_struct.c

/* struct module -- pack values into and (out of) bytes objects */

/* New version supporting byte order, alignment and size options,
   character strings, and unsigned numbers */

#define PY_SSIZE_T_CLEAN

#include "Python.h"
#include "structmember.h"
#include <ctype.h>

static PyTypeObject PyStructType;

/* The translation function for each format character is table driven */
typedef struct _formatdef {
    char format;
    Py_ssize_t size;
    Py_ssize_t alignment;
    PyObject* (*unpack)(const char *,
                        const struct _formatdef *);
    int (*pack)(char *, PyObject *,
                const struct _formatdef *);
} formatdef;

typedef struct _formatcode {
    const struct _formatdef *fmtdef;
    Py_ssize_t offset;
    Py_ssize_t size;
} formatcode;

/* Struct object interface */

typedef struct {
    PyObject_HEAD
    Py_ssize_t s_size;
    Py_ssize_t s_len;
    formatcode *s_codes;
    PyObject *s_format;
    PyObject *weakreflist; /* List of weak references */
} PyStructObject;


#define PyStruct_Check(op) PyObject_TypeCheck(op, &PyStructType)
#define PyStruct_CheckExact(op) (Py_TYPE(op) == &PyStructType)


/* Exception */

static PyObject *StructError;


/* Define various structs to figure out the alignments of types */


typedef struct { char c; short x; } st_short;
typedef struct { char c; int x; } st_int;
typedef struct { char c; long x; } st_long;
typedef struct { char c; float x; } st_float;
typedef struct { char c; double x; } st_double;
typedef struct { char c; void *x; } st_void_p;
typedef struct { char c; size_t x; } st_size_t;

#define SHORT_ALIGN (sizeof(st_short) - sizeof(short))
#define INT_ALIGN (sizeof(st_int) - sizeof(int))
#define LONG_ALIGN (sizeof(st_long) - sizeof(long))
#define FLOAT_ALIGN (sizeof(st_float) - sizeof(float))
#define DOUBLE_ALIGN (sizeof(st_double) - sizeof(double))
#define VOID_P_ALIGN (sizeof(st_void_p) - sizeof(void *))
#define SIZE_T_ALIGN (sizeof(st_size_t) - sizeof(size_t))

/* We can't support q and Q in native mode unless the compiler does;
   in std mode, they're 8 bytes on all platforms. */
#ifdef HAVE_LONG_LONG
typedef struct { char c; PY_LONG_LONG x; } s_long_long;
#define LONG_LONG_ALIGN (sizeof(s_long_long) - sizeof(PY_LONG_LONG))
#endif

#ifdef HAVE_C99_BOOL
#define BOOL_TYPE _Bool
typedef struct { char c; _Bool x; } s_bool;
#define BOOL_ALIGN (sizeof(s_bool) - sizeof(BOOL_TYPE))
#else
#define BOOL_TYPE char
#define BOOL_ALIGN 0
#endif

#define STRINGIFY(x)    #x

#ifdef __powerc
#pragma options align=reset
#endif

/* Helper for integer format codes: converts an arbitrary Python object to a
   PyLongObject if possible, otherwise fails.  Caller should decref. */

static PyObject *
get_pylong(PyObject *v)
{
    assert(v != NULL);
    if (!PyLong_Check(v)) {
        /* Not an integer;  try to use __index__ to convert. */
        if (PyIndex_Check(v)) {
            v = PyNumber_Index(v);
            if (v == NULL)
                return NULL;
        }
        else {
            PyErr_SetString(StructError,
                            "required argument is not an integer");
            return NULL;
        }
    }
    else
        Py_INCREF(v);

    assert(PyLong_Check(v));
    return v;
}

/* Helper routine to get a C long and raise the appropriate error if it isn't
   one */

static int
get_long(PyObject *v, long *p)
{
    long x;

    v = get_pylong(v);
    if (v == NULL)
        return -1;
    assert(PyLong_Check(v));
    x = PyLong_AsLong(v);
    Py_DECREF(v);
    if (x == (long)-1 && PyErr_Occurred()) {
        if (PyErr_ExceptionMatches(PyExc_OverflowError))
            PyErr_SetString(StructError,
                            "argument out of range");
        return -1;
    }
    *p = x;
    return 0;
}


