Adding upstream version 43.5.upstream/43.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 870 insertions, 0 deletions

diff --git a/lib/gs-download-utils.c b/lib/gs-download-utils.c
new file mode 100644
index 0000000..4949064
--- /dev/null
+++ b/lib/gs-download-utils.c
@@ -0,0 +1,870 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*-
+ * vi:set noexpandtab tabstop=8 shiftwidth=8:
+ *
+ * Copyright (C) 2021, 2022 Endless OS Foundation LLC
+ *
+ * Author: Philip Withnall <pwithnall@endlessos.org>
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+/**
+ * SECTION:gs-download-utils
+ * @short_description: Download and HTTP utilities
+ *
+ * A set of utilities for downloading things and doing HTTP requests.
+ *
+ * Since: 42
+ */
+
+#include "config.h"
+
+#include <gio/gio.h>
+#include <glib.h>
+#include <glib-object.h>
+#include <glib/gi18n.h>
+#include <libsoup/soup.h>
+
+#include "gs-download-utils.h"
+#include "gs-utils.h"
+
+G_DEFINE_QUARK (gs-download-error-quark, gs_download_error)
+
+/**
+ * gs_build_soup_session:
+ *
+ * Build a new #SoupSession configured with the gnome-software user agent.
+ *
+ * A new #SoupSession should be used for each independent download context, such
+ * as in different plugins. Each #SoupSession caches HTTP connections and
+ * authentication information, and these likely needn’t be shared between
+ * plugins. Using separate sessions reduces thread contention.
+ *
+ * Returns: (transfer full): a new #SoupSession
+ * Since: 42
+ */
+SoupSession *
+gs_build_soup_session (void)
+{
+	return soup_session_new_with_options ("user-agent", gs_user_agent (),
+					      "timeout", 10,
+					      NULL);
+}
+
+/* See https://httpwg.org/specs/rfc7231.html#http.date
+ * For example: Sun, 06 Nov 1994 08:49:37 GMT */
+static gchar *
+date_time_to_rfc7231 (GDateTime *date_time)
+{
+#if SOUP_CHECK_VERSION(3, 0, 0)
+	return soup_date_time_to_string (date_time, SOUP_DATE_HTTP);
+#else
+	const gchar *day_names[] = { "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun" };
+	const gchar *month_names[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
+
+	/* We can’t just use g_date_time_format() here because its output
+	 * (particularly day and month names) is locale-dependent.
+	 * #SoupDate is also a pain to use because there’s no easy way to
+	 * convert from a #GDateTime with libsoup-2.4, while preserving the timezone. */
+	g_autofree gchar *time_str = g_date_time_format (date_time, "%H:%M:%S %Z");
+
+	return g_strdup_printf ("%s, %02d %s %d %s",
+				day_names[g_date_time_get_day_of_week (date_time) - 1],
+				g_date_time_get_day_of_month (date_time),
+				month_names[g_date_time_get_month (date_time) - 1],
+				g_date_time_get_year (date_time),
+				time_str);
+#endif
+}
+
+static GDateTime *
+date_time_from_rfc7231 (const gchar *rfc7231_str)
+{
+#if SOUP_CHECK_VERSION(3, 0, 0)
+	return soup_date_time_new_from_http_string (rfc7231_str);
+#else
+	g_autoptr(SoupDate) soup_date = NULL;
+	g_autoptr(GTimeZone) tz = NULL;
+
+	soup_date = soup_date_new_from_string (rfc7231_str);
+	if (soup_date == NULL)
+		return NULL;
+
+	if (soup_date->utc)
+		tz = g_time_zone_new_utc ();
+	else
+		tz = g_time_zone_new_offset (soup_date->offset * 60);
+
+	return g_date_time_new (tz, soup_date->year, soup_date->month,
+				soup_date->day, soup_date->hour,
+				soup_date->minute, soup_date->second);
+#endif
+}
+
+typedef struct {
+	/* Input data. */
+	gchar *uri;  /* (not nullable) (owned) */
+	GInputStream *input_stream;  /* (nullable) (owned) */
+	GOutputStream *output_stream;  /* (nullable) (owned) */
+	gsize buffer_size_bytes;
+	gchar *last_etag;  /* (nullable) (owned) */
+	GDateTime *last_modified_date;  /* (nullable) (owned) */
+	int io_priority;
+	GsDownloadProgressCallback progress_callback;  /* (nullable) */
+	gpointer progress_user_data;
