BrlAPI's protocol(3)

NAME
BrlAPI's protocol - Instructions and constants for BrlAPI 's protocol.

  Data Structures
struct brlapi_header_t
struct brlapi_versionPacket_t
struct brlapi_authClientPacket_t
struct brlapi_authServerPacket_t
struct brlapi_errorPacket_t
struct brlapi_getDriverSpecificModePacket_t
struct brlapi_writeArgumentsPacket_t
union brlapi_packet_t

  Defines
#define BRLAPI_PROTOCOL_VERSION ((uint32_t) 8)
#define BRLAPI_MAXPACKETSIZE 512
#define BRLAPI_PACKET_VERSION 'v'
#define BRLAPI_PACKET_AUTH 'a'
#define BRLAPI_PACKET_GETDRIVERNAME 'n'
#define BRLAPI_PACKET_GETDISPLAYSIZE 's'
#define BRLAPI_PACKET_ENTERTTYMODE 't'
#define BRLAPI_PACKET_SETFOCUS 'F'
#define BRLAPI_PACKET_LEAVETTYMODE 'L'
#define BRLAPI_PACKET_KEY 'k'
#define BRLAPI_PACKET_IGNOREKEYRANGES 'm'
#define BRLAPI_PACKET_ACCEPTKEYRANGES 'u'
#define BRLAPI_PACKET_WRITE 'w'
#define BRLAPI_PACKET_ENTERRAWMODE '*'
#define BRLAPI_PACKET_LEAVERAWMODE '#'
#define BRLAPI_PACKET_PACKET 'p'
#define BRLAPI_PACKET_ACK 'A'
#define BRLAPI_PACKET_ERROR 'e'
#define BRLAPI_PACKET_EXCEPTION 'E'
#define BRLAPI_PACKET_SUSPENDDRIVER 'S'
#define BRLAPI_PACKET_RESUMEDRIVER 'R'
#define BRLAPI_DEVICE_MAGIC (0xdeadbeefL)
#define BRLAPI_HEADERSIZE sizeof(brlapi_header_t)
#define BRLAPI_AUTH_NONE 'N'
#define BRLAPI_AUTH_KEY 'K'
#define BRLAPI_AUTH_CRED 'C'
#define BRLAPI_WF_DISPLAYNUMBER 0X01
#define BRLAPI_WF_REGION 0X02
#define BRLAPI_WF_TEXT 0X04
#define BRLAPI_WF_ATTR_AND 0X08
#define BRLAPI_WF_ATTR_OR 0X10
#define BRLAPI_WF_CURSOR 0X20
#define BRLAPI_WF_CHARSET 0X40

  Functions
ssize_t brlapi_writePacket (brlapi_fileDescriptor fd, brlapi_packetType_t type, const void *buf, size_t size)
ssize_t brlapi_readPacketHeader (brlapi_fileDescriptor fd, brlapi_packetType_t *packetType)
ssize_t brlapi_readPacketContent (brlapi_fileDescriptor fd, size_t packetSize, void *buf, size_t bufSize)
ssize_t brlapi_readPacket (brlapi_fileDescriptor fd, brlapi_packetType_t *type, void *buf, size_t size)

  Variables
pthread_mutex_t brlapi_fd_mutex

Detailed Description

These are defines for the protocol between BrlAPI 's server and clients. Understanding is not needed to use the BrlAPI library, so reading this is not needed unless really wanting to connect to BrlAPI without BrlAPI 's library.

Define Documentation

  #define BRLAPI_AUTH_CRED 'C'

Explicit socket credentials authorization

  #define BRLAPI_AUTH_KEY 'K'

Key authorization

  #define BRLAPI_AUTH_NONE 'N'

No or implicit authorization

  #define BRLAPI_DEVICE_MAGIC (0xdeadbeefL)

Magic number to give when sending a BRLPACKET_ENTERRAWMODE or BRLPACKET_SUSPEND packet

  #define BRLAPI_HEADERSIZE sizeof(brlapi_header_t)

Size of packet headers

  #define BRLAPI_MAXPACKETSIZE 512

Maximum packet size for packets exchanged on sockets and with braille terminal

  #define BRLAPI_PACKET_ACCEPTKEYRANGES 'u'

Unmask key ranges

  #define BRLAPI_PACKET_ACK 'A'

Acknowledgement

  #define BRLAPI_PACKET_AUTH 'a'

Authorization

  #define BRLAPI_PACKET_ENTERRAWMODE '*'

Enter in raw mode

  #define BRLAPI_PACKET_ENTERTTYMODE 't'

Asks for a specified tty

  #define BRLAPI_PACKET_ERROR 'e'

non-fatal error

  #define BRLAPI_PACKET_EXCEPTION 'E'

Exception

  #define BRLAPI_PACKET_GETDISPLAYSIZE 's'

Dimensions of brl display

  #define BRLAPI_PACKET_GETDRIVERNAME 'n'

