source-engine/tracker/common/UtlMsgBuffer.cpp

//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose: 
//
// $NoKeywords: $
//=============================================================================

#include "UtlMsgBuffer.h"

#include <string.h>

//-----------------------------------------------------------------------------
// Purpose: bitfields for use in variable descriptors
//-----------------------------------------------------------------------------
enum
{
	PACKBIT_CONTROLBIT	= 0x01,		// this must always be set
	PACKBIT_INTNAME		= 0x02,		// if this is set then it's an int named variable, instead of a string
	PACKBIT_BINARYDATA  = 0x04,		// signifies the data in this variable is binary, it's not a string
};

//-----------------------------------------------------------------------------
// Purpose: Constructor
//-----------------------------------------------------------------------------
CUtlMsgBuffer::CUtlMsgBuffer(unsigned short msgID, int initialSize) : m_Memory(0, initialSize)
{
	m_iMsgID = msgID;
	m_iWritePos = 0;
	m_iReadPos = 0;
	m_iNextVarPos = 0;
}

//-----------------------------------------------------------------------------
// Purpose: Constructor, takes initial data
//-----------------------------------------------------------------------------
CUtlMsgBuffer::CUtlMsgBuffer(unsigned short msgID, void const *data, int dataSize) : m_Memory(0, dataSize)
{
	m_iMsgID = msgID;
	m_iWritePos = (short)dataSize;
	m_iReadPos = 0;
	m_iNextVarPos = 0;

	memcpy(Base(), data, dataSize);
}

//-----------------------------------------------------------------------------
// Purpose: Destructor
//-----------------------------------------------------------------------------
CUtlMsgBuffer::~CUtlMsgBuffer()
{
}

//-----------------------------------------------------------------------------
// Purpose: Copy
//-----------------------------------------------------------------------------
CUtlMsgBuffer &CUtlMsgBuffer::Copy(const CUtlMsgBuffer &rhs)
{
	m_iWritePos = rhs.m_iWritePos;
	m_iReadPos = rhs.m_iReadPos;
	m_iNextVarPos = rhs.m_iNextVarPos;

	m_Memory.EnsureCapacity(rhs.m_Memory.NumAllocated());
	if ( rhs.m_Memory.NumAllocated() > 0 )
	{
		memcpy(Base(), rhs.Base(), rhs.m_Memory.NumAllocated());
	}
	return *this;
}

//-----------------------------------------------------------------------------
// Purpose: Writes string data to the message
// Input  : *name - name of the variable
//			*data - pointer to the string data to write
//-----------------------------------------------------------------------------
void CUtlMsgBuffer::WriteString(const char *name, const char *data)
{
	// write out the variable type
	unsigned char vtype = PACKBIT_CONTROLBIT;	// stringname var, string data
	Write(&vtype, 1);
	
	// write out the variable name
	Write(name, strlen(name) + 1);

	// write out the size of the data
	unsigned short size = (unsigned short)(strlen(data) + 1);
	Write(&size, 2);

	// write out the data itself
	Write(data, size);
}

//-----------------------------------------------------------------------------
// Purpose: Writes out a named block of data
//-----------------------------------------------------------------------------
void CUtlMsgBuffer::WriteBlob(const char *name, const void *data, int dataSize)
{
	// write out the variable type
	unsigned char vtype = PACKBIT_CONTROLBIT | PACKBIT_BINARYDATA;	// stringname var, binary data
	Write(&vtype, 1);
	
	// write out the variable name
	Write(name, strlen(name) + 1);

	// write out the size of the data
	unsigned short size = (unsigned short)dataSize;
	Write(&size, 2);

	// write out the data itself
	Write(data, dataSize);
}

//-----------------------------------------------------------------------------
// Purpose: Writes out another UtlMsgBuffer as an element of this one
//-----------------------------------------------------------------------------
void CUtlMsgBuffer::WriteBuffer(const char *name, const CUtlMsgBuffer *buffer)
{
	// write out the variable type
	unsigned char vtype = PACKBIT_CONTROLBIT | PACKBIT_BINARYDATA;	// stringname var, binary data
	Write(&vtype, 1);

	// write out the variable name
	Write(name, strlen(name) + 1);

	// write out the size of the data
	unsigned short size = (unsigned short) buffer->DataSize();
	Write(&size, 2);

    // write out the data itself
    Write(buffer->Base(), size);
}

//-----------------------------------------------------------------------------
// Purpose: Reads from the buffer, increments read position
//			returns false if past end of buffer
//-----------------------------------------------------------------------------
bool CUtlMsgBuffer::Read(void *buffer, int readAmount)
{
	if (m_iReadPos + readAmount >= m_iWritePos)
		return false;

	memcpy(buffer, &m_Memory[m_iReadPos], readAmount);
	m_iReadPos += readAmount;
	return true;
}

//-----------------------------------------------------------------------------
// Purpose: Reads characterse from the buffer until a null is hit
//-----------------------------------------------------------------------------
bool CUtlMsgBuffer::ReadUntilNull(void *buffer, int bufferSize)
{
	int nullPos = m_iReadPos;

