unicodeobject.c

/*

Unicode implementation based on original code by Fredrik Lundh,
modified by Marc-Andre Lemburg <mal@lemburg.com> according to the
Unicode Integration Proposal (see file Misc/unicode.txt).

Major speed upgrades to the method implementations at the Reykjavik
NeedForSpeed sprint, by Fredrik Lundh and Andrew Dalke.

Copyright (c) Corporation for National Research Initiatives.

--------------------------------------------------------------------
The original string type implementation is:

  Copyright (c) 1999 by Secret Labs AB
  Copyright (c) 1999 by Fredrik Lundh

By obtaining, using, and/or copying this software and/or its
associated documentation, you agree that you have read, understood,
and will comply with the following terms and conditions:

Permission to use, copy, modify, and distribute this software and its
associated documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appears in all
copies, and that both that copyright notice and this permission notice
appear in supporting documentation, and that the name of Secret Labs
AB or the author not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.

SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO
THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR BE LIABLE FOR
ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
--------------------------------------------------------------------

*/

#define PY_SSIZE_T_CLEAN
#include "Python.h"
#include "ucnhash.h"

#ifdef MS_WINDOWS
#include <windows.h>
#endif

/* Limit for the Unicode object free list */

#define PyUnicode_MAXFREELIST       1024

/* Limit for the Unicode object free list stay alive optimization.

   The implementation will keep allocated Unicode memory intact for
   all objects on the free list having a size less than this
   limit. This reduces malloc() overhead for small Unicode objects.

   At worst this will result in PyUnicode_MAXFREELIST *
   (sizeof(PyUnicodeObject) + KEEPALIVE_SIZE_LIMIT +
   malloc()-overhead) bytes of unused garbage.

   Setting the limit to 0 effectively turns the feature off.

   Note: This is an experimental feature ! If you get core dumps when
   using Unicode objects, turn this feature off.

*/

#define KEEPALIVE_SIZE_LIMIT       9

/* Endianness switches; defaults to little endian */

#ifdef WORDS_BIGENDIAN
# define BYTEORDER_IS_BIG_ENDIAN
#else
# define BYTEORDER_IS_LITTLE_ENDIAN
#endif

/* --- Globals ------------------------------------------------------------

NOTE: In the interpreter's initialization phase, some globals are currently
      initialized dynamically as needed. In the process Unicode objects may
      be created before the Unicode type is ready.

*/


#ifdef __cplusplus
extern "C" {
#endif

/* This dictionary holds all interned unicode strings.  Note that references
   to strings in this dictionary are *not* counted in the string's ob_refcnt.
   When the interned string reaches a refcnt of 0 the string deallocation
   function will delete the reference from this dictionary.

   Another way to look at this is that to say that the actual reference
   count of a string is:  s->ob_refcnt + (s->state ? 2 : 0)
*/
static PyObject *interned = NULL;

/* Free list for Unicode objects */
static PyUnicodeObject *free_list = NULL;
static int numfree = 0;

/* The empty Unicode object is shared to improve performance. */
static PyUnicodeObject *unicode_empty = NULL;

#define _Py_RETURN_UNICODE_EMPTY()                      \
    do {                                                \
        if (unicode_empty != NULL)                      \
            Py_INCREF(unicode_empty);                   \
        else {                                          \
            unicode_empty = _PyUnicode_New(0);          \
            if (unicode_empty != NULL)                  \
                Py_INCREF(unicode_empty);               \
        }                                               \
        return (PyObject *)unicode_empty;               \
    } while (0)

/* Single character Unicode strings in the Latin-1 range are being
   shared as well. */
static PyUnicodeObject *unicode_latin1[256] = {NULL};

/* Fast detection of the most frequent whitespace characters */
const unsigned char _Py_ascii_whitespace[] = {
    0, 0, 0, 0, 0, 0, 0, 0,
/*     case 0x0009: * CHARACTER TABULATION */
/*     case 0x000A: * LINE FEED */
/*     case 0x000B: * LINE TABULATION */
/*     case 0x000C: * FORM FEED */
/*     case 0x000D: * CARRIAGE RETURN */
    0, 1, 1, 1, 1, 1, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
/*     case 0x001C: * FILE SEPARATOR */
/*     case 0x001D: * GROUP SEPARATOR */
/*     case 0x001E: * RECORD SEPARATOR */
/*     case 0x001F: * UNIT SEPARATOR */
    0, 0, 0, 0, 1, 1, 1, 1,
/*     case 0x0020: * SPACE */
    1, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,

