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###########################################################################/**
# @RdocFunction .readText
#
# @title "Reads the content of a local or an online text file"
#
# \description{
# @get "title".
# }
#
# @synopsis
#
# \arguments{
# \item{con}{A @character string specifying a local file or a URL,
# or a @connection.}
# \item{...}{Not used.}
# \item{maxAge}{A @numeric scalar specifying the maximum age (in seconds)
# of cached URL contents before downloading and recaching.
# If zero or less, the URL will always be downloaded.}
# }
#
# \value{
# Returns a @character string.
# }
#
# \section{Caching URL}{
# When reading online URLs, it may take time a significant time to
# read its content. If the content is changing rarely, it is possible
# to cache the content locally. If a cached version is found, then it
# is read instead.
# It is possible to control how often a file should be recached. If the
# cache is older than argument \code{maxAge} (in seconds), then the file
# is redownloaded and recached.
# }
#
# \section{Newline substitution}{
# All occurrences of \code{\\r\\n} and \code{\\r} are replaced with
# \code{\\n} such that all lines are ending in \code{\\n} regardless
# of encoding.
# }
#
# @author
#
# @keyword file
# @keyword IO
# @keyword internal
#*/###########################################################################
.readText <- function(con, ..., maxAge=getOption("R.rsp::downloadIfOlderThan", -Inf)) {
if (is.character(con)) {
file <- con
# Is the file local and an URL?
isUrl <- isUrl(file)
# (a) If URL, download to temporary directory
if (isUrl) {
url <- file
path <- tempdir()
filename <- getChecksum(url)
pathname <- file.path(path, filename)
# By default, download URL
download <- TRUE
# Unless...
if (isFile(pathname)) {
# Age (in seconds) when downloaded file is considered too old
maxAge <- as.double(maxAge)
if (is.na(maxAge)) maxAge <- -Inf
maxAge <- Arguments$getDouble(maxAge)
# Time when file was downloaded
mtime <- file.info(pathname)$mtime
# Age of downloaded file in seconds
dtime <- Sys.time() - mtime
units(dtime) <- "secs"
download <- isTRUE(dtime > maxAge)
}
if (download) {
withoutGString({
pathname <- downloadFile(url, filename=pathname, skip=FALSE)
})
}
if (isFile(pathname)) file <- pathname
} # if (isUrl)
# (b) Try to open file connection
con <- tryCatch({
suppressWarnings({
file(file, open="rb")
})
}, error = function(ex) {
# (b) If failed, try to download file first
if (regexpr("^https://", file, ignore.case=TRUE) == -1L) {
throw(ex)
}
url <- file
withoutGString({
pathname <- downloadFile(url, path=tempdir())
})
file(pathname, open="rb")
})
on.exit(close(con))
}
# Sanity check
stop_if_not(inherits(con, "connection"))
bfr <- NULL
while (TRUE) {
bfrT <- readChar(con, nchars=1e6)
if (length(bfrT) == 0L) break
bfrT <- gsub("\r\n", "\n", bfrT, fixed=TRUE)
bfrT <- gsub("\r", "\n", bfrT, fixed=TRUE)
bfr <- c(bfr, bfrT)
}
bfr <- paste(bfr, collapse="")
if (FALSE) {
bfr <- strsplit(bfr, split="\n", fixed=TRUE)
bfr <- unlist(bfr, use.names=FALSE)
}
## Sanity check
stop_if_not(is.character(bfr), length(bfr) == 1L)
bfr
} # .readText()
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