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path_to_connection <- function(path, check = c("file", "dir")) {
check <- match.arg(check)
if (!is.character(path) || length(path) != 1L)
return(path)
if (is_url(path)) {
if (requireNamespace("curl", quietly = TRUE)) {
return(curl::curl(path))
} else {
return(url(path))
}
}
if (check == "file") {
path <- check_path(path)
} else {
path <- file.path(check_path(dirname(path)), basename(path))
}
switch(tools::file_ext(path),
gz = gzfile(path, ""),
bz2 = bzfile(path, ""),
xz = xzfile(path, ""),
zip = zipfile(path, ""),
path
)
}
is_url <- function(path) {
grepl("^(http|ftp)s?://", path)
}
check_path <- function(path) {
if (file.exists(path))
return(normalizePath(path, "/", mustWork = FALSE))
stop("'", path, "' does not exist",
if (!is_absolute_path(path))
paste0(" in current working directory ('", getwd(), "')"),
".",
call. = FALSE
)
}
is_absolute_path <- function(path) {
grepl("^(/|[A-Za-z]:|\\\\|~)", path)
}
zipfile <- function(path, open = "r") {
files <- utils::unzip(path, list = TRUE)
file <- files$Name[[1]]
if (nrow(files) > 1) {
message("Multiple files in zip: reading '", file, "'")
}
unz(path, file, open = open)
}
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