    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0
};

static PyObject *unicode_encode_call_errorhandler(const char *errors,
       PyObject **errorHandler,const char *encoding, const char *reason,
       const Py_UNICODE *unicode, Py_ssize_t size, PyObject **exceptionObject,
       Py_ssize_t startpos, Py_ssize_t endpos, Py_ssize_t *newpos);

static void raise_encode_exception(PyObject **exceptionObject,
                                   const char *encoding,
                                   const Py_UNICODE *unicode, Py_ssize_t size,
                                   Py_ssize_t startpos, Py_ssize_t endpos,
                                   const char *reason);

/* Same for linebreaks */
static unsigned char ascii_linebreak[] = {
    0, 0, 0, 0, 0, 0, 0, 0,
/*         0x000A, * LINE FEED */
/*         0x000B, * LINE TABULATION */
/*         0x000C, * FORM FEED */
/*         0x000D, * CARRIAGE RETURN */
    0, 0, 1, 1, 1, 1, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
/*         0x001C, * FILE SEPARATOR */
/*         0x001D, * GROUP SEPARATOR */
/*         0x001E, * RECORD SEPARATOR */
    0, 0, 0, 0, 1, 1, 1, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,

    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0
};


Py_UNICODE
PyUnicode_GetMax(void)
{
#ifdef Py_UNICODE_WIDE
    return 0x10FFFF;
#else
    /* This is actually an illegal character, so it should
       not be passed to unichr. */
    return 0xFFFF;
#endif
}

/* --- Bloom Filters ----------------------------------------------------- */

/* stuff to implement simple "bloom filters" for Unicode characters.
   to keep things simple, we use a single bitmask, using the least 5
   bits from each unicode characters as the bit index. */

/* the linebreak mask is set up by Unicode_Init below */

#if LONG_BIT >= 128
#define BLOOM_WIDTH 128
#elif LONG_BIT >= 64
#define BLOOM_WIDTH 64
#elif LONG_BIT >= 32
#define BLOOM_WIDTH 32
#else
#error "LONG_BIT is smaller than 32"
#endif

#define BLOOM_MASK unsigned long

static BLOOM_MASK bloom_linebreak = ~(BLOOM_MASK)0;

#define BLOOM_ADD(mask, ch) ((mask |= (1UL << ((ch) & (BLOOM_WIDTH - 1)))))
#define BLOOM(mask, ch)     ((mask &  (1UL << ((ch) & (BLOOM_WIDTH - 1)))))

#define BLOOM_LINEBREAK(ch)                                             \
    ((ch) < 128U ? ascii_linebreak[(ch)] :                              \
     (BLOOM(bloom_linebreak, (ch)) && Py_UNICODE_ISLINEBREAK(ch)))

Py_LOCAL_INLINE(BLOOM_MASK) make_bloom_mask(Py_UNICODE* ptr, Py_ssize_t len)
{
    /* calculate simple bloom-style bitmask for a given unicode string */

    BLOOM_MASK mask;
    Py_ssize_t i;

    mask = 0;
    for (i = 0; i < len; i++)
        BLOOM_ADD(mask, ptr[i]);

    return mask;
}

Py_LOCAL_INLINE(int) unicode_member(Py_UNICODE chr, Py_UNICODE* set, Py_ssize_t setlen)
{
    Py_ssize_t i;

    for (i = 0; i < setlen; i++)
        if (set[i] == chr)
            return 1;

    return 0;
}

#define BLOOM_MEMBER(mask, chr, set, setlen)                    \
    BLOOM(mask, chr) && unicode_member(chr, set, setlen)

/* --- Unicode Object ----------------------------------------------------- */

static
int unicode_resize(register PyUnicodeObject *unicode,
                   Py_ssize_t length)
{
    void *oldstr;

    /* Shortcut if there's nothing much to do. */
    if (unicode->length == length)
        goto reset;

    /* Resizing shared object (unicode_empty or single character
       objects) in-place is not allowed. Use PyUnicode_Resize()
       instead ! */

    if (unicode == unicode_empty ||
        (unicode->length == 1 &&
         unicode->str[0] < 256U &&
         unicode_latin1[unicode->str[0]] == unicode)) {
        PyErr_SetString(PyExc_SystemError,
                        "can't resize shared str objects");
        return -1;
    }

