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cuberite-2a/src/ByteBuffer.cpp

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// ByteBuffer.cpp
// Implements the cByteBuffer class representing a ringbuffer of bytes
#include "Globals.h"
#include "ByteBuffer.h"
#include "Endianness.h"
#include "UUID.h"
#include "OSSupport/IsThread.h"
/** When defined, each access to a cByteBuffer object is checked whether it's done in the same thread.
cByteBuffer assumes that it is not used by multiple threads at once, this macro adds a runtime check for that.
Unfortunately it is very slow, so it is disabled even for regular DEBUG builds. */
// #define DEBUG_SINGLE_THREAD_ACCESS
// If a string sent over the protocol is larger than this, a warning is emitted to the console
#define MAX_STRING_SIZE (512 KiB)
#define NEEDBYTES(Num) if (!CanReadBytes(Num)) return false; // Check if at least Num bytes can be read from the buffer, return false if not
#define PUTBYTES(Num) if (!CanWriteBytes(Num)) return false; // Check if at least Num bytes can be written to the buffer, return false if not
#ifdef DEBUG_SINGLE_THREAD_ACCESS
/** Simple RAII class that is used for checking that no two threads are using an object simultanously.
It requires the monitored object to provide the storage for a thread ID.
It uses that storage to check if the thread ID of consecutive calls is the same all the time. */
class cSingleThreadAccessChecker
{
public:
cSingleThreadAccessChecker(std::thread::id * a_ThreadID) :
m_ThreadID(a_ThreadID)
{
ASSERT(
(*a_ThreadID == std::this_thread::get_id()) || // Either the object is used by current thread...
(*a_ThreadID == m_EmptyThreadID) // ... or by no thread at all
);
// Mark as being used by this thread:
*m_ThreadID = std::this_thread::get_id();
}
~cSingleThreadAccessChecker()
{
// Mark as not being used by any thread:
*m_ThreadID = std::thread::id();
}
protected:
/** Points to the storage used for ID of the thread using the object. */
std::thread::id * m_ThreadID;
/** The value of an unassigned thread ID, used to speed up checking. */
static std::thread::id m_EmptyThreadID;
};
std::thread::id cSingleThreadAccessChecker::m_EmptyThreadID;
#define CHECK_THREAD cSingleThreadAccessChecker Checker(&m_ThreadID);
#else
#define CHECK_THREAD
#endif
////////////////////////////////////////////////////////////////////////////////
// cByteBuffer:
cByteBuffer::cByteBuffer(size_t 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()
{
CheckValid();
delete[] m_Buffer;
m_Buffer = nullptr;
}
bool cByteBuffer::Write(const void * a_Bytes, size_t a_Count)
{
CHECK_THREAD
CheckValid();
// Store the current free space for a check after writing:
size_t CurFreeSpace = GetFreeSpace();
#ifdef _DEBUG
size_t CurReadableSpace = GetReadableSpace();
#endif
size_t WrittenBytes = 0;
if (CurFreeSpace < a_Count)
{
return false;
}
ASSERT(m_BufferSize >= m_WritePos);
size_t TillEnd = m_BufferSize - m_WritePos;
const char * Bytes = reinterpret_cast<const char *>(a_Bytes);
if (TillEnd <= a_Count)
{
// Need to wrap around the ringbuffer end
if (TillEnd > 0)
{
memcpy(m_Buffer + m_WritePos, Bytes, TillEnd);
Bytes += TillEnd;
a_Count -= TillEnd;
WrittenBytes = TillEnd;
}
m_WritePos = 0;
}
// We're guaranteed that we'll fit in a single write op
if (a_Count > 0)
{
memcpy(m_Buffer + m_WritePos, Bytes, a_Count);
m_WritePos += a_Count;
WrittenBytes += a_Count;
}
ASSERT(GetFreeSpace() == CurFreeSpace - WrittenBytes);
ASSERT(GetReadableSpace() == CurReadableSpace + WrittenBytes);
return true;
}
size_t cByteBuffer::GetFreeSpace(void) const
{
CHECK_THREAD
CheckValid();
if (m_WritePos >= m_DataStart)
{
// Wrap around the buffer end:
ASSERT(m_BufferSize >= m_WritePos);
ASSERT((m_BufferSize - m_WritePos + m_DataStart) >= 1);
return m_BufferSize - m_WritePos + m_DataStart - 1;
}
// Single free space partition:
ASSERT(m_BufferSize >= m_WritePos);
ASSERT(m_BufferSize - m_WritePos >= 1);
return m_DataStart - m_WritePos - 1;
}
size_t cByteBuffer::GetUsedSpace(void) const
{