/* Same, but handling unsigned long */

static int
get_ulong(PyObject *v, unsigned long *p)
{
    unsigned long x;

    v = get_pylong(v);
    if (v == NULL)
        return -1;
    assert(PyLong_Check(v));
    x = PyLong_AsUnsignedLong(v);
    Py_DECREF(v);
    if (x == (unsigned long)-1 && PyErr_Occurred()) {
        if (PyErr_ExceptionMatches(PyExc_OverflowError))
            PyErr_SetString(StructError,
                            "argument out of range");
        return -1;
    }
    *p = x;
    return 0;
}

#ifdef HAVE_LONG_LONG

/* Same, but handling native long long. */

static int
get_longlong(PyObject *v, PY_LONG_LONG *p)
{
    PY_LONG_LONG x;

    v = get_pylong(v);
    if (v == NULL)
        return -1;
    assert(PyLong_Check(v));
    x = PyLong_AsLongLong(v);
    Py_DECREF(v);
    if (x == (PY_LONG_LONG)-1 && PyErr_Occurred()) {
        if (PyErr_ExceptionMatches(PyExc_OverflowError))
            PyErr_SetString(StructError,
                            "argument out of range");
        return -1;
    }
    *p = x;
    return 0;
}

/* Same, but handling native unsigned long long. */

static int
get_ulonglong(PyObject *v, unsigned PY_LONG_LONG *p)
{
    unsigned PY_LONG_LONG x;

    v = get_pylong(v);
    if (v == NULL)
        return -1;
    assert(PyLong_Check(v));
    x = PyLong_AsUnsignedLongLong(v);
    Py_DECREF(v);
    if (x == (unsigned PY_LONG_LONG)-1 && PyErr_Occurred()) {
        if (PyErr_ExceptionMatches(PyExc_OverflowError))
            PyErr_SetString(StructError,
                            "argument out of range");
        return -1;
    }
    *p = x;
    return 0;
}

#endif

/* Same, but handling Py_ssize_t */

static int
get_ssize_t(PyObject *v, Py_ssize_t *p)
{
    Py_ssize_t x;

    v = get_pylong(v);
    if (v == NULL)
        return -1;
    assert(PyLong_Check(v));
    x = PyLong_AsSsize_t(v);
    Py_DECREF(v);
    if (x == (Py_ssize_t)-1 && PyErr_Occurred()) {
        if (PyErr_ExceptionMatches(PyExc_OverflowError))
            PyErr_SetString(StructError,
                            "argument out of range");
        return -1;
    }
    *p = x;
    return 0;
}

/* Same, but handling size_t */

static int
get_size_t(PyObject *v, size_t *p)
{
    size_t x;

    v = get_pylong(v);
    if (v == NULL)
        return -1;
    assert(PyLong_Check(v));
    x = PyLong_AsSize_t(v);
    Py_DECREF(v);
    if (x == (size_t)-1 && PyErr_Occurred()) {
        if (PyErr_ExceptionMatches(PyExc_OverflowError))
            PyErr_SetString(StructError,
                            "argument out of range");
        return -1;
    }
    *p = x;
    return 0;
}


#define RANGE_ERROR(x, f, flag, mask) return _range_error(f, flag)


/* Floating point helpers */

static PyObject *
unpack_float(const char *p,  /* start of 4-byte string */
         int le)             /* true for little-endian, false for big-endian */
{
    double x;

    x = _PyFloat_Unpack4((unsigned char *)p, le);
    if (x == -1.0 && PyErr_Occurred())
        return NULL;
    return PyFloat_FromDouble(x);
}

static PyObject *
unpack_double(const char *p,  /* start of 8-byte string */
          int le)         /* true for little-endian, false for big-endian */
{
    double x;

    x = _PyFloat_Unpack8((unsigned char *)p, le);
    if (x == -1.0 && PyErr_Occurred())
        return NULL;
    return PyFloat_FromDouble(x);
}

