cpython/Objects/stringlib/localeutil.h

/* stringlib: locale related helpers implementation */

#ifndef STRINGLIB_LOCALEUTIL_H
#define STRINGLIB_LOCALEUTIL_H

#include <locale.h>

/**
 * _Py_InsertThousandsGrouping:
 * @buffer: A pointer to the start of a string.
 * @n_buffer: The length of the string.
 * @n_digits: The number of digits in the string, in which we want
 *            to put the grouping chars.
 * @buf_size: The maximum size of the buffer pointed to by buffer.
 * @count: If non-NULL, points to a variable that will receive the
 *         number of characters we need to insert (and no formatting
 *         will actually occur).
 * @append_zero_char: If non-zero, put a trailing zero at the end of
 *         of the resulting string, if and only if we modified the
 *         string.
 *
 * Inserts thousand grouping characters (as defined in the current
 *  locale) into the string between buffer and buffer+n_digits.  If
 *  count is non-NULL, don't do any formatting, just count the number
 *  of characters to insert.  This is used by the caller to
 *  appropriately resize the buffer, if needed.  If count is non-NULL,
 *  buffer can be NULL (it is not dereferenced at all in that case).
 *
 * Return value: 0 on error, else 1.  Note that no error can occur if
 *  count is non-NULL.
 *
 * This name won't be used, the includer of this file should define
 *  it to be the actual function name, based on unicode or string.
 **/
int
_Py_InsertThousandsGrouping(STRINGLIB_CHAR *buffer,
                            Py_ssize_t n_buffer,
                            Py_ssize_t n_digits,
                            Py_ssize_t buf_size,
                            Py_ssize_t *count,
                            int append_zero_char)
{
    struct lconv *locale_data = localeconv();
    const char *grouping = locale_data->grouping;
    const char *thousands_sep = locale_data->thousands_sep;
    Py_ssize_t thousands_sep_len = strlen(thousands_sep);
    STRINGLIB_CHAR *pend = NULL; /* current end of buffer */
    STRINGLIB_CHAR *pmax = NULL; /* max of buffer */
    char current_grouping;
    Py_ssize_t remaining = n_digits; /* Number of chars remaining to
                                        be looked at */

    /* Initialize the character count, if we're just counting. */
    if (count)
        *count = 0;
    else {
        /* We're not just counting, we're modifying buffer */
        pend = buffer + n_buffer;
        pmax = buffer + buf_size;
    }

    /* Starting at the end and working right-to-left, keep track of
       what grouping needs to be added and insert that. */
    current_grouping = *grouping++;

    /* If the first character is 0, perform no grouping at all. */
    if (current_grouping == 0)
        return 1;

    while (remaining > current_grouping) {
        /* Always leave buffer and pend valid at the end of this
           loop, since we might leave with a return statement. */

        remaining -= current_grouping;
        if (count) {
            /* We're only counting, not touching the memory. */
            *count += thousands_sep_len;
        }
        else {
            /* Do the formatting. */

            STRINGLIB_CHAR *plast = buffer + remaining;

            /* Is there room to insert thousands_sep_len chars? */
            if (pmax - pend < thousands_sep_len)
                /* No room. */
                return 0;

            /* Move the rest of the string down. */
            memmove(plast + thousands_sep_len,
                plast,
                (pend - plast) * sizeof(STRINGLIB_CHAR));
            /* Copy the thousands_sep chars into the buffer. */
#if STRINGLIB_IS_UNICODE
            /* Convert from the char's of the thousands_sep from
               the locale into unicode. */
            {
                Py_ssize_t i;
                for (i = 0; i < thousands_sep_len; ++i)
                    plast[i] = thousands_sep[i];
            }
#else
            /* No conversion, just memcpy the thousands_sep. */
            memcpy(plast, thousands_sep, thousands_sep_len);
#endif
        }

        /* Adjust end pointer. */
        pend += thousands_sep_len;

        /* Move to the next grouping character, unless we're
           repeating (which is designated by a grouping of 0). */
        if (*grouping != 0) {
            current_grouping = *grouping++;
            if (current_grouping == CHAR_MAX)
                /* We're done. */
                break;
        }
    }
    if (append_zero_char) {
        /* Append a zero character to mark the end of the string,
           if there's room. */
        if (pend - (buffer + remaining) < 1)
            /* No room, error. */
            return 0;
        *pend = 0;
    }
    return 1;
}
#endif /* STRINGLIB_LOCALEUTIL_H */