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cpython/Modules/structmodule.c

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/* struct module -- pack values into and (out of) strings */
/* New version supporting byte order, alignment and size options,
character strings, and unsigned numbers */
static char struct__doc__[] = "\
Functions to convert between Python values and C structs.\n\
Python strings are used to hold the data representing the C struct\n\
and also as format strings to describe the layout of data in the C struct.\n\
\n\
The optional first format char indicates byte ordering and alignment:\n\
@: native w/native alignment(default)\n\
=: native w/standard alignment\n\
<: little-endian, std. alignment\n\
>: big-endian, std. alignment\n\
!: network, std (same as >)\n\
\n\
The remaining chars indicate types of args and must match exactly;\n\
these can be preceded by a decimal repeat count:\n\
x: pad byte (no data); c:char; b:signed byte; B:unsigned byte;\n\
h:short; H:unsigned short; i:int; I:unsigned int;\n\
l:long; L:unsigned long; f:float; d:double.\n\
Special cases (preceding decimal count indicates length):\n\
s:string (array of char); p: pascal string (w. count byte).\n\
Special case (only available in native format):\n\
P:an integer type that is wide enough to hold a pointer.\n\
Whitespace between formats is ignored.\n\
\n\
The variable struct.error is an exception raised on errors.";
#include "Python.h"
#include <limits.h>
#include <ctype.h>
/* Exception */
static PyObject *StructError;
/* Define various structs to figure out the alignments of types */
#ifdef __MWERKS__
/*
** XXXX We have a problem here. There are no unique alignment rules
** on the PowerPC mac.
*/
#ifdef __powerc
#pragma options align=mac68k
#endif
#endif /* __MWERKS__ */
typedef struct { char c; short x; } s_short;
typedef struct { char c; int x; } s_int;
typedef struct { char c; long x; } s_long;
typedef struct { char c; float x; } s_float;
typedef struct { char c; double x; } s_double;
typedef struct { char c; void *x; } s_void_p;
#define SHORT_ALIGN (sizeof(s_short) - sizeof(short))
#define INT_ALIGN (sizeof(s_int) - sizeof(int))
#define LONG_ALIGN (sizeof(s_long) - sizeof(long))
#define FLOAT_ALIGN (sizeof(s_float) - sizeof(float))
#define DOUBLE_ALIGN (sizeof(s_double) - sizeof(double))
#define VOID_P_ALIGN (sizeof(s_void_p) - sizeof(void *))
#define STRINGIFY(x) #x
#ifdef __powerc
#pragma options align=reset
#endif
/* Helper routine to get a Python integer and raise the appropriate error
if it isn't one */
static int
get_long(PyObject *v, long *p)
{
long x = PyInt_AsLong(v);
if (x == -1 && PyErr_Occurred()) {
if (PyErr_ExceptionMatches(PyExc_TypeError))
PyErr_SetString(StructError,
"required argument is not an integer");
return -1;
}
*p = x;
return 0;
}
/* Same, but handling unsigned long */
static int
get_ulong(PyObject *v, unsigned long *p)
{
if (PyLong_Check(v)) {
unsigned long x = PyLong_AsUnsignedLong(v);
if (x == (unsigned long)(-1) && PyErr_Occurred())
return -1;
*p = x;
return 0;
}
else {
return get_long(v, (long *)p);
}
}
/* Floating point helpers */
/* These use ANSI/IEEE Standard 754-1985 (Standard for Binary Floating
Point Arithmetic). See the following URL:
http://www.psc.edu/general/software/packages/ieee/ieee.html */
/* XXX Inf/NaN are not handled quite right (but underflow is!) */
static int
pack_float(double x, /* The number to pack */
char *p, /* Where to pack the high order byte */
int incr) /* 1 for big-endian; -1 for little-endian */
