brlapi_protocol(3)

brlapi_protocol 💅

okay bestie, welcome to the BrlAPI protocol page — this is from the Library Functions Manual section, and it's basically the group chat rules that BrlAPI's server and clients use to talk to each other. 🫶

---

✨ NAME ✨

brlapi_protocol — BrlAPI's protocol

• Instructions and constants for BrlAPI 's protocol.

---

🌸 SYNOPSIS 🌸

🎀 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
• struct brlapi_paramValuePacket_t
• struct brlapi_paramRequestPacket_t
• union brlapi_packet_t

🦋 Macros

#define BRLAPI_PROTOCOL_VERSION   ((uint32_t) 8) /** Communication
    protocol version */
#define BRLAPI_MAXPACKETSIZE   4096
#define BRLAPI_PACKET_VERSION   'v'
#define BRLAPI_PACKET_AUTH   'a'
#define BRLAPI_PACKET_GETDRIVERNAME   'n'
#define BRLAPI_PACKET_GETMODELID   'd'
#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_PACKET_SYNCHRONIZE   'Z'
#define BRLAPI_PACKET_PARAM_VALUE   (('P'<<8) + 'V')
#define BRLAPI_PACKET_PARAM_REQUEST   (('P'<<8) + 'R')
#define BRLAPI_PACKET_PARAM_UPDATE   (('P'<<8) + 'U')
#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
#define BRLAPI_PVF_GLOBAL   0X01    /** Value is the global value */
#define BRLAPI_MAXPARAMSIZE   (BRLAPI_MAXPACKETSIZE - (sizeof(uint32_t)
    + sizeof(brlapi_param_t) + 2*sizeof(uint32_t)))
#define BRLAPI_PARAMF_GET   0X100    /** Get current parameter value
    */
#define BRLAPI_PARAMF_SUBSCRIBE   0X200    /** Subscribe to parameter
    updates */
#define BRLAPI_PARAMF_UNSUBSCRIBE   0X400    /** Unsubscribe from
    parameter updates */

💜 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.

no cap — if you're just using the library normally, you can literally close this tab. this is for the girlies raw-dogging the socket 💀

---

💖 Macro Definition 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 4096

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

#define BRLAPI_MAXPARAMSIZE (BRLAPI_MAXPACKETSIZE - (sizeof(uint32_t) + sizeof(brlapi_param_t) + 2*sizeof(uint32_t)))

#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_GETMODELID 'd'

Ask which model 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_PARAM_REQUEST (('P'<<8) + 'R')

Parameter request

#define BRLAPI_PACKET_PARAM_UPDATE (('P'<<8) + 'U')

Parameter update

#define BRLAPI_PACKET_PARAM_VALUE (('P'<<8) + 'V')

Parameter value

#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_SYNCHRONIZE 'Z'

Synchronize exceptions

#define BRLAPI_PACKET_VERSION 'v'

Version

#define BRLAPI_PACKET_WRITE 'w'

Write

#define BRLAPI_PARAMF_GET 0X100 /** Get current parameter value */

Flags for parameter requests

#define BRLAPI_PARAMF_SUBSCRIBE 0X200 /** Subscribe to parameter updates */

#define BRLAPI_PARAMF_UNSUBSCRIBE 0X400 /** Unsubscribe from parameter updates */

#define BRLAPI_PROTOCOL_VERSION ((uint32_t) 8) /** Communication protocol version */

#define BRLAPI_PVF_GLOBAL 0X01 /** Value is the global value */

Flags for parameter values

#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... (iykyk)

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()

References brlapi_fd_mutex.

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 [extern]

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_getDriverName()
• brlapi_getDisplaySize()
• brlapi_enterTtyMode()
• brlapi_enterTtyModeWithPath()
• brlapi_leaveTtyMode()
• brlapi_*write*()
• brlapi_(un)?ignorekey(Range|Set)()
• brlapi_readKey()

⚠️ bestie listen — 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. no skipping, fr fr.

Referenced by brlapi_readPacket().

---

🌟 Author 🌟

Generated automatically by Doxygen for BrlAPI from the source code.

---

and that's the whole page, bestie!! 🎀 it was written for BrlAPI, Version 0.8, and it lives at brlapi_protocol(3) — mwah, go forth and slay your sockets 💖✨🦋