
/* Write Python objects to files and read them back.
   This is primarily intended for writing and reading compiled Python code,
   even though dicts, lists, sets and frozensets, not commonly seen in
   code objects, are supported.
   Version 3 of this protocol properly supports circular links
   and sharing. */

#define PY_SSIZE_T_CLEAN

#include "Python.h"
#include "longintrepr.h"
#include "code.h"
#include "marshal.h"
#include "../Modules/hashtable.h"

/* High water mark to determine when the marshalled object is dangerously deep
 * and risks coring the interpreter.  When the object stack gets this deep,
 * raise an exception instead of continuing.
 * On Windows debug builds, reduce this value.
 */
#if defined(MS_WINDOWS) && defined(_DEBUG)
#define MAX_MARSHAL_STACK_DEPTH 1000
#else
#define MAX_MARSHAL_STACK_DEPTH 2000
#endif

#define TYPE_NULL               '0'
#define TYPE_NONE               'N'
#define TYPE_FALSE              'F'
#define TYPE_TRUE               'T'
#define TYPE_STOPITER           'S'
#define TYPE_ELLIPSIS           '.'
#define TYPE_INT                'i'
/* TYPE_INT64 is not generated anymore.
   Supported for backward compatibility only. */
#define TYPE_INT64              'I'
#define TYPE_FLOAT              'f'
#define TYPE_BINARY_FLOAT       'g'
#define TYPE_COMPLEX            'x'
#define TYPE_BINARY_COMPLEX     'y'
#define TYPE_LONG               'l'
#define TYPE_STRING             's'
#define TYPE_INTERNED           't'
#define TYPE_REF                'r'
#define TYPE_TUPLE              '('
#define TYPE_LIST               '['
#define TYPE_DICT               '{'
#define TYPE_CODE               'c'
#define TYPE_UNICODE            'u'
#define TYPE_UNKNOWN            '?'
#define TYPE_SET                '<'
#define TYPE_FROZENSET          '>'
#define FLAG_REF                '\x80' /* with a type, add obj to index */

#define TYPE_ASCII              'a'
#define TYPE_ASCII_INTERNED     'A'
#define TYPE_SMALL_TUPLE        ')'
#define TYPE_SHORT_ASCII        'z'
#define TYPE_SHORT_ASCII_INTERNED 'Z'

#define WFERR_OK 0
#define WFERR_UNMARSHALLABLE 1
#define WFERR_NESTEDTOODEEP 2
#define WFERR_NOMEMORY 3

typedef struct {
    FILE *fp;
    int error;  /* see WFERR_* values */
    int depth;
    PyObject *str;
    char *ptr;
    char *end;
    char *buf;
    _Py_hashtable_t *hashtable;
    int version;
} WFILE;

#define w_byte(c, p) do {                               \
        if ((p)->ptr != (p)->end || w_reserve((p), 1))  \
            *(p)->ptr++ = (c);                          \
    } while(0)

static void
w_flush(WFILE *p)
{
    assert(p->fp != NULL);
    fwrite(p->buf, 1, p->ptr - p->buf, p->fp);
    p->ptr = p->buf;
}

static int
w_reserve(WFILE *p, Py_ssize_t needed)
{
    Py_ssize_t pos, size, delta;
    if (p->ptr == NULL)
        return 0; /* An error already occurred */
    if (p->fp != NULL) {
        w_flush(p);
        return needed <= p->end - p->ptr;
    }
    assert(p->str != NULL);
    pos = p->ptr - p->buf;
    size = PyBytes_Size(p->str);
    if (size > 16*1024*1024)
        delta = (size >> 3);            /* 12.5% overallocation */
    else
        delta = size + 1024;
    delta = Py_MAX(delta, needed);
    if (delta > PY_SSIZE_T_MAX - size) {
        p->error = WFERR_NOMEMORY;
        return 0;
    }
    size += delta;
    if (_PyBytes_Resize(&p->str, size) != 0) {
        p->ptr = p->buf = p->end = NULL;
        return 0;
    }
    else {
        p->buf = PyBytes_AS_STRING(p->str);
        p->ptr = p->buf + pos;
        p->end = p->buf + size;
        return 1;
    }
}

static void
w_string(const char *s, Py_ssize_t n, WFILE *p)
{
    Py_ssize_t m;
    if (!n || p->ptr == NULL)
        return;
    m = p->end - p->ptr;
    if (p->fp != NULL) {
        if (n <= m) {
            memcpy(p->ptr, s, n);
            p->ptr += n;
        }
        else {
            w_flush(p);
            fwrite(s, 1, n, p->fp);
        }
    }
    else {
        if (n <= m || w_reserve(p, n - m)) {
            memcpy(p->ptr, s, n);
            p->ptr += n;
        }
    }
}

static void
w_short(int x, WFILE *p)
{
    w_byte((char)( x      & 0xff), p);
    w_byte((char)((x>> 8) & 0xff), p);
}

static void
w_long(long x, WFILE *p)
{
    w_byte((char)( x      & 0xff), p);
    w_byte((char)((x>> 8) & 0xff), p);
    w_byte((char)((x>>16) & 0xff), p);
    w_byte((char)((x>>24) & 0xff), p);
}

#define SIZE32_MAX  0x7FFFFFFF

#if SIZEOF_SIZE_T > 4
# define W_SIZE(n, p)  do {                     \
        if ((n) > SIZE32_MAX) {                 \
            (p)->depth--;                       \
            (p)->error = WFERR_UNMARSHALLABLE;  \
            return;                             \
        }                                       \
        w_long((long)(n), p);                   \
    } while(0)
#else
# define W_SIZE  w_long
#endif

static void
w_pstring(const char *s, Py_ssize_t n, WFILE *p)
{
        W_SIZE(n, p);
        w_string(s, n, p);
}

static void
w_short_pstring(const char *s, Py_ssize_t n, WFILE *p)
{
    w_byte(Py_SAFE_DOWNCAST(n, Py_ssize_t, unsigned char), p);
    w_string(s, n, p);
}

/* We assume that Python ints are stored internally in base some power of
   2**15; for the sake of portability we'll always read and write them in base
   exactly 2**15. */

#define PyLong_MARSHAL_SHIFT 15
#define PyLong_MARSHAL_BASE ((short)1 << PyLong_MARSHAL_SHIFT)
#define PyLong_MARSHAL_MASK (PyLong_MARSHAL_BASE - 1)
#if PyLong_SHIFT % PyLong_MARSHAL_SHIFT != 0
#error "PyLong_SHIFT must be a multiple of PyLong_MARSHAL_SHIFT"
#endif
#define PyLong_MARSHAL_RATIO (PyLong_SHIFT / PyLong_MARSHAL_SHIFT)

#define W_TYPE(t, p) do { \
    w_byte((t) | flag, (p)); \
} while(0)

static void
w_PyLong(const PyLongObject *ob, char flag, WFILE *p)
{
    Py_ssize_t i, j, n, l;
    digit d;

    W_TYPE(TYPE_LONG, p);
    if (Py_SIZE(ob) == 0) {
        w_long((long)0, p);
        return;
    }