    /* We allocate one more byte to make sure the string is Ux0000 terminated.
       The overallocation is also used by fastsearch, which assumes that it's
       safe to look at str[length] (without making any assumptions about what
       it contains). */

    oldstr = unicode->str;
    unicode->str = PyObject_REALLOC(unicode->str,
                                    sizeof(Py_UNICODE) * (length + 1));
    if (!unicode->str) {
        unicode->str = (Py_UNICODE *)oldstr;
        PyErr_NoMemory();
        return -1;
    }
    unicode->str[length] = 0;
    unicode->length = length;

  reset:
    /* Reset the object caches */
    if (unicode->defenc) {
        Py_CLEAR(unicode->defenc);
    }
    unicode->hash = -1;

    return 0;
}

/* We allocate one more byte to make sure the string is
   Ux0000 terminated; some code (e.g. new_identifier)
   relies on that.

   XXX This allocator could further be enhanced by assuring that the
   free list never reduces its size below 1.

*/

static
PyUnicodeObject *_PyUnicode_New(Py_ssize_t length)
{
    register PyUnicodeObject *unicode;

    /* Optimization for empty strings */
    if (length == 0 && unicode_empty != NULL) {
        Py_INCREF(unicode_empty);
        return unicode_empty;
    }

    /* Ensure we won't overflow the size. */
    if (length > ((PY_SSIZE_T_MAX / sizeof(Py_UNICODE)) - 1)) {
        return (PyUnicodeObject *)PyErr_NoMemory();
    }

    /* Unicode freelist & memory allocation */
    if (free_list) {
        unicode = free_list;
        free_list = *(PyUnicodeObject **)unicode;
        numfree--;
        if (unicode->str) {
            /* Keep-Alive optimization: we only upsize the buffer,
               never downsize it. */
            if ((unicode->length < length) &&
                unicode_resize(unicode, length) < 0) {
                PyObject_DEL(unicode->str);
                unicode->str = NULL;
            }
        }
        else {
            size_t new_size = sizeof(Py_UNICODE) * ((size_t)length + 1);
            unicode->str = (Py_UNICODE*) PyObject_MALLOC(new_size);
        }
        PyObject_INIT(unicode, &PyUnicode_Type);
    }
    else {
        size_t new_size;
        unicode = PyObject_New(PyUnicodeObject, &PyUnicode_Type);
        if (unicode == NULL)
            return NULL;
        new_size = sizeof(Py_UNICODE) * ((size_t)length + 1);
        unicode->str = (Py_UNICODE*) PyObject_MALLOC(new_size);
    }

    if (!unicode->str) {
        PyErr_NoMemory();
        goto onError;
    }
    /* Initialize the first element to guard against cases where
     * the caller fails before initializing str -- unicode_resize()
     * reads str[0], and the Keep-Alive optimization can keep memory
     * allocated for str alive across a call to unicode_dealloc(unicode).
     * We don't want unicode_resize to read uninitialized memory in
     * that case.
     */
    unicode->str[0] = 0;
    unicode->str[length] = 0;
    unicode->length = length;
    unicode->hash = -1;
    unicode->state = 0;
    unicode->defenc = NULL;
    return unicode;

  onError:
    /* XXX UNREF/NEWREF interface should be more symmetrical */
    _Py_DEC_REFTOTAL;
    _Py_ForgetReference((PyObject *)unicode);
    PyObject_Del(unicode);
    return NULL;
}

static
void unicode_dealloc(register PyUnicodeObject *unicode)
{
    switch (PyUnicode_CHECK_INTERNED(unicode)) {
    case SSTATE_NOT_INTERNED:
        break;

    case SSTATE_INTERNED_MORTAL:
        /* revive dead object temporarily for DelItem */
        Py_REFCNT(unicode) = 3;
        if (PyDict_DelItem(interned, (PyObject *)unicode) != 0)
            Py_FatalError(
                "deletion of interned string failed");
        break;

    case SSTATE_INTERNED_IMMORTAL:
        Py_FatalError("Immortal interned string died.");

    default:
        Py_FatalError("Inconsistent interned string state.");
    }

    if (PyUnicode_CheckExact(unicode) &&
        numfree < PyUnicode_MAXFREELIST) {
        /* Keep-Alive optimization */
        if (unicode->length >= KEEPALIVE_SIZE_LIMIT) {
            PyObject_DEL(unicode->str);
            unicode->str = NULL;
            unicode->length = 0;
        }
        if (unicode->defenc) {
            Py_CLEAR(unicode->defenc);
        }
        /* Add to free list */
        *(PyUnicodeObject **)unicode = free_list;
        free_list = unicode;
        numfree++;
    }
    else {
        PyObject_DEL(unicode->str);
        Py_XDECREF(unicode->defenc);
        Py_TYPE(unicode)->tp_free((PyObject *)unicode);
    }
}

static
int _PyUnicode_Resize(PyUnicodeObject **unicode, Py_ssize_t length)
{
    register PyUnicodeObject *v;