+
+	/* In-progress state. */
+	SoupMessage *message;  /* (nullable) (owned) */
+	gboolean close_input_stream;
+	gboolean close_output_stream;
+	gboolean discard_output_stream;
+	gsize total_read_bytes;
+	gsize total_written_bytes;
+	gsize expected_stream_size_bytes;
+	GBytes *currently_unwritten_chunk;  /* (nullable) (owned) */
+
+	/* Output data. */
+	gchar *new_etag;  /* (nullable) (owned) */
+	GDateTime *new_last_modified_date;  /* (nullable) (owned) */
+	GError *error;  /* (nullable) (owned) */
+} DownloadData;
+
+static void
+download_data_free (DownloadData *data)
+{
+	g_assert (data->input_stream == NULL || g_input_stream_is_closed (data->input_stream));
+	g_assert (data->output_stream == NULL || g_output_stream_is_closed (data->output_stream));
+
+	g_assert (data->currently_unwritten_chunk == NULL || data->error != NULL);
+
+	g_clear_object (&data->input_stream);
+	g_clear_object (&data->output_stream);
+
+	g_clear_pointer (&data->last_etag, g_free);
+	g_clear_pointer (&data->last_modified_date, g_date_time_unref);
+	g_clear_object (&data->message);
+	g_clear_pointer (&data->uri, g_free);
+	g_clear_pointer (&data->new_etag, g_free);
+	g_clear_pointer (&data->new_last_modified_date, g_date_time_unref);
+	g_clear_pointer (&data->currently_unwritten_chunk, g_bytes_unref);
+	g_clear_error (&data->error);
+
+	g_free (data);
+}
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC (DownloadData, download_data_free)
+
+static void open_input_stream_cb (GObject      *source_object,
+                                  GAsyncResult *result,
+                                  gpointer      user_data);
+static void read_bytes_cb (GObject      *source_object,
+                           GAsyncResult *result,
+                           gpointer      user_data);
+static void write_bytes_cb (GObject      *source_object,
+                            GAsyncResult *result,
+                            gpointer      user_data);
+static void finish_download (GTask  *task,
+                             GError *error);
+static void close_stream_cb (GObject      *source_object,
+                             GAsyncResult *result,
+                             gpointer      user_data);
+static void download_progress (GTask *task);
+
+/**
+ * gs_download_stream_async:
+ * @soup_session: a #SoupSession
+ * @uri: (not nullable): the URI to download
+ * @output_stream: (not nullable): an output stream to write the download to
+ * @last_etag: (nullable): the last-known ETag of the URI, or %NULL if unknown
+ * @last_modified_date: (nullable): the last-known Last-Modified date of the
+ *   URI, or %NULL if unknown
+ * @io_priority: I/O priority to download and write at
+ * @progress_callback: (nullable): callback to call with progress information
+ * @progress_user_data: (nullable) (closure progress_callback): data to pass
+ *   to @progress_callback
+ * @cancellable: (nullable): a #GCancellable, or %NULL
+ * @callback: callback to call once the operation is complete
+ * @user_data: (closure callback): data to pass to @callback
+ *
+ * Download @uri and write it to @output_stream asynchronously.
+ *
+ * If @last_etag is non-%NULL or @last_modified_date is non-%NULL, they will be
+ * sent to the server, which may return a ‘not modified’ response. If so,
+ * @output_stream will not be written to, and will be closed with a cancelled
+ * close operation. This will ensure that the existing content of the output
+ * stream (if it’s a file, for example) will not be overwritten.
+ *
+ * Note that @last_etag must be the ETag value returned by the server last time
+ * the file was downloaded, not the local file ETag generated by GLib.
+ *
+ * If specified, @progress_callback will be called zero or more times until
+ * @callback is called, providing progress updates on the download.