    /* set l to number of base PyLong_MARSHAL_BASE digits */
    n = Py_ABS(Py_SIZE(ob));
    l = (n-1) * PyLong_MARSHAL_RATIO;
    d = ob->ob_digit[n-1];
    assert(d != 0); /* a PyLong is always normalized */
    do {
        d >>= PyLong_MARSHAL_SHIFT;
        l++;
    } while (d != 0);
    if (l > SIZE32_MAX) {
        p->depth--;
        p->error = WFERR_UNMARSHALLABLE;
        return;
    }
    w_long((long)(Py_SIZE(ob) > 0 ? l : -l), p);

    for (i=0; i < n-1; i++) {
        d = ob->ob_digit[i];
        for (j=0; j < PyLong_MARSHAL_RATIO; j++) {
            w_short(d & PyLong_MARSHAL_MASK, p);
            d >>= PyLong_MARSHAL_SHIFT;
        }
        assert (d == 0);
    }
    d = ob->ob_digit[n-1];
    do {
        w_short(d & PyLong_MARSHAL_MASK, p);
        d >>= PyLong_MARSHAL_SHIFT;
    } while (d != 0);
}

static int
w_ref(PyObject *v, char *flag, WFILE *p)
{
    _Py_hashtable_entry_t *entry;
    int w;

    if (p->version < 3 || p->hashtable == NULL)
        return 0; /* not writing object references */

    /* if it has only one reference, it definitely isn't shared */
    if (Py_REFCNT(v) == 1)
        return 0;

    entry = _Py_HASHTABLE_GET_ENTRY(p->hashtable, v);
    if (entry != NULL) {
        /* write the reference index to the stream */
        _Py_HASHTABLE_ENTRY_READ_DATA(p->hashtable, entry, w);
        /* we don't store "long" indices in the dict */
        assert(0 <= w && w <= 0x7fffffff);
        w_byte(TYPE_REF, p);
        w_long(w, p);
        return 1;
    } else {
        size_t s = p->hashtable->entries;
        /* we don't support long indices */
        if (s >= 0x7fffffff) {
            PyErr_SetString(PyExc_ValueError, "too many objects");
            goto err;
        }
        w = (int)s;
        Py_INCREF(v);
        if (_Py_HASHTABLE_SET(p->hashtable, v, w) < 0) {
            Py_DECREF(v);
            goto err;
        }
        *flag |= FLAG_REF;
        return 0;
    }
err:
    p->error = WFERR_UNMARSHALLABLE;
    return 1;
}

static void
w_complex_object(PyObject *v, char flag, WFILE *p);

static void
w_object(PyObject *v, WFILE *p)
{
    char flag = '\0';

    p->depth++;

    if (p->depth > MAX_MARSHAL_STACK_DEPTH) {
        p->error = WFERR_NESTEDTOODEEP;
    }
    else if (v == NULL) {
        w_byte(TYPE_NULL, p);
    }
    else if (v == Py_None) {
        w_byte(TYPE_NONE, p);
    }
    else if (v == PyExc_StopIteration) {
        w_byte(TYPE_STOPITER, p);
    }
    else if (v == Py_Ellipsis) {
        w_byte(TYPE_ELLIPSIS, p);
    }
    else if (v == Py_False) {
        w_byte(TYPE_FALSE, p);
    }
    else if (v == Py_True) {
        w_byte(TYPE_TRUE, p);
    }
    else if (!w_ref(v, &flag, p))
        w_complex_object(v, flag, p);

    p->depth--;
}

static void
w_complex_object(PyObject *v, char flag, WFILE *p)
{
    Py_ssize_t i, n;

    if (PyLong_CheckExact(v)) {
        long x = PyLong_AsLong(v);
        if ((x == -1)  && PyErr_Occurred()) {
            PyLongObject *ob = (PyLongObject *)v;
            PyErr_Clear();
            w_PyLong(ob, flag, p);
        }
        else {
#if SIZEOF_LONG > 4
            long y = Py_ARITHMETIC_RIGHT_SHIFT(long, x, 31);
            if (y && y != -1) {
                /* Too large for TYPE_INT */
                w_PyLong((PyLongObject*)v, flag, p);
            }
            else
#endif
            {
                W_TYPE(TYPE_INT, p);
                w_long(x, p);
            }
        }
    }
    else if (PyFloat_CheckExact(v)) {
        if (p->version > 1) {
            unsigned char buf[8];
            if (_PyFloat_Pack8(PyFloat_AsDouble(v),
                               buf, 1) < 0) {
                p->error = WFERR_UNMARSHALLABLE;
                return;
            }
            W_TYPE(TYPE_BINARY_FLOAT, p);
            w_string((char*)buf, 8, p);
        }
        else {
            char *buf = PyOS_double_to_string(PyFloat_AS_DOUBLE(v),
                                              'g', 17, 0, NULL);
            if (!buf) {
                p->error = WFERR_NOMEMORY;
                return;
            }
            n = strlen(buf);
            W_TYPE(TYPE_FLOAT, p);
            w_byte((int)n, p);
            w_string(buf, n, p);
            PyMem_Free(buf);
        }
    }
    else if (PyComplex_CheckExact(v)) {
        if (p->version > 1) {
            unsigned char buf[8];
            if (_PyFloat_Pack8(PyComplex_RealAsDouble(v),
                               buf, 1) < 0) {
                p->error = WFERR_UNMARSHALLABLE;
                return;
            }
            W_TYPE(TYPE_BINARY_COMPLEX, p);
            w_string((char*)buf, 8, p);
            if (_PyFloat_Pack8(PyComplex_ImagAsDouble(v),
                               buf, 1) < 0) {
                p->error = WFERR_UNMARSHALLABLE;
                return;
            }
            w_string((char*)buf, 8, p);
        }
        else {
            char *buf;
            W_TYPE(TYPE_COMPLEX, p);
            buf = PyOS_double_to_string(PyComplex_RealAsDouble(v),
                                        'g', 17, 0, NULL);
            if (!buf) {
                p->error = WFERR_NOMEMORY;
                return;
            }
            n = strlen(buf);
            w_byte((int)n, p);
            w_string(buf, n, p);
            PyMem_Free(buf);
            buf = PyOS_double_to_string(PyComplex_ImagAsDouble(v),
                                        'g', 17, 0, NULL);
            if (!buf) {
                p->error = WFERR_NOMEMORY;
                return;
            }
            n = strlen(buf);
            w_byte((int)n, p);
            w_string(buf, n, p);
            PyMem_Free(buf);
        }
    }
    else if (PyBytes_CheckExact(v)) {
        W_TYPE(TYPE_STRING, p);
        w_pstring(PyBytes_AS_STRING(v), PyBytes_GET_SIZE(v), p);
    }
    else if (PyUnicode_CheckExact(v)) {
        if (p->version >= 4 && PyUnicode_IS_ASCII(v)) {
            int is_short = PyUnicode_GET_LENGTH(v) < 256;
            if (is_short) {
                if (PyUnicode_CHECK_INTERNED(v))
                    W_TYPE(TYPE_SHORT_ASCII_INTERNED, p);
                else
                    W_TYPE(TYPE_SHORT_ASCII, p);
                w_short_pstring((char *) PyUnicode_1BYTE_DATA(v),
                                PyUnicode_GET_LENGTH(v), p);
            }
            else {
                if (PyUnicode_CHECK_INTERNED(v))
                    W_TYPE(TYPE_ASCII_INTERNED, p);
                else
                    W_TYPE(TYPE_ASCII, p);
                w_pstring((char *) PyUnicode_1BYTE_DATA(v),
                          PyUnicode_GET_LENGTH(v), p);
            }
        }
        else {
            PyObject *utf8;
            utf8 = PyUnicode_AsEncodedString(v, "utf8", "surrogatepass");
            if (utf8 == NULL) {
                p->depth--;
                p->error = WFERR_UNMARSHALLABLE;
                return;
            }
            if (p->version >= 3 &&  PyUnicode_CHECK_INTERNED(v))
                W_TYPE(TYPE_INTERNED, p);
            else
                W_TYPE(TYPE_UNICODE, p);
            w_pstring(PyBytes_AS_STRING(utf8), PyBytes_GET_SIZE(utf8), p);
            Py_DECREF(utf8);
        }
    }
    else if (PyTuple_CheckExact(v)) {
        n = PyTuple_Size(v);
        if (p->version >= 4 && n < 256) {
            W_TYPE(TYPE_SMALL_TUPLE, p);
            w_byte((unsigned char)n, p);
        }
        else {
            W_TYPE(TYPE_TUPLE, p);
            W_SIZE(n, p);
        }
        for (i = 0; i < n; i++) {
            w_object(PyTuple_GET_ITEM(v, i), p);
        }
    }
    else if (PyList_CheckExact(v)) {
        W_TYPE(TYPE_LIST, p);
        n = PyList_GET_SIZE(v);
        W_SIZE(n, p);
        for (i = 0; i < n; i++) {
            w_object(PyList_GET_ITEM(v, i), p);
        }
    }
    else if (PyDict_CheckExact(v)) {
        Py_ssize_t pos;
        PyObject *key, *value;
        W_TYPE(TYPE_DICT, p);
        /* This one is NULL object terminated! */
        pos = 0;
        while (PyDict_Next(v, &pos, &key, &value)) {
            w_object(key, p);
            w_object(value, p);
        }
        w_object((PyObject *)NULL, p);
    }
    else if (PyAnySet_CheckExact(v)) {
        PyObject *value, *it;

