in %errno. If the correct value would cause underflow,
* zero is returned and %ERANGE is stored in %errno.
* If memory allocation fails, %ENOMEM is stored in %errno.
*
* This function resets %errno before calling strtod() so that
* you can reliably detect overflow and underflow.
*
* Return value: the #gdouble value.
**/
double
PyOS_ascii_strtod(const char *nptr, char **endptr)
{
char *fail_pos;
double val = -1.0;
struct lconv *locale_data;
const char *decimal_point;
size_t decimal_point_len;
const char *p, *decimal_point_pos;
const char *end = NULL; /* Silence gcc */
const char *digits_pos = NULL;
int negate = 0;
assert(nptr != NULL);
fail_pos = NULL;
locale_data = localeconv();
decimal_point = locale_data->decimal_point;
decimal_point_len = strlen(decimal_point);
assert(decimal_point_len != 0);
decimal_point_pos = NULL;
/* We process any leading whitespace and the optional sign manually,
then pass the remainder to the system strtod. This ensures that
the result of an underflow has the correct sign. (bug #1725) */
p = nptr;
/* Skip leading space */
while (ISSPACE(*p))
p++;
/* Process leading sign, if present */
if (*p == '-') {
negate = 1;
p++;
} else if (*p == '+') {
p++;
}
/* What's left should begin with a digit, a decimal point, or one of
the letters i, I, n, N. It should not begin with 0x or 0X */
if ((!ISDIGIT(*p) &&
*p != '.' && *p != 'i' && *p != 'I' && *p != 'n' && *p != 'N')
||
(*p == '0' && (p[1] == 'x' || p[1] == 'X')))
{
if (endptr)
*endptr = (char*)nptr;
errno = EINVAL;
return val;
}
digits_pos = p;
if (decimal_point[0] != '.' ||
decimal_point[1] != 0)
{
while (ISDIGIT(*p))
p++;
if (*p == '.')
{
decimal_point_pos = p++;
while (ISDIGIT(*p))
p++;
if (*p == 'e' || *p == 'E')
p++;
if (*p == '+' || *p == '-')
p++;
while (ISDIGIT(*p))
p++;
end = p;
}
else if (strncmp(p, decimal_point, decimal_point_len) == 0)
{
/* Python bug #1417699 */
if (endptr)
*endptr = (char*)nptr;
errno = EINVAL;
return val;
}
/* For the other cases, we need not convert the decimal
point */
}
/* Set errno to zero, so that we can distinguish zero results
and underflows */
errno = 0;
if (decimal_point_pos)
{
char *copy, *c;
/* We need to convert the '.' to the locale specific decimal
point */
copy = (char *)PyMem_MALLOC(end - digits_pos +
1 + decimal_point_len);
if (copy == NULL) {
if (endptr)
*endptr = (char *)nptr;
errno = ENOMEM;
return val;
}
c = copy;
memcpy(c, digits_pos, decimal_point_pos - digits_pos);
c += decimal_point_pos - digits_pos;
memcpy(c, decimal_point, decimal_point_len);
c += decimal_point_len;
memcpy(c, decimal_point_pos + 1,
end - (decimal_point_pos + 1));
c += end - (decimal_point_pos + 1);
*c = 0;
val = strtod(copy, &fail_pos);
if (fail_pos)
{
if (fail_pos > decimal_point_pos)
fail_pos = (char *)digits_pos +
(fail_pos - copy) -
(decimal_point_len - 1);
else
fail_pos = (char *)digits_pos +
(fail_pos - copy);
}
PyMem_FREE(copy);
}
else {
val = strtod(digits_pos, &fail_pos);
}
if (fail_pos == digits_pos)
fail_pos = (char *)nptr;
if (negate && fail_pos != nptr)
val = -val;
if (endptr)
*endptr = fail_pos;
return val;
}
/* Given a string that may have a decimal point in the current
locale, change it back to a dot. Since the string cannot get
longer, no need for a maximum buffer size parameter. */
Py_LOCAL_INLINE(void)
change_decimal_from_locale_to_dot(char* buffer)
{
struct lconv *locale_data = localeconv();
const char *decimal_point = locale_data->decimal_point;
if (decimal_point[0] != '.' || decimal_point[1] != 0) {
size_t decimal_point_len = strlen(decimal_point);
if (*buffer == '+' || *buffer == '-')
buffer++;
while (isdigit(Py_CHARMASK(*buffer)))
buffer++;
if (strncmp(buffer, decimal_point, decimal_point_len) == 0) {
*buffer = '.';
buffer++;
if (decimal_point_len > 1) {
/* buffer needs to get smaller */
size_t rest_len = strlen(buffer +
(decimal_point_len - 1));
memmove(buffer,
buffer + (decimal_point_len - 1),
rest_len);
buffer[rest_len] = 0;
}
}
}
}
/* From the C99 standard, section 7.19.6:
The exponent always contains at least two digits, and only as many more digits
as necessary to represent the exponent.
