cpython/Objects/fileobject.c

/***********************************************************
Copyright (c) 2000, BeOpen.com.
Copyright (c) 1995-2000, Corporation for National Research Initiatives.
Copyright (c) 1990-1995, Stichting Mathematisch Centrum.
All rights reserved.

See the file "Misc/COPYRIGHT" for information on usage and
redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
******************************************************************/

/* File object implementation */

#include "Python.h"
#include "structmember.h"

#ifndef DONT_HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif /* DONT_HAVE_SYS_TYPES_H */

/* We expect that fstat exists on most systems.
   It's confirmed on Unix, Mac and Windows.
   If you don't have it, add #define DONT_HAVE_FSTAT to your config.h. */
#ifndef DONT_HAVE_FSTAT
#define HAVE_FSTAT

#ifndef DONT_HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

#ifndef DONT_HAVE_SYS_STAT_H
#include <sys/stat.h>
#else
#ifdef HAVE_STAT_H
#include <stat.h>
#endif
#endif

#endif /* DONT_HAVE_FSTAT */

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef MS_WIN32
#define ftruncate _chsize
#define fileno _fileno
#define HAVE_FTRUNCATE
#endif

#ifdef macintosh
#ifdef USE_GUSI
#define HAVE_FTRUNCATE
#endif
#endif

#ifdef __MWERKS__
/* Mwerks fopen() doesn't always set errno */
#define NO_FOPEN_ERRNO
#endif

#define BUF(v) PyString_AS_STRING((PyStringObject *)v)

#ifndef DONT_HAVE_ERRNO_H
#include <errno.h>
#endif

typedef struct {
	PyObject_HEAD
	FILE *f_fp;
	PyObject *f_name;
	PyObject *f_mode;
	int (*f_close)(FILE *);
	int f_softspace; /* Flag used by 'print' command */
	int f_binary; /* Flag which indicates whether the file is open
			 open in binary (1) or test (0) mode */
} PyFileObject;

FILE *
PyFile_AsFile(f)
	PyObject *f;
{
	if (f == NULL || !PyFile_Check(f))
		return NULL;
	else
		return ((PyFileObject *)f)->f_fp;
}

PyObject *
PyFile_Name(f)
	PyObject *f;
{
	if (f == NULL || !PyFile_Check(f))
		return NULL;
	else
		return ((PyFileObject *)f)->f_name;
}

PyObject *
PyFile_FromFile(fp, name, mode, close)
	FILE *fp;
	char *name;
	char *mode;
	int (*close)(FILE *);
{
	PyFileObject *f = PyObject_NEW(PyFileObject, &PyFile_Type);
	if (f == NULL)
		return NULL;
	f->f_fp = NULL;
	f->f_name = PyString_FromString(name);
	f->f_mode = PyString_FromString(mode);
	f->f_close = close;
	f->f_softspace = 0;
	if (strchr(mode,'b') != NULL)
	    f->f_binary = 1;
	else
	    f->f_binary = 0;
	if (f->f_name == NULL || f->f_mode == NULL) {
		Py_DECREF(f);
		return NULL;
	}
	f->f_fp = fp;
	return (PyObject *) f;
}

PyObject *
PyFile_FromString(name, mode)
	char *name, *mode;
{
	extern int fclose(FILE *);
	PyFileObject *f;
	f = (PyFileObject *) PyFile_FromFile((FILE *)NULL, name, mode, fclose);
	if (f == NULL)
		return NULL;
#ifdef HAVE_FOPENRF
	if (*mode == '*') {
		FILE *fopenRF();
		f->f_fp = fopenRF(name, mode+1);
	}
	else
#endif
	{
		Py_BEGIN_ALLOW_THREADS
		f->f_fp = fopen(name, mode);
		Py_END_ALLOW_THREADS
	}
	if (f->f_fp == NULL) {
#ifdef NO_FOPEN_ERRNO
		/* Metroworks only, not testable, so unchanged */
		if ( errno == 0 ) {
			PyErr_SetString(PyExc_IOError, "Cannot open file");
			Py_DECREF(f);
			return NULL;
		}
#endif
		PyErr_SetFromErrnoWithFilename(PyExc_IOError, name);
		Py_DECREF(f);
		return NULL;
	}
	return (PyObject *)f;
}

