Refactor common HTTP header handling

Move the common code out of HTTPRequest and HTTPResponse into the new
HTTPHeaders class, a container for headers with some sensible HTTP-specific
behaviour.

lib/httpserver/HTTPException.txt

@@ -15,3 +15,5 @@ BadResponse				11
 ResponseReadFailed			12
 NoStreamConfigured			13
 RequestFailedUnexpectedly		14	The request was expected to succeed, but it failed.
+ContentLengthAlreadySet			15	Tried to send a request without content, but the Content-Length header is already set.
+WrongContentLength			16	There was too much or not enough data in the request content stream.

lib/httpserver/HTTPHeaders.cpp

@@ -0,0 +1,311 @@
+// --------------------------------------------------------------------------
+//
+// File
+//		Name:    HTTPHeaders
+//		Purpose: Utility class to decode HTTP headers
+//		Created: 16/8/2015
+//
+// --------------------------------------------------------------------------
+
+#include "Box.h"
+
+#include <stdlib.h>
+
+#include "HTTPHeaders.h"
+#include "IOStreamGetLine.h"
+
+#include "MemLeakFindOn.h"
+
+
+// --------------------------------------------------------------------------
+//
+// Function
+//		Name:    HTTPHeaders::ReadFromStream(IOStreamGetLine &rGetLine,
+//			 int Timeout);
+//		Purpose: Read headers from a stream into internal storage.
+//		Created: 2015-08-22
+//
+// --------------------------------------------------------------------------
+void HTTPHeaders::ReadFromStream(IOStreamGetLine &rGetLine, int Timeout)
+{
+	std::string header;
+	bool haveHeader = false;
+	while(true)
+	{
+		if(rGetLine.IsEOF())
+		{
+			// Header terminates unexpectedly
+			THROW_EXCEPTION(HTTPException, BadRequest)
+		}
+
+		std::string currentLine;
+		if(!rGetLine.GetLine(currentLine, false /* no preprocess */, Timeout))
+		{
+			// Timeout
+			THROW_EXCEPTION(HTTPException, RequestReadFailed)
+		}
+
+		// Is this a continuation of the previous line?
+		bool processHeader = haveHeader;
+		if(!currentLine.empty() && (currentLine[0] == ' ' || currentLine[0] == '\t'))
+		{
+			// A continuation, don't process anything yet
+			processHeader = false;
+		}
+		//TRACE3("%d:%d:%s\n", processHeader, haveHeader, currentLine.c_str());
+
+		// Parse the header -- this will actually process the header
+		// from the previous run around the loop.
+		if(processHeader)
+		{
+			ParseHeaderLine(header);
+
+			// Unset have header flag, as it's now been processed
+			haveHeader = false;
+		}
+
+		// Store the chunk of header the for next time round
+		if(haveHeader)
+		{
+			header += currentLine;
+		}
+		else
+		{
+			header = currentLine;
+			haveHeader = true;
+		}
+
+		// End of headers?
+		if(currentLine.empty())
+		{
+			// All done!
+			break;
+		}
+	}
+}
+
+// --------------------------------------------------------------------------
+//
+// Function
+//		Name:    HTTPHeaders::ParseHeaderLine
+//		Purpose: Splits a line into name and value, and adds it to
+//			 this header set.
+//		Created: 2015-08-22
+//
+// --------------------------------------------------------------------------
+void HTTPHeaders::ParseHeaderLine(const std::string& rLine)
+{
+	// Find where the : is in the line
+	std::string::size_type colon = rLine.find(':');
+	if(colon == std::string::npos || colon == 0 ||
+		colon > rLine.size() - 2)
+	{
+		THROW_EXCEPTION_MESSAGE(HTTPException, BadResponse,
+			"Invalid header line: " << rLine);
+	}
+
+	std::string name = rLine.substr(0, colon);
+	std::string value = rLine.substr(colon + 2);
+	AddHeader(name, value);
+}
+
+// --------------------------------------------------------------------------
+//
+// Function
+//		Name:    HTTPHeaders::GetHeader(const std::string& name,
+//			 const std::string* pValueOut)
+//		Purpose: Get the value of a single header, with the specified
+//			 name, into the std::string pointed to by pValueOut.
+//			 Returns true if the header exists, and false if it
+//			 does not (in which case *pValueOut is not modified).
+//			 Certain headers are stored in specific fields, e.g.
+//			 content-length and host, but this should be done
+//			 transparently to callers of AddHeader and GetHeader.
+//		Created: 2016-03-12
+//
+// --------------------------------------------------------------------------
+bool HTTPHeaders::GetHeader(const std::string& rName, std::string* pValueOut) const
+{
+	const std::string name = ToLowerCase(rName);
+
