cpython/Modules/_multiprocessing/socket_connection.c

/*
 * A type which wraps a socket
 *
 * socket_connection.c
 *
 * Copyright (c) 2006-2008, R Oudkerk --- see COPYING.txt
 */

#include "multiprocessing.h"

#ifdef MS_WINDOWS
#  define WRITE(h, buffer, length) send((SOCKET)h, buffer, length, 0)
#  define READ(h, buffer, length) recv((SOCKET)h, buffer, length, 0)
#  define CLOSE(h) closesocket((SOCKET)h)
#else
#  define WRITE(h, buffer, length) write(h, buffer, length)
#  define READ(h, buffer, length) read(h, buffer, length)
#  define CLOSE(h) close(h)
#endif

/*
 * Send string to file descriptor
 */

static Py_ssize_t
_conn_sendall(HANDLE h, char *string, size_t length)
{
	char *p = string;
	Py_ssize_t res;

	while (length > 0) {
		res = WRITE(h, p, length);
		if (res < 0)
			return MP_SOCKET_ERROR;
		length -= res;
		p += res;
	}

	return MP_SUCCESS;
}

/*
 * Receive string of exact length from file descriptor 
 */

static Py_ssize_t
_conn_recvall(HANDLE h, char *buffer, size_t length)
{
	size_t remaining = length;
	Py_ssize_t temp;
	char *p = buffer;

	while (remaining > 0) {
		temp = READ(h, p, remaining);
		if (temp <= 0) {
			if (temp == 0)
				return remaining == length ? 
					MP_END_OF_FILE : MP_EARLY_END_OF_FILE;
			else
				return temp;
		}
		remaining -= temp;
		p += temp;
	}

	return MP_SUCCESS;
}

/*
 * Send a string prepended by the string length in network byte order
 */

static Py_ssize_t
conn_send_string(ConnectionObject *conn, char *string, size_t length)
{
	Py_ssize_t res;
	/* The "header" of the message is a 32 bit unsigned number (in
	   network order) which specifies the length of the "body".  If
	   the message is shorter than about 16kb then it is quicker to
	   combine the "header" and the "body" of the message and send
	   them at once. */
	if (length < (16*1024)) {
		char *message;

		message = PyMem_Malloc(length+4);
		if (message == NULL)
			return MP_MEMORY_ERROR;

		*(UINT32*)message = htonl((UINT32)length);     
		memcpy(message+4, string, length);
		Py_BEGIN_ALLOW_THREADS
		res = _conn_sendall(conn->handle, message, length+4);
		Py_END_ALLOW_THREADS
		PyMem_Free(message);
	} else {
		UINT32 lenbuff;

		if (length > MAX_MESSAGE_LENGTH)
			return MP_BAD_MESSAGE_LENGTH;

		lenbuff = htonl((UINT32)length);
		Py_BEGIN_ALLOW_THREADS
		res = _conn_sendall(conn->handle, (char*)&lenbuff, 4) || 
			_conn_sendall(conn->handle, string, length);
		Py_END_ALLOW_THREADS
	}
	return res;
}

/*
 * Attempts to read into buffer, or failing that into *newbuffer
 *
 * Returns number of bytes read.
 */

static Py_ssize_t
conn_recv_string(ConnectionObject *conn, char *buffer, 
		 size_t buflength, char **newbuffer, size_t maxlength)
{
	int res;
	UINT32 ulength;

	*newbuffer = NULL;

	Py_BEGIN_ALLOW_THREADS
	res = _conn_recvall(conn->handle, (char*)&ulength, 4);
	Py_END_ALLOW_THREADS
	if (res < 0)
		return res;

	ulength = ntohl(ulength);
	if (ulength > maxlength)
		return MP_BAD_MESSAGE_LENGTH;

	if (ulength <= buflength) {
		Py_BEGIN_ALLOW_THREADS
		res = _conn_recvall(conn->handle, buffer, (size_t)ulength);
		Py_END_ALLOW_THREADS
		return res < 0 ? res : ulength;
	} else {
		*newbuffer = PyMem_Malloc((size_t)ulength);
		if (*newbuffer == NULL)
			return MP_MEMORY_ERROR;
		Py_BEGIN_ALLOW_THREADS
		res = _conn_recvall(conn->handle, *newbuffer, (size_t)ulength);
		Py_END_ALLOW_THREADS
		return res < 0 ? (Py_ssize_t)res : (Py_ssize_t)ulength;
	}
}

/*
 * Check whether any data is available for reading -- neg timeout blocks
 */

static int
conn_poll(ConnectionObject *conn, double timeout)
{
	int res;
	fd_set rfds;

	FD_ZERO(&rfds);
	FD_SET((SOCKET)conn->handle, &rfds);

	if (timeout < 0.0) {
		res = select((int)conn->handle+1, &rfds, NULL, NULL, NULL);
	} else {
		struct timeval tv;
		tv.tv_sec = (long)timeout;
		tv.tv_usec = (long)((timeout - tv.tv_sec) * 1e6 + 0.5);
		res = select((int)conn->handle+1, &rfds, NULL, NULL, &tv);
	}

	if (res < 0) {
		return MP_SOCKET_ERROR;
	} else if (FD_ISSET(conn->handle, &rfds)) {
		return TRUE;
	} else {
		assert(res == 0);
		return FALSE;
	}
}

/*
 * "connection.h" defines the Connection type using defs above
 */

#define CONNECTION_NAME "Connection"
#define CONNECTION_TYPE ConnectionType

#include "connection.h"