HTTPMessageParser.cpp

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// HTTPMessageParser.cpp

// Implements the cHTTPMessageParser class that parses HTTP messages (request or response) being pushed into the parser,
// and reports the individual parts via callbacks

#include "Globals.h"
#include "HTTPMessageParser.h"





cHTTPMessageParser::cHTTPMessageParser(cHTTPMessageParser::cCallbacks & a_Callbacks):
    m_Callbacks(a_Callbacks),
    m_EnvelopeParser(*this)
{
    Reset();
}





size_t cHTTPMessageParser::Parse(const char * a_Data, size_t a_Size)
{
    // If parsing already finished or errorred, let the caller keep all the data:
    if (m_IsFinished || m_HasHadError)
    {
        return 0;
    }

    // If still waiting for the status line, add to buffer and try parsing it:
    auto inBufferSoFar = m_Buffer.size();
    if (m_FirstLine.empty())
    {
        m_Buffer.append(a_Data, a_Size);
        auto bytesConsumedFirstLine = ParseFirstLine();
        ASSERT(bytesConsumedFirstLine <= inBufferSoFar + a_Size);  // Haven't consumed more data than there is in the buffer
        ASSERT(bytesConsumedFirstLine > inBufferSoFar);  // Have consumed at least the previous buffer contents
        if (m_FirstLine.empty())
        {
            // All data used, but not a complete status line yet.
            return a_Size;
        }
        if (m_HasHadError)
        {
            return AString::npos;
        }
        // Status line completed, feed the rest of the buffer into the envelope parser:
        auto bytesConsumedEnvelope = m_EnvelopeParser.Parse(m_Buffer.data(), m_Buffer.size());
        if (bytesConsumedEnvelope == AString::npos)
        {
            m_HasHadError = true;
            m_Callbacks.OnError("Failed to parse the envelope");
            return AString::npos;
        }
        ASSERT(bytesConsumedEnvelope <= bytesConsumedFirstLine + a_Size);  // Haven't consumed more data than there was in the buffer
        m_Buffer.erase(0, bytesConsumedEnvelope);
        if (!m_EnvelopeParser.IsInHeaders())
        {
            HeadersFinished();
            // Process any data still left in the buffer as message body:
            auto bytesConsumedBody = ParseBody(m_Buffer.data(), m_Buffer.size());
            if (bytesConsumedBody == AString::npos)
            {
                // Error has already been reported by ParseBody, just bail out:
                return AString::npos;
            }
            return bytesConsumedBody + bytesConsumedEnvelope + bytesConsumedFirstLine - inBufferSoFar;
        }
        return a_Size;
    }  // if (m_FirstLine.empty())

    // If still parsing headers, send them to the envelope parser:
    if (m_EnvelopeParser.IsInHeaders())
    {
        auto bytesConsumed = m_EnvelopeParser.Parse(a_Data, a_Size);
        if (bytesConsumed == AString::npos)
        {
            m_HasHadError = true;
            m_Callbacks.OnError("Failed to parse the envelope");
            return AString::npos;
        }
        if (!m_EnvelopeParser.IsInHeaders())
        {
            HeadersFinished();
            // Process any data still left as message body:
            auto bytesConsumedBody = ParseBody(a_Data + bytesConsumed, a_Size - bytesConsumed);
            if (bytesConsumedBody == AString::npos)
            {
                // Error has already been reported by ParseBody, just bail out:
                return AString::npos;
            }
        }
        return a_Size;
    }

    // Already parsing the body
    return ParseBody(a_Data, a_Size);
}





void cHTTPMessageParser::Reset(void)
{
    m_HasHadError = false;
    m_IsFinished = false;
    m_FirstLine.clear();
    m_Buffer.clear();
    m_EnvelopeParser.Reset();
    m_TransferEncodingParser.reset();
    m_TransferEncoding.clear();
    m_ContentLength = 0;
}





size_t cHTTPMessageParser::ParseFirstLine(void)
{
    auto idxLineEnd = m_Buffer.find("\r\n");
    if (idxLineEnd == AString::npos)
    {
        // Not a complete line yet
        return m_Buffer.size();
    }
    m_FirstLine = m_Buffer.substr(0, idxLineEnd);
    m_Buffer.erase(0, idxLineEnd + 2);
    m_Callbacks.OnFirstLine(m_FirstLine);
    return idxLineEnd + 2;
}





size_t cHTTPMessageParser::ParseBody(const char * a_Data, size_t a_Size)
{
    if (m_TransferEncodingParser == nullptr)
    {
        // We have no Transfer-encoding parser assigned. This should have happened when finishing the envelope
        OnError("No transfer encoding parser");
        return AString::npos;
    }

    // Parse the body using the transfer encoding parser:
    // (Note that TE parser returns the number of bytes left, while we return the number of bytes consumed)
    return a_Size - m_TransferEncodingParser->Parse(a_Data, a_Size);
}





void cHTTPMessageParser::HeadersFinished(void)
{
    m_Callbacks.OnHeadersFinished();
    m_TransferEncodingParser = cTransferEncodingParser::Create(*this, m_TransferEncoding, m_ContentLength);
    if (m_TransferEncodingParser == nullptr)
    {
        OnError(Printf("Unknown transfer encoding: %s", m_TransferEncoding.c_str()));
        return;
    }
}





void cHTTPMessageParser::OnHeaderLine(const AString & a_Key, const AString & a_Value)
{
    m_Callbacks.OnHeaderLine(a_Key, a_Value);
    auto Key = StrToLower(a_Key);
    if (Key == "content-length")
    {
        if (!StringToInteger(a_Value, m_ContentLength))
        {
            OnError(Printf("Invalid content length header value: \"%s\"", a_Value.c_str()));
        }
        return;
    }
    if (Key == "transfer-encoding")
    {
        m_TransferEncoding = a_Value;
        return;
    }
}





void cHTTPMessageParser::OnError(const AString & a_ErrorDescription)
{
    m_HasHadError = true;
    m_Callbacks.OnError(a_ErrorDescription);
}





void cHTTPMessageParser::OnBodyData(const void * a_Data, size_t a_Size)
{
    m_Callbacks.OnBodyData(a_Data, a_Size);
}





void cHTTPMessageParser::OnBodyFinished(void)
{
    m_IsFinished = true;
    m_Callbacks.OnBodyFinished();
}