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Read-only HTTP-served FilesDaf.

Source: R/http_format.R
HttpDaf.Rd

A Daf reader that fetches a files_daf() directory served over HTTP(S). The server must expose the FilesDaf tree verbatim and include a metadata.zip bundle at the root (see pack_files_daf_metadata()). From dafr 0.2.0 onward, FilesDaf writes maintain metadata.zip automatically; for pre-0.2.0 stores call pack_files_daf_metadata() before publishing.

Usage

HttpDaf(
  name = character(0),
  internal = new.env(parent = emptyenv()),
  cache = new.env(parent = emptyenv()),
  axis_version_counter = new.env(parent = emptyenv()),
  vector_version_counter = new.env(parent = emptyenv()),
  matrix_version_counter = new.env(parent = emptyenv())
)

http_daf(url, name = NULL)

Arguments

name

Optional override; defaults to the daf's name scalar (if any) or the URL basename.

internal

Internal per-store environment used by format backends to stash backend-specific state; reserved for package use.

cache

Three-tier cache environment (mapped / memory / query). See new_cache_env().

axis_version_counter

Environment tracking per-axis mutation counters; invalidates cached reads when an axis is modified.

vector_version_counter

Environment tracking per-vector mutation counters.

matrix_version_counter

Environment tracking per-matrix mutation counters.

url

HTTP(S) URL pointing at a FilesDaf root.

Value

A HttpDaf instance (DafReadOnly subclass).

Details

The client downloads metadata.zip once at open time, parses it in memory, and serves all JSON metadata from it (no further HTTP traffic for format_has_* / format_*_set / scalar reads). Non-JSON payloads (axis .txt files, vector/matrix .data / .nzind / .nzval / .colptr / .rowval / .nztxt) are fetched lazily on first access via one HTTP GET each, cached by the standard cache layer.

Read-only — mutations are not supported. Server data is assumed stable while a HttpDaf is open; reopen to pick up changes.

HTTP timeout

Each GET uses a 30-second timeout. Override via options(dafr.http_timeout = N) (seconds) or environment variable DAFR_HTTP_TIMEOUT for slow links or large lazy payloads. Requests are issued without retry; flaky-network handling is on the caller.

URL-derived name

When neither name nor a name scalar in the daf is set, the default name is basename(url). Two HttpDafs opened from different hosts but the same basename will collide on name; pass an explicit name to disambiguate.

Examples

if (FALSE) { # \dontrun{
d <- http_daf("https://example.com/path/to/data.daf/")
get_scalar(d, "organism")
} # }