{
int s;
int e;
double f;
long fbits;
if (x < 0) {
s = 1;
x = -x;
}
else
s = 0;
f = frexp(x, &e);
/* Normalize f to be in the range [1.0, 2.0) */
if (0.5 <= f && f < 1.0) {
f *= 2.0;
e--;
}
else if (f == 0.0) {
e = 0;
}
else {
PyErr_SetString(PyExc_SystemError,
"frexp() result out of range");
return -1;
}
if (e >= 128) {
/* XXX 128 itself is reserved for Inf/NaN */
PyErr_SetString(PyExc_OverflowError,
"float too large to pack with f format");
return -1;
}
else if (e < -126) {
/* Gradual underflow */
f = ldexp(f, 126 + e);
e = 0;
}
else if (!(e == 0 && f == 0.0)) {
e += 127;
f -= 1.0; /* Get rid of leading 1 */
}
f *= 8388608.0; /* 2**23 */
fbits = (long) floor(f + 0.5); /* Round */
/* First byte */
*p = (s<<7) | (e>>1);
p += incr;
/* Second byte */
*p = (char) (((e&1)<<7) | (fbits>>16));
p += incr;
/* Third byte */
*p = (fbits>>8) & 0xFF;
p += incr;
/* Fourth byte */
*p = fbits&0xFF;
/* Done */
return 0;
}
static int
pack_double(double x, /* The number to pack */
char *p, /* Where to pack the high order byte */
int incr) /* 1 for big-endian; -1 for little-endian */
{
int s;
int e;
double f;
long fhi, flo;
if (x < 0) {
s = 1;
x = -x;
}
else
s = 0;
f = frexp(x, &e);
/* Normalize f to be in the range [1.0, 2.0) */
if (0.5 <= f && f < 1.0) {
f *= 2.0;
e--;
}
else if (f == 0.0) {
e = 0;
}
else {
PyErr_SetString(PyExc_SystemError,
"frexp() result out of range");
return -1;
}
if (e >= 1024) {
/* XXX 1024 itself is reserved for Inf/NaN */
PyErr_SetString(PyExc_OverflowError,
"float too large to pack with d format");
return -1;
}
else if (e < -1022) {
/* Gradual underflow */
f = ldexp(f, 1022 + e);
e = 0;
}
else if (!(e == 0 && f == 0.0)) {
e += 1023;
f -= 1.0; /* Get rid of leading 1 */
}
/* fhi receives the high 28 bits; flo the low 24 bits (== 52 bits) */
f *= 268435456.0; /* 2**28 */
fhi = (long) floor(f); /* Truncate */
f -= (double)fhi;
f *= 16777216.0; /* 2**24 */
flo = (long) floor(f + 0.5); /* Round */
/* First byte */
*p = (s<<7) | (e>>4);
p += incr;
/* Second byte */
*p = (char) (((e&0xF)<<4) | (fhi>>24));
p += incr;
/* Third byte */
*p = (fhi>>16) & 0xFF;
p += incr;
/* Fourth byte */
*p = (fhi>>8) & 0xFF;
p += incr;
/* Fifth byte */
*p = fhi & 0xFF;
p += incr;
/* Sixth byte */
*p = (flo>>16) & 0xFF;
p += incr;
/* Seventh byte */
*p = (flo>>8) & 0xFF;
p += incr;
/* Eighth byte */
*p = flo & 0xFF;
p += incr;
/* Done */
return 0;
}
static PyObject *
unpack_float(const char *p, /* Where the high order byte is */
int incr) /* 1 for big-endian; -1 for little-endian */
{
int s;
int e;
long f;
double x;
/* First byte */
s = (*p>>7) & 1;
e = (*p & 0x7F) << 1;
p += incr;
/* Second byte */
e |= (*p>>7) & 1;
f = (*p & 0x7F) << 16;
p += incr;
/* Third byte */
f |= (*p & 0xFF) << 8;
p += incr;
/* Fourth byte */
f |= *p & 0xFF;
x = (double)f / 8388608.0;
/* XXX This sadly ignores Inf/NaN issues */
if (e == 0)
e = -126;
else {
x += 1.0;
e -= 127;
}
x = ldexp(x, e);
if (s)
x = -x;
return PyFloat_FromDouble(x);
}
static PyObject *
unpack_double(const char *p, /* Where the high order byte is */
int incr) /* 1 for big-endian; -1 for little-endian */
{
int s;
int e;
long fhi, flo;
double x;
/* First byte */
s = (*p>>7) & 1;
e = (*p & 0x7F) << 4;
p += incr;
/* Second byte */
e |= (*p>>4) & 0xF;
fhi = (*p & 0xF) << 24;
p += incr;
/* Third byte */
fhi |= (*p & 0xFF) << 16;
p += incr;
/* Fourth byte */
fhi |= (*p & 0xFF) << 8;
p += incr;
/* Fifth byte */
fhi |= *p & 0xFF;
p += incr;
/* Sixth byte */
flo = (*p & 0xFF) << 16;
p += incr;
/* Seventh byte */