+ *
+ * Since: 43
+ */
+void
+gs_download_stream_async (SoupSession                *soup_session,
+                          const gchar                *uri,
+                          GOutputStream              *output_stream,
+                          const gchar                *last_etag,
+                          GDateTime                  *last_modified_date,
+                          int                         io_priority,
+                          GsDownloadProgressCallback  progress_callback,
+                          gpointer                    progress_user_data,
+                          GCancellable               *cancellable,
+                          GAsyncReadyCallback         callback,
+                          gpointer                    user_data)
+{
+	g_autoptr(GTask) task = NULL;
+	g_autoptr(GError) local_error = NULL;
+	g_autoptr(SoupMessage) msg = NULL;
+	DownloadData *data;
+	g_autoptr(DownloadData) data_owned = NULL;
+
+	g_return_if_fail (SOUP_IS_SESSION (soup_session));
+	g_return_if_fail (uri != NULL);
+	g_return_if_fail (G_IS_OUTPUT_STREAM (output_stream));
+	g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));
+
+	task = g_task_new (soup_session, cancellable, callback, user_data);
+	g_task_set_source_tag (task, gs_download_stream_async);
+
+	data = data_owned = g_new0 (DownloadData, 1);
+	data->uri = g_strdup (uri);
+	data->output_stream = g_object_ref (output_stream);
+	data->close_output_stream = TRUE;
+	data->buffer_size_bytes = 8192;  /* arbitrarily chosen */
+	data->io_priority = io_priority;
+	data->progress_callback = progress_callback;
+	data->progress_user_data = progress_user_data;
+
+	g_task_set_task_data (task, g_steal_pointer (&data_owned), (GDestroyNotify) download_data_free);
+
+	/* local */
+	if (g_str_has_prefix (uri, "file://")) {
+		g_autoptr(GFile) local_file = g_file_new_for_path (uri + strlen ("file://"));
+		g_file_read_async (local_file, io_priority, cancellable, open_input_stream_cb, g_steal_pointer (&task));
+		return;
+	}
+
+	/* remote */
+	g_debug ("Downloading %s to %s", uri, G_OBJECT_TYPE_NAME (output_stream));
+	msg = soup_message_new (SOUP_METHOD_GET, uri);
+	if (msg == NULL) {
+		finish_download (task,
+				 g_error_new (G_IO_ERROR,
+					      G_IO_ERROR_INVALID_ARGUMENT,
+					      "Failed to parse URI ‘%s’", uri));
+		return;
+	}
+
+	data->message = g_object_ref (msg);
+
+	/* Caching support. Prefer ETags to modification dates, as the latter
+	 * have problems with rapid updates and clock drift. */
+	if (last_etag != NULL && *last_etag == '\0')
+		last_etag = NULL;
+	data->last_etag = g_strdup (last_etag);
+
+	if (last_modified_date != NULL)
+		data->last_modified_date = g_date_time_ref (last_modified_date);
+
+	if (last_etag != NULL) {
+#if SOUP_CHECK_VERSION(3, 0, 0)
+		soup_message_headers_append (soup_message_get_request_headers (msg), "If-None-Match", last_etag);
+#else
+		soup_message_headers_append (msg->request_headers, "If-None-Match", last_etag);
+#endif
+	} else if (last_modified_date != NULL) {
+		g_autofree gchar *last_modified_date_str = date_time_to_rfc7231 (last_modified_date);
+#if SOUP_CHECK_VERSION(3, 0, 0)
+		soup_message_headers_append (soup_message_get_request_headers (msg), "If-Modified-Since", last_modified_date_str);
+#else
+		soup_message_headers_append (msg->request_headers, "If-Modified-Since", last_modified_date_str);
+#endif
+	}
+
+#if SOUP_CHECK_VERSION(3, 0, 0)
+	soup_session_send_async (soup_session, msg, data->io_priority, cancellable, open_input_stream_cb, g_steal_pointer (&task));
+#else
+	soup_session_send_async (soup_session, msg, cancellable, open_input_stream_cb, g_steal_pointer (&task));
+#endif
+}
+
+static void
+open_input_stream_cb (GObject      *source_object,
+                      GAsyncResult *result,
+                      gpointer      user_data)
+{
+	g_autoptr(GTask) task = g_steal_pointer (&user_data);
+	DownloadData *data = g_task_get_task_data (task);
+	GCancellable *cancellable = g_task_get_cancellable (task);
+	g_autoptr(GInputStream) input_stream = NULL;
+	g_autoptr(GError) local_error = NULL;
+
+	/* This function can be called as a result of either reading a local
+	 * file, or sending an HTTP request, so @source_object’s type can vary. */
+	if (G_IS_FILE (source_object)) {
+		GFile *local_file = G_FILE (source_object);
+
+		/* Local file. */
+		input_stream = G_INPUT_STREAM (g_file_read_finish (local_file, result, &local_error));
+
+		if (input_stream == NULL) {
+			g_prefix_error (&local_error, "Failed to read ‘%s’: ",
+					g_file_peek_path (local_file));
+			finish_download (task, g_steal_pointer (&local_error));
+			return;
+		}
+
+		g_assert (data->input_stream == NULL);
+		data->input_stream = g_object_ref (input_stream);
+		data->close_input_stream = TRUE;
+	} else if (SOUP_IS_SESSION (source_object)) {
+		SoupSession *soup_session = SOUP_SESSION (source_object);
+		guint status_code;
+		const gchar *new_etag, *new_last_modified_str;
+
+		/* HTTP request. */
+#if SOUP_CHECK_VERSION(3, 0, 0)
+		input_stream = soup_session_send_finish (soup_session, result, &local_error);
+		status_code = soup_message_get_status (data->message);
+#else
+		input_stream = soup_session_send_finish (soup_session, result, &local_error);
+		status_code = data->message->status_code;
+#endif
+
+		if (input_stream != NULL) {
+			g_assert (data->input_stream == NULL);
+			data->input_stream = g_object_ref (input_stream);
+			data->close_input_stream = TRUE;
+		}
+
+		if (status_code == SOUP_STATUS_NOT_MODIFIED) {
+			/* If the file has not been modified from the ETag or
+			 * Last-Modified date we have, finish the download
+			 * early. Ensure to close the output stream so that its
+			 * existing content is *not* overwritten.
