downloads: open FILE in advance and use default write handler

Now that the number of pending downloads is kept below a certain limit
(see poll_fewer_than()) it is possible to open files before starting
the transfer. Using the default curl write handler and explicit
open/close of the file makes the code simpler.

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>

include/swupd.h

@@ -91,7 +91,6 @@ struct file {
 	int last_change;
 	struct update_stat stat;
 
-	unsigned int fd_valid : 1;
 	unsigned int is_dir : 1;
 	unsigned int is_file : 1;
 	unsigned int is_link : 1;
@@ -112,7 +111,7 @@ struct file {
 
 	char *staging; /* output name used during download & staging */
 	CURL *curl;    /* curl handle if downloading */
-	int fd;        /* file written into during downloading, unset when fd_valid is false */
+	FILE *fh;      /* file written into during downloading */
 };
 
 extern bool download_only;
@@ -232,7 +231,7 @@ extern void swupd_curl_cleanup(void);
 extern void swupd_curl_set_current_version(int v);
 extern void swupd_curl_set_requested_version(int v);
 extern double swupd_query_url_content_size(char *url);
-extern size_t swupd_download_file(void *ptr, size_t size, size_t nmemb, void *userdata);
+extern CURLcode swupd_download_file_start(struct file *file);
 extern CURLcode swupd_download_file_complete(CURLcode curl_ret, struct file *file);
 extern int swupd_curl_get_file(const char *url, char *filename, struct file *file,
 			       struct version_container *tmp_version, bool pack);

src/curl.c

@@ -158,62 +158,28 @@ static size_t swupd_download_version_to_memory(void *ptr, size_t size, size_t nm
 	return data_len;
 }
 
-/* curl easy CURLOPT_WRITEFUNCTION callback */
-size_t swupd_download_file(void *ptr, size_t size, size_t nmemb, void *userdata)
+CURLcode swupd_download_file_start(struct file *file)
 {
-	struct file *file = (struct file *)userdata;
-	const char *outfile;
-	int fd;
-	FILE *f;
-	size_t written, remaining;
-
-	outfile = file->staging;
-	if (file->fd_valid) {
-		fd = file->fd;
-	} else {
-		fd = open(outfile, O_CREAT | O_RDWR | O_CLOEXEC | O_APPEND, 00600);
-		if (fd < 0) {
-			fprintf(stderr, "Cannot open file for write \\*outfile=\"%s\",strerror=\"%s\"*\\\n",
-				outfile, strerror(errno));
-			return -1;
-		}
-		file->fd = fd;
-		file->fd_valid = 1;
+	file->fh = fopen(file->staging, "w");
+	if (!file->fh) {
+		fprintf(stderr, "Cannot open file for write \\*outfile=\"%s\",strerror=\"%s\"*\\\n",
+			file->staging, strerror(errno));
+		return CURLE_WRITE_ERROR;
 	}
-
-	/* handle short writes with repeated write() calls */
-	for (remaining = size * nmemb; remaining; remaining -= written) {
-		written = write(fd, ptr, size*nmemb);
-		if (written < 0) {
-			if (errno == EINTR) {
-				written = 0;
-				continue;
-			}
-			fprintf(stderr, "write error \\*outfile=\"%s\",strerror=\"%s\"*\\\n",
-				outfile, strerror(errno));
-			return -1;
-		}
-	}
-
-	if (fdatasync(fd)) {
-		fprintf(stderr, "fdatasync \\*outfile=\"%s\",strerror=\"%s\"*\\\n", outfile, strerror(errno));
-		return -1;
-	}
-
-	return size*nmemb;
+	return CURLE_OK;
 }
 
 CURLcode swupd_download_file_complete(CURLcode curl_ret, struct file *file)
 {
-	if (file->fd_valid) {
-		if (close(file->fd)) {
+	if (file->fh) {
+		if (fclose(file->fh)) {
 			fprintf(stderr, "Cannot close file after write \\*outfile=\"%s\",strerror=\"%s\"*\\\n",
 				file->staging, strerror(errno));
 			if (curl_ret == CURLE_OK) {
 				curl_ret = CURLE_WRITE_ERROR;
 			}
 		}
-		file->fd_valid = 0;
+		file->fh = NULL;
 	}
 	return curl_ret;
 }
@@ -246,6 +212,7 @@ int swupd_curl_get_file(const char *url, char *filename, struct file *file,
 
 		if (file) {
 			local = file;
+			local->fh = NULL;
 		} else {
 			local = calloc(1, sizeof(struct file));
 			if (!local) {
@@ -266,11 +233,11 @@ int swupd_curl_get_file(const char *url, char *filename, struct file *file,
 		if (curl_ret != CURLE_OK) {
 			goto exit;
 		}
-		curl_ret = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, swupd_download_file);
+		curl_ret = swupd_download_file_start(local);
 		if (curl_ret != CURLE_OK) {
 			goto exit;
 		}
-		curl_ret = curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)local);
+		curl_ret = curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)local->fh);
 		if (curl_ret != CURLE_OK) {
 			goto exit;
 		}

src/download.c

@@ -525,6 +525,7 @@ void full_download(struct file *file)
 	CURLMcode curlm_ret = CURLM_OK;
 	CURLcode curl_ret = CURLE_OK;
 
+	file->fh = NULL;
 	ret = swupd_curl_hashmap_insert(file);
 	if (ret > 0) { /* no download needed */
 		/* File already exists - report success */
@@ -567,11 +568,11 @@ void full_download(struct file *file)
 	if (curl_ret != CURLE_OK) {
 		goto out_bad;
 	}
-	curl_ret = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, swupd_download_file);
+	curl_ret = swupd_download_file_start(file);
 	if (curl_ret != CURLE_OK) {
 		goto out_bad;
 	}
-	curl_ret = curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)file);
+	curl_ret = curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)file->fh);
 	if (curl_ret != CURLE_OK) {
 		goto out_bad;
 	}
@@ -597,6 +598,7 @@ void full_download(struct file *file)
 	goto out_good;
 
 out_bad:
+	(void) swupd_download_file_complete(CURLE_OK, file);
 	failed = list_prepend_data(failed, file);
 	if (curl != NULL) {
 		/* Must remove handle out of multi queue first!*/