    /* Argument checks */
    if (unicode == NULL) {
        PyErr_BadInternalCall();
        return -1;
    }
    v = *unicode;
    if (v == NULL || !PyUnicode_Check(v) || Py_REFCNT(v) != 1 || length < 0) {
        PyErr_BadInternalCall();
        return -1;
    }

    /* Resizing unicode_empty and single character objects is not
       possible since these are being shared. We simply return a fresh
       copy with the same Unicode content. */
    if (v->length != length &&
        (v == unicode_empty || v->length == 1)) {
        PyUnicodeObject *w = _PyUnicode_New(length);
        if (w == NULL)
            return -1;
        Py_UNICODE_COPY(w->str, v->str,
                        length < v->length ? length : v->length);
        Py_DECREF(*unicode);
        *unicode = w;
        return 0;
    }

    /* Note that we don't have to modify *unicode for unshared Unicode
       objects, since we can modify them in-place. */
    return unicode_resize(v, length);
}

int PyUnicode_Resize(PyObject **unicode, Py_ssize_t length)
{
    return _PyUnicode_Resize((PyUnicodeObject **)unicode, length);
}

PyObject *PyUnicode_FromUnicode(const Py_UNICODE *u,
                                Py_ssize_t size)
{
    PyUnicodeObject *unicode;

    /* If the Unicode data is known at construction time, we can apply
       some optimizations which share commonly used objects. */
    if (u != NULL) {

        /* Optimization for empty strings */
        if (size == 0)
            _Py_RETURN_UNICODE_EMPTY();

        /* Single character Unicode objects in the Latin-1 range are
           shared when using this constructor */
        if (size == 1 && *u < 256) {
            unicode = unicode_latin1[*u];
            if (!unicode) {
                unicode = _PyUnicode_New(1);
                if (!unicode)
                    return NULL;
                unicode->str[0] = *u;
                unicode_latin1[*u] = unicode;
            }
            Py_INCREF(unicode);
            return (PyObject *)unicode;
        }
    }

    unicode = _PyUnicode_New(size);
    if (!unicode)
        return NULL;

    /* Copy the Unicode data into the new object */
    if (u != NULL)
        Py_UNICODE_COPY(unicode->str, u, size);

    return (PyObject *)unicode;
}

PyObject *PyUnicode_FromStringAndSize(const char *u, Py_ssize_t size)
{
    PyUnicodeObject *unicode;

    if (size < 0) {
        PyErr_SetString(PyExc_SystemError,
                        "Negative size passed to PyUnicode_FromStringAndSize");
        return NULL;
    }

    /* If the Unicode data is known at construction time, we can apply
       some optimizations which share commonly used objects.
       Also, this means the input must be UTF-8, so fall back to the
       UTF-8 decoder at the end. */
    if (u != NULL) {

        /* Optimization for empty strings */
        if (size == 0)
            _Py_RETURN_UNICODE_EMPTY();

        /* Single characters are shared when using this constructor.
           Restrict to ASCII, since the input must be UTF-8. */
        if (size == 1 && Py_CHARMASK(*u) < 128) {
            unicode = unicode_latin1[Py_CHARMASK(*u)];
            if (!unicode) {
                unicode = _PyUnicode_New(1);
                if (!unicode)
                    return NULL;
                unicode->str[0] = Py_CHARMASK(*u);
                unicode_latin1[Py_CHARMASK(*u)] = unicode;
            }
            Py_INCREF(unicode);
            return (PyObject *)unicode;
        }

        return PyUnicode_DecodeUTF8(u, size, NULL);
    }

    unicode = _PyUnicode_New(size);
    if (!unicode)
        return NULL;

    return (PyObject *)unicode;
}

PyObject *PyUnicode_FromString(const char *u)
{
    size_t size = strlen(u);
    if (size > PY_SSIZE_T_MAX) {
        PyErr_SetString(PyExc_OverflowError, "input too long");
        return NULL;
    }

    return PyUnicode_FromStringAndSize(u, size);
}

#ifdef HAVE_WCHAR_H

#if (Py_UNICODE_SIZE == 2) && defined(SIZEOF_WCHAR_T) && (SIZEOF_WCHAR_T == 4)
# define CONVERT_WCHAR_TO_SURROGATES
#endif