CHECK_THREAD
CheckValid();
ASSERT(m_BufferSize >= GetFreeSpace());
ASSERT((m_BufferSize - GetFreeSpace()) >= 1);
return m_BufferSize - GetFreeSpace() - 1;
}
size_t cByteBuffer::GetReadableSpace(void) const
{
CHECK_THREAD
CheckValid();
if (m_ReadPos > m_WritePos)
{
// Wrap around the buffer end:
ASSERT(m_BufferSize >= m_ReadPos);
return m_BufferSize - m_ReadPos + m_WritePos;
}
// Single readable space partition:
ASSERT(m_WritePos >= m_ReadPos);
return m_WritePos - m_ReadPos;
}
bool cByteBuffer::CanReadBytes(size_t a_Count) const
{
CHECK_THREAD
CheckValid();
return (a_Count <= GetReadableSpace());
}
bool cByteBuffer::CanWriteBytes(size_t a_Count) const
{
CHECK_THREAD
CheckValid();
return (a_Count <= GetFreeSpace());
}
bool cByteBuffer::ReadBEInt8(Int8 & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(1);
ReadBuf(&a_Value, 1);
return true;
}
bool cByteBuffer::ReadBEUInt8(UInt8 & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(1);
ReadBuf(&a_Value, 1);
return true;
}
bool cByteBuffer::ReadBEInt16(Int16 & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(2);
UInt16 val;
ReadBuf(&val, 2);
val = ntohs(val);
memcpy(&a_Value, &val, 2);
return true;
}
bool cByteBuffer::ReadBEUInt16(UInt16 & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(2);
ReadBuf(&a_Value, 2);
a_Value = ntohs(a_Value);
return true;
}
bool cByteBuffer::ReadBEInt32(Int32 & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(4);
UInt32 val;
ReadBuf(&val, 4);
val = ntohl(val);
memcpy(&a_Value, &val, 4);
return true;
}
bool cByteBuffer::ReadBEUInt32(UInt32 & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(4);
ReadBuf(&a_Value, 4);
a_Value = ntohl(a_Value);
return true;
}
bool cByteBuffer::ReadBEInt64(Int64 & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(8);
ReadBuf(&a_Value, 8);
a_Value = NetworkToHostLong8(&a_Value);
return true;
}
bool cByteBuffer::ReadBEUInt64(UInt64 & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(8);
ReadBuf(&a_Value, 8);
a_Value = NetworkToHostULong8(&a_Value);
return true;
}
bool cByteBuffer::ReadBEFloat(float & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(4);
ReadBuf(&a_Value, 4);
a_Value = NetworkToHostFloat4(&a_Value);
return true;
}
bool cByteBuffer::ReadBEDouble(double & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(8);
ReadBuf(&a_Value, 8);
a_Value = NetworkToHostDouble8(&a_Value);
return true;
}
bool cByteBuffer::ReadBool(bool & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(1);
UInt8 Value = 0;
ReadBuf(&Value, 1);
a_Value = (Value != 0);
return true;
}
bool cByteBuffer::ReadVarInt32(UInt32 & a_Value)
{
CHECK_THREAD
CheckValid();
UInt32 Value = 0;
int Shift = 0;
unsigned char b = 0;
do
{
NEEDBYTES(1);
ReadBuf(&b, 1);
Value = Value | ((static_cast<UInt32>(b & 0x7f)) << Shift);
Shift += 7;
} while ((b & 0x80) != 0);
a_Value = Value;
return true;
}
bool cByteBuffer::ReadVarInt64(UInt64 & a_Value)
{
CHECK_THREAD
CheckValid();
UInt64 Value = 0;
int Shift = 0;
unsigned char b = 0;
do
{
NEEDBYTES(1);
ReadBuf(&b, 1);
Value = Value | ((static_cast<UInt64>(b & 0x7f)) << Shift);
Shift += 7;
} while ((b & 0x80) != 0);
a_Value = Value;
return true;
}
bool cByteBuffer::ReadVarUTF8String(AString & a_Value)
{
CHECK_THREAD
CheckValid();
UInt32 Size = 0;
if (!ReadVarInt(Size))
{
return false;
}
if (Size > MAX_STRING_SIZE)
{
LOGWARNING("%s: String too large: %u (%u KiB)", __FUNCTION__, Size, Size / 1024);
}
return ReadString(a_Value, static_cast<size_t>(Size));
}
bool cByteBuffer::ReadLEInt(int & a_Value)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(4);
ReadBuf(&a_Value, 4);
#ifdef IS_BIG_ENDIAN
// Convert:
a_Value = ((a_Value >> 24) & 0xff) | ((a_Value >> 16) & 0xff00) | ((a_Value >> 8) & 0xff0000) | (a_Value & 0xff000000);
#endif
return true;
}
bool cByteBuffer::ReadPosition64(int & a_BlockX, int & a_BlockY, int & a_BlockZ)
{
CHECK_THREAD
Int64 Value;
if (!ReadBEInt64(Value))
{
return false;
}
// Convert the 64 received bits into 3 coords:
UInt32 BlockXRaw = (Value >> 38) & 0x03ffffff; // Top 26 bits
