local_ctype <- function(mode = c("C", "UTF-8"), env = parent.frame()) {
  mode <- match.arg(mode)

  if (mode == "UTF-8") {
    sysname <- Sys.info()[["sysname"]]
    if (sysname == "Windows") {
      ctype <- "English_United States.1252"
    } else if (sysname == "Darwin") {
      ctype <- "UTF-8"
    } else {
      ctype <- "en_US.utf8"
    }
  } else {
    ctype <- "C"
  }

  ctype0 <- Sys.getlocale("LC_CTYPE")
  suppressWarnings({
    withr::local_locale(LC_CTYPE = ctype, .local_envir = env)
  })
  if (Sys.getlocale("LC_CTYPE") != ctype) {
    skip(paste0("Cannot change locale to '", ctype, "'"))
  }
  if (mode == "UTF-8" && !output_utf8()) {
    skip("Cannot change to UTF-8 output")
  }

  ctype0
}

with_ctype <- function(mode = c("C", "UTF-8"), code) {
  local_ctype(mode)
  force(code)
}