void
PyFile_SetBufSize(f, bufsize)
	PyObject *f;
	int bufsize;
{
	if (bufsize >= 0) {
#ifdef HAVE_SETVBUF
		int type;
		switch (bufsize) {
		case 0:
			type = _IONBF;
			break;
		case 1:
			type = _IOLBF;
			bufsize = BUFSIZ;
			break;
		default:
			type = _IOFBF;
		}
		setvbuf(((PyFileObject *)f)->f_fp, (char *)NULL,
			type, bufsize);
#else /* !HAVE_SETVBUF */
		if (bufsize <= 1)
			setbuf(((PyFileObject *)f)->f_fp, (char *)NULL);
#endif /* !HAVE_SETVBUF */
	}
}

static PyObject *
err_closed()
{
	PyErr_SetString(PyExc_ValueError, "I/O operation on closed file");
	return NULL;
}

/* Methods */

static void
file_dealloc(f)
	PyFileObject *f;
{
	if (f->f_fp != NULL && f->f_close != NULL) {
		Py_BEGIN_ALLOW_THREADS
		(*f->f_close)(f->f_fp);
		Py_END_ALLOW_THREADS
	}
	if (f->f_name != NULL) {
		Py_DECREF(f->f_name);
	}
	if (f->f_mode != NULL) {
		Py_DECREF(f->f_mode);
	}
	PyObject_DEL(f);
}

static PyObject *
file_repr(f)
	PyFileObject *f;
{
	char buf[300];
	sprintf(buf, "<%s file '%.256s', mode '%.10s' at %p>",
		f->f_fp == NULL ? "closed" : "open",
		PyString_AsString(f->f_name),
		PyString_AsString(f->f_mode),
		f);
	return PyString_FromString(buf);
}

static PyObject *
file_close(f, args)
	PyFileObject *f;
	PyObject *args;
{
	int sts = 0;
	if (!PyArg_NoArgs(args))
		return NULL;
	if (f->f_fp != NULL) {
		if (f->f_close != NULL) {
			Py_BEGIN_ALLOW_THREADS
			errno = 0;
			sts = (*f->f_close)(f->f_fp);
			Py_END_ALLOW_THREADS
		}
		f->f_fp = NULL;
	}
	if (sts == EOF)
		return PyErr_SetFromErrno(PyExc_IOError);
	if (sts != 0)
		return PyInt_FromLong((long)sts);
	Py_INCREF(Py_None);
	return Py_None;
}

static PyObject *
file_seek(f, args)
	PyFileObject *f;
	PyObject *args;
{
	int whence;
	int ret;
	off_t offset;
	PyObject *offobj;
	
	if (f->f_fp == NULL)
		return err_closed();
	whence = 0;
	if (!PyArg_ParseTuple(args, "O|i:seek", &offobj, &whence))
		return NULL;
#if !defined(HAVE_LARGEFILE_SUPPORT)
	offset = PyInt_AsLong(offobj);
#else
	offset = PyLong_Check(offobj) ?
		PyLong_AsLongLong(offobj) : PyInt_AsLong(offobj);
#endif
	if (PyErr_Occurred())
		return NULL;
	Py_BEGIN_ALLOW_THREADS
	errno = 0;
#if defined(HAVE_FSEEKO)
	ret = fseeko(f->f_fp, offset, whence);
#elif defined(HAVE_FSEEK64)
	ret = fseek64(f->f_fp, offset, whence);
#else
	ret = fseek(f->f_fp, offset, whence);
#endif
	Py_END_ALLOW_THREADS
	if (ret != 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		clearerr(f->f_fp);
		return NULL;
	}
	Py_INCREF(Py_None);
	return Py_None;
}

