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cuberite-2a/source/ByteBuffer.cpp

325 lines
5.4 KiB
C++

// ByteBuffer.cpp
// Implements the cByteBuffer class representing a ringbuffer of bytes
#include "Globals.h"
#include "ByteBuffer.h"
#include "Endianness.h"
#define NEEDBYTES(Num) if (!CanReadBytes(Num)) return false;
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// cByteBuffer:
cByteBuffer::cByteBuffer(int a_BufferSize) :
m_Buffer(new char[a_BufferSize + 1]),
m_BufferSize(a_BufferSize + 1),
m_DataStart(0),
m_WritePos(0),
m_ReadPos(0)
{
// Allocating one byte more than the buffer size requested, so that we can distinguish between
// completely-full and completely-empty states
}
cByteBuffer::~cByteBuffer()
{
delete m_Buffer;
}
bool cByteBuffer::Write(const char * a_Bytes, int a_Count)
{
if (GetFreeSpace() < a_Count)
{
return false;
}
int TillEnd = m_BufferSize - m_WritePos;
if (TillEnd < a_Count)
{
// Need to wrap around the ringbuffer end
memcpy(m_Buffer + m_WritePos, a_Bytes, TillEnd);
m_WritePos = 0;
a_Bytes += TillEnd;
a_Count -= TillEnd;
}
// We're guaranteed that we'll fit in a single write op
memcpy(m_Buffer + m_WritePos, a_Bytes, a_Count);
m_WritePos += a_Count;
return true;
}
int cByteBuffer::GetFreeSpace(void) const
{
if (m_WritePos >= m_DataStart)
{
// Wrap around the buffer end:
return m_BufferSize - m_WritePos + m_DataStart - 1;
}
// Single free space partition:
return m_DataStart - m_WritePos - 1;
}
/// Returns the number of bytes that are currently in the ringbuffer. Note GetReadableBytes()
int cByteBuffer::GetUsedSpace(void) const
{
return m_BufferSize - GetFreeSpace();
}
/// Returns the number of bytes that are currently available for reading (may be less than UsedSpace due to some data having been read already)
int cByteBuffer::GetReadableSpace(void) const
{
if (m_ReadPos > m_WritePos)
{
// Wrap around the buffer end:
return m_BufferSize - m_ReadPos + m_WritePos;
}
// Single readable space partition:
return m_WritePos - m_ReadPos ;
}
bool cByteBuffer::CanReadBytes(int a_Count) const
{
return (a_Count <= GetReadableSpace());
}
bool cByteBuffer::ReadChar(char & a_Value)
{
NEEDBYTES(1);
a_Value = m_Buffer[m_ReadPos++];
return true;
}
bool cByteBuffer::ReadByte(unsigned char & a_Value)
{
NEEDBYTES(1);
a_Value = (unsigned char)(m_Buffer[m_ReadPos++]);
return true;
}
bool cByteBuffer::ReadBEShort(short & a_Value)
{
NEEDBYTES(2);
ReadBuf(&a_Value, 2);
a_Value = ntohs(a_Value);
return true;
}
bool cByteBuffer::ReadBEInt(int & a_Value)
{
NEEDBYTES(4);
ReadBuf(&a_Value, 4);
a_Value = ntohl(a_Value);
return true;
}
bool cByteBuffer::ReadBEInt64(Int64 & a_Value)
{
NEEDBYTES(8);
ReadBuf(&a_Value, 8);
a_Value = NetworkToHostLong8(&a_Value);
return true;
}
bool cByteBuffer::ReadBEFloat(float & a_Value)
{
NEEDBYTES(4);
ReadBuf(&a_Value, 4);
a_Value = NetworkToHostFloat4(&a_Value);
return true;
}
bool cByteBuffer::ReadBEDouble(double & a_Value)
{
NEEDBYTES(8);
ReadBuf(&a_Value, 8);
a_Value = NetworkToHostDouble8(&a_Value);
return true;
}
bool cByteBuffer::ReadBool(bool & a_Value)
{
NEEDBYTES(1);
a_Value = (m_Buffer[m_ReadPos++] != 0);
return true;
}
bool cByteBuffer::ReadBEUTF16String16(AString & a_Value)
{
short Length;
if (!ReadBEShort(Length))
{
return false;
}
return ReadUTF16String(a_Value, Length);
}
bool cByteBuffer::ReadBuf(void * a_Buffer, int a_Count)
{
NEEDBYTES(a_Count);
char * Dst = (char *)a_Buffer; // So that we can do byte math
int BytesToEndOfBuffer = m_BufferSize - m_ReadPos;
if (BytesToEndOfBuffer < a_Count)
{
// Reading across the ringbuffer end, read the first part and adjust parameters:
memcpy(Dst, m_Buffer + m_ReadPos, BytesToEndOfBuffer);
Dst += BytesToEndOfBuffer;
a_Count -= BytesToEndOfBuffer;
m_ReadPos = 0;
}
// Read the rest of the bytes in a single read (guaranteed to fit):
memcpy(Dst, m_Buffer + m_ReadPos, a_Count);
m_ReadPos += a_Count;
return true;
}
bool cByteBuffer::ReadString(AString & a_String, int a_Count)
{
NEEDBYTES(a_Count);
a_String.clear();
a_String.reserve(a_Count);
int BytesToEndOfBuffer = m_BufferSize - m_ReadPos;
if (BytesToEndOfBuffer < a_Count)
{
// Reading across the ringbuffer end, read the first part and adjust parameters:
a_String.assign(m_Buffer + m_ReadPos, BytesToEndOfBuffer);
a_Count -= BytesToEndOfBuffer;
m_ReadPos = 0;
}
// Read the rest of the bytes in a single read (guaranteed to fit):
a_String.append(m_Buffer + m_ReadPos, a_Count);
m_ReadPos += a_Count;
return true;
}
bool cByteBuffer::ReadUTF16String(AString & a_String, int a_NumChars)
{
// Reads 2 * a_NumChars bytes and interprets it as a UTF16 string, converting it into UTF8 string a_String
AString RawData;
if (!ReadString(RawData, a_NumChars * 2))
{
return false;
}
RawBEToUTF8((short *)(RawData.data()), a_NumChars, a_String);
return true;
}
void cByteBuffer::CommitRead(void)
{
m_DataStart = m_ReadPos;
}
void cByteBuffer::ResetRead(void)
{
m_ReadPos = m_DataStart;
}
void cByteBuffer::AdvanceReadPos(int a_Count)
{
m_ReadPos += a_Count;
if (m_ReadPos > m_BufferSize)
{
m_ReadPos -= m_BufferSize;
}
}