flo |= (*p & 0xFF) << 8;
p += incr;
/* Eighth byte */
flo |= *p & 0xFF;
p += incr;
x = (double)fhi + (double)flo / 16777216.0; /* 2**24 */
x /= 268435456.0; /* 2**28 */
/* XXX This sadly ignores Inf/NaN */
if (e == 0)
e = -1022;
else {
x += 1.0;
e -= 1023;
}
x = ldexp(x, e);
if (s)
x = -x;
return PyFloat_FromDouble(x);
}
/* The translation function for each format character is table driven */
typedef struct _formatdef {
char format;
int size;
int alignment;
PyObject* (*unpack)(const char *,
const struct _formatdef *);
int (*pack)(char *, PyObject *,
const struct _formatdef *);
} formatdef;
static PyObject *
nu_char(const char *p, const formatdef *f)
{
return PyString_FromStringAndSize(p, 1);
}
static PyObject *
nu_byte(const char *p, const formatdef *f)
{
return PyInt_FromLong((long) *(signed char *)p);
}
static PyObject *
nu_ubyte(const char *p, const formatdef *f)
{
return PyInt_FromLong((long) *(unsigned char *)p);
}
static PyObject *
nu_short(const char *p, const formatdef *f)
{
return PyInt_FromLong((long) *(short *)p);
}
static PyObject *
nu_ushort(const char *p, const formatdef *f)
{
return PyInt_FromLong((long) *(unsigned short *)p);
}
static PyObject *
nu_int(const char *p, const formatdef *f)
{
return PyInt_FromLong((long) *(int *)p);
}
static PyObject *
nu_uint(const char *p, const formatdef *f)
{
unsigned int x = *(unsigned int *)p;
return PyLong_FromUnsignedLong((unsigned long)x);
}
static PyObject *
nu_long(const char *p, const formatdef *f)
{
return PyInt_FromLong(*(long *)p);
}
static PyObject *
nu_ulong(const char *p, const formatdef *f)
{
return PyLong_FromUnsignedLong(*(unsigned long *)p);
}
static PyObject *
nu_float(const char *p, const formatdef *f)
{
float x;
memcpy((char *)&x, p, sizeof(float));
return PyFloat_FromDouble((double)x);
}
static PyObject *
nu_double(const char *p, const formatdef *f)
{
double x;
memcpy((char *)&x, p, sizeof(double));
return PyFloat_FromDouble(x);
}
static PyObject *
nu_void_p(const char *p, const formatdef *f)
{
return PyLong_FromVoidPtr(*(void **)p);
}
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 (!PyString_Check(v) || PyString_Size(v) != 1) {
PyErr_SetString(StructError,
"char format require string of length 1");
return -1;
}
*p = *PyString_AsString(v);
return 0;
}
static int
np_short(char *p, PyObject *v, const formatdef *f)
{
long x;
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;
}
* (short *)p = (short)x;
return 0;
}
static int
np_ushort(char *p, PyObject *v, const formatdef *f)
{
long x;
if (get_long(v, &x) < 0)
return -1;
if (x < 0 || x > USHRT_MAX){
PyErr_SetString(StructError,
"short format requires 0<=number<=" STRINGIFY(USHRT_MAX));
return -1;
}
* (unsigned short *)p = (unsigned short)x;
return 0;
}
static int
np_int(char *p, PyObject *v, const formatdef *f)
{
long x;
if (get_long(v, &x) < 0)
return -1;
* (int *)p = x;
return 0;
}
static int
np_uint(char *p, PyObject *v, const formatdef *f)
{
unsigned long x;
if (get_ulong(v, &x) < 0)
return -1;
* (unsigned int *)p = x;
return 0;
}
static int
np_long(char *p, PyObject *v, const formatdef *f)
{
long x;
if (get_long(v, &x) < 0)
return -1;
* (long *)p = 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;
* (unsigned long *)p = 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(float));
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 = PyLong_AsVoidPtr(v);
if (x == NULL && PyErr_Occurred()) {
/* ### hrm. PyLong_AsVoidPtr raises SystemError */
if (PyErr_ExceptionMatches(PyExc_TypeError))
PyErr_SetString(StructError,