#ifdef HAVE_FTRUNCATE
static PyObject *
file_truncate(f, args)
	PyFileObject *f;
	PyObject *args;
{
	int ret;
	off_t newsize;
	PyObject *newsizeobj;
	
	if (f->f_fp == NULL)
		return err_closed();
	newsizeobj = NULL;
	if (!PyArg_ParseTuple(args, "|O:truncate", &newsizeobj))
		return NULL;
	if (newsizeobj != NULL) {
#if !defined(HAVE_LARGEFILE_SUPPORT)
		newsize = PyInt_AsLong(newsizeobj);
#else
		newsize = PyLong_Check(newsizeobj) ?
				PyLong_AsLongLong(newsizeobj) :
				PyInt_AsLong(newsizeobj);
#endif
		if (PyErr_Occurred())
			return NULL;
	} else {
		/* Default to current position*/
		Py_BEGIN_ALLOW_THREADS
		errno = 0;
#if defined(HAVE_FTELLO) && defined(HAVE_LARGEFILE_SUPPORT)
		newsize =  ftello(f->f_fp);
#elif defined(HAVE_FTELL64) && defined(HAVE_LARGEFILE_SUPPORT)
		newsize =  ftell64(f->f_fp);
#else
		newsize =  ftell(f->f_fp);
#endif
		Py_END_ALLOW_THREADS
		if (newsize == -1) {
		        PyErr_SetFromErrno(PyExc_IOError);
			clearerr(f->f_fp);
			return NULL;
		}
	}
	Py_BEGIN_ALLOW_THREADS
	errno = 0;
	ret = fflush(f->f_fp);
	Py_END_ALLOW_THREADS
	if (ret == 0) {
	        Py_BEGIN_ALLOW_THREADS
		errno = 0;
		ret = ftruncate(fileno(f->f_fp), newsize);
		Py_END_ALLOW_THREADS
	}
	if (ret != 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		clearerr(f->f_fp);
		return NULL;
	}
	Py_INCREF(Py_None);
	return Py_None;
}
#endif /* HAVE_FTRUNCATE */

static PyObject *
file_tell(f, args)
	PyFileObject *f;
	PyObject *args;
{
	off_t offset;
	if (f->f_fp == NULL)
		return err_closed();
	if (!PyArg_NoArgs(args))
		return NULL;
	Py_BEGIN_ALLOW_THREADS
	errno = 0;
#if defined(HAVE_FTELLO) && defined(HAVE_LARGEFILE_SUPPORT)
	offset = ftello(f->f_fp);
#elif defined(HAVE_FTELL64) && defined(HAVE_LARGEFILE_SUPPORT)
	offset = ftell64(f->f_fp);
#else
	offset = ftell(f->f_fp);
#endif
	Py_END_ALLOW_THREADS
	if (offset == -1) {
		PyErr_SetFromErrno(PyExc_IOError);
		clearerr(f->f_fp);
		return NULL;
	}
#if !defined(HAVE_LARGEFILE_SUPPORT)
	return PyInt_FromLong(offset);
#else
	return PyLong_FromLongLong(offset);
#endif
}

static PyObject *
file_fileno(f, args)
	PyFileObject *f;
	PyObject *args;
{
	if (f->f_fp == NULL)
		return err_closed();
	if (!PyArg_NoArgs(args))
		return NULL;
	return PyInt_FromLong((long) fileno(f->f_fp));
}

static PyObject *
file_flush(f, args)
	PyFileObject *f;
	PyObject *args;
{
	int res;
	
	if (f->f_fp == NULL)
		return err_closed();
	if (!PyArg_NoArgs(args))
		return NULL;
	Py_BEGIN_ALLOW_THREADS
	errno = 0;
	res = fflush(f->f_fp);
	Py_END_ALLOW_THREADS
	if (res != 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		clearerr(f->f_fp);
		return NULL;
	}
	Py_INCREF(Py_None);
	return Py_None;
}

static PyObject *
file_isatty(f, args)
	PyFileObject *f;
	PyObject *args;
{
	long res;
	if (f->f_fp == NULL)
		return err_closed();
	if (!PyArg_NoArgs(args))
		return NULL;
	Py_BEGIN_ALLOW_THREADS
	res = isatty((int)fileno(f->f_fp));
	Py_END_ALLOW_THREADS
	return PyInt_FromLong(res);
}


