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#' Filesystem Cache
#'
#' Use a cache on the local filesystem that will persist between R sessions.
#'
#' @param path Directory in which to store cached items.
#' @param compress Argument passed to \code{saveRDS}. One of FALSE, "gzip",
#' "bzip2" or "xz". Default: FALSE.
#'
#' @examples
#'
#' \dontrun{
#' # Use with Dropbox
#'
#' db <- cache_filesystem("~/Dropbox/.rcache")
#'
#' mem_runif <- memoise(runif, cache = db)
#'
#' # Use with Google Drive
#'
#' gd <- cache_filesystem("~/Google Drive/.rcache")
#'
#' mem_runif <- memoise(runif, cache = gd)
#'
#' }
#'
#' @export
#' @inheritParams cache_memory
cache_filesystem <- function(path, algo = "xxhash64", compress = FALSE) {
if (!(requireNamespace("digest"))) { stop("Package `digest` must be installed for `cache_filesystem()`.") } # nocov
if (!dir.exists(path)) {
dir.create(path, showWarnings = FALSE)
}
# convert to absolute path so it will work with user working directory changes
path <- normalizePath(path)
cache_reset <- function() {
cache_files <- list.files(path, full.names = TRUE)
file.remove(cache_files)
}
cache_set <- function(key, value) {
saveRDS(value, file = file.path(path, key), compress = compress)
}
cache_get <- function(key) {
readRDS(file = file.path(path, key))
}
cache_has_key <- function(key) {
file.exists(file.path(path, key))
}
cache_drop_key <- function(key) {
file.remove(file.path(path, key))
}
list(
digest = function(...) digest::digest(..., algo = algo),
reset = cache_reset,
set = cache_set,
get = cache_get,
has_key = cache_has_key,
drop_key = cache_drop_key,
keys = function() list.files(path)
)
}
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