"required argument is not an integer");
return -1;
}
*(void **)p = 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},
{'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}
};
static PyObject *
bu_int(const char *p, const formatdef *f)
{
long x = 0;
int i = f->size;
do {
x = (x<<8) | (*p++ & 0xFF);
} while (--i > 0);
i = 8*(sizeof(long) - f->size);
if (i) {
x <<= i;
x >>= i;
}
return PyInt_FromLong(x);
}
static PyObject *
bu_uint(const char *p, const formatdef *f)
{
unsigned long x = 0;
int i = f->size;
do {
x = (x<<8) | (*p++ & 0xFF);
} while (--i > 0);
if (f->size >= 4)
return PyLong_FromUnsignedLong(x);
else
return PyInt_FromLong((long)x);
}
static PyObject *
bu_float(const char *p, const formatdef *f)
{
return unpack_float(p, 1);
}
static PyObject *
bu_double(const char *p, const formatdef *f)
{
return unpack_double(p, 1);
}
static int
bp_int(char *p, PyObject *v, const formatdef *f)
{
long x;
int i;
if (get_long(v, &x) < 0)
return -1;
i = f->size;
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;
int i;
if (get_ulong(v, &x) < 0)
return -1;
i = f->size;
do {
p[--i] = (char)x;
x >>= 8;
} while (i > 0);
return 0;
}
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 pack_float(x, p, 1);
}
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 pack_double(x, p, 1);
}
static formatdef bigendian_table[] = {
{'x', 1, 0, NULL},
{'b', 1, 0, bu_int, bp_int},
{'B', 1, 0, bu_uint, bp_int},
{'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},
{'f', 4, 0, bu_float, bp_float},
{'d', 8, 0, bu_double, bp_double},
{0}
};
static PyObject *
lu_int(const char *p, const formatdef *f)
{
long x = 0;
int i = f->size;
do {
x = (x<<8) | (p[--i] & 0xFF);
} while (i > 0);
i = 8*(sizeof(long) - f->size);
if (i) {
x <<= i;
x >>= i;
}
return PyInt_FromLong(x);
}
static PyObject *
lu_uint(const char *p, const formatdef *f)
{
unsigned long x = 0;
int i = f->size;
do {
x = (x<<8) | (p[--i] & 0xFF);
} while (i > 0);
if (f->size >= 4)
return PyLong_FromUnsignedLong(x);
else
return PyInt_FromLong((long)x);
}
static PyObject *
lu_float(const char *p, const formatdef *f)
{
return unpack_float(p+3, -1);
}
static PyObject *
lu_double(const char *p, const formatdef *f)
{
return unpack_double(p+7, -1);
}
static int
lp_int(char *p, PyObject *v, const formatdef *f)
{
long x;
int i;
if (get_long(v, &x) < 0)
return -1;
i = f->size;
do {
*p++ = (char)x;
x >>= 8;
} while (--i > 0);
return 0;
}
static int
lp_uint(char *p, PyObject *v, const formatdef *f)
{
unsigned long x;
int i;
if (get_ulong(v, &x) < 0)
return -1;
i = f->size;
do {
*p++ = (char)x;
x >>= 8;
} while (--i > 0);
return 0;
}
static int
lp_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 pack_float(x, p+3, -1);
}
static int
lp_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 pack_double(x, p+7, -1);
}
static formatdef lilendian_table[] = {
{'x', 1, 0, NULL},
{'b', 1, 0, lu_int, lp_int},
{'B', 1, 0, lu_uint, lp_int},
{'c', 1, 0, nu_char, np_char},
{'s', 1, 0, NULL},
{'p', 1, 0, NULL},
{'h', 2, 0, lu_int, lp_int},
{'H', 2, 0, lu_uint, lp_uint},
{'i', 4, 0, lu_int, lp_int},
{'I', 4, 0, lu_uint, lp_uint},
{'l', 4, 0, lu_int, lp_int},
{'L', 4, 0, lu_uint, lp_uint},
{'f', 4, 0, lu_float, lp_float},
{'d', 8, 0, lu_double, lp_double},
{0}
};
static const formatdef *
whichtable(char **pfmt)
{
const char *fmt = (*pfmt)++; /* May be backed out of later */
switch (*fmt) {
case '<':
return lilendian_table;
case '>':
case '!': /* Network byte order is big-endian */
return bigendian_table;
