Merge pull request #33 from jhiemstrawisc/issue-32

Switch static variable to thread_local to fix underflow bug

src/HTTPCommands.cc

@@ -135,28 +135,31 @@ int debug_callback(CURL *, curl_infotype ci, char *data, size_t size, void *) {
 	return 0;
 }
 
+// A callback function that gets passed to curl_easy_setopt for reading data
+// from the payload
 size_t read_callback(char *buffer, size_t size, size_t n, void *v) {
-	// This can be static because only one curl_easy_perform() can be
-	// running at a time.
-	static size_t sentSoFar = 0;
-	std::string *payload = (std::string *)v;
-
-	if (sentSoFar == payload->size()) {
-		sentSoFar = 0;
+	// The callback gets the void pointer that we set with CURLOPT_READDATA. In
+	// this case, it's a pointer to an HTTPRequest::Payload struct that contains
+	// the data to be sent, along with the offset of the data that has already
+	// been sent.
+	HTTPRequest::Payload *payload = (HTTPRequest::Payload *)v;
+
+	if (payload->sentSoFar == payload->data->size()) {
+		payload->sentSoFar = 0;
 		return 0;
 	}
 
 	size_t request = size * n;
-	if (request > payload->size()) {
-		request = payload->size();
+	if (request > payload->data->size()) {
+		request = payload->data->size();
 	}
 
-	if (sentSoFar + request > payload->size()) {
-		request = payload->size() - sentSoFar;
+	if (payload->sentSoFar + request > payload->data->size()) {
+		request = payload->data->size() - payload->sentSoFar;
 	}
 
-	memcpy(buffer, payload->data() + sentSoFar, request);
-	sentSoFar += request;
+	memcpy(buffer, payload->data->data() + payload->sentSoFar, request);
+	payload->sentSoFar += request;
 
 	return request;
 }
@@ -230,7 +233,13 @@ bool HTTPRequest::sendPreparedRequest(const std::string &protocol,
 			return false;
 		}
 
-		rv = curl_easy_setopt(curl.get(), CURLOPT_READDATA, &payload);
+		// Our HTTPRequest instance should have a pointer to the payload data
+		// and the offset of the data Here, we tell curl_easy_setopt to use the
+		// read_callback function to read the data from the payload
+		this->callback_payload = std::unique_ptr<HTTPRequest::Payload>(
+			new HTTPRequest::Payload{&payload, 0});
+		rv = curl_easy_setopt(curl.get(), CURLOPT_READDATA,
+							  callback_payload.get());
 		if (rv != CURLE_OK) {
 			this->errorCode = "E_CURL_LIB";
 			this->errorMessage = "curl_easy_setopt( CURLOPT_READDATA ) failed.";

src/HTTPCommands.hh

@@ -19,6 +19,7 @@
 #pragma once
 
 #include <map>
+#include <memory>
 #include <string>
 
 class XrdSysError;
@@ -48,6 +49,12 @@ class HTTPRequest {
 	unsigned long getResponseCode() const { return responseCode; }
 	const std::string &getResultString() const { return resultString; }
 
+	// Currently only used in PUTS, but potentially useful elsewhere
+	struct Payload {
+		const std::string *data;
+		size_t sentSoFar;
+	};
+
   protected:
 	bool sendPreparedRequest(const std::string &protocol,
 							 const std::string &uri,
@@ -72,6 +79,7 @@ class HTTPRequest {
 	bool includeResponseHeader;
 
 	std::string httpVerb;
+	std::unique_ptr<HTTPRequest::Payload> callback_payload;
 
 	XrdSysError &m_log;
 };