Ask which driver is used

  #define BRLAPI_PACKET_IGNOREKEYRANGES 'm'

Mask key ranges

  #define BRLAPI_PACKET_KEY 'k'

Braille key

  #define BRLAPI_PACKET_LEAVERAWMODE '#'

Leave raw mode

  #define BRLAPI_PACKET_LEAVETTYMODE 'L'

Release the tty

  #define BRLAPI_PACKET_PACKET 'p'

Raw packets

  #define BRLAPI_PACKET_RESUMEDRIVER 'R'

Resume driver

  #define BRLAPI_PACKET_SETFOCUS 'F'

Set current tty focus

  #define BRLAPI_PACKET_SUSPENDDRIVER 'S'

Suspend driver

  #define BRLAPI_PACKET_VERSION 'v'

Version

  #define BRLAPI_PACKET_WRITE 'w'

Write

  #define BRLAPI_PROTOCOL_VERSION ((uint32_t) 8)

  #define BRLAPI_WF_ATTR_AND 0X08

And attributes

  #define BRLAPI_WF_ATTR_OR 0X10

Or attributes

  #define BRLAPI_WF_CHARSET 0X40

Charset

  #define BRLAPI_WF_CURSOR 0X20

Cursor position

  #define BRLAPI_WF_DISPLAYNUMBER 0X01

Flags for writing Display number

  #define BRLAPI_WF_REGION 0X02

Region parameter

  #define BRLAPI_WF_TEXT 0X04

Contains some text

Function Documentation

  ssize_t brlapi_readPacket (brlapi_fileDescriptor fd, brlapi_packetType_t * type, void * buf, size_t size)

Read a packet from BrlAPI server

This function is for internal use, but one might use it if one really knows what one is doing...

type is where the function will store the packet type; it should always be one of the above defined BRLPACKET_* (or else something very nasty must have happened :/).

The syntax is the same as read()'s.

Returns:
    packet's size, -2 if EOF occurred, -1 on error or signal interruption.

If the packet is larger than the supplied buffer, the buffer will be filled with the beginning of the packet, the rest of the packet being discarded. This follows the semantics of the recv system call when the MSG_TRUNC option is given.

See also:
    brlapi_writePacket()

  ssize_t brlapi_readPacketContent (brlapi_fileDescriptor fd, size_t packetSize, void * buf, size_t bufSize)

Read the content of a packet from BrlAPI server

This function is for internal use, but one might use it if one really knows what one is doing...

packetSize is the size announced by brlapi_readPacketHeader()

bufSize is the size of buf

Returns:
    packetSize, -2 if EOF occurred, -1 on error.

If the packet is larger than the supplied buffer, the buffer will be filled with the beginning of the packet, the rest of the packet being discarded. This follows the semantics of the recv system call when the MSG_TRUNC option is given.

See also:
    brlapi_writePacket() brlapi_readPacketHeader() brlapi_readPacket()

  ssize_t brlapi_readPacketHeader (brlapi_fileDescriptor fd, brlapi_packetType_t * packetType)

Read the header (type+size) of a packet from BrlAPI server

This function is for internal use, but one might use it if one really knows what one is doing...

type is where the function will store the packet type; it should always be one of the above defined BRLPACKET_* (or else something very nasty must have happened :/).

Returns:
    packet's size, -2 if EOF occurred, -1 on error or signal interruption.

See also:
    brlapi_writePacket() brlapi_readPacketContent brlapi_readPacket

  ssize_t brlapi_writePacket (brlapi_fileDescriptor fd, brlapi_packetType_t type, const void * buf, size_t size)

Send a packet to BrlAPI server

This function is for internal use, but one might use it if one really knows what one is doing...

type should only be one of the above defined BRLPACKET_*.

The syntax is the same as write()'s.

Returns:
    0 on success, -1 on failure.

See also:
    brlapi_readPacketHeader() brlapi_readPacketContent() brlapi_readPacket()

Variable Documentation

  pthread_mutex_t brlapi_fd_mutex

Mutex for protecting concurrent fd access

In order to regulate concurrent access to the library's file descriptor and requests to / answers from BrlAPI server, every function of the library locks this mutex, namely

•   brlapi_openConnection()

•   brlapi_closeConnection()

•   brlapi_enterRawMode()

•   brlapi_leaveRawMode()

•   brlapi_sendRaw()

•   brlapi_recvRaw()

•   brlapi_getDriverId()

•   brlapi_getDriverName()

•   brlapi_getDisplaySize()

•   brlapi_enterTtyMode()

•   brlapi_enterTtyModeWithPath()

•   brlapi_leaveTtyMode()

•   brlapi_*write*()

•   brlapi_(un)?ignorekey(Range|Set)()

•   brlapi_readKey()

If both these functions and brlapi_writePacket() or brlapi_readPacket() are used in a multithreaded application, this mutex must be locked before calling brlapi_writePacket() or brlapi_readPacket(), and unlocked afterwards.

Author

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