/* Helper to format the range error exceptions */
static int
_range_error(const formatdef *f, int is_unsigned)
{
    /* ulargest is the largest unsigned value with f->size bytes.
     * Note that the simpler:
     *     ((size_t)1 << (f->size * 8)) - 1
     * doesn't work when f->size == sizeof(size_t) because C doesn't
     * define what happens when a left shift count is >= the number of
     * bits in the integer being shifted; e.g., on some boxes it doesn't
     * shift at all when they're equal.
     */
    const size_t ulargest = (size_t)-1 >> ((SIZEOF_SIZE_T - f->size)*8);
    assert(f->size >= 1 && f->size <= SIZEOF_SIZE_T);
    if (is_unsigned)
        PyErr_Format(StructError,
            "'%c' format requires 0 <= number <= %zu",
            f->format,
            ulargest);
    else {
        const Py_ssize_t largest = (Py_ssize_t)(ulargest >> 1);
        PyErr_Format(StructError,
            "'%c' format requires %zd <= number <= %zd",
            f->format,
            ~ largest,
            largest);
    }

    return -1;
}



/* A large number of small routines follow, with names of the form

   [bln][up]_TYPE

   [bln] distiguishes among big-endian, little-endian and native.
   [pu] distiguishes between pack (to struct) and unpack (from struct).
   TYPE is one of char, byte, ubyte, etc.
*/

/* Native mode routines. ****************************************************/
/* NOTE:
   In all n[up]_<type> routines handling types larger than 1 byte, there is
   *no* guarantee that the p pointer is properly aligned for each type,
   therefore memcpy is called.  An intermediate variable is used to
   compensate for big-endian architectures.
   Normally both the intermediate variable and the memcpy call will be
   skipped by C optimisation in little-endian architectures (gcc >= 2.91
   does this). */

static PyObject *
nu_char(const char *p, const formatdef *f)
{
    return PyBytes_FromStringAndSize(p, 1);
}

static PyObject *
nu_byte(const char *p, const formatdef *f)
{
    return PyLong_FromLong((long) *(signed char *)p);
}

static PyObject *
nu_ubyte(const char *p, const formatdef *f)
{
    return PyLong_FromLong((long) *(unsigned char *)p);
}

static PyObject *
nu_short(const char *p, const formatdef *f)
{
    short x;
    memcpy((char *)&x, p, sizeof x);
    return PyLong_FromLong((long)x);
}

static PyObject *
nu_ushort(const char *p, const formatdef *f)
{
    unsigned short x;
    memcpy((char *)&x, p, sizeof x);
    return PyLong_FromLong((long)x);
}

static PyObject *
nu_int(const char *p, const formatdef *f)
{
    int x;
    memcpy((char *)&x, p, sizeof x);
    return PyLong_FromLong((long)x);
}

static PyObject *
nu_uint(const char *p, const formatdef *f)
{
    unsigned int x;
    memcpy((char *)&x, p, sizeof x);
#if (SIZEOF_LONG > SIZEOF_INT)
    return PyLong_FromLong((long)x);
#else
    if (x <= ((unsigned int)LONG_MAX))
        return PyLong_FromLong((long)x);
    return PyLong_FromUnsignedLong((unsigned long)x);
#endif
}

static PyObject *
nu_long(const char *p, const formatdef *f)
{
    long x;
    memcpy((char *)&x, p, sizeof x);
    return PyLong_FromLong(x);
}

static PyObject *
nu_ulong(const char *p, const formatdef *f)
{
    unsigned long x;
    memcpy((char *)&x, p, sizeof x);
    if (x <= LONG_MAX)
        return PyLong_FromLong((long)x);
    return PyLong_FromUnsignedLong(x);
}

static PyObject *
nu_ssize_t(const char *p, const formatdef *f)
{
    Py_ssize_t x;
    memcpy((char *)&x, p, sizeof x);
    return PyLong_FromSsize_t(x);
}

static PyObject *
nu_size_t(const char *p, const formatdef *f)
{
    size_t x;
    memcpy((char *)&x, p, sizeof x);
    return PyLong_FromSize_t(x);
}


/* Native mode doesn't support q or Q unless the platform C supports
   long long (or, on Windows, __int64). */

