curl: Made --metalink option toggle Metalink functionality

In this change, --metalink option no longer takes argument.  If
it is specified, given URIs are processed as Metalink XML file.
If given URIs are remote (e.g., http URI), curl downloads it
first. Regardless URI is local file (e.g., file URI scheme) or
remote, Metalink XML file is not written to local file system and
the received data is fed into Metalink XML parser directly.  This
means with --metalink option, filename related options like -O
and -o are ignored.

Usage examples:

$ curl --metalink http://example.org/foo.metalink

This will download foo.metalink and parse it and then download
the URI described there.

$ curl --metalink file://foo.metalink

This will parse local file foo.metalink and then download the URI
described there.

1 files changed, 9 insertions, 1 deletions

diff --git a/src/tool_metalink.h b/src/tool_metalink.h
index 36b4b02c7..c2568a31e 100644
--- a/src/tool_metalink.h
+++ b/src/tool_metalink.h
@@ -82,13 +82,21 @@ extern const digest_params MD5_DIGEST_PARAMS[1];
 extern const digest_params SHA1_DIGEST_PARAMS[1];
 extern const digest_params SHA256_DIGEST_PARAMS[1];
 
+#include <metalink/metalink_parser.h>
+
 /*
  * Counts the resource in the metalinkfile.
  */
 int count_next_metalink_resource(metalinkfile *mlfile);
 void clean_metalink(struct Configurable *config);
 
-int parse_metalink(struct Configurable *config, const char *infile);
+int parse_metalink(struct Configurable *config, struct OutStruct *outs);
+
+/*
+ * Callback function for CURLOPT_WRITEFUNCTION
+ */
+size_t metalink_write_cb(void *buffer, size_t sz, size_t nmemb,
+                         void *userdata);
 
 /*
  * Returns nonzero if content_type includes "application/metalink+xml"