Att Server: support "Prepare Write Request" and "Execute Write Request"

[chenkaie]

Description

Implement below two operation

• Prepare Write Request [3.4.6.1 & 3.4.6.2]
• Execute Write Request [3.4.6.3]

Test

• Test with LightBlue

  • Test ASCII string: 12345567890x20
    

• Before : can not receive message longer than MTU

$ sudo ./server -device "prepare_write" -du 1000000s
Advertising for 277h46m40s...

handleExchangeMTURequest ... 104, 104

2017/10/16 17:05:06 TODO: indicate client when the services are changed
2017/10/16 17:05:10 count: Read 0
2017/10/16 17:05:40 count: Wrote 123
2017/10/16 17:06:46 count: Wrote 1234556789012345567890
2017/10/16 17:06:56 count: Wrote 12345567890

2017/10/16 17:07:05 count: Wrote 123455678901234556789012345567890
2017/10/16 17:07:12 count: Wrote 123455678901234556789012345567890123455678901234556789012345567890

<<<<------ CAN NOT RECEVIE LONGER STRING HERE ----->>>>

• After : can recive message longer than MTU

$ sudo ./server -device "prepare_write" -du 1000000s
Advertising for 277h46m40s...

handleExchangeMTURequest ... 104, 104
>>> handleWriteRequest -> r.AttributeHandle:  15
2017/10/16 16:58:53 count: Read 0

>>> handlePrepareWriteRequest -> r.AttributeHandle:  18
>>>> data: 3132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373
83930, offset: 0, 0x0

>>> handlePrepareWriteRequest -> r.AttributeHandle:  18
>>>> data: 3132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373
83930, offset: 99, 0xc4200d6d80

>>> handlePrepareWriteRequest -> r.AttributeHandle:  18
>>>> data: 313233343535363738393031323334353536373839303132333435353637383930, offset: 198, 0xc4200d6d80
2017/10/16 16:59:01 count: Wrote 123455678901234556789012345567890123455678901234556789012345567890123455678901234556789012345567890123455678901234556789012345567890123455678901234556789012345567890123455
678901234556789012345567890123455678901234556789012345567890
q
>>> handlePrepareWriteRequest -> r.AttributeHandle:  18
>>>> data: 3132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373
83930, offset: 0, 0x0

>>> handlePrepareWriteRequest -> r.AttributeHandle:  18
>>>> data: 3132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373
83930, offset: 99, 0xc4200d6d80

>>> handlePrepareWriteRequest -> r.AttributeHandle:  18
>>>> data: 3132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373
83930, offset: 198, 0xc4200d6d80

>>> handlePrepareWriteRequest -> r.AttributeHandle:  18
>>>> data: 3132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373
83930, offset: 297, 0xc4200d6d80

>>> handlePrepareWriteRequest -> r.AttributeHandle:  18
>>>> data: 313233343535363738393031323334353536373839303132333435353637383930313233343535363738393031323334353536373839303132333435353637383930, offset: 396, 0xc4200d6d80
2017/10/16 16:59:26 count: Wrote 123455678901234556789012345567890123455678901234556789012345567890123455678901234556789012345567890123455678901234556789012345567890123455678901234556789012345567890123455
678901234556789012345567890123455678901234556789012345567890123455678901234556789012345567890123455678901234556789012345567890123455678901234556789012345567890123455678901234556789012345567890123455678901
234556789012345567890123455678901234556789012345567890123455678901234556789012345567890