#ifdef HAVE_LONG_LONG

static PyObject *
nu_longlong(const char *p, const formatdef *f)
{
    PY_LONG_LONG x;
    memcpy((char *)&x, p, sizeof x);
    if (x >= LONG_MIN && x <= LONG_MAX)
        return PyLong_FromLong(Py_SAFE_DOWNCAST(x, PY_LONG_LONG, long));
    return PyLong_FromLongLong(x);
}

static PyObject *
nu_ulonglong(const char *p, const formatdef *f)
{
    unsigned PY_LONG_LONG x;
    memcpy((char *)&x, p, sizeof x);
    if (x <= LONG_MAX)
        return PyLong_FromLong(Py_SAFE_DOWNCAST(x, unsigned PY_LONG_LONG, long));
    return PyLong_FromUnsignedLongLong(x);
}

#endif

static PyObject *
nu_bool(const char *p, const formatdef *f)
{
    BOOL_TYPE x;
    memcpy((char *)&x, p, sizeof x);
    return PyBool_FromLong(x != 0);
}


static PyObject *
nu_float(const char *p, const formatdef *f)
{
    float x;
    memcpy((char *)&x, p, sizeof x);
    return PyFloat_FromDouble((double)x);
}

static PyObject *
nu_double(const char *p, const formatdef *f)
{
    double x;
    memcpy((char *)&x, p, sizeof x);
    return PyFloat_FromDouble(x);
}

static PyObject *
nu_void_p(const char *p, const formatdef *f)
{
    void *x;
    memcpy((char *)&x, p, sizeof x);
    return PyLong_FromVoidPtr(x);
}

static int
np_byte(char *p, PyObject *v, const formatdef *f)
{
    long x;
    if (get_long(v, &x) < 0)
        return -1;
    if (x < -128 || x > 127){
        PyErr_SetString(StructError,
                        "byte format requires -128 <= number <= 127");
        return -1;
    }
    *p = (char)x;
    return 0;
}

static int
np_ubyte(char *p, PyObject *v, const formatdef *f)
{
    long x;
    if (get_long(v, &x) < 0)
        return -1;
    if (x < 0 || x > 255){
        PyErr_SetString(StructError,
                        "ubyte format requires 0 <= number <= 255");
        return -1;
    }
    *p = (char)x;
    return 0;
}

static int
np_char(char *p, PyObject *v, const formatdef *f)
{
    if (!PyBytes_Check(v) || PyBytes_Size(v) != 1) {
        PyErr_SetString(StructError,
                        "char format requires a bytes object of length 1");
        return -1;
    }
    *p = *PyBytes_AsString(v);
    return 0;
}

static int
np_short(char *p, PyObject *v, const formatdef *f)
{
    long x;
    short y;
    if (get_long(v, &x) < 0)
        return -1;
    if (x < SHRT_MIN || x > SHRT_MAX){
        PyErr_SetString(StructError,
                        "short format requires " STRINGIFY(SHRT_MIN)
                        " <= number <= " STRINGIFY(SHRT_MAX));
        return -1;
    }
    y = (short)x;
    memcpy(p, (char *)&y, sizeof y);
    return 0;
}

static int
np_ushort(char *p, PyObject *v, const formatdef *f)
{
    long x;
    unsigned short y;
    if (get_long(v, &x) < 0)
        return -1;
    if (x < 0 || x > USHRT_MAX){
        PyErr_SetString(StructError,
                        "ushort format requires 0 <= number <= " STRINGIFY(USHRT_MAX));
        return -1;
    }
    y = (unsigned short)x;
    memcpy(p, (char *)&y, sizeof y);
    return 0;
}

static int
np_int(char *p, PyObject *v, const formatdef *f)
{
    long x;
    int y;
    if (get_long(v, &x) < 0)
        return -1;
#if (SIZEOF_LONG > SIZEOF_INT)
    if ((x < ((long)INT_MIN)) || (x > ((long)INT_MAX)))
        RANGE_ERROR(x, f, 0, -1);
#endif
    y = (int)x;
    memcpy(p, (char *)&y, sizeof y);
    return 0;
}

static int
np_uint(char *p, PyObject *v, const formatdef *f)
{
    unsigned long x;
    unsigned int y;
    if (get_ulong(v, &x) < 0)
        return -1;
    y = (unsigned int)x;
#if (SIZEOF_LONG > SIZEOF_INT)
    if (x > ((unsigned long)UINT_MAX))
        RANGE_ERROR(y, f, 1, -1);
#endif
    memcpy(p, (char *)&y, sizeof y);
    return 0;
}