	// look through the buffer for the null terminator
	while (nullPos < m_Memory.NumAllocated() && m_Memory[nullPos] != 0)
	{
		nullPos++;
	}
	
	if (nullPos >= m_Memory.NumAllocated())
	{
		// never found a null terminator
		((char *)buffer)[0] = 0;
		return false;
	}

	// copy from the null terminator
	int copySize = nullPos - m_iReadPos;
	if (copySize > bufferSize)
	{
		copySize = bufferSize - 1;
	}

	// copy out the data and return
	memcpy(buffer, &m_Memory[m_iReadPos], copySize);
	((char *)buffer)[copySize] = 0;
	m_iReadPos += (copySize+1);
	return true;
}

//-----------------------------------------------------------------------------
// Purpose: Writes to the buffer, incrementing the write position
//			assumes enough space has already been allocated for the write
//-----------------------------------------------------------------------------
void CUtlMsgBuffer::Write(void const *data, int size)
{
	// make sure it will fit
	m_Memory.EnsureCapacity(m_iWritePos + size);
		
	// normal write
	memcpy(&m_Memory[m_iWritePos], data, size);

	// increment write position
	m_iWritePos += size;
}

//-----------------------------------------------------------------------------
// Purpose: Reads in a named variable length data blob
//			returns number of bytes read, 0 on failure
//-----------------------------------------------------------------------------
int CUtlMsgBuffer::ReadBlob(const char *name, void *data, int dataBufferSize)
{
	int dataSize = 0;
	char *readData = (char *)FindVar(name, dataSize);
	if (!readData)
	{
		memset(data, 0, dataBufferSize);
		return 0;
	}

	// ensure against buffer overflow
	if (dataSize > dataBufferSize)
		dataSize = dataBufferSize;

	// copy out data
	memcpy(data, readData, dataSize);
	return dataSize;
}

//-----------------------------------------------------------------------------
// Purpose: Reads a blob of binary data into it's own buffer
//-----------------------------------------------------------------------------
bool CUtlMsgBuffer::ReadBuffer(const char *name, CUtlMsgBuffer &buffer)
{
	int dataSize = 0;
	char *readData = (char *)FindVar(name, dataSize);
	if (!readData)
	{
		return false;
	}

	buffer.m_Memory.EnsureCapacity(dataSize);
	memcpy(&buffer.m_Memory[0], readData, dataSize);
	buffer.m_iReadPos = 0;
	buffer.m_iWritePos = (short)dataSize;
	return true;
}

//-----------------------------------------------------------------------------
// Purpose: reads out the next variable available in the buffer
//			fills out parameters with var details and data
//			returns false if no more vars available
//-----------------------------------------------------------------------------
bool CUtlMsgBuffer::ReadNextVar(char varname[32], bool &stringData, void *data, int &dataSize)
{
	// read the type
	unsigned char vtype = 1;
	if (!Read(&vtype, 1))
		return false;

	// check for null-termination type
	if (vtype == 0)
		return false;

	stringData = !(vtype & PACKBIT_BINARYDATA);

	// read the variable name
	if (!ReadUntilNull(varname, 31))
		return false;

	// read the data size
	unsigned short size = 0;
	if (!Read(&size, 2))
		return false;

	// ensure against buffer overflows
	if (dataSize > size)
		dataSize = size;

	// copy data
	memcpy(data, &m_Memory[m_iReadPos], dataSize);

	// store of the next position, since that is probably where the next read needs to occur
	m_iReadPos += size;
	m_iNextVarPos = m_iReadPos;
	return true;
}


//-----------------------------------------------------------------------------
// Purpose: sets the read/write position to be at the specified variable
//			returns pointer to buffer position on success, NULL if not found
//-----------------------------------------------------------------------------
void *CUtlMsgBuffer::FindVar(const char *name, int &dataSize)
{
	// reset to where we Think the next var will be read from
	m_iReadPos = m_iNextVarPos;
	int loopCount = 2;

	// loop through looking for the specified variable
	while (loopCount--)
	{
		unsigned char vtype = 1;
		while (Read(&vtype, 1))
		{
			// check for null-termination type
			if (vtype == 0)
				break;

			// read the variable name
			char varname[32];
			if (!ReadUntilNull(varname, 31))
				break;

			// read the data size
			unsigned short size = 0;
			if (!Read(&size, 2))
				break;

			// is this our variable?
			if (!stricmp(varname, name))
			{
				dataSize = size;
				void *data = &m_Memory[m_iReadPos];

				// store of the next position, since that is probably where the next read needs to occur
				m_iReadPos += size;
				m_iNextVarPos = m_iReadPos;
				return data;
			}

			// skip over the data block to the next variable
			m_iReadPos += size;
			if (m_iReadPos >= m_iWritePos)
				break;
		}

		// we haven't found the data yet, Start again
		m_iReadPos = 0;
	}

	return NULL;
}