fix(unit): use correct byte length for enum resolution in procGetUnit

[glichtner]

This pull request fixes a bug in procGetUnit where the result of execIExpression (stored in a 4-byte int) was passed to bytes2Enum using only the first byte, but an incorrect length parameter (recvLen) was still being used. This led to enum resolution failing or succeeding by coincidence, depending on the content of unrelated bytes.

We now explicitly pass 1 as the byte length to bytes2Enum, as only a single byte (res) is intended to be used for the lookup.

Example log from vcontrold before the fix

The getBedarfWarmwasser is a command that reads in 10 bytes and extracts byte 2 to map it onto an enum.

Command vito.xml:

<command name="getBedarfWarmwasser" protocmd="getaddr">            <!--EventTypeId: 7322-->
    <addr>1185</addr>
    <len>10</len>
    <unit>BEDARF_10B</unit>
    <description>Bedarf Warmwasser</description>
</command>

unit in vcontrold.xml

<!-- Bedarf (1 byte at offset 2) -->
<unit name="Bedarf (10 byte)">
	<icalc get="B2"/>
	<abbrev>BEDARF_10B</abbrev>
	<type>uchar</type>
	<enum bytes="00" text="kein Bedarf" />
	<enum bytes="01" text="minimaler Bedarf" />
	<enum bytes="02" text="geringer Bedarf" />
	<enum bytes="03" text="mittlerer Bedarf" />
	<enum bytes="04" text="hoher Bedarf" />
	<enum bytes="05" text="maximaler Bedarf" />
	<enum text="UNKNOWN" />
	<entity></entity>
</unit>

After initiating the connection to vcontrold and sending the command, the response is initially parsed correctly:

vcontrold log - correctly parsed (click to show)

Command: getBedarfWarmwasser
>SENT: 41
>SENT: 05
>SENT: 00
>SENT: 01
>SENT: 11
>SENT: 85
>SENT: 0A
>SENT: A6
<RECV: len=1 06
<RECV: received 06
>FRAMER: framer_set_actaddr framer_current_addr = 8511 (was FFFF)
>FRAMER: Command send
>FRAMER: no preset result
<RECV: len=1 41
<RECV: len=1 0F
<RECV: len=1 01
<RECV: len=1 01
<RECV: len=1 11
<RECV: len=1 85
<RECV: len=1 0A
<RECV: len=1 02
<RECV: len=1 03
<RECV: len=1 00
<RECV: received 41 0F 01 01 11 85 0A 02 03 00
<RECV: len=1 00
<RECV: len=1 F4
<RECV: len=1 01
<RECV: len=1 00
<RECV: len=1 00
<RECV: len=1 80
<RECV: len=1 01
<RECV: len=1 2C
<RECV: received 00 F4 01 00 00 80 01 2C
>FRAMER: framer_reset_actaddr framer_current_addr = FRAMER_NO_ADDR (was 8511)
(INT) Exp: B2 [BP:255] [B0:02 B1:03 B2:00 B3:00 B4:F4 B5:01 B6:00 B7:00 B8:80 B9:01 BA:00 BB:00 BC:00 BD:00 BE:00 BF:00 ]
Res: (Hex max. 4 bytes) 00000000
00 00 00 00 00 00 00 00 00 00 -> kein Bedarf

After some time, the response is the exact same, but the conversion to enum fails:

vcontrold log - parse error (click to show)

Command: getBedarfWarmwasser
>SENT: 41
>SENT: 05
>SENT: 00
>SENT: 01
>SENT: 11
>SENT: 85
>SENT: 0A
>SENT: A6
<RECV: len=1 06
<RECV: received 06
>FRAMER: framer_set_actaddr framer_current_addr = 8511 (was FFFF)
>FRAMER: Command send
>FRAMER: no preset result
<RECV: len=1 41
<RECV: len=1 0F
<RECV: len=1 01
<RECV: len=1 01
<RECV: len=1 11
<RECV: len=1 85
<RECV: len=1 0A
<RECV: len=1 02
<RECV: len=1 03
<RECV: len=1 00
<RECV: received 41 0F 01 01 11 85 0A 02 03 00
<RECV: len=1 00
<RECV: len=1 F4
<RECV: len=1 01
<RECV: len=1 00
<RECV: len=1 00
<RECV: len=1 80
<RECV: len=1 01
<RECV: len=1 2C
<RECV: received 00 F4 01 00 00 80 01 2C
>FRAMER: framer_reset_actaddr framer_current_addr = FRAMER_NO_ADDR (was 8511)
(INT) Exp: B2 [BP:255] [B0:02 B1:03 B2:00 B3:00 B4:F4 B5:01 B6:00 B7:00 B8:80 B9:01 BA:00 BB:00 BC:00 BD:00 BE:00 BF:00 ]
Res: (Hex max. 4 bytes) 00000000
00 38 86 72 01 00 00 00 00 00 -> UNKNOWN

Reason

The enum lookup sometimes fails due to recvLen being passed as 10, causing bytes2Enum to look at 10 bytes instead of 1 in:

if ( uPtr->ePtr && bytes2Enum(uPtr->ePtr, &res, &tPtr, recvLen)) {

Fix

The fix changes:

if ( uPtr->ePtr && bytes2Enum(uPtr->ePtr, &res, &tPtr, recvLen)) {

to:

if ( uPtr->ePtr && bytes2Enum(uPtr->ePtr, &res, &tPtr, 1)) {

Now the lookup works consistently as expected.