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Read a streaming body a chunk at a time

Source: R/resp-stream.R, R/resp-stream-aws.R
resp_stream_raw.Rd

  • resp_stream_raw() retrieves bytes (raw vectors).

  • resp_stream_lines() retrieves lines of text (character vectors).

  • resp_stream_sse() retrieves a single server-sent event.

  • resp_stream_aws() retrieves a single event from an AWS stream (i.e. mime type `application/vnd.amazon.eventstream“).

Use resp_stream_is_complete() to determine if there is further data waiting on the stream.

Usage

resp_stream_raw(resp, kb = 32)

resp_stream_lines(resp, lines = 1, max_size = Inf, warn = TRUE)

resp_stream_sse(resp, max_size = Inf)

resp_stream_aws(resp, max_size = Inf)

# S3 method for class 'httr2_response'
close(con, ...)

resp_stream_is_complete(resp)

Arguments

resp, con

A streaming response created by req_perform_connection().

kb

How many kilobytes (1024 bytes) of data to read.

lines

The maximum number of lines to return at once.

max_size

The maximum number of bytes to buffer; once this number of bytes has been exceeded without a line/event boundary, an error is thrown.

warn

Like readLines(): warn if the connection ends without a final EOL.

...

Not used; included for compatibility with generic.

Value

  • resp_stream_raw(): a raw vector.

  • resp_stream_lines(): a character vector.

  • resp_stream_sse(): a list with components type, data, and id

  • resp_stream_aws(): a list with components headers and body. body will be automatically parsed if the event contents a :content-type header with application/json.

resp_stream_sse() and resp_stream_aws() will return NULL to signal that the end of the stream has been reached or, if in nonblocking mode, that no event is currently available.

Examples

req <- request(example_url()) |>
  req_template("GET /stream/:n", n = 5)

con <- req |> req_perform_connection()
while (!resp_stream_is_complete(con)) {
  lines <- con |> resp_stream_lines(2)
  cat(length(lines), " lines received\n", sep = "")
}
#> 2 lines received
#> 2 lines received
#> 1 lines received
close(con)

# You can also see what's happening by setting verbosity
con <- req |> req_perform_connection(verbosity = 2)
#> -> GET /stream/5 HTTP/1.1
#> -> Host: 127.0.0.1:41599
#> -> User-Agent: httr2/1.1.0.9000 r-curl/6.1.0 libcurl/8.5.0
#> -> Accept: */*
#> -> Accept-Encoding: deflate, gzip, br, zstd
#> -> 
#> <- HTTP/1.1 200 OK
#> <- Date: Tue, 21 Jan 2025 17:58:52 GMT
#> <- Content-Type: application/json
#> <- Transfer-Encoding: chunked
#> <- 
while (!resp_stream_is_complete(con)) {
  lines <- con |> resp_stream_lines(2)
}
#> << {"url":"http://127.0.0.1:41599/stream/5","args":{},"headers":{"Host":"127.0.0.1:41599","User-Agent":"httr2/1.1.0.9000 r-curl/6.1.0 libcurl/8.5.0","Accept":"*/*","Accept-Encoding":"deflate, gzip, br, zstd"},"origin":"127.0.0.1","id":0}<< {"url":"http://127.0.0.1:41599/stream/5","args":{},"headers":{"Host":"127.0.0.1:41599","User-Agent":"httr2/1.1.0.9000 r-curl/6.1.0 libcurl/8.5.0","Accept":"*/*","Accept-Encoding":"deflate, gzip, br, zstd"},"origin":"127.0.0.1","id":1}
#> 
#> << {"url":"http://127.0.0.1:41599/stream/5","args":{},"headers":{"Host":"127.0.0.1:41599","User-Agent":"httr2/1.1.0.9000 r-curl/6.1.0 libcurl/8.5.0","Accept":"*/*","Accept-Encoding":"deflate, gzip, br, zstd"},"origin":"127.0.0.1","id":2}<< {"url":"http://127.0.0.1:41599/stream/5","args":{},"headers":{"Host":"127.0.0.1:41599","User-Agent":"httr2/1.1.0.9000 r-curl/6.1.0 libcurl/8.5.0","Accept":"*/*","Accept-Encoding":"deflate, gzip, br, zstd"},"origin":"127.0.0.1","id":3}
#> 
#> << {"url":"http://127.0.0.1:41599/stream/5","args":{},"headers":{"Host":"127.0.0.1:41599","User-Agent":"httr2/1.1.0.9000 r-curl/6.1.0 libcurl/8.5.0","Accept":"*/*","Accept-Encoding":"deflate, gzip, br, zstd"},"origin":"127.0.0.1","id":4}
#> 
close(con)