#if BUFSIZ < 8192
#define SMALLCHUNK 8192
#else
#define SMALLCHUNK BUFSIZ
#endif

#if SIZEOF_INT < 4
#define BIGCHUNK  (512 * 32)
#else
#define BIGCHUNK  (512 * 1024)
#endif

static size_t
new_buffersize(f, currentsize)
	PyFileObject *f;
	size_t currentsize;
{
#ifdef HAVE_FSTAT
	long pos, end;
	struct stat st;
	if (fstat(fileno(f->f_fp), &st) == 0) {
		end = st.st_size;
		/* The following is not a bug: we really need to call lseek()
		   *and* ftell().  The reason is that some stdio libraries
		   mistakenly flush their buffer when ftell() is called and
		   the lseek() call it makes fails, thereby throwing away
		   data that cannot be recovered in any way.  To avoid this,
		   we first test lseek(), and only call ftell() if lseek()
		   works.  We can't use the lseek() value either, because we
		   need to take the amount of buffered data into account.
		   (Yet another reason why stdio stinks. :-) */
		pos = lseek(fileno(f->f_fp), 0L, SEEK_CUR);
		if (pos >= 0)
			pos = ftell(f->f_fp);
		if (pos < 0)
			clearerr(f->f_fp);
		if (end > pos && pos >= 0)
			return currentsize + end - pos + 1;
		/* Add 1 so if the file were to grow we'd notice. */
	}
#endif
	if (currentsize > SMALLCHUNK) {
		/* Keep doubling until we reach BIGCHUNK;
		   then keep adding BIGCHUNK. */
		if (currentsize <= BIGCHUNK)
			return currentsize + currentsize;
		else
			return currentsize + BIGCHUNK;
	}
	return currentsize + SMALLCHUNK;
}

static PyObject *
file_read(f, args)
	PyFileObject *f;
	PyObject *args;
{
	long bytesrequested = -1;
	size_t bytesread, buffersize, chunksize;
	PyObject *v;
	
	if (f->f_fp == NULL)
		return err_closed();
	if (!PyArg_ParseTuple(args, "|l:read", &bytesrequested))
		return NULL;
	if (bytesrequested < 0)
		buffersize = new_buffersize(f, (size_t)0);
	else
		buffersize = bytesrequested;
	v = PyString_FromStringAndSize((char *)NULL, buffersize);
	if (v == NULL)
		return NULL;
	bytesread = 0;
	for (;;) {
		Py_BEGIN_ALLOW_THREADS
		errno = 0;
		chunksize = fread(BUF(v) + bytesread, 1,
				  buffersize - bytesread, f->f_fp);
		Py_END_ALLOW_THREADS
		if (chunksize == 0) {
			if (!ferror(f->f_fp))
				break;
			PyErr_SetFromErrno(PyExc_IOError);
			clearerr(f->f_fp);
			Py_DECREF(v);
			return NULL;
		}
		bytesread += chunksize;
		if (bytesread < buffersize)
			break;
		if (bytesrequested < 0) {
			buffersize = new_buffersize(f, buffersize);
			if (_PyString_Resize(&v, buffersize) < 0)
				return NULL;
		}
	}
	if (bytesread != buffersize)
		_PyString_Resize(&v, bytesread);
	return v;
}

static PyObject *
file_readinto(f, args)
	PyFileObject *f;
	PyObject *args;
{
	char *ptr;
	int ntodo, ndone, nnow;
	
	if (f->f_fp == NULL)
		return err_closed();
	if (!PyArg_Parse(args, "w#", &ptr, &ntodo))
		return NULL;
	ndone = 0;
	while (ntodo > 0) {
		Py_BEGIN_ALLOW_THREADS
		errno = 0;
		nnow = fread(ptr+ndone, 1, ntodo, f->f_fp);
		Py_END_ALLOW_THREADS
		if (nnow == 0) {
			if (!ferror(f->f_fp))
				break;
			PyErr_SetFromErrno(PyExc_IOError);
			clearerr(f->f_fp);
			return NULL;
		}
		ndone += nnow;
		ntodo -= nnow;
	}
	return PyInt_FromLong(ndone);
}