+			 *
+			 * Preserve the existing ETag. */
+			data->discard_output_stream = TRUE;
+			data->new_etag = g_strdup (data->last_etag);
+			data->new_last_modified_date = (data->last_modified_date != NULL) ? g_date_time_ref (data->last_modified_date) : NULL;
+			finish_download (task,
+					 g_error_new (GS_DOWNLOAD_ERROR,
+						      GS_DOWNLOAD_ERROR_NOT_MODIFIED,
+						      "Skipped downloading ‘%s’: %s",
+						      data->uri, soup_status_get_phrase (status_code)));
+			return;
+		} else if (status_code != SOUP_STATUS_OK) {
+			g_autoptr(GString) str = g_string_new (NULL);
+			g_string_append (str, soup_status_get_phrase (status_code));
+
+			if (local_error != NULL) {
+				g_string_append (str, ": ");
+				g_string_append (str, local_error->message);
+			}
+
+			finish_download (task,
+					 g_error_new (G_IO_ERROR,
+						      G_IO_ERROR_FAILED,
+						      "Failed to download ‘%s’: %s",
+						      data->uri, str->str));
+			return;
+		}
+
+		g_assert (input_stream != NULL);
+
+		/* Get the expected download size. */
+#if SOUP_CHECK_VERSION(3, 0, 0)
+		data->expected_stream_size_bytes = soup_message_headers_get_content_length (soup_message_get_response_headers (data->message));
+#else
+		data->expected_stream_size_bytes = soup_message_headers_get_content_length (data->message->response_headers);
+#endif
+
+		/* Store the new ETag for later use. */
+#if SOUP_CHECK_VERSION(3, 0, 0)
+		new_etag = soup_message_headers_get_one (soup_message_get_response_headers (data->message), "ETag");
+#else
+		new_etag = soup_message_headers_get_one (data->message->response_headers, "ETag");
+#endif
+		if (new_etag != NULL && *new_etag == '\0')
+			new_etag = NULL;
+		data->new_etag = g_strdup (new_etag);
+
+		/* Store the Last-Modified date for later use. */
+#if SOUP_CHECK_VERSION(3, 0, 0)
+		new_last_modified_str = soup_message_headers_get_one (soup_message_get_response_headers (data->message), "Last-Modified");
+#else
+		new_last_modified_str = soup_message_headers_get_one (data->message->response_headers, "Last-Modified");
+#endif
+		if (new_last_modified_str != NULL && *new_last_modified_str == '\0')
+			new_last_modified_str = NULL;
+		if (new_last_modified_str != NULL)
+			data->new_last_modified_date = date_time_from_rfc7231 (new_last_modified_str);
+	} else {
+		g_assert_not_reached ();
+	}
+
+	/* Splice in an asynchronous loop. We unfortunately can’t use
+	 * g_output_stream_splice_async() here, as it doesn’t provide a progress
+	 * callback. The approach is the same though. */
+	g_input_stream_read_bytes_async (input_stream, data->buffer_size_bytes, data->io_priority,
+					 cancellable, read_bytes_cb, g_steal_pointer (&task));
+}
+
+static void
+read_bytes_cb (GObject      *source_object,
+               GAsyncResult *result,
+               gpointer      user_data)
+{
+	GInputStream *input_stream = G_INPUT_STREAM (source_object);
+	g_autoptr(GTask) task = g_steal_pointer (&user_data);
+	DownloadData *data = g_task_get_task_data (task);
+	GCancellable *cancellable = g_task_get_cancellable (task);
+	g_autoptr(GBytes) bytes = NULL;
+	g_autoptr(GError) local_error = NULL;
+
+	bytes = g_input_stream_read_bytes_finish (input_stream, result, &local_error);
+
+	if (bytes == NULL) {
+		finish_download (task, g_steal_pointer (&local_error));
+		return;
+	}
+
+	/* Report progress. */
+	data->total_read_bytes += g_bytes_get_size (bytes);
+	data->expected_stream_size_bytes = MAX (data->expected_stream_size_bytes, data->total_read_bytes);
+	download_progress (task);
+
+	/* Write the downloaded data. */
+	if (g_bytes_get_size (bytes) > 0) {