        if (PyObject_TypeCheck(v, &PySet_Type))
            W_TYPE(TYPE_SET, p);
        else
            W_TYPE(TYPE_FROZENSET, p);
        n = PyObject_Size(v);
        if (n == -1) {
            p->depth--;
            p->error = WFERR_UNMARSHALLABLE;
            return;
        }
        W_SIZE(n, p);
        it = PyObject_GetIter(v);
        if (it == NULL) {
            p->depth--;
            p->error = WFERR_UNMARSHALLABLE;
            return;
        }
        while ((value = PyIter_Next(it)) != NULL) {
            w_object(value, p);
            Py_DECREF(value);
        }
        Py_DECREF(it);
        if (PyErr_Occurred()) {
            p->depth--;
            p->error = WFERR_UNMARSHALLABLE;
            return;
        }
    }
    else if (PyCode_Check(v)) {
        PyCodeObject *co = (PyCodeObject *)v;
        W_TYPE(TYPE_CODE, p);
        w_long(co->co_argcount, p);
        w_long(co->co_kwonlyargcount, p);
        w_long(co->co_nlocals, p);
        w_long(co->co_stacksize, p);
        w_long(co->co_flags, p);
        w_object(co->co_code, p);
        w_object(co->co_consts, p);
        w_object(co->co_names, p);
        w_object(co->co_varnames, p);
        w_object(co->co_freevars, p);
        w_object(co->co_cellvars, p);
        w_object(co->co_filename, p);
        w_object(co->co_name, p);
        w_long(co->co_firstlineno, p);
        w_object(co->co_lnotab, p);
    }
    else if (PyObject_CheckBuffer(v)) {
        /* Write unknown bytes-like objects as a bytes object */
        Py_buffer view;
        if (PyObject_GetBuffer(v, &view, PyBUF_SIMPLE) != 0) {
            w_byte(TYPE_UNKNOWN, p);
            p->depth--;
            p->error = WFERR_UNMARSHALLABLE;
            return;
        }
        W_TYPE(TYPE_STRING, p);
        w_pstring(view.buf, view.len, p);
        PyBuffer_Release(&view);
    }
    else {
        W_TYPE(TYPE_UNKNOWN, p);
        p->error = WFERR_UNMARSHALLABLE;
    }
}

static int
w_init_refs(WFILE *wf, int version)
{
    if (version >= 3) {
        wf->hashtable = _Py_hashtable_new(sizeof(PyObject *), sizeof(int),
                                          _Py_hashtable_hash_ptr,
                                          _Py_hashtable_compare_direct);
        if (wf->hashtable == NULL) {
            PyErr_NoMemory();
            return -1;
        }
    }
    return 0;
}

static int
w_decref_entry(_Py_hashtable_t *ht, _Py_hashtable_entry_t *entry,
               void *Py_UNUSED(data))
{
    PyObject *entry_key;

    _Py_HASHTABLE_ENTRY_READ_KEY(ht, entry, entry_key);
    Py_XDECREF(entry_key);
    return 0;
}

static void
w_clear_refs(WFILE *wf)
{
    if (wf->hashtable != NULL) {
        _Py_hashtable_foreach(wf->hashtable, w_decref_entry, NULL);
        _Py_hashtable_destroy(wf->hashtable);
    }
}

/* version currently has no effect for writing ints. */
void
PyMarshal_WriteLongToFile(long x, FILE *fp, int version)
{
    char buf[4];
    WFILE wf;
    memset(&wf, 0, sizeof(wf));
    wf.fp = fp;
    wf.ptr = wf.buf = buf;
    wf.end = wf.ptr + sizeof(buf);
    wf.error = WFERR_OK;
    wf.version = version;
    w_long(x, &wf);
    w_flush(&wf);
}

void
PyMarshal_WriteObjectToFile(PyObject *x, FILE *fp, int version)
{
    char buf[BUFSIZ];
    WFILE wf;
    memset(&wf, 0, sizeof(wf));
    wf.fp = fp;
    wf.ptr = wf.buf = buf;
    wf.end = wf.ptr + sizeof(buf);
    wf.error = WFERR_OK;
    wf.version = version;
    if (w_init_refs(&wf, version))
        return; /* caller mush check PyErr_Occurred() */
    w_object(x, &wf);
    w_clear_refs(&wf);
    w_flush(&wf);
}

typedef struct {
    FILE *fp;
    int depth;
    PyObject *readable;  /* Stream-like object being read from */
    PyObject *current_filename;
    char *ptr;
    char *end;
    char *buf;
    Py_ssize_t buf_size;
    PyObject *refs;  /* a list */
} RFILE;