*/
#define MIN_EXPONENT_DIGITS 2
/* Ensure that any exponent, if present, is at least MIN_EXPONENT_DIGITS
in length. */
Py_LOCAL_INLINE(void)
ensure_minimum_exponent_length(char* buffer, size_t buf_size)
{
char *p = strpbrk(buffer, "eE");
if (p && (*(p + 1) == '-' || *(p + 1) == '+')) {
char *start = p + 2;
int exponent_digit_cnt = 0;
int leading_zero_cnt = 0;
int in_leading_zeros = 1;
int significant_digit_cnt;
/* Skip over the exponent and the sign. */
p += 2;
/* Find the end of the exponent, keeping track of leading
zeros. */
while (*p && isdigit(Py_CHARMASK(*p))) {
if (in_leading_zeros && *p == '0')
++leading_zero_cnt;
if (*p != '0')
in_leading_zeros = 0;
++p;
++exponent_digit_cnt;
}
significant_digit_cnt = exponent_digit_cnt - leading_zero_cnt;
if (exponent_digit_cnt == MIN_EXPONENT_DIGITS) {
/* If there are 2 exactly digits, we're done,
regardless of what they contain */
}
else if (exponent_digit_cnt > MIN_EXPONENT_DIGITS) {
int extra_zeros_cnt;
/* There are more than 2 digits in the exponent. See
if we can delete some of the leading zeros */
if (significant_digit_cnt < MIN_EXPONENT_DIGITS)
significant_digit_cnt = MIN_EXPONENT_DIGITS;
extra_zeros_cnt = exponent_digit_cnt -
significant_digit_cnt;
/* Delete extra_zeros_cnt worth of characters from the
front of the exponent */
assert(extra_zeros_cnt >= 0);
/* Add one to significant_digit_cnt to copy the
trailing 0 byte, thus setting the length */
memmove(start,
start + extra_zeros_cnt,
significant_digit_cnt + 1);
}
else {
/* If there are fewer than 2 digits, add zeros
until there are 2, if there's enough room */
int zeros = MIN_EXPONENT_DIGITS - exponent_digit_cnt;
if (start + zeros + exponent_digit_cnt + 1
< buffer + buf_size) {
memmove(start + zeros, start,
exponent_digit_cnt + 1);
memset(start, '0', zeros);
}
}
}
}
/* Ensure that buffer has a decimal point in it. The decimal point
will not be in the current locale, it will always be '.' */
Py_LOCAL_INLINE(void)
ensure_decimal_point(char* buffer, size_t buf_size)
{
int insert_count = 0;
char* chars_to_insert;
/* search for the first non-digit character */
char *p = buffer;
if (*p == '-' || *p == '+')
/* Skip leading sign, if present. I think this could only
ever be '-', but it can't hurt to check for both. */
++p;
while (*p && isdigit(Py_CHARMASK(*p)))
++p;
if (*p == '.') {
if (isdigit(Py_CHARMASK(*(p+1)))) {
/* Nothing to do, we already have a decimal
point and a digit after it */
}
else {
/* We have a decimal point, but no following
digit. Insert a zero after the decimal. */
++p;
chars_to_insert = "0";
insert_count = 1;
}
}
else {
chars_to_insert = ".0";
insert_count = 2;
}
if (insert_count) {
size_t buf_len = strlen(buffer);
if (buf_len + insert_count + 1 >= buf_size) {
/* If there is not enough room in the buffer
for the additional text, just skip it. It's
not worth generating an error over. */
}
else {
memmove(p + insert_count, p,
buffer + strlen(buffer) - p + 1);
memcpy(p, chars_to_insert, insert_count);
}
}
}
/* Add the locale specific grouping characters to buffer. Note
that any decimal point (if it's present) in buffer is already
locale-specific. Return 0 on error, else 1. */
Py_LOCAL_INLINE(int)
add_thousands_grouping(char* buffer, size_t buf_size)
{
Py_ssize_t len = strlen(buffer);
struct lconv *locale_data = localeconv();
const char *decimal_point = locale_data->decimal_point;
/* Find the decimal point, if any. We're only concerned
about the characters to the left of the decimal when
adding grouping. */
char *p = strstr(buffer, decimal_point);
if (!p) {
/* No decimal, use the entire string. */
/* If any exponent, adjust p. */
p = strpbrk(buffer, "eE");
if (!p)
/* No exponent and no decimal. Use the entire
string. */
p = buffer + len;
}
/* At this point, p points just past the right-most character we
want to format. We need to add the grouping string for the
characters between buffer and p. */
return _PyString_InsertThousandsGrouping(buffer, len, p-buffer,
buf_size, NULL, 1);
}
/* see FORMATBUFLEN in unicodeobject.c */
#define FLOAT_FORMATBUFLEN 120
/**
* PyOS_ascii_formatd:
* @buffer: A buffer to place the resulting string in
* @buf_size: The length of the buffer.