+		g_clear_pointer (&data->currently_unwritten_chunk, g_bytes_unref);
+		data->currently_unwritten_chunk = g_bytes_ref (bytes);
+
+		g_output_stream_write_bytes_async (data->output_stream, bytes, data->io_priority,
+						   cancellable, write_bytes_cb, g_steal_pointer (&task));
+	} else {
+		finish_download (task, NULL);
+	}
+}
+
+static void
+write_bytes_cb (GObject      *source_object,
+                GAsyncResult *result,
+                gpointer      user_data)
+{
+	GOutputStream *output_stream = G_OUTPUT_STREAM (source_object);
+	g_autoptr(GTask) task = g_steal_pointer (&user_data);
+	DownloadData *data = g_task_get_task_data (task);
+	GCancellable *cancellable = g_task_get_cancellable (task);
+	gssize bytes_written_signed;
+	gsize bytes_written;
+	g_autoptr(GError) local_error = NULL;
+
+	bytes_written_signed = g_output_stream_write_bytes_finish (output_stream, result, &local_error);
+
+	if (bytes_written_signed < 0) {
+		finish_download (task, g_steal_pointer (&local_error));
+		return;
+	}
+
+	/* We know this is non-negative now. */
+	bytes_written = (gsize) bytes_written_signed;
+
+	/* Report progress. */
+	data->total_written_bytes += bytes_written;
+	download_progress (task);
+
+	g_assert (data->currently_unwritten_chunk != NULL);
+
+	if (bytes_written < g_bytes_get_size (data->currently_unwritten_chunk)) {
+		/* Partial write; try again with the remaining bytes. */
+		g_autoptr(GBytes) sub_bytes = g_bytes_new_from_bytes (data->currently_unwritten_chunk, bytes_written, g_bytes_get_size (data->currently_unwritten_chunk) - bytes_written);
+		g_assert (bytes_written > 0);
+
+		g_clear_pointer (&data->currently_unwritten_chunk, g_bytes_unref);
+		data->currently_unwritten_chunk = g_bytes_ref (sub_bytes);
+
+		g_output_stream_write_bytes_async (output_stream, sub_bytes, data->io_priority,
+						   cancellable, write_bytes_cb, g_steal_pointer (&task));
+	} else {
+		/* Full write succeeded. Start the next read. */
+		g_clear_pointer (&data->currently_unwritten_chunk, g_bytes_unref);
+
+		g_input_stream_read_bytes_async (data->input_stream, data->buffer_size_bytes, data->io_priority,
+						 cancellable, read_bytes_cb, g_steal_pointer (&task));
+	}
+}
+
+static inline gboolean
+is_not_modidifed_error (GError *error)
+{
+	return g_error_matches (error, GS_DOWNLOAD_ERROR, GS_DOWNLOAD_ERROR_NOT_MODIFIED);
+}
+
+/* error is (transfer full) */
+static void
+finish_download (GTask  *task,
+                 GError *error)
+{
+	DownloadData *data = g_task_get_task_data (task);
+	GCancellable *cancellable = g_task_get_cancellable (task);
+
+	/* Final progress update. */
+	if (error == NULL || is_not_modidifed_error (error)) {
+		data->expected_stream_size_bytes = data->total_read_bytes;
+		download_progress (task);
+	}
+
+	/* Record the error from the operation, if set. */
+	g_assert (data->error == NULL);
+	data->error = g_steal_pointer (&error);
+
+	g_assert (!data->discard_output_stream || data->close_output_stream);
+
+	if (data->close_output_stream) {
+		g_autoptr(GCancellable) output_cancellable = NULL;
+
+		g_assert (data->output_stream != NULL);
+
+		/* If there’s been a prior error, or we are aborting writing the
+		 * output stream (perhaps because of a cache hit), close the
+		 * output stream but cancel the close operation so that the old
+		 * output file is not overwritten. */
+		if ((data->error != NULL && !is_not_modidifed_error (data->error)) || data->discard_output_stream) {
+			output_cancellable = g_cancellable_new ();
+			g_cancellable_cancel (output_cancellable);