static const char *
r_string(Py_ssize_t n, RFILE *p)
{
    Py_ssize_t read = -1;

    if (p->ptr != NULL) {
        /* Fast path for loads() */
        char *res = p->ptr;
        Py_ssize_t left = p->end - p->ptr;
        if (left < n) {
            PyErr_SetString(PyExc_EOFError,
                            "marshal data too short");
            return NULL;
        }
        p->ptr += n;
        return res;
    }
    if (p->buf == NULL) {
        p->buf = PyMem_MALLOC(n);
        if (p->buf == NULL) {
            PyErr_NoMemory();
            return NULL;
        }
        p->buf_size = n;
    }
    else if (p->buf_size < n) {
        p->buf = PyMem_REALLOC(p->buf, n);
        if (p->buf == NULL) {
            PyErr_NoMemory();
            return NULL;
        }
        p->buf_size = n;
    }

    if (!p->readable) {
        assert(p->fp != NULL);
        read = fread(p->buf, 1, n, p->fp);
    }
    else {
        _Py_IDENTIFIER(readinto);
        PyObject *res, *mview;
        Py_buffer buf;

        if (PyBuffer_FillInfo(&buf, NULL, p->buf, n, 0, PyBUF_CONTIG) == -1)
            return NULL;
        mview = PyMemoryView_FromBuffer(&buf);
        if (mview == NULL)
            return NULL;

        res = _PyObject_CallMethodId(p->readable, &PyId_readinto, "N", mview);
        if (res != NULL) {
            read = PyNumber_AsSsize_t(res, PyExc_ValueError);
            Py_DECREF(res);
        }
    }
    if (read != n) {
        if (!PyErr_Occurred()) {
            if (read > n)
                PyErr_Format(PyExc_ValueError,
                             "read() returned too much data: "
                             "%zd bytes requested, %zd returned",
                             n, read);
            else
                PyErr_SetString(PyExc_EOFError,
                                "EOF read where not expected");
        }
        return NULL;
    }
    return p->buf;
}

static int
r_byte(RFILE *p)
{
    int c = EOF;

    if (p->ptr != NULL) {
        if (p->ptr < p->end)
            c = (unsigned char) *p->ptr++;
        return c;
    }
    if (!p->readable) {
        assert(p->fp);
        c = getc(p->fp);
    }
    else {
        const char *ptr = r_string(1, p);
        if (ptr != NULL)
            c = *(unsigned char *) ptr;
    }
    return c;
}

static int
r_short(RFILE *p)
{
    short x = -1;
    const unsigned char *buffer;

    buffer = (const unsigned char *) r_string(2, p);
    if (buffer != NULL) {
        x = buffer[0];
        x |= buffer[1] << 8;
        /* Sign-extension, in case short greater than 16 bits */
        x |= -(x & 0x8000);
    }
    return x;
}

static long
r_long(RFILE *p)
{
    long x = -1;
    const unsigned char *buffer;

    buffer = (const unsigned char *) r_string(4, p);
    if (buffer != NULL) {
        x = buffer[0];
        x |= (long)buffer[1] << 8;
        x |= (long)buffer[2] << 16;
        x |= (long)buffer[3] << 24;
#if SIZEOF_LONG > 4
        /* Sign extension for 64-bit machines */
        x |= -(x & 0x80000000L);
#endif
    }
    return x;
}

/* r_long64 deals with the TYPE_INT64 code. */
static PyObject *
r_long64(RFILE *p)
{
    const unsigned char *buffer = (const unsigned char *) r_string(8, p);
    if (buffer == NULL) {
        return NULL;
    }
    return _PyLong_FromByteArray(buffer, 8,
                                 1 /* little endian */,
                                 1 /* signed */);
}

static PyObject *
r_PyLong(RFILE *p)
{
    PyLongObject *ob;
    long n, size, i;
    int j, md, shorts_in_top_digit;
    digit d;

    n = r_long(p);
    if (PyErr_Occurred())
        return NULL;
    if (n == 0)
        return (PyObject *)_PyLong_New(0);
    if (n < -SIZE32_MAX || n > SIZE32_MAX) {
        PyErr_SetString(PyExc_ValueError,
                       "bad marshal data (long size out of range)");
        return NULL;
    }

    size = 1 + (Py_ABS(n) - 1) / PyLong_MARSHAL_RATIO;
    shorts_in_top_digit = 1 + (Py_ABS(n) - 1) % PyLong_MARSHAL_RATIO;
    ob = _PyLong_New(size);
    if (ob == NULL)
        return NULL;

    Py_SIZE(ob) = n > 0 ? size : -size;

    for (i = 0; i < size-1; i++) {
        d = 0;
        for (j=0; j < PyLong_MARSHAL_RATIO; j++) {
            md = r_short(p);
            if (PyErr_Occurred()) {
                Py_DECREF(ob);
                return NULL;
            }
            if (md < 0 || md > PyLong_MARSHAL_BASE)
                goto bad_digit;
            d += (digit)md << j*PyLong_MARSHAL_SHIFT;
        }
        ob->ob_digit[i] = d;
    }

    d = 0;
    for (j=0; j < shorts_in_top_digit; j++) {
        md = r_short(p);
        if (PyErr_Occurred()) {
            Py_DECREF(ob);
            return NULL;
        }
        if (md < 0 || md > PyLong_MARSHAL_BASE)
            goto bad_digit;
        /* topmost marshal digit should be nonzero */
        if (md == 0 && j == shorts_in_top_digit - 1) {
            Py_DECREF(ob);
            PyErr_SetString(PyExc_ValueError,
                "bad marshal data (unnormalized long data)");
            return NULL;
        }
        d += (digit)md << j*PyLong_MARSHAL_SHIFT;
    }
    if (PyErr_Occurred()) {
        Py_DECREF(ob);
        return NULL;
    }
    /* top digit should be nonzero, else the resulting PyLong won't be
       normalized */
    ob->ob_digit[size-1] = d;
    return (PyObject *)ob;
  bad_digit:
    Py_DECREF(ob);
    PyErr_SetString(PyExc_ValueError,
                    "bad marshal data (digit out of range in long)");
    return NULL;
}

/* allocate the reflist index for a new object. Return -1 on failure */
static Py_ssize_t
r_ref_reserve(int flag, RFILE *p)
{
    if (flag) { /* currently only FLAG_REF is defined */
        Py_ssize_t idx = PyList_GET_SIZE(p->refs);
        if (idx >= 0x7ffffffe) {
            PyErr_SetString(PyExc_ValueError, "bad marshal data (index list too large)");
            return -1;
        }
        if (PyList_Append(p->refs, Py_None) < 0)
            return -1;
        return idx;
    } else
        return 0;
}

