This is an R6 class that implements a concurrency safe package cache.
Details
By default these fields are included for every package:
fullpath
Full package path.path
Package path, within the repository.package
Package name.url
URL it was downloaded from.etag
ETag for the last download, from the given URL.sha256
SHA256 hash of the file.
Additional fields can be added as needed.
For a simple API to a session-wide instance of this class, see
pkg_cache_summary()
and the other functions listed there.
Usage
pc <- package_cache$new(path = NULL)
pc$list()
pc$find(..., .list = NULL)
pc$copy_to(..., .list = NULL)
pc$add(file, path, sha256 = shasum256(file), ..., .list = NULL)
pc$add_url(url, path, ..., .list = NULL, on_progress = NULL,
http_headers = NULL)
pc$async_add_url(url, path, ..., .list = NULL, on_progress = NULL,
http_headers = NULL)
pc$copy_or_add(target, urls, path, sha256 = NULL, ..., .list = NULL,
on_progress = NULL, http_headers = NULL)
pc$async_copy_or_add(target, urls, path, ..., sha256 = NULL, ...,
.list = NULL, on_progress = NULL, http_headers = NULL)
pc$update_or_add(target, urls, path, ..., .list = NULL,
on_progress = NULL, http_headers = NULL)
pc$async_update_or_add(target, urls, path, ..., .list = NULL,
on_progress = NULL, http_headers = NULL)
pc$delete(..., .list = NULL)
Arguments
path
: Forpackage_cache$new()
the location of the cache. For other functions the location of the file inside the cache....
: Extra attributes to search for. They have to be named..list
: Extra attributes to search for, they have to in a named list.file
: Path to the file to add.url
: URL attribute. This is used to update the file, if requested.sha256
: SHA256 hash of the file.on_progress
: Callback to create progress bar. Passed to internal functionhttp_get()
.target
: Path to copy the (first) to hit to.urls
: Character vector or URLs to try to download the file from.http_headers
: HTTP headers to add to all HTTP queries.
Details
package_cache$new()
attaches to the cache at path
. (By default
a platform dependent user level cache directory.) If the cache does
not exists, it creates it.
pc$list()
lists all files in the cache, returns a data frame with all the
default columns, and potentially extra columns as well.
pc$find()
list all files that match the specified criteria (fullpath
,
path
, package
, etc.). Custom columns can be searched for as well.
pc$copy_to()
will copy the first matching file from the cache to
target
. It returns the data frame of all matching records, invisibly.
If no file matches, it returns an empty (zero-row) data frame.
pc$add()
adds a file to the cache.
pc$add_url()
downloads a file and adds it to the cache.
pc$async_add_url()
is the same, but it is asynchronous.
pc$copy_or_add()
works like pc$copy_to()
, but if the file is not in
the cache, it tries to download it from one of the specified URLs first.
pc$async_copy_or_add()
is the same, but asynchronous.
pc$update_or_add()
is like pc$copy_to_add()
, but if the file is in
the cache it tries to update it from the urls, using the stored ETag to
avoid unnecessary downloads.
pc$async_update_or_add()
is the same, but it is asynchronous.
pc$delete()
deletes the file(s) from the cache.
Examples
## Although package_cache usually stores packages, it may store
## arbitrary files, that can be search by metadata
pc <- package_cache$new(path = tempfile())
pc$list()
#> [1] fullpath path package url etag sha256
#> <0 rows> (or 0-length row.names)
cat("foo\n", file = f1 <- tempfile())
cat("bar\n", file = f2 <- tempfile())
pc$add(f1, "/f1")
#> fullpath path package url etag
#> 1 /tmp/RtmpTiw2uQ/file179e1fd3b6c0//f1 /f1 NA NA NA
#> sha256
#> 1 b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c
pc$add(f2, "/f2")
#> fullpath path package url etag
#> 2 /tmp/RtmpTiw2uQ/file179e1fd3b6c0//f2 /f2 NA NA NA
#> sha256
#> 2 7d865e959b2466918c9863afca942d0fb89d7c9ac0c99bafc3749504ded97730
pc$list()
#> fullpath path package url etag
#> 1 /tmp/RtmpTiw2uQ/file179e1fd3b6c0//f1 /f1 NA NA NA
#> 2 /tmp/RtmpTiw2uQ/file179e1fd3b6c0//f2 /f2 NA NA NA
#> sha256
#> 1 b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c
#> 2 7d865e959b2466918c9863afca942d0fb89d7c9ac0c99bafc3749504ded97730
pc$find(path = "/f1")
#> fullpath path package url etag
#> 1 /tmp/RtmpTiw2uQ/file179e1fd3b6c0//f1 /f1 NA NA NA
#> sha256
#> 1 b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c
pc$copy_to(target = f3 <- tempfile(), path = "/f1")
#> fullpath path package url etag
#> 1 /tmp/RtmpTiw2uQ/file179e1fd3b6c0//f1 /f1 NA NA NA
#> sha256
#> 1 b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c
readLines(f3)
#> [1] "foo"