#ifdef CONVERT_WCHAR_TO_SURROGATES

/* Here sizeof(wchar_t) is 4 but Py_UNICODE_SIZE == 2, so we need
   to convert from UTF32 to UTF16. */

PyObject *PyUnicode_FromWideChar(register const wchar_t *w,
                                 Py_ssize_t size)
{
    PyUnicodeObject *unicode;
    register Py_ssize_t i;
    Py_ssize_t alloc;
    const wchar_t *orig_w;

    if (w == NULL) {
        if (size == 0)
            return PyUnicode_FromStringAndSize(NULL, 0);
        PyErr_BadInternalCall();
        return NULL;
    }

    if (size == -1) {
        size = wcslen(w);
    }

    alloc = size;
    orig_w = w;
    for (i = size; i > 0; i--) {
        if (*w > 0xFFFF)
            alloc++;
        w++;
    }
    w = orig_w;
    unicode = _PyUnicode_New(alloc);
    if (!unicode)
        return NULL;

    /* Copy the wchar_t data into the new object */
    {
        register Py_UNICODE *u;
        u = PyUnicode_AS_UNICODE(unicode);
        for (i = size; i > 0; i--) {
            if (*w > 0xFFFF) {
                wchar_t ordinal = *w++;
                ordinal -= 0x10000;
                *u++ = 0xD800 | (ordinal >> 10);
                *u++ = 0xDC00 | (ordinal & 0x3FF);
            }
            else
                *u++ = *w++;
        }
    }
    return (PyObject *)unicode;
}

#else

PyObject *PyUnicode_FromWideChar(register const wchar_t *w,
                                 Py_ssize_t size)
{
    PyUnicodeObject *unicode;

    if (w == NULL) {
        if (size == 0)
            return PyUnicode_FromStringAndSize(NULL, 0);
        PyErr_BadInternalCall();
        return NULL;
    }

    if (size == -1) {
        size = wcslen(w);
    }

    unicode = _PyUnicode_New(size);
    if (!unicode)
        return NULL;

    /* Copy the wchar_t data into the new object */
#if Py_UNICODE_SIZE == SIZEOF_WCHAR_T
    memcpy(unicode->str, w, size * sizeof(wchar_t));
#else
    {
        register Py_UNICODE *u;
        register Py_ssize_t i;
        u = PyUnicode_AS_UNICODE(unicode);
        for (i = size; i > 0; i--)
            *u++ = *w++;
    }
#endif

    return (PyObject *)unicode;
}

#endif /* CONVERT_WCHAR_TO_SURROGATES */

#undef CONVERT_WCHAR_TO_SURROGATES

static void
makefmt(char *fmt, int longflag, int longlongflag, int size_tflag,
        int zeropad, int width, int precision, char c)
{
    *fmt++ = '%';
    if (width) {
        if (zeropad)
            *fmt++ = '0';
        fmt += sprintf(fmt, "%d", width);
    }
    if (precision)
        fmt += sprintf(fmt, ".%d", precision);
    if (longflag)
        *fmt++ = 'l';
    else if (longlongflag) {
        /* longlongflag should only ever be nonzero on machines with
           HAVE_LONG_LONG defined */
#ifdef HAVE_LONG_LONG
        char *f = PY_FORMAT_LONG_LONG;
        while (*f)
            *fmt++ = *f++;
#else
        /* we shouldn't ever get here */
        assert(0);
        *fmt++ = 'l';
#endif
    }
    else if (size_tflag) {
        char *f = PY_FORMAT_SIZE_T;
        while (*f)
            *fmt++ = *f++;
    }
    *fmt++ = c;
    *fmt = '\0';
}

