Utility that collects data from the HTTP reply into lines and calls user-provided function.

When one provides an R function to process the body of the R rep

Usage

chunkToLineReader(f, verbose = FALSE)

Arguments

f: a function that is to be called each time the read function is invoked and there are complete lines in that input.
verbose: a logical value. If TRUE, information is displayed when there is any text that does not form a complete line and is held for processing in the next chunk.

Details

This constructs a closure and then processes each chunk as they are passed to the read function. It strips away any text that does not form a complete line at the end of the chunk and holds this to be added to the next chunk being processed.

Value

A list with two components

read: the function that will do the actual reading from the HTTP response stream and call the function f on each step (assuming the chunk has a line marker.
comp2: Description of 'comp2'

...

References

Curl homepage https://curl.se/

Author

Duncan Temple Lang

Examples

# Read a rectangular table of data into R from the URL
# and add up the values and the number of values read.

summer =
function()
{
  total = 0.0
  numValues = 0

  list(read = function(txt) {
                 con = textConnection(txt)
                 on.exit(close(con))
                 els = scan(con)
                 numValues <<- numValues + length(els)
                 total <<- total + sum(els)

                 ""
              },
       result = function() c(total = total, numValues = numValues))
}

s = summer()

tryCatch(
  getURL("https://aitap.grebedoc.dev/RCurl/matrix.data", write = chunkToLineReader(s$read)$read),
  GenericCurlError = identity
)
#> function (txt) 
#> {
#>     if (nzchar(leftOvers)) {
#>         txt = paste(leftOvers, txt, sep = "")
#>         leftOvers <<- ""
#>     }
#>     leftOvers <<- gsub("^.*\n", "", txt)
#>     if (verbose && nchar(leftOvers)) 
#>         cat("Left over:", leftOvers, "\n")
#>     Lines = strsplit(txt, "\n")[[1]]
#>     if (nchar(leftOvers)) 
#>         Lines = Lines[-length(Lines)]
#>     if (length(Lines)) 
#>         f(Lines)
#>     nchar(txt)
#> }
#> <bytecode: 0x55c5b60b0c40>
#> <environment: 0x55c5b60b3180>