/* Internal routine to get a line.
   Size argument interpretation:
   > 0: max length;
   = 0: read arbitrary line;
   < 0: strip trailing '\n', raise EOFError if EOF reached immediately
*/

static PyObject *
get_line(f, n)
	PyFileObject *f;
	int n;
{
	register FILE *fp;
	register int c;
	register char *buf, *end;
	int n1, n2;
	PyObject *v;

	fp = f->f_fp;
	n2 = n > 0 ? n : 100;
	v = PyString_FromStringAndSize((char *)NULL, n2);
	if (v == NULL)
		return NULL;
	buf = BUF(v);
	end = buf + n2;

	Py_BEGIN_ALLOW_THREADS
	for (;;) {
		if ((c = getc(fp)) == EOF) {
			clearerr(fp);
			Py_BLOCK_THREADS
			if (PyErr_CheckSignals()) {
				Py_DECREF(v);
				return NULL;
			}
			if (n < 0 && buf == BUF(v)) {
				Py_DECREF(v);
				PyErr_SetString(PyExc_EOFError,
					   "EOF when reading a line");
				return NULL;
			}
			Py_UNBLOCK_THREADS
			break;
		}
		if ((*buf++ = c) == '\n') {
			if (n < 0)
				buf--;
			break;
		}
		if (buf == end) {
			if (n > 0)
				break;
			n1 = n2;
			n2 += 1000;
			Py_BLOCK_THREADS
			if (_PyString_Resize(&v, n2) < 0)
				return NULL;
			Py_UNBLOCK_THREADS
			buf = BUF(v) + n1;
			end = BUF(v) + n2;
		}
	}
	Py_END_ALLOW_THREADS

	n1 = buf - BUF(v);
	if (n1 != n2)
		_PyString_Resize(&v, n1);
	return v;
}

/* External C interface */

PyObject *
PyFile_GetLine(f, n)
	PyObject *f;
	int n;
{
	if (f == NULL) {
		PyErr_BadInternalCall();
		return NULL;
	}
	if (!PyFile_Check(f)) {
		PyObject *reader;
		PyObject *args;
		PyObject *result;
		reader = PyObject_GetAttrString(f, "readline");
		if (reader == NULL)
			return NULL;
		if (n <= 0)
			args = Py_BuildValue("()");
		else
			args = Py_BuildValue("(i)", n);
		if (args == NULL) {
			Py_DECREF(reader);
			return NULL;
		}
		result = PyEval_CallObject(reader, args);
		Py_DECREF(reader);
		Py_DECREF(args);
		if (result != NULL && !PyString_Check(result)) {
			Py_DECREF(result);
			result = NULL;
			PyErr_SetString(PyExc_TypeError,
				   "object.readline() returned non-string");
		}
		if (n < 0 && result != NULL) {
			char *s = PyString_AsString(result);
			int len = PyString_Size(result);
			if (len == 0) {
				Py_DECREF(result);
				result = NULL;
				PyErr_SetString(PyExc_EOFError,
					   "EOF when reading a line");
			}
			else if (s[len-1] == '\n') {
				if (result->ob_refcnt == 1)
					_PyString_Resize(&result, len-1);
				else {
					PyObject *v;
					v = PyString_FromStringAndSize(s,
								       len-1);
					Py_DECREF(result);
					result = v;
				}
			}
		}
		return result;
	}
	if (((PyFileObject*)f)->f_fp == NULL)
		return err_closed();
	return get_line((PyFileObject *)f, n);
}