+		} else if (g_task_get_cancellable (task) != NULL) {
+			output_cancellable = g_object_ref (g_task_get_cancellable (task));
+		}
+
+		g_output_stream_close_async (data->output_stream, data->io_priority, output_cancellable, close_stream_cb, g_object_ref (task));
+	}
+
+	if (data->close_input_stream && data->input_stream != NULL) {
+		g_input_stream_close_async (data->input_stream, data->io_priority, cancellable, close_stream_cb, g_object_ref (task));
+	}
+
+	/* Check in case both streams are already closed. */
+	close_stream_cb (NULL, NULL, g_object_ref (task));
+}
+
+static void
+close_stream_cb (GObject      *source_object,
+                 GAsyncResult *result,
+                 gpointer      user_data)
+{
+	g_autoptr(GTask) task = g_steal_pointer (&user_data);
+	DownloadData *data = g_task_get_task_data (task);
+	g_autoptr(GError) local_error = NULL;
+
+	if (G_IS_INPUT_STREAM (source_object)) {
+		/* Errors in closing the input stream are not fatal. */
+		if (!g_input_stream_close_finish (G_INPUT_STREAM (source_object),
+						  result, &local_error))
+			g_debug ("Error closing input stream: %s", local_error->message);
+		g_clear_error (&local_error);
+
+		data->close_input_stream = FALSE;
+	} else if (G_IS_OUTPUT_STREAM (source_object)) {
+		/* Errors in closing the output stream are fatal, but don’t
+		 * overwrite errors set earlier in the operation. */
+		if (!g_output_stream_close_finish (G_OUTPUT_STREAM (source_object),
+						   result, &local_error)) {
+			/* If we are aborting writing the output stream (perhaps
+			 * because of a cache hit), don’t report the error at
+			 * all. */
+			if (data->discard_output_stream &&
+			    g_error_matches (local_error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+				g_clear_error (&local_error);
+			else if (data->error == NULL)
+				data->error = g_steal_pointer (&local_error);
+			else if (!g_error_matches (local_error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+				g_debug ("Error closing output stream: %s", local_error->message);
+		}
+		g_clear_error (&local_error);
+
+		data->close_output_stream = FALSE;
+		data->discard_output_stream = FALSE;
+	} else {
+		/* finish_download() calls this with a NULL source_object */
+	}
+
+	/* Still waiting for one of the streams to close? */
+	if (data->close_input_stream || data->close_output_stream)
+		return;
+
+	if (data->error != NULL) {
+		g_task_return_error (task, g_error_copy (data->error));
+	} else {
+		g_task_return_boolean (task, TRUE);
+	}
+}
+
+static void
+download_progress (GTask *task)
+{
+	DownloadData *data = g_task_get_task_data (task);
+
+	if (data->progress_callback != NULL) {
+		/* This should be guaranteed by the rest of the download code. */
+		g_assert (data->expected_stream_size_bytes >= data->total_written_bytes);
+
+		data->progress_callback (data->total_written_bytes, data->expected_stream_size_bytes,
+					 data->progress_user_data);
+	}
+}
+
+/**
+ * gs_download_stream_finish:
+ * @soup_session: a #SoupSession
+ * @result: result of the asynchronous operation
+ * @new_etag_out: (out callee-allocates) (transfer full) (optional) (nullable):
+ *   return location for the ETag of the downloaded file (which may be %NULL),
+ *   or %NULL to ignore it
+ * @new_last_modified_date_out: (out callee-allocates) (transfer full) (optional) (nullable):
+ *   return location for the new Last-Modified date of the downloaded file
+ *   (which may be %NULL), or %NULL to ignore it
+ * @error: return location for a #GError
+ *
+ * Finish an asynchronous download operation started with
+ * gs_download_stream_async().