static int
np_long(char *p, PyObject *v, const formatdef *f)
{
    long x;
    if (get_long(v, &x) < 0)
        return -1;
    memcpy(p, (char *)&x, sizeof x);
    return 0;
}

static int
np_ulong(char *p, PyObject *v, const formatdef *f)
{
    unsigned long x;
    if (get_ulong(v, &x) < 0)
        return -1;
    memcpy(p, (char *)&x, sizeof x);
    return 0;
}

static int
np_ssize_t(char *p, PyObject *v, const formatdef *f)
{
    Py_ssize_t x;
    if (get_ssize_t(v, &x) < 0)
        return -1;
    memcpy(p, (char *)&x, sizeof x);
    return 0;
}

static int
np_size_t(char *p, PyObject *v, const formatdef *f)
{
    size_t x;
    if (get_size_t(v, &x) < 0)
        return -1;
    memcpy(p, (char *)&x, sizeof x);
    return 0;
}

#ifdef HAVE_LONG_LONG

static int
np_longlong(char *p, PyObject *v, const formatdef *f)
{
    PY_LONG_LONG x;
    if (get_longlong(v, &x) < 0)
        return -1;
    memcpy(p, (char *)&x, sizeof x);
    return 0;
}

static int
np_ulonglong(char *p, PyObject *v, const formatdef *f)
{
    unsigned PY_LONG_LONG x;
    if (get_ulonglong(v, &x) < 0)
        return -1;
    memcpy(p, (char *)&x, sizeof x);
    return 0;
}
#endif


static int
np_bool(char *p, PyObject *v, const formatdef *f)
{
    int y;
    BOOL_TYPE x;
    y = PyObject_IsTrue(v);
    if (y < 0)
        return -1;
    x = y;
    memcpy(p, (char *)&x, sizeof x);
    return 0;
}

static int
np_float(char *p, PyObject *v, const formatdef *f)
{
    float x = (float)PyFloat_AsDouble(v);
    if (x == -1 && PyErr_Occurred()) {
        PyErr_SetString(StructError,
                        "required argument is not a float");
        return -1;
    }
    memcpy(p, (char *)&x, sizeof x);
    return 0;
}

static int
np_double(char *p, PyObject *v, const formatdef *f)
{
    double x = PyFloat_AsDouble(v);
    if (x == -1 && PyErr_Occurred()) {
        PyErr_SetString(StructError,
                        "required argument is not a float");
        return -1;
    }
    memcpy(p, (char *)&x, sizeof(double));
    return 0;
}

static int
np_void_p(char *p, PyObject *v, const formatdef *f)
{
    void *x;

    v = get_pylong(v);
    if (v == NULL)
        return -1;
    assert(PyLong_Check(v));
    x = PyLong_AsVoidPtr(v);
    Py_DECREF(v);
    if (x == NULL && PyErr_Occurred())
        return -1;
    memcpy(p, (char *)&x, sizeof x);
    return 0;
}

static formatdef native_table[] = {
    {'x',       sizeof(char),   0,              NULL},
    {'b',       sizeof(char),   0,              nu_byte,        np_byte},
    {'B',       sizeof(char),   0,              nu_ubyte,       np_ubyte},
    {'c',       sizeof(char),   0,              nu_char,        np_char},
    {'s',       sizeof(char),   0,              NULL},
    {'p',       sizeof(char),   0,              NULL},
    {'h',       sizeof(short),  SHORT_ALIGN,    nu_short,       np_short},
    {'H',       sizeof(short),  SHORT_ALIGN,    nu_ushort,      np_ushort},
    {'i',       sizeof(int),    INT_ALIGN,      nu_int,         np_int},
    {'I',       sizeof(int),    INT_ALIGN,      nu_uint,        np_uint},
    {'l',       sizeof(long),   LONG_ALIGN,     nu_long,        np_long},
    {'L',       sizeof(long),   LONG_ALIGN,     nu_ulong,       np_ulong},
    {'n',       sizeof(size_t), SIZE_T_ALIGN,   nu_ssize_t,     np_ssize_t},
    {'N',       sizeof(size_t), SIZE_T_ALIGN,   nu_size_t,      np_size_t},
#ifdef HAVE_LONG_LONG
    {'q',       sizeof(PY_LONG_LONG), LONG_LONG_ALIGN, nu_longlong, np_longlong},
    {'Q',       sizeof(PY_LONG_LONG), LONG_LONG_ALIGN, nu_ulonglong,np_ulonglong},
#endif
    {'?',       sizeof(BOOL_TYPE),      BOOL_ALIGN,     nu_bool,        np_bool},
    {'f',       sizeof(float),  FLOAT_ALIGN,    nu_float,       np_float},
    {'d',       sizeof(double), DOUBLE_ALIGN,   nu_double,      np_double},
    {'P',       sizeof(void *), VOID_P_ALIGN,   nu_void_p,      np_void_p},
    {0}
};

