cpython/Modules/_multiprocessing/pipe_connection.c

/*
 * A type which wraps a pipe handle in message oriented mode
 *
 * pipe_connection.c
 *
 * Copyright (c) 2006-2008, R Oudkerk --- see COPYING.txt
 */

#include "multiprocessing.h"

#define CLOSE(h) CloseHandle(h)

/*
 * Send string to the pipe; assumes in message oriented mode
 */

static Py_ssize_t
conn_send_string(ConnectionObject *conn, char *string, size_t length)
{
	DWORD amount_written;
	BOOL ret;

	Py_BEGIN_ALLOW_THREADS
	ret = WriteFile(conn->handle, string, length, &amount_written, NULL);
	Py_END_ALLOW_THREADS

	if (ret == 0 && GetLastError() == ERROR_NO_SYSTEM_RESOURCES) {
		PyErr_Format(PyExc_ValueError, "Cannnot send %" PY_FORMAT_SIZE_T "d bytes over connection", length);
		return MP_STANDARD_ERROR;
	}

	return ret ? MP_SUCCESS : MP_STANDARD_ERROR;
}

/*
 * Attempts to read into buffer, or if buffer too small into *newbuffer.
 *
 * Returns number of bytes read.  Assumes in message oriented mode.
 */

static Py_ssize_t
conn_recv_string(ConnectionObject *conn, char *buffer, 
		 size_t buflength, char **newbuffer, size_t maxlength)
{
	DWORD left, length, full_length, err;
	BOOL ret;
	*newbuffer = NULL;

	Py_BEGIN_ALLOW_THREADS
	ret = ReadFile(conn->handle, buffer, MIN(buflength, maxlength), 
		      &length, NULL);
	Py_END_ALLOW_THREADS
	if (ret)
		return length;

	err = GetLastError();
	if (err != ERROR_MORE_DATA) {
		if (err == ERROR_BROKEN_PIPE)
			return MP_END_OF_FILE;
		return MP_STANDARD_ERROR;
	}

	if (!PeekNamedPipe(conn->handle, NULL, 0, NULL, NULL, &left))
		return MP_STANDARD_ERROR;

	full_length = length + left;
	if (full_length > maxlength)
		return MP_BAD_MESSAGE_LENGTH;

	*newbuffer = PyMem_Malloc(full_length);
	if (*newbuffer == NULL)
		return MP_MEMORY_ERROR;

	memcpy(*newbuffer, buffer, length);

	Py_BEGIN_ALLOW_THREADS
	ret = ReadFile(conn->handle, *newbuffer+length, left, &length, NULL);
	Py_END_ALLOW_THREADS
	if (ret) {
		assert(length == left);
		return full_length;
	} else {
		PyMem_Free(*newbuffer);
		return MP_STANDARD_ERROR;
	}
}

/*
 * Check whether any data is available for reading
 */

static int
conn_poll(ConnectionObject *conn, double timeout, PyThreadState *_save)
{
	DWORD bytes, deadline, delay;
	int difference, res;
	BOOL block = FALSE;

	if (!PeekNamedPipe(conn->handle, NULL, 0, NULL, &bytes, NULL))
		return MP_STANDARD_ERROR;

	if (timeout == 0.0)
		return bytes > 0;

	if (timeout < 0.0)
		block = TRUE;
	else
		/* XXX does not check for overflow */
		deadline = GetTickCount() + (DWORD)(1000 * timeout + 0.5);

	Sleep(0);

	for (delay = 1 ; ; delay += 1) {
		if (!PeekNamedPipe(conn->handle, NULL, 0, NULL, &bytes, NULL))
			return MP_STANDARD_ERROR;
		else if (bytes > 0)
			return TRUE;

		if (!block) {
			difference = deadline - GetTickCount();
			if (difference < 0)
				return FALSE;
			if ((int)delay > difference)
				delay = difference;
		}

		if (delay > 20)
			delay = 20;

		Sleep(delay);

		/* check for signals */
		Py_BLOCK_THREADS 
		res = PyErr_CheckSignals();
		Py_UNBLOCK_THREADS

		if (res)
			return MP_EXCEPTION_HAS_BEEN_SET;
	}
}

/*
 * "connection.h" defines the PipeConnection type using the definitions above
 */

#define CONNECTION_NAME "PipeConnection"
#define CONNECTION_TYPE PipeConnectionType

#include "connection.h"