/* Python method */

static PyObject *
file_readline(f, args)
	PyFileObject *f;
	PyObject *args;
{
	int n = -1;

	if (f->f_fp == NULL)
		return err_closed();
	if (!PyArg_ParseTuple(args, "|i:readline", &n))
		return NULL;
	if (n == 0)
		return PyString_FromString("");
	if (n < 0)
		n = 0;
	return get_line(f, n);
}

static PyObject *
file_readlines(f, args)
	PyFileObject *f;
	PyObject *args;
{
	long sizehint = 0;
	PyObject *list;
	PyObject *line;
	char small_buffer[SMALLCHUNK];
	char *buffer = small_buffer;
	size_t buffersize = SMALLCHUNK;
	PyObject *big_buffer = NULL;
	size_t nfilled = 0;
	size_t nread;
	size_t totalread = 0;
	char *p, *q, *end;
	int err;

	if (f->f_fp == NULL)
		return err_closed();
	if (!PyArg_ParseTuple(args, "|l:readlines", &sizehint))
		return NULL;
	if ((list = PyList_New(0)) == NULL)
		return NULL;
	for (;;) {
		Py_BEGIN_ALLOW_THREADS
		errno = 0;
		nread = fread(buffer+nfilled, 1, buffersize-nfilled, f->f_fp);
		Py_END_ALLOW_THREADS
		if (nread == 0) {
			sizehint = 0;
			if (!ferror(f->f_fp))
				break;
			PyErr_SetFromErrno(PyExc_IOError);
			clearerr(f->f_fp);
		  error:
			Py_DECREF(list);
			list = NULL;
			goto cleanup;
		}
		totalread += nread;
		p = memchr(buffer+nfilled, '\n', nread);
		if (p == NULL) {
			/* Need a larger buffer to fit this line */
			nfilled += nread;
			buffersize *= 2;
			if (big_buffer == NULL) {
				/* Create the big buffer */
				big_buffer = PyString_FromStringAndSize(
					NULL, buffersize);
				if (big_buffer == NULL)
					goto error;
				buffer = PyString_AS_STRING(big_buffer);
				memcpy(buffer, small_buffer, nfilled);
			}
			else {
				/* Grow the big buffer */
				_PyString_Resize(&big_buffer, buffersize);
				buffer = PyString_AS_STRING(big_buffer);
			}
			continue;
		}
		end = buffer+nfilled+nread;
		q = buffer;
		do {
			/* Process complete lines */
			p++;
			line = PyString_FromStringAndSize(q, p-q);
			if (line == NULL)
				goto error;
			err = PyList_Append(list, line);
			Py_DECREF(line);
			if (err != 0)
				goto error;
			q = p;
			p = memchr(q, '\n', end-q);
		} while (p != NULL);
		/* Move the remaining incomplete line to the start */
		nfilled = end-q;
		memmove(buffer, q, nfilled);
		if (sizehint > 0)
			if (totalread >= (size_t)sizehint)
				break;
	}
	if (nfilled != 0) {
		/* Partial last line */
		line = PyString_FromStringAndSize(buffer, nfilled);
		if (line == NULL)
			goto error;
		if (sizehint > 0) {
			/* Need to complete the last line */
			PyObject *rest = get_line(f, 0);
			if (rest == NULL) {
				Py_DECREF(line);
				goto error;
			}
			PyString_Concat(&line, rest);
			Py_DECREF(rest);
			if (line == NULL)
				goto error;
		}
		err = PyList_Append(list, line);
		Py_DECREF(line);
		if (err != 0)
			goto error;
	}
  cleanup:
	if (big_buffer) {
		Py_DECREF(big_buffer);
	}
	return list;
}

static PyObject *
file_write(f, args)
	PyFileObject *f;
	PyObject *args;
{
	char *s;
	int n, n2;
	if (f->f_fp == NULL)
		return err_closed();
	if (!PyArg_Parse(args, f->f_binary ? "s#" : "t#", &s, &n))
		return NULL;
	f->f_softspace = 0;
	Py_BEGIN_ALLOW_THREADS
	errno = 0;
	n2 = fwrite(s, 1, n, f->f_fp);
	Py_END_ALLOW_THREADS
	if (n2 != n) {
		PyErr_SetFromErrno(PyExc_IOError);
		clearerr(f->f_fp);
		return NULL;
	}
	Py_INCREF(Py_None);
	return Py_None;
}

static PyObject *
file_writelines(f, args)
	PyFileObject *f;
	PyObject *args;
{
#define CHUNKSIZE 1000
	PyObject *list, *line;
	PyObject *result;
	int i, j, index, len, nwritten, islist;

	if (f->f_fp == NULL)
		return err_closed();
	if (args == NULL || !PySequence_Check(args)) {
		PyErr_SetString(PyExc_TypeError,
			   "writelines() requires sequence of strings");
		return NULL;
	}
	islist = PyList_Check(args);