/* Big-endian routines. *****************************************************/

static PyObject *
bu_int(const char *p, const formatdef *f)
{
    long x = 0;
    Py_ssize_t i = f->size;
    const unsigned char *bytes = (const unsigned char *)p;
    do {
        x = (x<<8) | *bytes++;
    } while (--i > 0);
    /* Extend the sign bit. */
    if (SIZEOF_LONG > f->size)
        x |= -(x & (1L << ((8 * f->size) - 1)));
    return PyLong_FromLong(x);
}

static PyObject *
bu_uint(const char *p, const formatdef *f)
{
    unsigned long x = 0;
    Py_ssize_t i = f->size;
    const unsigned char *bytes = (const unsigned char *)p;
    do {
        x = (x<<8) | *bytes++;
    } while (--i > 0);
    if (x <= LONG_MAX)
        return PyLong_FromLong((long)x);
    return PyLong_FromUnsignedLong(x);
}

static PyObject *
bu_longlong(const char *p, const formatdef *f)
{
#ifdef HAVE_LONG_LONG
    PY_LONG_LONG x = 0;
    Py_ssize_t i = f->size;
    const unsigned char *bytes = (const unsigned char *)p;
    do {
        x = (x<<8) | *bytes++;
    } while (--i > 0);
    /* Extend the sign bit. */
    if (SIZEOF_LONG_LONG > f->size)
        x |= -(x & ((PY_LONG_LONG)1 << ((8 * f->size) - 1)));
    if (x >= LONG_MIN && x <= LONG_MAX)
        return PyLong_FromLong(Py_SAFE_DOWNCAST(x, PY_LONG_LONG, long));
    return PyLong_FromLongLong(x);
#else
    return _PyLong_FromByteArray((const unsigned char *)p,
                                  8,
                                  0, /* little-endian */
                      1  /* signed */);
#endif
}

static PyObject *
bu_ulonglong(const char *p, const formatdef *f)
{
#ifdef HAVE_LONG_LONG
    unsigned PY_LONG_LONG x = 0;
    Py_ssize_t i = f->size;
    const unsigned char *bytes = (const unsigned char *)p;
    do {
        x = (x<<8) | *bytes++;
    } while (--i > 0);
    if (x <= LONG_MAX)
        return PyLong_FromLong(Py_SAFE_DOWNCAST(x, unsigned PY_LONG_LONG, long));
    return PyLong_FromUnsignedLongLong(x);
#else
    return _PyLong_FromByteArray((const unsigned char *)p,
                                  8,
                                  0, /* little-endian */
                      0  /* signed */);
#endif
}

static PyObject *
bu_float(const char *p, const formatdef *f)
{
    return unpack_float(p, 0);
}

static PyObject *
bu_double(const char *p, const formatdef *f)
{
    return unpack_double(p, 0);
}

static PyObject *
bu_bool(const char *p, const formatdef *f)
{
    char x;
    memcpy((char *)&x, p, sizeof x);
    return PyBool_FromLong(x != 0);
}

static int
bp_int(char *p, PyObject *v, const formatdef *f)
{
    long x;
    Py_ssize_t i;
    if (get_long(v, &x) < 0)
        return -1;
    i = f->size;
    if (i != SIZEOF_LONG) {
        if ((i == 2) && (x < -32768 || x > 32767))
            RANGE_ERROR(x, f, 0, 0xffffL);
#if (SIZEOF_LONG != 4)
        else if ((i == 4) && (x < -2147483648L || x > 2147483647L))
            RANGE_ERROR(x, f, 0, 0xffffffffL);
#endif
    }
    do {
        p[--i] = (char)x;
        x >>= 8;
    } while (i > 0);
    return 0;
}

