Perform a request and handle data as it streams back

After preparing a request, call req_perform_stream() to perform the request and handle the result with a streaming callback. This is useful for streaming HTTP APIs where potentially the stream never ends.

Usage

req_perform_stream(
  req,
  callback,
  timeout_sec = Inf,
  buffer_kb = 64,
  round = c("byte", "line")
)

Arguments

req: A request.
callback: A single argument callback function. It will be called repeatedly with a raw vector whenever there is at least buffer_kb worth of data to process. It must return TRUE to continue streaming.
timeout_sec: Number of seconds to process stream for.
buffer_kb: Buffer size, in kilobytes.
round: How should the raw vector sent to callback be rounded? Choose "byte", "line", or supply your own function that takes a raw vector of bytes and returns the locations of possible cut points (or integer() if there are none).

Value

An HTTP response.

Examples

show_bytes <- function(x) {
  cat("Got ", length(x), " bytes\n", sep = "")
  TRUE
}
resp <- request(example_url()) |>
  req_url_path("/stream-bytes/100000") |>
  req_perform_stream(show_bytes, buffer_kb = 32)
#> Got 32768 bytes
#> Got 32768 bytes
#> Got 32768 bytes
#> Got 1696 bytes