	/* Strategy: slurp CHUNKSIZE lines into a private list,
	   checking that they are all strings, then write that list
	   without holding the interpreter lock, then come back for more. */
	index = 0;
	if (islist)
		list = NULL;
	else {
		list = PyList_New(CHUNKSIZE);
		if (list == NULL)
			return NULL;
	}
	result = NULL;

	for (;;) {
		if (islist) {
			Py_XDECREF(list);
			list = PyList_GetSlice(args, index, index+CHUNKSIZE);
			if (list == NULL)
				return NULL;
			j = PyList_GET_SIZE(list);
		}
		else {
			for (j = 0; j < CHUNKSIZE; j++) {
				line = PySequence_GetItem(args, index+j);
				if (line == NULL) {
					if (PyErr_ExceptionMatches(
						PyExc_IndexError))
					{
						PyErr_Clear();
						break;
					}
					/* Some other error occurred.
					   XXX We may lose some output. */
					goto error;
				}
				if (!PyString_Check(line)) {
					Py_DECREF(line);
					PyErr_SetString(PyExc_TypeError,
				 "writelines() requires sequences of strings");
					goto error;
				}
				PyList_SetItem(list, j, line);
			}
		}
		if (j == 0)
			break;

		Py_BEGIN_ALLOW_THREADS
		f->f_softspace = 0;
		errno = 0;
		for (i = 0; i < j; i++) {
			line = PyList_GET_ITEM(list, i);
			len = PyString_GET_SIZE(line);
			nwritten = fwrite(PyString_AS_STRING(line),
					  1, len, f->f_fp);
			if (nwritten != len) {
				Py_BLOCK_THREADS
				PyErr_SetFromErrno(PyExc_IOError);
				clearerr(f->f_fp);
				goto error;
			}
		}
		Py_END_ALLOW_THREADS

		if (j < CHUNKSIZE)
			break;
		index += CHUNKSIZE;
	}

	Py_INCREF(Py_None);
	result = Py_None;
  error:
	Py_XDECREF(list);
	return result;
}

static PyMethodDef file_methods[] = {
	{"readline",	(PyCFunction)file_readline, 1},
	{"read",	(PyCFunction)file_read, 1},
	{"write",	(PyCFunction)file_write, 0},
	{"fileno",	(PyCFunction)file_fileno, 0},
	{"seek",	(PyCFunction)file_seek, 1},
#ifdef HAVE_FTRUNCATE
	{"truncate",	(PyCFunction)file_truncate, 1},
#endif
	{"tell",	(PyCFunction)file_tell, 0},
	{"readinto",	(PyCFunction)file_readinto, 0},
	{"readlines",	(PyCFunction)file_readlines, 1},
	{"writelines",	(PyCFunction)file_writelines, 0},
	{"flush",	(PyCFunction)file_flush, 0},
	{"close",	(PyCFunction)file_close, 0},
	{"isatty",	(PyCFunction)file_isatty, 0},
	{NULL,		NULL}		/* sentinel */
};

#define OFF(x) offsetof(PyFileObject, x)

static struct memberlist file_memberlist[] = {
	{"softspace",	T_INT,		OFF(f_softspace)},
	{"mode",	T_OBJECT,	OFF(f_mode),	RO},
	{"name",	T_OBJECT,	OFF(f_name),	RO},
	/* getattr(f, "closed") is implemented without this table */
	{"closed",	T_INT,		0,		RO},
	{NULL}	/* Sentinel */
};

static PyObject *
file_getattr(f, name)
	PyFileObject *f;
	char *name;
{
	PyObject *res;

	res = Py_FindMethod(file_methods, (PyObject *)f, name);
	if (res != NULL)
		return res;
	PyErr_Clear();
	if (strcmp(name, "closed") == 0)
		return PyInt_FromLong((long)(f->f_fp == 0));
	return PyMember_Get((char *)f, file_memberlist, name);
}

static int
file_setattr(f, name, v)
	PyFileObject *f;
	char *name;
	PyObject *v;
{
	if (v == NULL) {
		PyErr_SetString(PyExc_AttributeError,
				"can't delete file attributes");
		return -1;
	}
	return PyMember_Set((char *)f, file_memberlist, name, v);
}