#define appendstring(string) {for (copy = string;*copy;) *s++ = *copy++;}

/* size of fixed-size buffer for formatting single arguments */
#define ITEM_BUFFER_LEN 21
/* maximum number of characters required for output of %ld.  21 characters
   allows for 64-bit integers (in decimal) and an optional sign. */
#define MAX_LONG_CHARS 21
/* maximum number of characters required for output of %lld.
   We need at most ceil(log10(256)*SIZEOF_LONG_LONG) digits,
   plus 1 for the sign.  53/22 is an upper bound for log10(256). */
#define MAX_LONG_LONG_CHARS (2 + (SIZEOF_LONG_LONG*53-1) / 22)

PyObject *
PyUnicode_FromFormatV(const char *format, va_list vargs)
{
    va_list count;
    Py_ssize_t callcount = 0;
    PyObject **callresults = NULL;
    PyObject **callresult = NULL;
    Py_ssize_t n = 0;
    int width = 0;
    int precision = 0;
    int zeropad;
    const char* f;
    Py_UNICODE *s;
    PyObject *string;
    /* used by sprintf */
    char buffer[ITEM_BUFFER_LEN+1];
    /* use abuffer instead of buffer, if we need more space
     * (which can happen if there's a format specifier with width). */
    char *abuffer = NULL;
    char *realbuffer;
    Py_ssize_t abuffersize = 0;
    char fmt[61]; /* should be enough for %0width.precisionlld */
    const char *copy;

    Py_VA_COPY(count, vargs);
    /* step 1: count the number of %S/%R/%A/%s format specifications
     * (we call PyObject_Str()/PyObject_Repr()/PyObject_ASCII()/
     * PyUnicode_DecodeUTF8() for these objects once during step 3 and put the
     * result in an array) */
    for (f = format; *f; f++) {
         if (*f == '%') {
             f++;
             while (*f && *f != '%' && !Py_ISALPHA((unsigned)*f))
                 f++;
             if (!*f)
                 break;
             if (*f == 's' || *f=='S' || *f=='R' || *f=='A' || *f=='V')
                 ++callcount;
         }
         else if (128 <= (unsigned char)*f) {
             PyErr_Format(PyExc_ValueError,
                "PyUnicode_FromFormatV() expects an ASCII-encoded format "
                "string, got a non-ASCII byte: 0x%02x",
                (unsigned char)*f);
             return NULL;
         }
    }
    /* step 2: allocate memory for the results of
     * PyObject_Str()/PyObject_Repr()/PyUnicode_DecodeUTF8() calls */
    if (callcount) {
        callresults = PyObject_Malloc(sizeof(PyObject *)*callcount);
        if (!callresults) {
            PyErr_NoMemory();
            return NULL;
        }
        callresult = callresults;
    }
    /* step 3: figure out how large a buffer we need */
    for (f = format; *f; f++) {
        if (*f == '%') {
#ifdef HAVE_LONG_LONG
            int longlongflag = 0;
#endif
            const char* p = f++;
            width = 0;
            while (Py_ISDIGIT((unsigned)*f))
                width = (width*10) + *f++ - '0';
            precision = 0;
            if (*f == '.') {
                f++;
                while (Py_ISDIGIT((unsigned)*f))
                    precision = (precision*10) + *f++ - '0';
            }

            /* skip the 'l' or 'z' in {%ld, %zd, %lu, %zu} since
             * they don't affect the amount of space we reserve.
             */
            if (*f == 'l') {
                if (f[1] == 'd' || f[1] == 'u') {
                    ++f;
                }
#ifdef HAVE_LONG_LONG
                else if (f[1] == 'l' &&
                         (f[2] == 'd' || f[2] == 'u')) {
                    longlongflag = 1;
                    f += 2;
                }
#endif
            }
            else if (*f == 'z' && (f[1] == 'd' || f[1] == 'u')) {
                ++f;
            }

