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Updates to Release Notes and links.html

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This commit is contained in:
Andrew Johnson
2017-04-25 22:52:08 -05:00
parent c71afb631c
commit 33f3145fcc
2 changed files with 194 additions and 74 deletions
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45
src/std/link/links.dbd.pod
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@@ -1,8 +1,11 @@
=head1 JSON Links
=head1 Extensible Links
JSON Links are an extensible mechanism for adding new kinds of database link,
using JSON for the link address.
The following link types are available in this release:
The extensible link mechanism allows new kinds of record links to be created,
using JSON for the link address syntax.
The IOC continues to support the older link types that do not use JSON to
specify their link addresses.
The following additional link types are available in this release:
=over
@@ -12,14 +15,16 @@ The following link types are available in this release:
=back
=head2 Using Links
=head2 Using JSON Links
...
When setting a record link field to a JSON link, the link specification must
appear inside a pair of braces C< {} > expressed as a JSON (L<JavaScript Object
Notation|http://www.json.org/>) object, which allows link parameters to be
defined as needed by the particular link type.
When setting a record link field to a JSON link address, the link specification
must appear inside a pair of braces C< {} > expressed as a JSON (L<JavaScript
Object Notation|http://www.json.org/>) object, which allows link parameters to
be defined as needed by the particular link type. When link fields are set from
an IOC database file at initialization time, the field definitions may take
advantage of a "relaxed JSON" syntax that reduces the number of double-quote
characters required and maintains backwards compatibility with the older
database file syntax.
=head2 Link Type Reference
@@ -36,12 +41,12 @@ support the use of constant links by calling C<recGblInitConstantLink()> at
record initialization, which results in the constant value being loaded into the
target field at that time.
Note that for most record types (the C<printf> and C<calcout> records are
exceptions) it is pointless to set an input link to a constant link at runtime
since the link initialization that loads the field value usually only happens
when a record is initialized. A constant link that is embedded inside another
input link type such as a calculation link should be OK though since the link
initialization will take place when the record's field gets set.
Note that for most record types (the C<printf> and C<calcout> records are the
main exceptions) it is pointless to set an input link to a constant link at
runtime since the link initialization that loads the field value usually only
happens when a record is initialized. A constant link that is embedded inside
another input link type such as a calculation link should be OK though since the
link initialization will take place when the record's field gets set.
=head4 Parameters
@@ -76,13 +81,13 @@ evaluated by the EPICS Calc engine, and up to 12 inputs can be provided.
=head4 Parameters
The link value is a map with the following keys:
The link address is a JSON map with the following keys:
=over
=item expr
The primary expression to be evaluated, provided as a string.
The primary expression to be evaluated, given as a string.
=item major
@@ -113,6 +118,6 @@ result should be displayed. Equivalent to the C<PREC> field of a record.
=head4 Example
{calc: {expr:"A*B", args:[{db:"record.VAL"}, 1.5]}}
{calc: {expr:"A*B", args:[{db:"record.VAL"}, 1.5], prec:3}}
=cut