PyTypeObject PyFile_Type = {
	PyObject_HEAD_INIT(&PyType_Type)
	0,
	"file",
	sizeof(PyFileObject),
	0,
	(destructor)file_dealloc, /*tp_dealloc*/
	0,		/*tp_print*/
	(getattrfunc)file_getattr, /*tp_getattr*/
	(setattrfunc)file_setattr, /*tp_setattr*/
	0,		/*tp_compare*/
	(reprfunc)file_repr, /*tp_repr*/
};

/* Interface for the 'soft space' between print items. */

int
PyFile_SoftSpace(f, newflag)
	PyObject *f;
	int newflag;
{
	int oldflag = 0;
	if (f == NULL) {
		/* Do nothing */
	}
	else if (PyFile_Check(f)) {
		oldflag = ((PyFileObject *)f)->f_softspace;
		((PyFileObject *)f)->f_softspace = newflag;
	}
	else {
		PyObject *v;
		v = PyObject_GetAttrString(f, "softspace");
		if (v == NULL)
			PyErr_Clear();
		else {
			if (PyInt_Check(v))
				oldflag = PyInt_AsLong(v);
			Py_DECREF(v);
		}
		v = PyInt_FromLong((long)newflag);
		if (v == NULL)
			PyErr_Clear();
		else {
			if (PyObject_SetAttrString(f, "softspace", v) != 0)
				PyErr_Clear();
			Py_DECREF(v);
		}
	}
	return oldflag;
}

/* Interfaces to write objects/strings to file-like objects */

int
PyFile_WriteObject(v, f, flags)
	PyObject *v;
	PyObject *f;
	int flags;
{
	PyObject *writer, *value, *args, *result;
	if (f == NULL) {
		PyErr_SetString(PyExc_TypeError, "writeobject with NULL file");
		return -1;
	}
	else if (PyFile_Check(f)) {
		FILE *fp = PyFile_AsFile(f);
		if (fp == NULL) {
			err_closed();
			return -1;
		}
		return PyObject_Print(v, fp, flags);
	}
	writer = PyObject_GetAttrString(f, "write");
	if (writer == NULL)
		return -1;
	if (flags & Py_PRINT_RAW)
		value = PyObject_Str(v);
	else
		value = PyObject_Repr(v);
	if (value == NULL) {
		Py_DECREF(writer);
		return -1;
	}
	args = Py_BuildValue("(O)", value);
	if (args == NULL) {
		Py_DECREF(value);
		Py_DECREF(writer);
		return -1;
	}
	result = PyEval_CallObject(writer, args);
	Py_DECREF(args);
	Py_DECREF(value);
	Py_DECREF(writer);
	if (result == NULL)
		return -1;
	Py_DECREF(result);
	return 0;
}

int
PyFile_WriteString(s, f)
	char *s;
	PyObject *f;
{
	if (f == NULL) {
		/* Should be caused by a pre-existing error */
		if(!PyErr_Occurred())
			PyErr_SetString(PyExc_SystemError,
					"null file for PyFile_WriteString");
		return -1;
	}
	else if (PyFile_Check(f)) {
		FILE *fp = PyFile_AsFile(f);
		if (fp == NULL) {
			err_closed();
			return -1;
		}
		fputs(s, fp);
		return 0;
	}
	else if (!PyErr_Occurred()) {
		PyObject *v = PyString_FromString(s);
		int err;
		if (v == NULL)
			return -1;
		err = PyFile_WriteObject(v, f, Py_PRINT_RAW);
		Py_DECREF(v);
		return err;
	}
	else
		return -1;
}