            switch (*f) {
            case 'c':
            {
                int ordinal = va_arg(count, int);
                if (ordinal < 0 || ordinal > 0x10ffff) {
                    PyErr_SetString(PyExc_OverflowError,
                                    "%c arg not in range(0x110000)");
                    goto fail;
                }
#ifndef Py_UNICODE_WIDE
                if (ordinal > 0xffff)
                    n += 2;
                else
#endif
                n++;
                break;
            }
            case '%':
                n++;
                break;
            case 'd': case 'u': case 'i': case 'x':
                (void) va_arg(count, int);
                if (width < precision)
                    width = precision;
#ifdef HAVE_LONG_LONG
                if (longlongflag) {
                    if (width < MAX_LONG_LONG_CHARS)
                        width = MAX_LONG_LONG_CHARS;
                }
                else
#endif
                    /* MAX_LONG_CHARS is enough to hold a 64-bit integer,
                       including sign.  Decimal takes the most space.  This
                       isn't enough for octal.  If a width is specified we
                       need more (which we allocate later). */
                    if (width < MAX_LONG_CHARS)
                        width = MAX_LONG_CHARS;
                n += width;
                /* XXX should allow for large precision here too. */
                if (abuffersize < width)
                    abuffersize = width;
                break;
            case 's':
            {
                /* UTF-8 */
                const char *s = va_arg(count, const char*);
                PyObject *str = PyUnicode_DecodeUTF8(s, strlen(s), "replace");
                if (!str)
                    goto fail;
                n += PyUnicode_GET_SIZE(str);
                /* Remember the str and switch to the next slot */
                *callresult++ = str;
                break;
            }
            case 'U':
            {
                PyObject *obj = va_arg(count, PyObject *);
                assert(obj && PyUnicode_Check(obj));
                n += PyUnicode_GET_SIZE(obj);
                break;
            }
            case 'V':
            {
                PyObject *obj = va_arg(count, PyObject *);
                const char *str = va_arg(count, const char *);
                PyObject *str_obj;
                assert(obj || str);
                assert(!obj || PyUnicode_Check(obj));
                if (obj) {
                    n += PyUnicode_GET_SIZE(obj);
                    *callresult++ = NULL;
                }
                else {
                    str_obj = PyUnicode_DecodeUTF8(str, strlen(str), "replace");
                    if (!str_obj)
                        goto fail;
                    n += PyUnicode_GET_SIZE(str_obj);
                    *callresult++ = str_obj;
                }
                break;
            }
            case 'S':
            {
                PyObject *obj = va_arg(count, PyObject *);
                PyObject *str;
                assert(obj);
                str = PyObject_Str(obj);
                if (!str)
                    goto fail;
                n += PyUnicode_GET_SIZE(str);
                /* Remember the str and switch to the next slot */
                *callresult++ = str;
                break;
            }
            case 'R':
            {
                PyObject *obj = va_arg(count, PyObject *);
                PyObject *repr;
                assert(obj);
                repr = PyObject_Repr(obj);
                if (!repr)
                    goto fail;
                n += PyUnicode_GET_SIZE(repr);
                /* Remember the repr and switch to the next slot */
                *callresult++ = repr;
                break;
            }
            case 'A':
            {
                PyObject *obj = va_arg(count, PyObject *);
                PyObject *ascii;
                assert(obj);
                ascii = PyObject_ASCII(obj);
                if (!ascii)
                    goto fail;
                n += PyUnicode_GET_SIZE(ascii);
                /* Remember the repr and switch to the next slot */
                *callresult++ = ascii;
                break;
            }
            case 'p':
                (void) va_arg(count, int);
                /* maximum 64-bit pointer representation:
                 * 0xffffffffffffffff
                 * so 19 characters is enough.
                 * XXX I count 18 -- what's the extra for?
                 */
                n += 19;
                break;
            default:
                /* if we stumble upon an unknown
                   formatting code, copy the rest of
                   the format string to the output
                   string. (we cannot just skip the
                   code, since there's no way to know
                   what's in the argument list) */
                n += strlen(p);
                goto expand;
            }
        } else
            n++;
    }
  expand:
    if (abuffersize > ITEM_BUFFER_LEN) {
        /* add 1 for sprintf's trailing null byte */
        abuffer = PyObject_Malloc(abuffersize + 1);
        if (!abuffer) {
            PyErr_NoMemory();
            goto fail;
        }
        realbuffer = abuffer;
    }
    else
        realbuffer = buffer;
    /* step 4: fill the buffer */
    /* Since we've analyzed how much space we need for the worst case,
       we don't have to resize the string.
       There can be no errors beyond this point. */
    string = PyUnicode_FromUnicode(NULL, n);
    if (!string)
        goto fail;

    s = PyUnicode_AS_UNICODE(string);
    callresult = callresults;

    for (f = format; *f; f++) {
        if (*f == '%') {
            const char* p = f++;
            int longflag = 0;
            int longlongflag = 0;
            int size_tflag = 0;
            zeropad = (*f == '0');
            /* parse the width.precision part */
            width = 0;
            while (Py_ISDIGIT((unsigned)*f))
                width = (width*10) + *f++ - '0';
            precision = 0;