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Fixed bug

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[#521782] unreliable file.read() error handling

* Objects/fileobject.c
  (file_read): Clear errors before leaving the loop in all situations,
  and also check if some data was read before exiting the loop with an
  EWOULDBLOCK exception.

* Doc/lib/libstdtypes.tex
* Objects/fileobject.c
  Document that sometimes a read() operation can return less data than
  what the user asked, if running in non-blocking mode.

* Misc/NEWS
  Document the fix.
This commit is contained in:
Gustavo Niemeyer 2002-12-16 18:12:53 +00:00
parent 17c5a33582
commit 786ddb29c9
3 changed files with 36 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

33
Objects/fileobject.c
View file

@ -741,6 +741,20 @@ new_buffersize(PyFileObject *f, size_t currentsize)
return currentsize + SMALLCHUNK;
}
#if defined(EWOULDBLOCK) && defined(EAGAIN) && EWOULDBLOCK != EAGAIN
#define BLOCKED_ERRNO(x) ((x) == EWOULDBLOCK || (x) == EAGAIN)
#else
#ifdef EWOULDBLOCK
#define BLOCKED_ERRNO(x) ((x) == EWOULDBLOCK)
#else
#ifdef EAGAIN
#define BLOCKED_ERRNO(x) ((x) == EAGAIN)
#else
#define BLOCKED_ERRNO(x) 0
#endif
#endif
#endif
static PyObject *
file_read(PyFileObject *f, PyObject *args)
{
@ -774,18 +788,29 @@ file_read(PyFileObject *f, PyObject *args)
if (chunksize == 0) {
if (!ferror(f->f_fp))
break;
PyErr_SetFromErrno(PyExc_IOError);
clearerr(f->f_fp);
/* When in non-blocking mode, data shouldn't
* be discarded if a blocking signal was
* received. That will also happen if
* chunksize != 0, but bytesread < buffersize. */
if (bytesread > 0 && BLOCKED_ERRNO(errno))
break;
PyErr_SetFromErrno(PyExc_IOError);
Py_DECREF(v);
return NULL;
}
bytesread += chunksize;
if (bytesread < buffersize)
if (bytesread < buffersize) {
clearerr(f->f_fp);
break;
}
if (bytesrequested < 0) {
buffersize = new_buffersize(f, buffersize);
if (_PyString_Resize(&v, buffersize) < 0)
return NULL;
} else {
assert(bytesread == bytesrequested);
break;
}
}
if (bytesread != buffersize)
@ -1518,7 +1543,9 @@ PyDoc_STRVAR(readline_doc,
PyDoc_STRVAR(read_doc,
"read([size]) -> read at most size bytes, returned as a string.\n"
"\n"
"If the size argument is negative or omitted, read until EOF is reached.");
"If the size argument is negative or omitted, read until EOF is reached.\n"
"Notice that when in non-blocking mode, less data than what was requested\n"
"may be returned, even if no size parameter was given.");
PyDoc_STRVAR(write_doc,
"write(str) -> None. Write string str to file.\n"