static int
bp_uint(char *p, PyObject *v, const formatdef *f)
{
    unsigned long x;
    Py_ssize_t i;
    if (get_ulong(v, &x) < 0)
        return -1;
    i = f->size;
    if (i != SIZEOF_LONG) {
        unsigned long maxint = 1;
        maxint <<= (unsigned long)(i * 8);
        if (x >= maxint)
            RANGE_ERROR(x, f, 1, maxint - 1);
    }
    do {
        p[--i] = (char)x;
        x >>= 8;
    } while (i > 0);
    return 0;
}

static int
bp_longlong(char *p, PyObject *v, const formatdef *f)
{
    int res;
    v = get_pylong(v);
    if (v == NULL)
        return -1;
    res = _PyLong_AsByteArray((PyLongObject *)v,
                              (unsigned char *)p,
                              8,
                              0, /* little_endian */
                  1  /* signed */);
    Py_DECREF(v);
    return res;
}

static int
bp_ulonglong(char *p, PyObject *v, const formatdef *f)
{
    int res;
    v = get_pylong(v);
    if (v == NULL)
        return -1;
    res = _PyLong_AsByteArray((PyLongObject *)v,
                              (unsigned char *)p,
                              8,
                              0, /* little_endian */
                  0  /* signed */);
    Py_DECREF(v);
    return res;
}

static int
bp_float(char *p, PyObject *v, const formatdef *f)
{
    double x = PyFloat_AsDouble(v);
    if (x == -1 && PyErr_Occurred()) {
        PyErr_SetString(StructError,
                        "required argument is not a float");
        return -1;
    }
    return _PyFloat_Pack4(x, (unsigned char *)p, 0);
}

static int
bp_double(char *p, PyObject *v, const formatdef *f)
{
    double x = PyFloat_AsDouble(v);
    if (x == -1 && PyErr_Occurred()) {
        PyErr_SetString(StructError,
                        "required argument is not a float");
        return -1;
    }
    return _PyFloat_Pack8(x, (unsigned char *)p, 0);
}

static int
bp_bool(char *p, PyObject *v, const formatdef *f)
{
    int y;
    y = PyObject_IsTrue(v);
    if (y < 0)
        return -1;
    *p = (char)y;
    return 0;
}

static formatdef bigendian_table[] = {
    {'x',       1,              0,              NULL},
    {'b',       1,              0,              nu_byte,        np_byte},
    {'B',       1,              0,              nu_ubyte,       np_ubyte},
    {'c',       1,              0,              nu_char,        np_char},
    {'s',       1,              0,              NULL},
    {'p',       1,              0,              NULL},
    {'h',       2,              0,              bu_int,         bp_int},
    {'H',       2,              0,              bu_uint,        bp_uint},
    {'i',       4,              0,              bu_int,         bp_int},
    {'I',       4,              0,              bu_uint,        bp_uint},
    {'l',       4,              0,              bu_int,         bp_int},
    {'L',       4,              0,              bu_uint,        bp_uint},
    {'q',       8,              0,              bu_longlong,    bp_longlong},
    {'Q',       8,              0,              bu_ulonglong,   bp_ulonglong},
    {'?',       1,              0,              bu_bool,        bp_bool},
    {'f',       4,              0,              bu_float,       bp_float},
    {'d',       8,              0,              bu_double,      bp_double},
    {0}
};

/* Little-endian routines. *****************************************************/

static PyObject *
lu_int(const char *p, const formatdef *f)
{
    long x = 0;
    Py_ssize_t i = f->size;
    const unsigned char *bytes = (const unsigned char *)p;
    do {
        x = (x<<8) | bytes[--i];
    } while (i > 0);
    /* Extend the sign bit. */
    if (SIZEOF_LONG > f->size)
        x |= -(x & (1L << ((8 * f->size) - 1)));
    return PyLong_FromLong(x);
}

static PyObject *
lu_uint(const char *p, const formatdef *f)
{
    unsigned long x = 0;