MultipartParser.cpp

Go to the documentation of this file.

// MultipartParser.cpp

// Implements the cMultipartParser class that parses messages in "multipart/*" encoding into the separate parts

#include "Globals.h"
#include "MultipartParser.h"
#include "NameValueParser.h"





// Disable MSVC warnings:
#if defined(_MSC_VER)
    #pragma warning(push)
    #pragma warning(disable:4355)  // 'this' : used in base member initializer list
#endif





// self-test:

#if 0

class cMultipartParserTest :
    public cMultipartParser::cCallbacks
{
public:
    cMultipartParserTest(void)
    {
        cMultipartParser Parser("multipart/mixed; boundary=\"MyBoundaryString\"; foo=bar", *this);
        const char Data[] =
"ThisIsIgnoredPrologue\r\n\
--MyBoundaryString\r\n\
\r\n\
Body with confusing strings\r\n\
--NotABoundary\r\n\
--MyBoundaryStringWithPostfix\r\n\
--\r\n\
--MyBoundaryString\r\n\
content-disposition: inline\r\n\
\r\n\
This is body\r\n\
--MyBoundaryString\r\n\
\r\n\
Headerless body with trailing CRLF\r\n\
\r\n\
--MyBoundaryString--\r\n\
ThisIsIgnoredEpilogue";
        printf("Multipart parsing test commencing.\n");
        Parser.Parse(Data, sizeof(Data) - 1);
        // DEBUG: Check if the onscreen output corresponds with the data above
        printf("Multipart parsing test finished\n");
    }

    virtual void OnPartStart(void) override
    {
        printf("Starting a new part\n");
    }


    virtual void OnPartHeader(const AString & a_Key, const AString & a_Value) override
    {
        printf("  Hdr: \"%s\"=\"%s\"\n", a_Key.c_str(), a_Value.c_str());
    }


    virtual void OnPartData(const char * a_Data, int a_Size) override
    {
        printf("  Data: %d bytes, \"%.*s\"\n", a_Size, a_Size, a_Data);
    }


    virtual void OnPartEnd(void) override
    {
        printf("Part end\n");
    }
} g_Test;

#endif





// cMultipartParser:


cMultipartParser::cMultipartParser(const AString & a_ContentType, cCallbacks & a_Callbacks) :
    m_Callbacks(a_Callbacks),
    m_IsValid(true),
    m_EnvelopeParser(*this),
    m_HasHadData(false)
{
    // Check that the content type is multipart:
    AString ContentType(a_ContentType);
    if (strncmp(ContentType.c_str(), "multipart/", 10) != 0)
    {
        m_IsValid = false;
        return;
    }
    size_t idxSC = ContentType.find(';', 10);
    if (idxSC == AString::npos)
    {
        m_IsValid = false;
        return;
    }

    // Find the multipart boundary:
    ContentType.erase(0, idxSC + 1);
    cNameValueParser CTParser(ContentType.c_str(), ContentType.size());
    CTParser.Finish();
    if (!CTParser.IsValid())
    {
        m_IsValid = false;
        return;
    }
    m_Boundary = CTParser["boundary"];
    m_IsValid = !m_Boundary.empty();
    if (!m_IsValid)
    {
        return;
    }

    // Set the envelope parser for parsing the body, so that our Parse() function parses the ignored prefix data as a body
    m_EnvelopeParser.SetIsInHeaders(false);

    // Append an initial CRLF to the incoming data, so that a body starting with the boundary line will get caught
    m_IncomingData.assign("\r\n");

    /*
    m_Boundary = AString("\r\n--") + m_Boundary
    m_BoundaryEnd = m_Boundary + "--\r\n";
    m_Boundary = m_Boundary + "\r\n";
    */
}





void cMultipartParser::Parse(const char * a_Data, size_t a_Size)
{
    // Skip parsing if invalid
    if (!m_IsValid)
    {
        return;
    }

    // Append to buffer, then parse it:
    m_IncomingData.append(a_Data, a_Size);
    for (;;)
    {
        if (m_EnvelopeParser.IsInHeaders())
        {
            size_t BytesConsumed = m_EnvelopeParser.Parse(m_IncomingData.data(), m_IncomingData.size());
            if (BytesConsumed == AString::npos)
            {
                m_IsValid = false;
                return;
            }
            if ((BytesConsumed == a_Size) && m_EnvelopeParser.IsInHeaders())
            {
                // All the incoming data has been consumed and still waiting for more
                return;
            }
            m_IncomingData.erase(0, BytesConsumed);
        }

        // Search for boundary / boundary end:
        size_t idxBoundary = m_IncomingData.find("\r\n--");
        if (idxBoundary == AString::npos)
        {
            // Boundary string start not present, present as much data to the part callback as possible
            if (m_IncomingData.size() > m_Boundary.size() + 8)
            {
                size_t BytesToReport = m_IncomingData.size() - m_Boundary.size() - 8;
                m_Callbacks.OnPartData(m_IncomingData.data(), BytesToReport);
                m_IncomingData.erase(0, BytesToReport);
            }
            return;
        }
        if (idxBoundary > 0)
        {
            m_Callbacks.OnPartData(m_IncomingData.data(), idxBoundary);
            m_IncomingData.erase(0, idxBoundary);
        }
        idxBoundary = 4;
        size_t LineEnd = m_IncomingData.find("\r\n", idxBoundary);
        if (LineEnd == AString::npos)
        {
            // Not a complete line yet, present as much data to the part callback as possible
            if (m_IncomingData.size() > m_Boundary.size() + 8)
            {
                size_t BytesToReport = m_IncomingData.size() - m_Boundary.size() - 8;
                m_Callbacks.OnPartData(m_IncomingData.data(), BytesToReport);
                m_IncomingData.erase(0, BytesToReport);
            }
            return;
        }
        if (
            (LineEnd - idxBoundary != m_Boundary.size()) &&  // Line length not equal to boundary
            (LineEnd - idxBoundary != m_Boundary.size() + 2)  // Line length not equal to boundary end
        )
        {
            // Got a line, but it's not a boundary, report it as data:
            m_Callbacks.OnPartData(m_IncomingData.data(), LineEnd);
            m_IncomingData.erase(0, LineEnd);
            continue;
        }

        if (strncmp(m_IncomingData.c_str() + idxBoundary, m_Boundary.c_str(), m_Boundary.size()) == 0)
        {
            // Boundary or BoundaryEnd found:
            m_Callbacks.OnPartEnd();
            size_t idxSlash = idxBoundary + m_Boundary.size();
            if ((m_IncomingData[idxSlash] == '-') && (m_IncomingData[idxSlash + 1] == '-'))
            {
                // This was the last part
                m_Callbacks.OnPartData(m_IncomingData.data() + idxSlash + 4, m_IncomingData.size() - idxSlash - 4);
                m_IncomingData.clear();
                return;
            }
            m_Callbacks.OnPartStart();
            m_IncomingData.erase(0, LineEnd + 2);

            // Keep parsing for the headers that may have come with this data:
            m_EnvelopeParser.Reset();
            continue;
        }

        // It's a line, but not a boundary. It can be fully sent to the data receiver, since a boundary cannot cross lines
        m_Callbacks.OnPartData(m_IncomingData.c_str(), LineEnd);
        m_IncomingData.erase(0, LineEnd);
    }  // while (true)
}





void cMultipartParser::OnHeaderLine(const AString & a_Key, const AString & a_Value)
{
    m_Callbacks.OnPartHeader(a_Key, a_Value);
}