/* insert the new object 'o' to the reflist at previously
 * allocated index 'idx'.
 * 'o' can be NULL, in which case nothing is done.
 * if 'o' was non-NULL, and the function succeeds, 'o' is returned.
 * if 'o' was non-NULL, and the function fails, 'o' is released and
 * NULL returned. This simplifies error checking at the call site since
 * a single test for NULL for the function result is enough.
 */
static PyObject *
r_ref_insert(PyObject *o, Py_ssize_t idx, int flag, RFILE *p)
{
    if (o != NULL && flag) { /* currently only FLAG_REF is defined */
        PyObject *tmp = PyList_GET_ITEM(p->refs, idx);
        Py_INCREF(o);
        PyList_SET_ITEM(p->refs, idx, o);
        Py_DECREF(tmp);
    }
    return o;
}

/* combination of both above, used when an object can be
 * created whenever it is seen in the file, as opposed to
 * after having loaded its sub-objects.
 */
static PyObject *
r_ref(PyObject *o, int flag, RFILE *p)
{
    assert(flag & FLAG_REF);
    if (o == NULL)
        return NULL;
    if (PyList_Append(p->refs, o) < 0) {
        Py_DECREF(o); /* release the new object */
        return NULL;
    }
    return o;
}

static PyObject *
r_object(RFILE *p)
{
    /* NULL is a valid return value, it does not necessarily means that
       an exception is set. */
    PyObject *v, *v2;
    Py_ssize_t idx = 0;
    long i, n;
    int type, code = r_byte(p);
    int flag, is_interned = 0;
    PyObject *retval = NULL;

    if (code == EOF) {
        PyErr_SetString(PyExc_EOFError,
                        "EOF read where object expected");
        return NULL;
    }

    p->depth++;

    if (p->depth > MAX_MARSHAL_STACK_DEPTH) {
        p->depth--;
        PyErr_SetString(PyExc_ValueError, "recursion limit exceeded");
        return NULL;
    }

    flag = code & FLAG_REF;
    type = code & ~FLAG_REF;

#define R_REF(O) do{\
    if (flag) \
        O = r_ref(O, flag, p);\
} while (0)

    switch (type) {

    case TYPE_NULL:
        break;

    case TYPE_NONE:
        Py_INCREF(Py_None);
        retval = Py_None;
        break;

    case TYPE_STOPITER:
        Py_INCREF(PyExc_StopIteration);
        retval = PyExc_StopIteration;
        break;

    case TYPE_ELLIPSIS:
        Py_INCREF(Py_Ellipsis);
        retval = Py_Ellipsis;
        break;

    case TYPE_FALSE:
        Py_INCREF(Py_False);
        retval = Py_False;
        break;

    case TYPE_TRUE:
        Py_INCREF(Py_True);
        retval = Py_True;
        break;

    case TYPE_INT:
        n = r_long(p);
        retval = PyErr_Occurred() ? NULL : PyLong_FromLong(n);
        R_REF(retval);
        break;

    case TYPE_INT64:
        retval = r_long64(p);
        R_REF(retval);
        break;

    case TYPE_LONG:
        retval = r_PyLong(p);
        R_REF(retval);
        break;

    case TYPE_FLOAT:
        {
            char buf[256];
            const char *ptr;
            double dx;
            n = r_byte(p);
            if (n == EOF) {
                PyErr_SetString(PyExc_EOFError,
                    "EOF read where object expected");
                break;
            }
            ptr = r_string(n, p);
            if (ptr == NULL)
                break;
            memcpy(buf, ptr, n);
            buf[n] = '\0';
            dx = PyOS_string_to_double(buf, NULL, NULL);
            if (dx == -1.0 && PyErr_Occurred())
                break;
            retval = PyFloat_FromDouble(dx);
            R_REF(retval);
            break;
        }

    case TYPE_BINARY_FLOAT:
        {
            const unsigned char *buf;
            double x;
            buf = (const unsigned char *) r_string(8, p);
            if (buf == NULL)
                break;
            x = _PyFloat_Unpack8(buf, 1);
            if (x == -1.0 && PyErr_Occurred())
                break;
            retval = PyFloat_FromDouble(x);
            R_REF(retval);
            break;
        }

    case TYPE_COMPLEX:
        {
            char buf[256];
            const char *ptr;
            Py_complex c;
            n = r_byte(p);
            if (n == EOF) {
                PyErr_SetString(PyExc_EOFError,
                    "EOF read where object expected");
                break;
            }
            ptr = r_string(n, p);
            if (ptr == NULL)
                break;
            memcpy(buf, ptr, n);
            buf[n] = '\0';
            c.real = PyOS_string_to_double(buf, NULL, NULL);
            if (c.real == -1.0 && PyErr_Occurred())
                break;
            n = r_byte(p);
            if (n == EOF) {
                PyErr_SetString(PyExc_EOFError,
                    "EOF read where object expected");
                break;
            }
            ptr = r_string(n, p);
            if (ptr == NULL)
                break;
            memcpy(buf, ptr, n);
            buf[n] = '\0';
            c.imag = PyOS_string_to_double(buf, NULL, NULL);
            if (c.imag == -1.0 && PyErr_Occurred())
                break;
            retval = PyComplex_FromCComplex(c);
            R_REF(retval);
            break;
        }

    case TYPE_BINARY_COMPLEX:
        {
            const unsigned char *buf;
            Py_complex c;
            buf = (const unsigned char *) r_string(8, p);
            if (buf == NULL)
                break;
            c.real = _PyFloat_Unpack8(buf, 1);
            if (c.real == -1.0 && PyErr_Occurred())
                break;
            buf = (const unsigned char *) r_string(8, p);
            if (buf == NULL)
                break;
            c.imag = _PyFloat_Unpack8(buf, 1);
            if (c.imag == -1.0 && PyErr_Occurred())
                break;
            retval = PyComplex_FromCComplex(c);
            R_REF(retval);
            break;
        }

    case TYPE_STRING:
        {
            const char *ptr;
            n = r_long(p);
            if (PyErr_Occurred())
                break;
            if (n < 0 || n > SIZE32_MAX) {
                PyErr_SetString(PyExc_ValueError, "bad marshal data (bytes object size out of range)");
                break;
            }
            v = PyBytes_FromStringAndSize((char *)NULL, n);
            if (v == NULL)
                break;
            ptr = r_string(n, p);
            if (ptr == NULL) {
                Py_DECREF(v);
                break;
            }
            memcpy(PyBytes_AS_STRING(v), ptr, n);
            retval = v;
            R_REF(retval);
            break;
        }

    case TYPE_ASCII_INTERNED:
        is_interned = 1;
        /* fall through */
    case TYPE_ASCII:
        n = r_long(p);
        if (PyErr_Occurred())
            break;
        if (n < 0 || n > SIZE32_MAX) {
            PyErr_SetString(PyExc_ValueError, "bad marshal data (string size out of range)");
            break;
        }
        goto _read_ascii;

