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rfile-iobinaryfiles

textConnection equivalent that can readBin

I'm writing tests for a binary format parser, whose API accepts a Connection object. I'd like to put examples of binary data directly into test cases, as these examples are short and numerous.

If it was a text format, I'd just write:

test_that("readFoo parses message X", {
    data <- readFoo(textConnection("Bar"))
    expect_that(data$q, 1)
})

…but readFoo uses readBin(…, 'raw') internally, and this requires a binary connection, which textConnection is not. Therefore,

test_that("readFoo parses message X", {
    data <- readFoo(textConnection('\x01\x7a\x02\x2c\x7d\x0d\x5a\x0b\x0c\x01'))
    expect_that(data$q, 1)
})

fails with:

Error in readBin(conn, "raw", 10) : can only read from a binary connection

Is it possible to make this work?

Solution

  • You probably want to use a "raw connection" via the rawConnection() function, which behaves basically like textConnection(). The cross-references in the base package documentation aren't great, so it can be easy to miss this one.