From 246826ecb4d2dcb99418ce67cd927a0df46243ab Mon Sep 17 00:00:00 2001
From: Arvid Norberg <arvid@libtorrent.org>
Date: Sat, 27 Apr 2013 22:35:06 +0000
Subject: [PATCH] support arbitrarily long magnet URIs in make_magnet_uri

---
 src/magnet_uri.cpp       | 40 +++++++++++++++++++++-------------------
 test/test_primitives.cpp | 10 +++++++---
 2 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/src/magnet_uri.cpp b/src/magnet_uri.cpp
index e54ba4b37..7644bc8e0 100644
--- a/src/magnet_uri.cpp
+++ b/src/magnet_uri.cpp
@@ -44,25 +44,25 @@ namespace libtorrent
 	{
 		if (!handle.is_valid()) return "";
 
-		char ret[2048];
+		std::string ret;
 		sha1_hash const& ih = handle.info_hash();
-		int num_chars = snprintf(ret, sizeof(ret), "magnet:?xt=urn:btih:%s"
-			, to_hex(ih.to_string()).c_str());
+		ret += "magnet:?xt=urn:btih:";
+		ret += to_hex(ih.to_string());
 
 		torrent_status st = handle.status(torrent_handle::query_name);
-		std::string name = st.name;
 
-		if (!name.empty() && sizeof(ret) - 5 > num_chars)
-			num_chars += snprintf(ret + num_chars, sizeof(ret) - num_chars, "&dn=%s"
-				, escape_string(name.c_str(), name.length()).c_str());
+		if (!st.name.empty())
+		{
+			ret += "&dn=";
+			ret += escape_string(st.name.c_str(), st.name.length());
+		}
 
 		std::vector<announce_entry> const& tr = handle.trackers();
 
 		for (std::vector<announce_entry>::const_iterator i = tr.begin(), end(tr.end()); i != end; ++i)
 		{
-			if (num_chars >= sizeof(ret)) break;
-			num_chars += snprintf(ret + num_chars, sizeof(ret) - num_chars, "&tr=%s"
-				, escape_string(i->url.c_str(), i->url.length()).c_str());
+			ret += "&tr=";
+			ret += escape_string(i->url.c_str(), i->url.length());
 		}
 
 		return ret;
@@ -70,23 +70,25 @@ namespace libtorrent
 
 	std::string make_magnet_uri(torrent_info const& info)
 	{
-		char ret[2048];
+		std::string ret;
 		sha1_hash const& ih = info.info_hash();
-		int num_chars = snprintf(ret, sizeof(ret), "magnet:?xt=urn:btih:%s"
-			, to_hex(ih.to_string()).c_str());
+		ret += "magnet:?xt=urn:btih:";
+		ret += to_hex(ih.to_string());
 
 		std::string const& name = info.name();
 
-		if (!name.empty() && sizeof(ret) - 5 > num_chars)
-			num_chars += snprintf(ret + num_chars, sizeof(ret) - num_chars, "&dn=%s"
-				, escape_string(name.c_str(), name.length()).c_str());
+		if (!name.empty())
+		{
+			ret += "&dn=";
+			ret += escape_string(name.c_str(), name.length());
+		}
 
 		std::vector<announce_entry> const& tr = info.trackers();
+
 		for (std::vector<announce_entry>::const_iterator i = tr.begin(), end(tr.end()); i != end; ++i)
 		{
-			if (num_chars >= sizeof(ret)) break;
-			num_chars += snprintf(ret + num_chars, sizeof(ret) - num_chars, "&tr=%s"
-				, escape_string(i->url.c_str(), i->url.length()).c_str());
+			ret += "&tr=";
+			ret += escape_string(i->url.c_str(), i->url.length());
 		}
 
 		return ret;
diff --git a/test/test_primitives.cpp b/test/test_primitives.cpp
index 133860fc6..a3f7e7ce2 100644
--- a/test/test_primitives.cpp
+++ b/test/test_primitives.cpp
@@ -1385,8 +1385,11 @@ int test_main()
 		"abcdefghij0123456789abcdefghij0123456789abcdefghij0123456789abcdefghij0123456789abcdefghij012345.txt";
 	std::string comparison = test;
 	trim_path_element(test);
-	comparison.resize(TORRENT_MAX_PATH - 4);
-	comparison += ".txt"; // the extension is supposed to be preserved
+	if (comparison.size() > TORRENT_MAX_PATH)
+	{
+		comparison.resize(TORRENT_MAX_PATH - 4);
+		comparison += ".txt"; // the extension is supposed to be preserved
+	}
 	TEST_EQUAL(test, comparison);
 
 	// extensions > 15 characters are ignored
@@ -1403,7 +1406,8 @@ int test_main()
 		"abcdefghij0123456789abcdefghij0123456789abcdefghij0123456789abcdefghij.123456789abcdefghij0123456789";
 	comparison = test;
 	trim_path_element(test);
-	comparison.resize(TORRENT_MAX_PATH);
+	if (comparison.size() > TORRENT_MAX_PATH)
+		comparison.resize(TORRENT_MAX_PATH);
 	TEST_EQUAL(test, comparison);