AndrewJohnson: Add const arrays

2016-06-01T21:06:47Z

Add const arrays

← Older revision		Revision as of 21:06, 1 June 2016
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	})		})
	field(INPI, {ca:"$(IOC):dblink MS"})		field(INPI, {ca:"$(IOC):dblink MS"})

			# These are constant arrays
			field(INPJ, [1, 2, 3, 4, 5])
			field(INPK, ["Constant strings should also be possible"]

	# This is a JSON-formatted info-tag		# This is a JSON-formatted info-tag

AndrewJohnson: First pass

2016-06-01T20:52:01Z

First pass

New page

== JSON Field Values ==

The current state of my Link Support development includes changes to the parsing of record instance data in database (.db) files.

At present the code adds the ability to parse simplified JSON in specific places in the .db file, and converts that to proper JSON stored in a string for later parts of the IOC parsing process. The places where I see JSON as being accepted are in record field values, and in info tag values. Some examples of JSON link addresses are shown below, although the specific syntax supported by the link types has not been decided yet so these are just illustrations of what might be possible. Note that currently only link fields would be expected to accept JSON objects, although the code shouldn't prevent additional support being added later for other field types if desired.

This modification does change the set of characters allowed in a bare-word string used as a field or info-tag value; the characters <code>:</code>, <code>;</code>, <code><></code> and <code>[]</code> can no longer be used without enclosing the string inside double-quotes.

record(aSub, "$(IOC):sub1") {
# These are all database links
field(INPA, "$(IOC):dblink MS")
field(INPB, {db:"$(IOC):dblink MS"})
field(INPC, {db:["$(IOC):dblink", MS]})
field(INPD, { # Comments are allowed inside JSON
db: {
pv:"$(IOC):dblink",
MS:true
}
})

# These are channel access links
field(INPE, "remote:calink.{\"ts\":{}} CP")
field(INPF, {ca:["remote:calink.{\"ts\":{}}", CP]})
field(INPG, {ca:["remote:calink", {ts:{}}, CP]})
field(INPH, {
ca: {
pv:"remote:calink",
filter: {ts:{}},
CP:true
}
})
field(INPI, {ca:"$(IOC):dblink MS"})

# This is a JSON-formatted info-tag
info(autosave, {
fields: [SCAN, DESC],
pass0: [VAL],
})
}

My rules for simplified JSON are that double-quotes are optional around any string (used as a key or a value) that only contains the characters <code>a</code>-<code>z</code>, <code>A</code>-<code>Z</code>, <code>9</code>-<code>0</code>, <code>_</code>, <code>-</code>, <code>+</code> or <code>.</code>. The JSON keywords <code>null</code>, <code>true</code> and <code>false</code> will not be recognized as strings, nor will numbers that match the JSON encoding rules. Since JSON numbers don't include Infinity or NaN they will be recognized as unquoted strings, but should be handled correctly by the later parsing code. The <code>#</code> character can also be used inside simplified JSON to introduce a comment that lasts until the end of the current line.

JSON Field Values - Revision history

AndrewJohnson: Add const arrays

AndrewJohnson: First pass