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Make dbgf display something for an empty array

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Also significantly expands on Dirk's Release Notes entries.
This commit is contained in:
Andrew Johnson
2020-10-30 13:37:50 -05:00
parent a7bf59079f
commit 297f04bddc
2 changed files with 68 additions and 26 deletions
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86
documentation/RELEASE_NOTES.md
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@@ -17,42 +17,84 @@ should also be read to understand what has changed since earlier releases.
<!-- Insert new items immediately below here ... -->
### Support for empty arrays
### Support for zero-length arrays
Several problems with empty arrays have been fixed.
Several modifications have been made to properly support zero-length
array values inside the IOC and over Channel Access. Some of these changes
may affect external code that interfaces with the IOC, either directly or
over the CA client API so we recommend thorough testing of any external
code that handles array fields when upgrading to this release.
#### Changed dbr_size_n(TYPE,COUNT) macro
Since these changes affect the Channel Access client-side API they will
require rebuilding any CA Gateways against this version or Base to
properly handle zero-length arrays. The `caget`, `caput` and `camonitor`
client programs are known to work with empty arrays as long as they were
built with this or a later version of EPICS.
When called with COUNT=0 the macro no longer returns the number of bytes
#### Change to the db_access.h `dbr_size_n(TYPE, COUNT)` macro
When called with COUNT=0 this macro no longer returns the number of bytes
required for a scalar (1 element) but for an empty array (0 elements).
Make sure you don't call it with COUNT=0 when you really mean COUNT=1.
Make sure code that uses this doesn't call it with COUNT=0 when it really
means COUNT=1.
Note that the db_access.h header file is included by cadef.h so the change
can impact Channel Access client programs that use this macro.
#### Channel Access support for zero-length arrays
The `ca_array_put()` and `ca_array_put_callback()` routines now accept an
element count of zero, and will write a zero-length array to the PV if
possible. No error will be raised if the target is a scalar field though,
and the field's value will not be changed.
The `ca_array_get_callback()` and `ca_create_subscription()` routines
still accept a count of zero to mean fetch as many elements as the PV
currently holds.
Client programs should be prepared for the `count` fields of any
`struct event_handler_args` or `struct exception_handler_args` passed to
their callback routines to be zero.
#### Array records
The soft supports of array records aai, waveform, and subArray as well as
the aSub record type have been fixed to correctly report 0 elements read
when reading empty arrays from an input link.
The soft device support for the array records aai, waveform, and subArray
as well as the aSub record type now correctly report reading 0 elements
when getting an empty array from an input link.
#### Array support for dbpf
The dbpf function now accepts arrays, including empty arrays as a JSON string.
The dbpf command now accepts array values, including empty arrays, when
provided as a JSON string. This must be enclosed in quotes so the iocsh
argument parser sees the JSON as a single argument:
#### Scalar records reading from empty arrays
```
epics> dbpf wf10:i32 '[1, 2, 3, 4, 5]'
DBF_LONG[5]: 1 = 0x1 2 = 0x2 3 = 0x3 4 = 0x4 5 = 0x5
```
Records reading scalar fields from empty arrays are now set to INVALID/LINK
alarm status.
Links have to call dbGetLink with pnRequest=NULL to be recognized as requests
for scalars.
This changes the semantics of pnRequest=NULL. It is now different from
requesting up to 1 array element, which may return a valid empty array.
#### Reading empty arrays as scalar values
### Writing empty arrays to scalar records
Record links that get a scalar value from an array that is currently
empty will cause the record that has the link field to be set to an
`INVALID/LINK` alarm status.
The record code must call `dbGetLink()` with `pnRequest=NULL` for it to
be recognized as a request for a scalar value though.
Witing an empty array to a scalar field now sets the target record to
INVALID/LINK alarm but does not modify the value. Before, the value used
to be set to 0 (without any alarm).
A target field needs to have the SPC_DBADDR tag to be recognized as an array
field and the record support must define a put_array_info method.
This changes the semantics of passing `pnRequest=NULL` to `dbGetLink()`,
which now behaves differently than passing it a pointer to a long integer
containing the value 1, which was previously equivalent.
The latter can successfully fetch a zero-element array without triggering
a LINK alarm.
#### Writing empty arrays to scalar fields
Record links that put a zero-element array into a scalar field will now set
the target record to `INVALID/LINK` alarm without changing the field's value.
Previously the field was set to 0 in this case (with no alarm).
The target field must be marked as `special(SPC_DBADDR)` to be recognized
as an array field, and its record support must define a `put_array_info()`
routine.
### Add registerAllRecordDeviceDrivers()

8
modules/database/src/ioc/db/dbTest.c
View File

@@ -954,13 +954,13 @@ static void printBuffer(
}
/* Now print values */
if (no_elements == 0)
return;
if (no_elements == 1)
sprintf(pmsg, "DBF_%s: ", dbr[dbr_type]);
else
else {
sprintf(pmsg, "DBF_%s[%ld]: ", dbr[dbr_type], no_elements);
if (no_elements == 0)
strcat(pmsg, "(empty)");
}
dbpr_msgOut(pMsgBuff, tab_size);
if (status != 0) {