[WIP Patch 03/12] Two new functions for the http API

[Mike Hommey <mh@glandium.org>]

http_get_strbuf and http_get_file allow respectively to retrieve contents of
an URL to a strbuf or an opened file handle.

Both these functions are the beginning of the http code refactoring.

Signed-off-by: Mike Hommey <mh@glandium.org>
---
 http.c |   85 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 http.h |   17 +++++++++++++
 2 files changed, 102 insertions(+), 0 deletions(-)

diff --git a/http.c b/http.c
index ee58799..82534cf 100644
--- a/http.c
+++ b/http.c
@@ -638,3 +638,88 @@ int http_fetch_ref(const char *base, struct ref *ref)
 	free(url);
 	return ret;
 }
+
+/* http_request() targets */
+#define HTTP_REQUEST_STRBUF	0
+#define HTTP_REQUEST_FILE	1
+
+static int http_request(const char *url, void *result, int target, int options)
+{
+	struct active_request_slot *slot;
+	struct slot_results results;
+	struct curl_slist *headers = NULL;
+	struct strbuf buf = STRBUF_INIT;
+
+	slot = get_active_slot();
+	slot->results = &results;
+	curl_easy_setopt(slot->curl, CURLOPT_HTTPGET, 1);
+
+	if (result == NULL) {
+		curl_easy_setopt(slot->curl, CURLOPT_NOBODY, 1);
+	} else {
+		curl_easy_setopt(slot->curl, CURLOPT_NOBODY, 0);
+		curl_easy_setopt(slot->curl, CURLOPT_FILE, result);
+
+		if (target == HTTP_REQUEST_FILE) {
+			long posn = ftell(result);
+			curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION,
+					 fwrite);
+			if (posn > 0) {
+				strbuf_addf(&buf, "Range: bytes=%ld-", posn);
+				headers = curl_slist_append(headers, buf.buf);
+				strbuf_reset(&buf);
+			}
+			slot->local = result;
+		} else
+			curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION,
+					 fwrite_buffer);
+	}
+
+	strbuf_addstr(&buf, "Pragma:");
+	if (options & HTTP_NO_CACHE)
+		strbuf_addstr(&buf, " no-cache");
+
+	headers = curl_slist_append(headers, buf.buf);
+	strbuf_release(&buf);
+
+	curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, headers);
+
+	if (start_active_slot(slot)) {
+		run_active_slot(slot);
+		if (results.curl_result == CURLE_OK)
+			return HTTP_OK;
+		else if (missing_target(&results))
+			return HTTP_MISSING_TARGET;
+	}
+	return HTTP_ERROR;
+}
+
+int http_get_strbuf(const char *url, struct strbuf *result, int options)
+{
+	return http_request(url, result, HTTP_REQUEST_STRBUF, options);
+}
+
+int http_get_file(const char *url, const char *filename, int options)
+{
+	int ret;
+	struct strbuf tmpfile = STRBUF_INIT;
+	FILE *result;
+
+	strbuf_addf(&tmpfile, "%s.temp", filename);
+	result = fopen(tmpfile.buf, "a");
+	if (! result) {
+		error("Unable to open local file %s", tmpfile.buf);
+		ret = HTTP_ERROR;
+		goto cleanup;
+	}
+
+	ret = http_request(url, result, HTTP_REQUEST_FILE, options);
+	fclose(result);
+
+	if ((ret == HTTP_OK) && move_temp_to_file(tmpfile.buf, filename))
+		ret = HTTP_ERROR;
+cleanup:
+	strbuf_release(&tmpfile);
+	return ret;
+}
diff --git a/http.h b/http.h
index 905b462..323c780 100644
--- a/http.h
+++ b/http.h
@@ -104,4 +104,21 @@ static inline int missing__target(int code, int result)
 
 extern int http_fetch_ref(const char *base, struct ref *ref);
 
+/* Options for http_request_*() */
+#define HTTP_NO_CACHE		1
+
+/* Return values for http_request_*() */
+#define HTTP_OK			0
+#define HTTP_MISSING_TARGET	1
+#define HTTP_ERROR		2
+
+/* Requests an url and stores the result in a strbuf.
+ * If the result pointer is NULL, a HTTP HEAD request is made instead of GET. */
+int http_get_strbuf(const char *url, struct strbuf *result, int options);
+
+/* Downloads an url and stores the result in the given file.
+ * If a previous interrupted download is detected (i.e. a previous temporary
+ * file is still around) the download is resumed. */
+int http_get_file(const char *url, const char *filename, int options);
+
 #endif /* HTTP_H */
-- 
1.6.1.141.gb32a