Lua: Capturing String Based on Number of Symbols Received - string

Question

I currently have a string that can be any length in size based on a single digit in one or two specific locations (based on the first digit captured). For example:
Changed
First digit captured tells me IF a file name is to follow: "1" = Object Name Follows. "0" = Next input captured is Length Multiplier.
"1" is not always received. But "0" is always received.
With "1" Capture it looks like this:
START|(1)|NAMEOFGRAPHIC|(0)|(#)|INPUT|INPUT|INPUT|INPUT|... etc
With "0" (no "1" captured)
START|(0)|(#)|INPUT|INPUT|INPUT|INPUT|... etc
The Length Multiplier bit (always follows "0") is the number of INPUT groups to follow. A "group" is a set of 4xINPUT's. So, if it was a "4", the string I want to completely capture looks like this:
With a "1":
START|(1)|NAMEOFGRAPHIC|(0)|(4)|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|
With a "0":
START|(0)|(4)|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|INPUT|
As each INPUT is received, a pipe symbol is added after. I want to use the pipes to monitor the length of the input based on the digit. If the digit is 5, for example, it would capture the 3x INPUT, 5, then 5x INPUT after (with all pipes included). Once this is done, the function would send the fully captured string to other function(s) for use.
I am having problems working out the receiving function to capture this full string. I have tried to count the number of pipes in different loop functions and all are resulting in errors.
Attempts include (please understand I'm pretty new to all of this):
local buffer = ""
function pipe_count(input)
a = "|"
buffer = buffer..input.."|"
while #a < 5 do
buffer = buffer..input.."|"
return buffer
end
end
local buffer = ""
function pipe_count(input)
buffer = buffer..input.."|"
mult = tonumber(buffer:match("(.-|.-|.-|(%d)|.*)"))
while buffer do
for i = 1, mult do
buffer = buffer..input.."|"
end
return buffer
end
Those were two examples I tried. I deleted my other futile attempts to capture the exact string length. My current issue that it is taking the INPUT captures, as each one is received, and sending it to the next function prior to capturing the entire string. So, if I had received the string at the top, it would look like this:
`INPUT`
`INPUT|INPUT`
`INPUT|INPUT|INPUT`
`INPUT|INPUT|INPUT|5`
`INPUT|INPUT|INPUT|5|INPUT`
`INPUT|INPUT|INPUT|5|INPUT|INPUT` etc
until finally the string below is received:
`INPUT|INPUT|INPUT|5|INPUT|INPUT|INPUT|INPUT|INPUT|`
At this point, my file runs as it should. But up until this point, I'm getting errors since the parameters of the function(s) aren't fully met.
Ideally, I want that last string before moving on.
Any ideas would be very welcomed and appreciated.
Cheers
ETA: These INPUT's are filling a buffer. I want that check digit to be responsible for the string to only be used if the length value is met. Again, I really appreciate all input. Thank you.
ETA: Example code tried and more input details.

Answer 1

All strings in Lua are internalized, so it's usually a better idea to push strings onto an array than to repeatedly rebuild the same string. This example takes input line by line from stdin. 3 data inputs, followed by a number, followed by that number of data inputs. There are plenty of other ways to do it, but this is pretty easy to follow.
local buffer = {}
function process_input(input)
if #buffer == 3 then
input = tonumber(input)
end
table.insert(buffer,input)
if #buffer > 4 and #buffer == buffer[4] + 4 then
local pipe_delim = table.concat(buffer,'|')
buffer = {}
return pipe_delim
end
end
repeat
local input = io.read()
local pipe_delim = process_input( input )
if pipe_delim then
print('Got:', pipe_delim)
end
until false