+	// Remember to change AddHeader() and GetHeader() together for each
+	// item in this list!
+	if(name == "content-length")
+	{
+		// Convert number to string.
+		std::ostringstream out;
+		out << mContentLength;
+		*pValueOut = out.str();
+	}
+	else if(name == "content-type")
+	{
+		*pValueOut = mContentType;
+	}
+	else if(name == "connection")
+	{
+		// TODO FIXME: not all values of the Connection header can be
+		// stored and retrieved at the moment.
+		*pValueOut = mKeepAlive ? "keep-alive" : "close";
+	}
+	else if (name == "host")
+	{
+		std::ostringstream out;
+		out << mHostName;
+		if(mHostPort != DEFAULT_PORT)
+		{
+			out << ":" << mHostPort;
+		}
+		*pValueOut = out.str();
+	}
+	else
+	{
+		// All other headers are stored in mExtraHeaders.
+
+		for (std::vector<Header>::const_iterator
+			i  = mExtraHeaders.begin();
+			i != mExtraHeaders.end(); i++)
+		{
+			if (i->first == name)
+			{
+				*pValueOut = i->second;
+				return true;
+			}
+		}
+
+		// Not found in mExtraHeaders.
+		return false;
+	}
+
+	// For all except the else case above (searching mExtraHeaders), we must have
+	// found a value, as there will always be one.
+	return true;
+}
+
+// --------------------------------------------------------------------------
+//
+// Function
+//		Name:    HTTPHeaders::AddHeader(const std::string& name,
+//			 const std::string& value)
+//		Purpose: Add a single header, with the specified name and
+//			 value, to the internal list of headers. Certain
+//			 headers are stored in specific fields, e.g.
+//			 content-length and host, but this should be done
+//			 transparently to callers of AddHeader and GetHeader.
+//		Created: 2015-08-22
+//
+// --------------------------------------------------------------------------
+void HTTPHeaders::AddHeader(const std::string& rName, const std::string& value)
+{
+	std::string name = ToLowerCase(rName);
+
+	// Remember to change AddHeader() and GetHeader() together for each
+	// item in this list!
+	if(name == "content-length")
+	{
+		// Decode number
+		long len = ::strtol(value.c_str(), NULL, 10);
+		// returns zero in error case, this is OK
+		if(len < 0) len = 0;
+		// Store
+		mContentLength = len;
+	}
+	else if(name == "content-type")
+	{
+		// Store rest of string as content type
+		mContentType = value;
+	}
+	else if(name == "connection")
+	{
+		// Connection header, what is required?
+		if(::strcasecmp(value.c_str(), "close") == 0)
+		{
+			mKeepAlive = false;
+		}
+		else if(::strcasecmp(value.c_str(), "keep-alive") == 0)
+		{
+			mKeepAlive = true;
+		}
+		// else don't understand, just assume default for protocol version
+	}
+	else if (name == "host")
+	{
+		// Store host header
+		mHostName = value;
+
+		// Is there a port number to split off?
+		std::string::size_type colon = mHostName.find_first_of(':');
+		if(colon != std::string::npos)
+		{
+			// There's a port in the string... attempt to turn it into an int
+			mHostPort = ::strtol(mHostName.c_str() + colon + 1, 0, 10);
+
+			// Truncate the string to just the hostname
+			mHostName = mHostName.substr(0, colon);
+		}
+	}
+	else
+	{
+		mExtraHeaders.push_back(Header(name, value));
+	}
+}
+
+// --------------------------------------------------------------------------
+//
+// Function
+//		Name:    HTTPHeaders::WriteTo(IOStream& rOutput, int Timeout)
+//		Purpose: Write all headers to the supplied stream.
+//		Created: 2015-08-22
+//
+// --------------------------------------------------------------------------
+void HTTPHeaders::WriteTo(IOStream& rOutput, int Timeout) const
+{
+	std::ostringstream oss;
+
+	if (mContentLength != -1)
+	{
+		oss << "Content-Length: " << mContentLength << "\r\n";
+	}
+
+	if (mContentType != "")
+	{
+		oss << "Content-Type: " << mContentType << "\r\n";
+	}
+
+	if (mHostName != "")
+	{
+		oss << "Host: " << GetHostNameWithPort() << "\r\n";
+	}
+
+	if (mKeepAlive)
+	{
+		oss << "Connection: keep-alive\r\n";
+	}
+	else
+	{
+		oss << "Connection: close\r\n";
+	}
+
+	for (std::vector<Header>::const_iterator i = mExtraHeaders.begin();
+		i != mExtraHeaders.end(); i++)
+	{
+		oss << i->first << ": " << i->second << "\r\n";
+	}
+
+	rOutput.Write(oss.str(), Timeout);
+}
+
+std::string HTTPHeaders::GetHostNameWithPort() const
+{
+
+	if (mHostPort != 80)
+	{
+		std::ostringstream oss;
+		oss << mHostName << ":" << mHostPort;
+		return oss.str();
+	}
+	else
+	{
+		return mHostName;
+	}
+}
+