    case TYPE_SHORT_ASCII_INTERNED:
        is_interned = 1;
        /* fall through */
    case TYPE_SHORT_ASCII:
        n = r_byte(p);
        if (n == EOF) {
            PyErr_SetString(PyExc_EOFError,
                "EOF read where object expected");
            break;
        }
    _read_ascii:
        {
            const char *ptr;
            ptr = r_string(n, p);
            if (ptr == NULL)
                break;
            v = PyUnicode_FromKindAndData(PyUnicode_1BYTE_KIND, ptr, n);
            if (v == NULL)
                break;
            if (is_interned)
                PyUnicode_InternInPlace(&v);
            retval = v;
            R_REF(retval);
            break;
        }

    case TYPE_INTERNED:
        is_interned = 1;
        /* fall through */
    case TYPE_UNICODE:
        {
        const char *buffer;

        n = r_long(p);
        if (PyErr_Occurred())
            break;
        if (n < 0 || n > SIZE32_MAX) {
            PyErr_SetString(PyExc_ValueError, "bad marshal data (string size out of range)");
            break;
        }
        if (n != 0) {
            buffer = r_string(n, p);
            if (buffer == NULL)
                break;
            v = PyUnicode_DecodeUTF8(buffer, n, "surrogatepass");
        }
        else {
            v = PyUnicode_New(0, 0);
        }
        if (v == NULL)
            break;
        if (is_interned)
            PyUnicode_InternInPlace(&v);
        retval = v;
        R_REF(retval);
        break;
        }

    case TYPE_SMALL_TUPLE:
        n = (unsigned char) r_byte(p);
        if (PyErr_Occurred())
            break;
        goto _read_tuple;
    case TYPE_TUPLE:
        n = r_long(p);
        if (PyErr_Occurred())
            break;
        if (n < 0 || n > SIZE32_MAX) {
            PyErr_SetString(PyExc_ValueError, "bad marshal data (tuple size out of range)");
            break;
        }
    _read_tuple:
        v = PyTuple_New(n);
        R_REF(v);
        if (v == NULL)
            break;

        for (i = 0; i < n; i++) {
            v2 = r_object(p);
            if ( v2 == NULL ) {
                if (!PyErr_Occurred())
                    PyErr_SetString(PyExc_TypeError,
                        "NULL object in marshal data for tuple");
                Py_DECREF(v);
                v = NULL;
                break;
            }
            PyTuple_SET_ITEM(v, i, v2);
        }
        retval = v;
        break;

    case TYPE_LIST:
        n = r_long(p);
        if (PyErr_Occurred())
            break;
        if (n < 0 || n > SIZE32_MAX) {
            PyErr_SetString(PyExc_ValueError, "bad marshal data (list size out of range)");
            break;
        }
        v = PyList_New(n);
        R_REF(v);
        if (v == NULL)
            break;
        for (i = 0; i < n; i++) {
            v2 = r_object(p);
            if ( v2 == NULL ) {
                if (!PyErr_Occurred())
                    PyErr_SetString(PyExc_TypeError,
                        "NULL object in marshal data for list");
                Py_DECREF(v);
                v = NULL;
                break;
            }
            PyList_SET_ITEM(v, i, v2);
        }
        retval = v;
        break;

    case TYPE_DICT:
        v = PyDict_New();
        R_REF(v);
        if (v == NULL)
            break;
        for (;;) {
            PyObject *key, *val;
            key = r_object(p);
            if (key == NULL)
                break;
            val = r_object(p);
            if (val == NULL) {
                Py_DECREF(key);
                break;
            }
            if (PyDict_SetItem(v, key, val) < 0) {
                Py_DECREF(key);
                Py_DECREF(val);
                break;
            }
            Py_DECREF(key);
            Py_DECREF(val);
        }
        if (PyErr_Occurred()) {
            Py_DECREF(v);
            v = NULL;
        }
        retval = v;
        break;

    case TYPE_SET:
    case TYPE_FROZENSET:
        n = r_long(p);
        if (PyErr_Occurred())
            break;
        if (n < 0 || n > SIZE32_MAX) {
            PyErr_SetString(PyExc_ValueError, "bad marshal data (set size out of range)");
            break;
        }

        if (n == 0 && type == TYPE_FROZENSET) {
            /* call frozenset() to get the empty frozenset singleton */
            v = PyObject_CallFunction((PyObject*)&PyFrozenSet_Type, NULL);
            if (v == NULL)
                break;
            R_REF(v);
            retval = v;
        }
        else {
            v = (type == TYPE_SET) ? PySet_New(NULL) : PyFrozenSet_New(NULL);
            if (type == TYPE_SET) {
                R_REF(v);
            } else {
                /* must use delayed registration of frozensets because they must
                 * be init with a refcount of 1
                 */
                idx = r_ref_reserve(flag, p);
                if (idx < 0)
                    Py_CLEAR(v); /* signal error */
            }
            if (v == NULL)
                break;

            for (i = 0; i < n; i++) {
                v2 = r_object(p);
                if ( v2 == NULL ) {
                    if (!PyErr_Occurred())
                        PyErr_SetString(PyExc_TypeError,
                            "NULL object in marshal data for set");
                    Py_DECREF(v);
                    v = NULL;
                    break;
                }
                if (PySet_Add(v, v2) == -1) {
                    Py_DECREF(v);
                    Py_DECREF(v2);
                    v = NULL;
                    break;
                }
                Py_DECREF(v2);
            }
            if (type != TYPE_SET)
                v = r_ref_insert(v, idx, flag, p);
            retval = v;
        }
        break;

    case TYPE_CODE:
        {
            int argcount;
            int kwonlyargcount;
            int nlocals;
            int stacksize;
            int flags;
            PyObject *code = NULL;
            PyObject *consts = NULL;
            PyObject *names = NULL;
            PyObject *varnames = NULL;
            PyObject *freevars = NULL;
            PyObject *cellvars = NULL;
            PyObject *filename = NULL;
            PyObject *name = NULL;
            int firstlineno;
            PyObject *lnotab = NULL;

            idx = r_ref_reserve(flag, p);
            if (idx < 0)
                break;

            v = NULL;

            /* XXX ignore long->int overflows for now */
            argcount = (int)r_long(p);
            if (PyErr_Occurred())
                goto code_error;
            kwonlyargcount = (int)r_long(p);
            if (PyErr_Occurred())
                goto code_error;
            nlocals = (int)r_long(p);
            if (PyErr_Occurred())
                goto code_error;
            stacksize = (int)r_long(p);
            if (PyErr_Occurred())
                goto code_error;
            flags = (int)r_long(p);
            if (PyErr_Occurred())
                goto code_error;
            code = r_object(p);
            if (code == NULL)
                goto code_error;
            consts = r_object(p);
            if (consts == NULL)
                goto code_error;
            names = r_object(p);
            if (names == NULL)
                goto code_error;
            varnames = r_object(p);
            if (varnames == NULL)
                goto code_error;
            freevars = r_object(p);
            if (freevars == NULL)
                goto code_error;
            cellvars = r_object(p);
            if (cellvars == NULL)
                goto code_error;
            filename = r_object(p);
            if (filename == NULL)
                goto code_error;
            if (PyUnicode_CheckExact(filename)) {
                if (p->current_filename != NULL) {
                    if (!PyUnicode_Compare(filename, p->current_filename)) {
                        Py_DECREF(filename);
                        Py_INCREF(p->current_filename);
                        filename = p->current_filename;
                    }
                }
                else {
                    p->current_filename = filename;
                }
            }
            name = r_object(p);
            if (name == NULL)
                goto code_error;
            firstlineno = (int)r_long(p);
            if (firstlineno == -1 && PyErr_Occurred())
                break;
            lnotab = r_object(p);
            if (lnotab == NULL)
                goto code_error;