case '=': { /* Host byte order -- different from native in aligment! */
int n = 1;
char *p = (char *) &n;
if (*p == 1)
return lilendian_table;
else
return bigendian_table;
}
default:
--*pfmt; /* Back out of pointer increment */
/* Fall through */
case '@':
return native_table;
}
}
/* Get the table entry for a format code */
static const formatdef *
getentry(int c, const formatdef *f)
{
for (; f->format != '\0'; f++) {
if (f->format == c) {
return f;
}
}
PyErr_SetString(StructError, "bad char in struct format");
return NULL;
}
/* Align a size according to a format code */
static int
align(int size, int c, const formatdef *e)
{
if (e->format == c) {
if (e->alignment) {
size = ((size + e->alignment - 1)
/ e->alignment)
* e->alignment;
}
}
return size;
}
/* calculate the size of a format string */
static int
calcsize(const char *fmt, const formatdef *f)
{
const formatdef *e;
const char *s;
char c;
int size, num, itemsize, x;
s = fmt;
size = 0;
while ((c = *s++) != '\0') {
if (isspace((int)c))
continue;
if ('0' <= c && c <= '9') {
num = c - '0';
while ('0' <= (c = *s++) && c <= '9') {
x = num*10 + (c - '0');
if (x/10 != num) {
PyErr_SetString(
StructError,
"overflow in item count");
return -1;
}
num = x;
}
if (c == '\0')
break;
}
else
num = 1;
e = getentry(c, f);
if (e == NULL)
return -1;
itemsize = e->size;
size = align(size, c, e);
x = num * itemsize;
size += x;
if (x/itemsize != num || size < 0) {
PyErr_SetString(StructError,
"total struct size too long");
return -1;
}
}
return size;
}
static char calcsize__doc__[] = "\
calcsize(fmt) -> int\n\
Return size of C struct described by format string fmt.\n\
See struct.__doc__ for more on format strings.";
static PyObject *
struct_calcsize(PyObject *self, PyObject *args)
{
char *fmt;
const formatdef *f;
int size;
if (!PyArg_ParseTuple(args, "s:calcsize", &fmt))
return NULL;
f = whichtable(&fmt);
size = calcsize(fmt, f);
if (size < 0)
return NULL;
return PyInt_FromLong((long)size);
}
static char pack__doc__[] = "\
pack(fmt, v1, v2, ...) -> string\n\
Return string containing values v1, v2, ... packed according to fmt.\n\
See struct.__doc__ for more on format strings.";
static PyObject *
struct_pack(PyObject *self, PyObject *args)
{
const formatdef *f, *e;
PyObject *format, *result, *v;
char *fmt;
int size, num;
int i, n;
char *s, *res, *restart, *nres;
char c;
if (args == NULL || !PyTuple_Check(args) ||
(n = PyTuple_Size(args)) < 1)
{
PyErr_SetString(PyExc_TypeError,
"struct.pack requires at least one argument");
return NULL;
}
format = PyTuple_GetItem(args, 0);
if (!PyArg_Parse(format, "s", &fmt))
return NULL;
f = whichtable(&fmt);
size = calcsize(fmt, f);
if (size < 0)
return NULL;
result = PyString_FromStringAndSize((char *)NULL, size);
if (result == NULL)
return NULL;
s = fmt;
i = 1;
res = restart = PyString_AsString(result);
while ((c = *s++) != '\0') {
if (isspace((int)c))
continue;
if ('0' <= c && c <= '9') {
num = c - '0';
while ('0' <= (c = *s++) && c <= '9')
num = num*10 + (c - '0');
if (c == '\0')
break;
}
else
num = 1;
e = getentry(c, f);
if (e == NULL)
goto fail;
nres = restart + align((int)(res-restart), c, e);
/* Fill padd bytes with zeros */
while (res < nres)
*res++ = '\0';
if (num == 0 && c != 's')
continue;
do {
if (c == 'x') {
/* doesn't consume arguments */
memset(res, '\0', num);
res += num;
break;
}
if (i >= n) {
PyErr_SetString(StructError,
"insufficient arguments to pack");
goto fail;
}
v = PyTuple_GetItem(args, i++);
if (v == NULL)
goto fail;
if (c == 's') {
/* num is string size, not repeat count */