+ *
+ * Returns: %TRUE on success, %FALSE otherwise
+ * Since: 43
+ */
+gboolean
+gs_download_stream_finish (SoupSession   *soup_session,
+                           GAsyncResult  *result,
+                           gchar        **new_etag_out,
+                           GDateTime    **new_last_modified_date_out,
+                           GError       **error)
+{
+	DownloadData *data;
+
+	g_return_val_if_fail (g_task_is_valid (result, soup_session), FALSE);
+	g_return_val_if_fail (g_task_get_source_tag (G_TASK (result)) == gs_download_stream_async, FALSE);
+	g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+	data = g_task_get_task_data (G_TASK (result));
+
+	if (new_etag_out != NULL)
+		*new_etag_out = g_strdup (data->new_etag);
+	if (new_last_modified_date_out != NULL)
+		*new_last_modified_date_out = (data->new_last_modified_date != NULL) ? g_date_time_ref (data->new_last_modified_date) : NULL;
+
+	return g_task_propagate_boolean (G_TASK (result), error);
+}
+
+typedef struct {
+	/* Input data. */
+	gchar *uri;  /* (not nullable) (owned) */
+	GFile *output_file;  /* (not nullable) (owned) */
+	int io_priority;
+	GsDownloadProgressCallback progress_callback;
+	gpointer progress_user_data;
+
+	/* In-progress data. */
+	gchar *last_etag;  /* (nullable) (owned) */
+	GDateTime *last_modified_date;  /* (nullable) (owned) */
+} DownloadFileData;
+
+static void
+download_file_data_free (DownloadFileData *data)
+{
+	g_free (data->uri);
+	g_clear_object (&data->output_file);
+	g_free (data->last_etag);
+	g_clear_pointer (&data->last_modified_date, g_date_time_unref);
+	g_free (data);
+}
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC (DownloadFileData, download_file_data_free)
+
+static void download_replace_file_cb (GObject      *source_object,
+                                      GAsyncResult *result,
+                                      gpointer      user_data);
+static void download_file_cb (GObject      *source_object,
+                              GAsyncResult *result,
+                              gpointer      user_data);
+
+/**
+ * gs_download_file_async:
+ * @soup_session: a #SoupSession
+ * @uri: (not nullable): the URI to download
+ * @output_file: (not nullable): an output file to write the download to
+ * @io_priority: I/O priority to download and write at
+ * @progress_callback: (nullable): callback to call with progress information
+ * @progress_user_data: (nullable) (closure progress_callback): data to pass
+ *   to @progress_callback
+ * @cancellable: (nullable): a #GCancellable, or %NULL
+ * @callback: callback to call once the operation is complete
+ * @user_data: (closure callback): data to pass to @callback
+ *
+ * Download @uri and write it to @output_file asynchronously, overwriting the
+ * existing content of @output_file.
+ *
+ * The ETag and modification time of @output_file will be queried and, if known,
+ * used to skip the download if @output_file is already up to date.
+ *
+ * If specified, @progress_callback will be called zero or more times until
+ * @callback is called, providing progress updates on the download.
+ *
+ * Since: 42
+ */
+void
+gs_download_file_async (SoupSession                *soup_session,
+                        const gchar                *uri,
+                        GFile                      *output_file,
+                        int                         io_priority,
+                        GsDownloadProgressCallback  progress_callback,
+                        gpointer                    progress_user_data,
+                        GCancellable               *cancellable,
+                        GAsyncReadyCallback         callback,
+                        gpointer                    user_data)
+{
+	g_autoptr(GTask) task = NULL;
+	DownloadFileData *data;
+	g_autoptr(DownloadFileData) data_owned = NULL;
+	g_autoptr(GFile) output_file_parent = NULL;
+	g_autoptr(GError) local_error = NULL;
+
+	g_return_if_fail (SOUP_IS_SESSION (soup_session));
+	g_return_if_fail (uri != NULL);
+	g_return_if_fail (G_IS_FILE (output_file));
+	g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));
+
+	task = g_task_new (soup_session, cancellable, callback, user_data);
+	g_task_set_source_tag (task, gs_download_file_async);
+
+	data = data_owned = g_new0 (DownloadFileData, 1);
+	data->uri = g_strdup (uri);
+	data->output_file = g_object_ref (output_file);
+	data->io_priority = io_priority;
+	data->progress_callback = progress_callback;
+	data->progress_user_data = progress_user_data;
+	g_task_set_task_data (task, g_steal_pointer (&data_owned), (GDestroyNotify) download_file_data_free);
+
+	/* Create the destination file’s directory.
+	 * FIXME: This should be made async; it hasn’t done for now as it’s
+	 * likely to be fast. */
+	output_file_parent = g_file_get_parent (output_file);
+
+	if (output_file_parent != NULL &&
+	    !g_file_make_directory_with_parents (output_file_parent, cancellable, &local_error) &&
+	    !g_error_matches (local_error, G_IO_ERROR, G_IO_ERROR_EXISTS)) {
+		g_task_return_error (task, g_steal_pointer (&local_error));
+		return;
+	}
+
+	g_clear_error (&local_error);
+
+	/* Query the old ETag and modification date if the file already exists. */
+	data->last_etag = gs_utils_get_file_etag (output_file, &data->last_modified_date, cancellable);
+
+	/* Create the output file.