            v = (PyObject *) PyCode_New(
                            argcount, kwonlyargcount,
                            nlocals, stacksize, flags,
                            code, consts, names, varnames,
                            freevars, cellvars, filename, name,
                            firstlineno, lnotab);
            v = r_ref_insert(v, idx, flag, p);

          code_error:
            Py_XDECREF(code);
            Py_XDECREF(consts);
            Py_XDECREF(names);
            Py_XDECREF(varnames);
            Py_XDECREF(freevars);
            Py_XDECREF(cellvars);
            Py_XDECREF(filename);
            Py_XDECREF(name);
            Py_XDECREF(lnotab);
        }
        retval = v;
        break;

    case TYPE_REF:
        n = r_long(p);
        if (n < 0 || n >= PyList_GET_SIZE(p->refs)) {
            if (n == -1 && PyErr_Occurred())
                break;
            PyErr_SetString(PyExc_ValueError, "bad marshal data (invalid reference)");
            break;
        }
        v = PyList_GET_ITEM(p->refs, n);
        if (v == Py_None) {
            PyErr_SetString(PyExc_ValueError, "bad marshal data (invalid reference)");
            break;
        }
        Py_INCREF(v);
        retval = v;
        break;

    default:
        /* Bogus data got written, which isn't ideal.
           This will let you keep working and recover. */
        PyErr_SetString(PyExc_ValueError, "bad marshal data (unknown type code)");
        break;

    }
    p->depth--;
    return retval;
}

static PyObject *
read_object(RFILE *p)
{
    PyObject *v;
    if (PyErr_Occurred()) {
        fprintf(stderr, "XXX readobject called with exception set\n");
        return NULL;
    }
    v = r_object(p);
    if (v == NULL && !PyErr_Occurred())
        PyErr_SetString(PyExc_TypeError, "NULL object in marshal data for object");
    return v;
}

int
PyMarshal_ReadShortFromFile(FILE *fp)
{
    RFILE rf;
    int res;
    assert(fp);
    rf.readable = NULL;
    rf.fp = fp;
    rf.current_filename = NULL;
    rf.end = rf.ptr = NULL;
    rf.buf = NULL;
    res = r_short(&rf);
    if (rf.buf != NULL)
        PyMem_FREE(rf.buf);
    return res;
}

long
PyMarshal_ReadLongFromFile(FILE *fp)
{
    RFILE rf;
    long res;
    rf.fp = fp;
    rf.readable = NULL;
    rf.current_filename = NULL;
    rf.ptr = rf.end = NULL;
    rf.buf = NULL;
    res = r_long(&rf);
    if (rf.buf != NULL)
        PyMem_FREE(rf.buf);
    return res;
}

/* Return size of file in bytes; < 0 if unknown or INT_MAX if too big */
static off_t
getfilesize(FILE *fp)
{
    struct _Py_stat_struct st;
    if (_Py_fstat_noraise(fileno(fp), &st) != 0)
        return -1;
#if SIZEOF_OFF_T == 4
    else if (st.st_size >= INT_MAX)
        return (off_t)INT_MAX;
#endif
    else
        return (off_t)st.st_size;
}

/* If we can get the size of the file up-front, and it's reasonably small,
 * read it in one gulp and delegate to ...FromString() instead.  Much quicker
 * than reading a byte at a time from file; speeds .pyc imports.
 * CAUTION:  since this may read the entire remainder of the file, don't
 * call it unless you know you're done with the file.
 */
PyObject *
PyMarshal_ReadLastObjectFromFile(FILE *fp)
{
/* REASONABLE_FILE_LIMIT is by defn something big enough for Tkinter.pyc. */
#define REASONABLE_FILE_LIMIT (1L << 18)
    off_t filesize;
    filesize = getfilesize(fp);
    if (filesize > 0 && filesize <= REASONABLE_FILE_LIMIT) {
        char* pBuf = (char *)PyMem_MALLOC(filesize);
        if (pBuf != NULL) {
            size_t n = fread(pBuf, 1, (size_t)filesize, fp);
            PyObject* v = PyMarshal_ReadObjectFromString(pBuf, n);
            PyMem_FREE(pBuf);
            return v;
        }

    }
    /* We don't have fstat, or we do but the file is larger than
     * REASONABLE_FILE_LIMIT or malloc failed -- read a byte at a time.
     */
    return PyMarshal_ReadObjectFromFile(fp);

#undef REASONABLE_FILE_LIMIT
}

PyObject *
PyMarshal_ReadObjectFromFile(FILE *fp)
{
    RFILE rf;
    PyObject *result;
    rf.fp = fp;
    rf.readable = NULL;
    rf.current_filename = NULL;
    rf.depth = 0;
    rf.ptr = rf.end = NULL;
    rf.buf = NULL;
    rf.refs = PyList_New(0);
    if (rf.refs == NULL)
        return NULL;
    result = r_object(&rf);
    Py_DECREF(rf.refs);
    if (rf.buf != NULL)
        PyMem_FREE(rf.buf);
    return result;
}

PyObject *
PyMarshal_ReadObjectFromString(const char *str, Py_ssize_t len)
{
    RFILE rf;
    PyObject *result;
    rf.fp = NULL;
    rf.readable = NULL;
    rf.current_filename = NULL;
    rf.ptr = (char *)str;
    rf.end = (char *)str + len;
    rf.buf = NULL;
    rf.depth = 0;
    rf.refs = PyList_New(0);
    if (rf.refs == NULL)
        return NULL;
    result = r_object(&rf);
    Py_DECREF(rf.refs);
    if (rf.buf != NULL)
        PyMem_FREE(rf.buf);
    return result;
}

PyObject *
PyMarshal_WriteObjectToString(PyObject *x, int version)
{
    WFILE wf;

    memset(&wf, 0, sizeof(wf));
    wf.str = PyBytes_FromStringAndSize((char *)NULL, 50);
    if (wf.str == NULL)
        return NULL;
    wf.ptr = wf.buf = PyBytes_AS_STRING((PyBytesObject *)wf.str);
    wf.end = wf.ptr + PyBytes_Size(wf.str);
    wf.error = WFERR_OK;
    wf.version = version;
    if (w_init_refs(&wf, version)) {
        Py_DECREF(wf.str);
        return NULL;
    }
    w_object(x, &wf);
    w_clear_refs(&wf);
    if (wf.str != NULL) {
        char *base = PyBytes_AS_STRING((PyBytesObject *)wf.str);
        if (wf.ptr - base > PY_SSIZE_T_MAX) {
            Py_DECREF(wf.str);
            PyErr_SetString(PyExc_OverflowError,
                            "too much marshal data for a bytes object");
            return NULL;
        }
        if (_PyBytes_Resize(&wf.str, (Py_ssize_t)(wf.ptr - base)) < 0)
            return NULL;
    }
    if (wf.error != WFERR_OK) {
        Py_XDECREF(wf.str);
        if (wf.error == WFERR_NOMEMORY)
            PyErr_NoMemory();
        else
            PyErr_SetString(PyExc_ValueError,
              (wf.error==WFERR_UNMARSHALLABLE)?"unmarshallable object"
               :"object too deeply nested to marshal");
        return NULL;
    }
    return wf.str;
}