* @format: The printf()-style format to use for the
* code to use for converting.
* @d: The #gdouble to convert
*
* Converts a #gdouble to a string, using the '.' as
* decimal point. To format the number you pass in
* a printf()-style format string. Allowed conversion
* specifiers are 'e', 'E', 'f', 'F', 'g', 'G', and 'n'.
*
* 'n' is the same as 'g', except it uses the current locale.
* 'Z' is the same as 'g', except it always has a decimal and
* at least one digit after the decimal.
*
* Return value: The pointer to the buffer with the converted string.
**/
char *
PyOS_ascii_formatd(char *buffer,
size_t buf_size,
const char *format,
double d)
{
char format_char;
size_t format_len = strlen(format);
/* For type 'n', we need to make a copy of the format string, because
we're going to modify 'n' -> 'g', and format is const char*, so we
can't modify it directly. FLOAT_FORMATBUFLEN should be longer than
we ever need this to be. There's an upcoming check to ensure it's
big enough. */
/* Issue 2264: code 'Z' requires copying the format. 'Z' is 'g', but
also with at least one character past the decimal. */
char tmp_format[FLOAT_FORMATBUFLEN];
/* The last character in the format string must be the format char */
format_char = format[format_len - 1];
if (format[0] != '%')
return NULL;
/* I'm not sure why this test is here. It's ensuring that the format
string after the first character doesn't have a single quote, a
lowercase l, or a percent. This is the reverse of the commented-out
test about 10 lines ago. */
if (strpbrk(format + 1, "'l%"))
return NULL;
/* Also curious about this function is that it accepts format strings
like "%xg", which are invalid for floats. In general, the
interface to this function is not very good, but changing it is
difficult because it's a public API. */
if (!(format_char == 'e' || format_char == 'E' ||
format_char == 'f' || format_char == 'F' ||
format_char == 'g' || format_char == 'G' ||
format_char == 'n' || format_char == 'Z'))
return NULL;
/* Map 'n' or 'Z' format_char to 'g', by copying the format string and
replacing the final char with a 'g' */
if (format_char == 'n' || format_char == 'Z') {
if (format_len + 1 >= sizeof(tmp_format)) {
/* The format won't fit in our copy. Error out. In
practice, this will never happen and will be
detected by returning NULL */
return NULL;
}
strcpy(tmp_format, format);
tmp_format[format_len - 1] = 'g';
format = tmp_format;
}
/* Have PyOS_snprintf do the hard work */
PyOS_snprintf(buffer, buf_size, format, d);
/* Do various fixups on the return string */
/* Get the current locale, and find the decimal point string.
Convert that string back to a dot. Do not do this if using the
'n' (number) format code, since we want to keep the localized
decimal point in that case. */
if (format_char != 'n')
change_decimal_from_locale_to_dot(buffer);
/* If an exponent exists, ensure that the exponent is at least
MIN_EXPONENT_DIGITS digits, providing the buffer is large enough
for the extra zeros. Also, if there are more than
MIN_EXPONENT_DIGITS, remove as many zeros as possible until we get
back to MIN_EXPONENT_DIGITS */
ensure_minimum_exponent_length(buffer, buf_size);
/* If format_char is 'Z', make sure we have at least one character
after the decimal point (and make sure we have a decimal point). */
if (format_char == 'Z')
ensure_decimal_point(buffer, buf_size);
/* If format_char is 'n', add the thousands grouping. */
if (format_char == 'n')
if (!add_thousands_grouping(buffer, buf_size))
return NULL;
return buffer;
}
double
PyOS_ascii_atof(const char *nptr)
{
return PyOS_ascii_strtod(nptr, NULL);
}
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