+	 *
+	 * Note that `data->last_etag` is *not* passed in here, as the ETag from
+	 * the server and the file modification ETag that GLib uses are
+	 * different things. For g_file_replace_async(), GLib always uses an
+	 * ETag it generates internally based on the file mtime (see
+	 * _g_local_file_info_create_etag()), which will never match what the
+	 * server returns in its ETag header.
+	 *
+	 * This is fine, as we are using the ETag to avoid an unnecessary HTTP
+	 * download if possible. We don’t care about tracking changes to the
+	 * file on disk. */
+	g_file_replace_async (output_file,
+			      NULL,  /* ETag */
+			      FALSE,  /* make_backup */
+			      G_FILE_CREATE_PRIVATE | G_FILE_CREATE_REPLACE_DESTINATION,
+			      io_priority,
+			      cancellable,
+			      download_replace_file_cb,
+			      g_steal_pointer (&task));
+}
+
+static void
+download_replace_file_cb (GObject      *source_object,
+                          GAsyncResult *result,
+                          gpointer      user_data)
+{
+	GFile *output_file = G_FILE (source_object);
+	g_autoptr(GTask) task = g_steal_pointer (&user_data);
+	SoupSession *soup_session = g_task_get_source_object (task);
+	GCancellable *cancellable = g_task_get_cancellable (task);
+	DownloadFileData *data = g_task_get_task_data (task);
+	g_autoptr(GFileOutputStream) output_stream = NULL;
+	g_autoptr(GError) local_error = NULL;
+
+	output_stream = g_file_replace_finish (output_file, result, &local_error);
+
+	if (output_stream == NULL) {
+		g_task_return_error (task, g_steal_pointer (&local_error));
+		return;
+	}
+
+	/* Do the download. */
+	gs_download_stream_async (soup_session, data->uri, G_OUTPUT_STREAM (output_stream),
+				  data->last_etag, data->last_modified_date, data->io_priority,
+				  data->progress_callback, data->progress_user_data,
+				  cancellable, download_file_cb, g_steal_pointer (&task));
+}
+
+static void
+download_file_cb (GObject      *source_object,
+                  GAsyncResult *result,
+                  gpointer      user_data)
+{
+	SoupSession *soup_session = SOUP_SESSION (source_object);
+	g_autoptr(GTask) task = g_steal_pointer (&user_data);
+	GCancellable *cancellable = g_task_get_cancellable (task);
+	DownloadFileData *data = g_task_get_task_data (task);
+	g_autofree gchar *new_etag = NULL;
+	g_autoptr(GError) local_error = NULL;
+
+	if (!gs_download_stream_finish (soup_session, result, &new_etag, NULL, &local_error)) {
+		g_task_return_error (task, g_steal_pointer (&local_error));
+		return;
+	}
+
+	/* Update the stored HTTP ETag.
+	 *
+	 * Under the assumption that this code is only ever used for locally
+	 * cached copies of remote files (i.e. the local copies are never
+	 * modified except by downloading an updated version from the server),
+	 * it’s safe to use the local file modification date for Last-Modified,
+	 * and save having to update that explicitly. This is because the
+	 * modification time of the local file equals when gnome-software last
+	 * checked for updates to it — which is correct to send as the
+	 * If-Modified-Since the next time gnome-software checks for updates to
+	 * the file. */
+	gs_utils_set_file_etag (data->output_file, new_etag, cancellable);
+
+	g_task_return_boolean (task, TRUE);
+}
+
+/**
+ * gs_download_file_finish:
+ * @soup_session: a #SoupSession
+ * @result: result of the asynchronous operation
+ * @error: return location for a #GError
+ *
+ * Finish an asynchronous download operation started with
+ * gs_download_file_async().
+ *
+ * Returns: %TRUE on success, %FALSE otherwise
+ * Since: 42
+ */
+gboolean
+gs_download_file_finish (SoupSession   *soup_session,
+                         GAsyncResult  *result,
+                         GError       **error)
+{
+	g_return_val_if_fail (g_task_is_valid (result, soup_session), FALSE);
+	g_return_val_if_fail (g_task_get_source_tag (G_TASK (result)) == gs_download_file_async, FALSE);
+	g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+	return g_task_propagate_boolean (G_TASK (result), error);
+}