int n;
if (!PyString_Check(v)) {
PyErr_SetString(StructError,
"argument for 's' must be a string");
goto fail;
}
n = PyString_Size(v);
if (n > num)
n = num;
if (n > 0)
memcpy(res, PyString_AsString(v), n);
if (n < num)
memset(res+n, '\0', num-n);
res += num;
break;
}
else if (c == 'p') {
/* num is string size + 1,
to fit in the count byte */
int n;
num--; /* now num is max string size */
if (!PyString_Check(v)) {
PyErr_SetString(StructError,
"argument for 'p' must be a string");
goto fail;
}
n = PyString_Size(v);
if (n > num)
n = num;
if (n > 0)
memcpy(res+1, PyString_AsString(v), n);
if (n < num)
/* no real need, just to be nice */
memset(res+1+n, '\0', num-n);
*res++ = n; /* store the length byte */
res += num;
break;
}
else {
if (e->pack(res, v, e) < 0)
goto fail;
res += e->size;
}
} while (--num > 0);
}
if (i < n) {
PyErr_SetString(StructError,
"too many arguments for pack format");
goto fail;
}
return result;
fail:
Py_DECREF(result);
return NULL;
}
static char unpack__doc__[] = "\
unpack(fmt, string) -> (v1, v2, ...)\n\
Unpack the string, containing packed C structure data, according\n\
to fmt. Requires len(string)==calcsize(fmt).\n\
See struct.__doc__ for more on format strings.";
static PyObject *
struct_unpack(PyObject *self, PyObject *args)
{
const formatdef *f, *e;
char *str, *start, *fmt, *s;
char c;
int len, size, num;
PyObject *res, *v;
if (!PyArg_ParseTuple(args, "ss#:unpack", &fmt, &start, &len))
return NULL;
f = whichtable(&fmt);
size = calcsize(fmt, f);
if (size < 0)
return NULL;
if (size != len) {
PyErr_SetString(StructError,
"unpack str size does not match format");
return NULL;
}
res = PyList_New(0);
if (res == NULL)
return NULL;
str = start;
s = fmt;
while ((c = *s++) != '\0') {
if (isspace((int)c))
continue;
if ('0' <= c && c <= '9') {
num = c - '0';
while ('0' <= (c = *s++) && c <= '9')
num = num*10 + (c - '0');
if (c == '\0')
break;
}
else
num = 1;
e = getentry(c, f);
if (e == NULL)
goto fail;
str = start + align((int)(str-start), c, e);
if (num == 0 && c != 's')
continue;
do {
if (c == 'x') {
str += num;
break;
}
if (c == 's') {
/* num is string size, not repeat count */
v = PyString_FromStringAndSize(str, num);
if (v == NULL)
goto fail;
str += num;
num = 0;
}
else if (c == 'p') {
/* num is string buffer size,
not repeat count */
int n = *(unsigned char*)str;
/* first byte (unsigned) is string size */
if (n >= num)
n = num-1;
v = PyString_FromStringAndSize(str+1, n);
if (v == NULL)
goto fail;
str += num;
num = 0;
}
else {
v = e->unpack(str, e);
if (v == NULL)
goto fail;
str += e->size;
}
if (v == NULL || PyList_Append(res, v) < 0)
goto fail;
Py_DECREF(v);
} while (--num > 0);
}
v = PyList_AsTuple(res);
Py_DECREF(res);
return v;
fail:
Py_DECREF(res);
return NULL;
}
/* List of functions */
static PyMethodDef struct_methods[] = {
{"calcsize", struct_calcsize, METH_VARARGS, calcsize__doc__},
{"pack", struct_pack, METH_VARARGS, pack__doc__},
{"unpack", struct_unpack, METH_VARARGS, unpack__doc__},
{NULL, NULL} /* sentinel */
};
/* Module initialization */
DL_EXPORT(void)
initstruct(void)
{
PyObject *m, *d;
/* Create the module and add the functions */
m = Py_InitModule4("struct", struct_methods, struct__doc__,
(PyObject*)NULL, PYTHON_API_VERSION);
/* Add some symbolic constants to the module */
d = PyModule_GetDict(m);
StructError = PyErr_NewException("struct.error", NULL, NULL);
if (StructError == NULL)
return;
PyDict_SetItemString(d, "error", StructError);
}
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