Peter M. Groen / libmodbus

- move termios header in RTU backend
- move TCP headers in TCP backend
- use native serial on Win32 for Cygwin
- avoid too many defines

This change fixes a compilation problem in MinGW. As general rule,
each header must be as independent as possible.

I prefer to remove the check rather than to add the solution used
by Wine as we don't care about the associated define:

AC_CHECK_HEADERS([ \
    ...
    netinet/ip.h \
    netinet/tcp.h \
    ...
],,,[
    #ifdef HAVE_NETINET_IP_H
    # include <netinet/ip.h>
    #endif
])

This change is asked by Barry Grumbine to fix build on OpenBSD

Rename the function _modbus_tcp_init to _modbus_tcp_init_win32 and
warp the call with #ifdef.

Before using any functions of the Win32 Socket API we first have to
initialise it by calling WSAStartup(). Fixes non-working tests on native
Win32.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

Some small modifications were neccessary to make libmodbus build using
a MinGW (cross-)compiler. Libtool is now configured to build DLL files
on Win32. The wsock32 library has been added to the list of libraries
to link against.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

Reported by Viet Nguyen Quoc.

Added support for native Win32 based on
https://code.launchpad.net/~thepyper/libmodbus/win32-native
This mainly affects the RTU implementation as the TCP/IP socket
interface is the same thanks to the winsocks library. The interface
for using the serial port is completely different on Win32 and is now
implemented accordingly.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

Introduced the select() operation for backends as the WAIT_DATA macro
approach is not very extensible and causes trouble when adding platform-
specific codepaths.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

On Win32 the second argument to recv() and send() is not a void pointer
but a char pointer, therefore cast the buffer from uint8_t to char.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

There are several header files that are already included in modbus.h
and thus do not have to be included in the C files.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

The send() and recv() functions of the backends might require more
information than just a file descriptor, therefore pass the complete
modbus_t structure.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

In modbus_flush() we should return the return value of the backend's
flush() function.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

Renamed error_print() to _error_print() in order to indicate it's a
private method and make it globally accessible so functions in
modbus-rtu.c and modbus-tcp.c can make use of it as well.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

All declarations in modbus-rtu.h and modbus-tcp.h should be inside
MODBUS_BEGIN_DECLS and MODBUS_END_DECLS in order to make that functions
properly accessible in C++ files.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

All private functions and constants are now prefixed by _.
The modbus protocol uses entry points to call specific functions.

The cycle will end on a 3.0 release instead of 2.2 as intended.
There are too many changes in the API to keep the same major number.

If <sys/time.h> is not included before "modbus.h" as struct timeval
is not declared. This behavior was observed while building libmodbus
for QNX.

Signed-off-by: Matthias Weisser <weisserm@arcor.de>