cpython/Objects/fileobject.c

/* File object implementation (what's left of it -- see io.py) */

#define PY_SSIZE_T_CLEAN
#include "Python.h"

#ifdef HAVE_GETC_UNLOCKED
#define GETC(f) getc_unlocked(f)
#define FLOCKFILE(f) flockfile(f)
#define FUNLOCKFILE(f) funlockfile(f)
#else
#define GETC(f) getc(f)
#define FLOCKFILE(f)
#define FUNLOCKFILE(f)
#endif

/* Newline flags */
#define NEWLINE_UNKNOWN	0	/* No newline seen, yet */
#define NEWLINE_CR 1		/* \r newline seen */
#define NEWLINE_LF 2		/* \n newline seen */
#define NEWLINE_CRLF 4		/* \r\n newline seen */

#ifdef __cplusplus
extern "C" {
#endif

/* External C interface */

PyObject *
PyFile_FromFd(int fd, char *name, char *mode, int buffering, char *encoding,
	      char *newline)
{
	PyObject *io, *stream, *nameobj = NULL;

	io = PyImport_ImportModule("io");
	if (io == NULL)
		return NULL;
	stream = PyObject_CallMethod(io, "open", "isiss", fd, mode,
				     buffering, encoding, newline);
	Py_DECREF(io);
	if (stream == NULL)
		return NULL;
	if (name != NULL) {
		nameobj = PyUnicode_FromString(name);
		if (nameobj == NULL)
			PyErr_Clear();
		else {
			if (PyObject_SetAttrString(stream, "name", nameobj) < 0)
				PyErr_Clear();
			Py_DECREF(nameobj);
		}
	}
	return stream;
}

PyObject *
PyFile_GetLine(PyObject *f, int n)
{
	PyObject *result;

	if (f == NULL) {
		PyErr_BadInternalCall();
		return NULL;
	}

	{
		PyObject *reader;
		PyObject *args;

		reader = PyObject_GetAttrString(f, "readline");
		if (reader == NULL)
			return NULL;
		if (n <= 0)
			args = PyTuple_New(0);
		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) &&
		    !PyUnicode_Check(result)) {
			Py_DECREF(result);
			result = NULL;
			PyErr_SetString(PyExc_TypeError,
				   "object.readline() returned non-string");
		}
	}

	if (n < 0 && result != NULL && PyString_Check(result)) {
		char *s = PyString_AS_STRING(result);
		Py_ssize_t len = PyString_GET_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;
			}
		}
	}
	if (n < 0 && result != NULL && PyUnicode_Check(result)) {
		Py_UNICODE *s = PyUnicode_AS_UNICODE(result);
		Py_ssize_t len = PyUnicode_GET_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)
				PyUnicode_Resize(&result, len-1);
			else {
				PyObject *v;
				v = PyUnicode_FromUnicode(s, len-1);
				Py_DECREF(result);
				result = v;
			}
		}
	}
	return result;
}

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

int
PyFile_WriteObject(PyObject *v, PyObject *f, int flags)
{
	PyObject *writer, *value, *args, *result;
	if (f == NULL) {
		PyErr_SetString(PyExc_TypeError, "writeobject with NULL file");
		return -1;
	}
	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 = PyTuple_Pack(1, 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(const 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 (!PyErr_Occurred()) {
		PyObject *v = PyUnicode_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;
}

/* Try to get a file-descriptor from a Python object.  If the object
   is an integer or long integer, its value is returned.  If not, the
   object's fileno() method is called if it exists; the method must return
   an integer or long integer, which is returned as the file descriptor value.
   -1 is returned on failure.
*/

int
PyObject_AsFileDescriptor(PyObject *o)
{
	int fd;
	PyObject *meth;

	if (PyLong_Check(o)) {
		fd = PyLong_AsLong(o);
	}
	else if ((meth = PyObject_GetAttrString(o, "fileno")) != NULL)
	{
		PyObject *fno = PyEval_CallObject(meth, NULL);
		Py_DECREF(meth);
		if (fno == NULL)
			return -1;

		if (PyLong_Check(fno)) {
			fd = PyLong_AsLong(fno);
			Py_DECREF(fno);
		}
		else {
			PyErr_SetString(PyExc_TypeError,
					"fileno() returned a non-integer");
			Py_DECREF(fno);
			return -1;
		}
	}
	else {
		PyErr_SetString(PyExc_TypeError,
				"argument must be an int, or have a fileno() method.");
		return -1;
	}

	if (fd == -1 && PyErr_Occurred())
		return -1;
	if (fd < 0) {
		PyErr_Format(PyExc_ValueError,
			     "file descriptor cannot be a negative integer (%i)",
			     fd);
		return -1;
	}
	return fd;
}

/*
** Py_UniversalNewlineFgets is an fgets variation that understands
** all of \r, \n and \r\n conventions.
** The stream should be opened in binary mode.
** If fobj is NULL the routine always does newline conversion, and
** it may peek one char ahead to gobble the second char in \r\n.
** If fobj is non-NULL it must be a PyFileObject. In this case there
** is no readahead but in stead a flag is used to skip a following
** \n on the next read. Also, if the file is open in binary mode
** the whole conversion is skipped. Finally, the routine keeps track of
** the different types of newlines seen.
** Note that we need no error handling: fgets() treats error and eof
** identically.
*/
char *
Py_UniversalNewlineFgets(char *buf, int n, FILE *stream, PyObject *fobj)
{
	char *p = buf;
	int c;
	int newlinetypes = 0;
	int skipnextlf = 0;

	if (fobj) {
		errno = ENXIO;	/* What can you do... */
		return NULL;
	}
	FLOCKFILE(stream);
	c = 'x'; /* Shut up gcc warning */
	while (--n > 0 && (c = GETC(stream)) != EOF ) {
		if (skipnextlf ) {
			skipnextlf = 0;
			if (c == '\n') {
				/* Seeing a \n here with skipnextlf true
				** means we saw a \r before.
				*/
				newlinetypes |= NEWLINE_CRLF;
				c = GETC(stream);
				if (c == EOF) break;
			} else {
				/*
				** Note that c == EOF also brings us here,
				** so we're okay if the last char in the file
				** is a CR.
				*/
				newlinetypes |= NEWLINE_CR;
			}
		}
		if (c == '\r') {
			/* A \r is translated into a \n, and we skip
			** an adjacent \n, if any. We don't set the
			** newlinetypes flag until we've seen the next char.
			*/
			skipnextlf = 1;
			c = '\n';
		} else if ( c == '\n') {
			newlinetypes |= NEWLINE_LF;
		}
		*p++ = c;
		if (c == '\n') break;
	}
	if ( c == EOF && skipnextlf )
		newlinetypes |= NEWLINE_CR;
	FUNLOCKFILE(stream);
	*p = '\0';
	if ( skipnextlf ) {
		/* If we have no file object we cannot save the
		** skipnextlf flag. We have to readahead, which
		** will cause a pause if we're reading from an
		** interactive stream, but that is very unlikely
		** unless we're doing something silly like
		** exec(open("/dev/tty").read()).
		*/
		c = GETC(stream);
		if ( c != '\n' )
			ungetc(c, stream);
	}
	if (p == buf)
		return NULL;
	return buf;
}

#ifdef __cplusplus
}
#endif