/* And an interface for Python programs... */

static PyObject *
marshal_dump(PyObject *self, PyObject *args)
{
    /* XXX Quick hack -- need to do this differently */
    PyObject *x;
    PyObject *f;
    int version = Py_MARSHAL_VERSION;
    PyObject *s;
    PyObject *res;
    _Py_IDENTIFIER(write);

    if (!PyArg_ParseTuple(args, "OO|i:dump", &x, &f, &version))
        return NULL;
    s = PyMarshal_WriteObjectToString(x, version);
    if (s == NULL)
        return NULL;
    res = _PyObject_CallMethodId(f, &PyId_write, "O", s);
    Py_DECREF(s);
    return res;
}

PyDoc_STRVAR(dump_doc,
"dump(value, file[, version])\n\
\n\
Write the value on the open file. The value must be a supported type.\n\
The file must be a writeable binary file.\n\
\n\
If the value has (or contains an object that has) an unsupported type, a\n\
ValueError exception is raised - but garbage data will also be written\n\
to the file. The object will not be properly read back by load()\n\
\n\
The version argument indicates the data format that dump should use.");

static PyObject *
marshal_load(PyObject *self, PyObject *f)
{
    PyObject *data, *result;
    _Py_IDENTIFIER(read);
    RFILE rf;

    /*
     * Make a call to the read method, but read zero bytes.
     * This is to ensure that the object passed in at least
     * has a read method which returns bytes.
     * This can be removed if we guarantee good error handling
     * for r_string()
     */
    data = _PyObject_CallMethodId(f, &PyId_read, "i", 0);
    if (data == NULL)
        return NULL;
    if (!PyBytes_Check(data)) {
        PyErr_Format(PyExc_TypeError,
                     "f.read() returned not bytes but %.100s",
                     data->ob_type->tp_name);
        result = NULL;
    }
    else {
        rf.depth = 0;
        rf.fp = NULL;
        rf.readable = f;
        rf.current_filename = NULL;
        rf.ptr = rf.end = NULL;
        rf.buf = NULL;
        if ((rf.refs = PyList_New(0)) != NULL) {
            result = read_object(&rf);
            Py_DECREF(rf.refs);
            if (rf.buf != NULL)
                PyMem_FREE(rf.buf);
        } else
            result = NULL;
    }
    Py_DECREF(data);
    return result;
}

PyDoc_STRVAR(load_doc,
"load(file)\n\
\n\
Read one value from the open file and return it. If no valid value is\n\
read (e.g. because the data has a different Python version's\n\
incompatible marshal format), raise EOFError, ValueError or TypeError.\n\
The file must be a readable binary file.\n\
\n\
Note: If an object containing an unsupported type was marshalled with\n\
dump(), load() will substitute None for the unmarshallable type.");


static PyObject *
marshal_dumps(PyObject *self, PyObject *args)
{
    PyObject *x;
    int version = Py_MARSHAL_VERSION;
    if (!PyArg_ParseTuple(args, "O|i:dumps", &x, &version))
        return NULL;
    return PyMarshal_WriteObjectToString(x, version);
}

PyDoc_STRVAR(dumps_doc,
"dumps(value[, version])\n\
\n\
Return the bytes object that would be written to a file by dump(value, file).\n\
The value must be a supported type. Raise a ValueError exception if\n\
value has (or contains an object that has) an unsupported type.\n\
\n\
The version argument indicates the data format that dumps should use.");


static PyObject *
marshal_loads(PyObject *self, PyObject *args)
{
    RFILE rf;
    Py_buffer p;
    char *s;
    Py_ssize_t n;
    PyObject* result;
    if (!PyArg_ParseTuple(args, "y*:loads", &p))
        return NULL;
    s = p.buf;
    n = p.len;
    rf.fp = NULL;
    rf.readable = NULL;
    rf.current_filename = NULL;
    rf.ptr = s;
    rf.end = s + n;
    rf.depth = 0;
    if ((rf.refs = PyList_New(0)) == NULL)
        return NULL;
    result = read_object(&rf);
    PyBuffer_Release(&p);
    Py_DECREF(rf.refs);
    return result;
}

PyDoc_STRVAR(loads_doc,
"loads(bytes)\n\
\n\
Convert the bytes-like object to a value. If no valid value is found,\n\
raise EOFError, ValueError or TypeError. Extra bytes in the input are\n\
ignored.");

static PyMethodDef marshal_methods[] = {
    {"dump",            marshal_dump,   METH_VARARGS,   dump_doc},
    {"load",            marshal_load,   METH_O,         load_doc},
    {"dumps",           marshal_dumps,  METH_VARARGS,   dumps_doc},
    {"loads",           marshal_loads,  METH_VARARGS,   loads_doc},
    {NULL,              NULL}           /* sentinel */
};


PyDoc_STRVAR(module_doc,
"This module contains functions that can read and write Python values in\n\
a binary format. The format is specific to Python, but independent of\n\
machine architecture issues.\n\
\n\
Not all Python object types are supported; in general, only objects\n\
whose value is independent from a particular invocation of Python can be\n\
written and read by this module. The following types are supported:\n\
None, integers, floating point numbers, strings, bytes, bytearrays,\n\
tuples, lists, sets, dictionaries, and code objects, where it\n\
should be understood that tuples, lists and dictionaries are only\n\
supported as long as the values contained therein are themselves\n\
supported; and recursive lists and dictionaries should not be written\n\
(they will cause infinite loops).\n\
\n\
Variables:\n\
\n\
version -- indicates the format that the module uses. Version 0 is the\n\
    historical format, version 1 shares interned strings and version 2\n\
    uses a binary format for floating point numbers.\n\
    Version 3 shares common object references (New in version 3.4).\n\
\n\
Functions:\n\
\n\
dump() -- write value to a file\n\
load() -- read value from a file\n\
dumps() -- marshal value as a bytes object\n\
loads() -- read value from a bytes-like object");


static struct PyModuleDef marshalmodule = {
    PyModuleDef_HEAD_INIT,
    "marshal",
    module_doc,
    0,
    marshal_methods,
    NULL,
    NULL,
    NULL,
    NULL
};

PyMODINIT_FUNC
PyMarshal_Init(void)
{
    PyObject *mod = PyModule_Create(&marshalmodule);
    if (mod == NULL)
        return NULL;
    PyModule_AddIntConstant(mod, "version", Py_MARSHAL_VERSION);
    return mod;
}