UInt32 BlockYRaw = (Value >> 26) & 0x0fff; // Middle 12 bits
UInt32 BlockZRaw = (Value & 0x03ffffff); // Bottom 26 bits
// If the highest bit in the number's range is set, convert the number into negative:
a_BlockX = ((BlockXRaw & 0x02000000) == 0) ? static_cast<int>(BlockXRaw) : -(0x04000000 - static_cast<int>(BlockXRaw));
a_BlockY = ((BlockYRaw & 0x0800) == 0) ? static_cast<int>(BlockYRaw) : -(0x0800 - static_cast<int>(BlockYRaw));
a_BlockZ = ((BlockZRaw & 0x02000000) == 0) ? static_cast<int>(BlockZRaw) : -(0x04000000 - static_cast<int>(BlockZRaw));
return true;
}
bool cByteBuffer::ReadUUID(cUUID & a_Value)
{
CHECK_THREAD
std::array<Byte, 16> UUIDBuf;
if (!ReadBuf(UUIDBuf.data(), UUIDBuf.size()))
{
return false;
}
a_Value.FromRaw(UUIDBuf);
return true;
}
bool cByteBuffer::WriteBEInt8(Int8 a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(1);
return WriteBuf(&a_Value, 1);
}
bool cByteBuffer::WriteBEUInt8(UInt8 a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(1);
return WriteBuf(&a_Value, 1);
}
bool cByteBuffer::WriteBEInt16(Int16 a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(2);
UInt16 val;
memcpy(&val, &a_Value, 2);
val = htons(val);
return WriteBuf(&val, 2);
}
bool cByteBuffer::WriteBEUInt16(UInt16 a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(2);
a_Value = htons(a_Value);
return WriteBuf(&a_Value, 2);
}
bool cByteBuffer::WriteBEInt32(Int32 a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(4);
UInt32 Converted = HostToNetwork4(&a_Value);
return WriteBuf(&Converted, 4);
}
bool cByteBuffer::WriteBEUInt32(UInt32 a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(4);
UInt32 Converted = HostToNetwork4(&a_Value);
return WriteBuf(&Converted, 4);
}
bool cByteBuffer::WriteBEInt64(Int64 a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(8);
UInt64 Converted = HostToNetwork8(&a_Value);
return WriteBuf(&Converted, 8);
}
bool cByteBuffer::WriteBEUInt64(UInt64 a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(8);
UInt64 Converted = HostToNetwork8(&a_Value);
return WriteBuf(&Converted, 8);
}
bool cByteBuffer::WriteBEFloat(float a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(4);
UInt32 Converted = HostToNetwork4(&a_Value);
return WriteBuf(&Converted, 4);
}
bool cByteBuffer::WriteBEDouble(double a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(8);
UInt64 Converted = HostToNetwork8(&a_Value);
return WriteBuf(&Converted, 8);
}
bool cByteBuffer::WriteBool(bool a_Value)
{
CHECK_THREAD
CheckValid();
UInt8 val = a_Value ? 1 : 0;
return Write(&val, 1);
}
bool cByteBuffer::WriteVarInt32(UInt32 a_Value)
{
CHECK_THREAD
CheckValid();
// A 32-bit integer can be encoded by at most 5 bytes:
unsigned char b[5];
size_t idx = 0;
do
{
b[idx] = (a_Value & 0x7f) | ((a_Value > 0x7f) ? 0x80 : 0x00);
a_Value = a_Value >> 7;
idx++;
} while (a_Value > 0);
return WriteBuf(b, idx);
}
bool cByteBuffer::WriteVarInt64(UInt64 a_Value)
{
CHECK_THREAD
CheckValid();
// A 64-bit integer can be encoded by at most 10 bytes:
unsigned char b[10];
size_t idx = 0;
do
{
b[idx] = (a_Value & 0x7f) | ((a_Value > 0x7f) ? 0x80 : 0x00);
a_Value = a_Value >> 7;
idx++;
} while (a_Value > 0);
return WriteBuf(b, idx);
}
bool cByteBuffer::WriteVarUTF8String(const AString & a_Value)
{
CHECK_THREAD
CheckValid();
PUTBYTES(a_Value.size() + 1); // This is a lower-bound on the bytes that will be actually written. Fail early.
bool res = WriteVarInt32(static_cast<UInt32>(a_Value.size()));
if (!res)
{
return false;
}
return WriteBuf(a_Value.data(), a_Value.size());
}
bool cByteBuffer::WritePosition64(Int32 a_BlockX, Int32 a_BlockY, Int32 a_BlockZ)
{
CHECK_THREAD
CheckValid();
return WriteBEInt64(
(static_cast<Int64>(a_BlockX & 0x3FFFFFF) << 38) |
(static_cast<Int64>(a_BlockY & 0xFFF) << 26) |
(static_cast<Int64>(a_BlockZ & 0x3FFFFFF))
);
}
bool cByteBuffer::ReadBuf(void * a_Buffer, size_t a_Count)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(a_Count);
char * Dst = reinterpret_cast<char *>(a_Buffer); // So that we can do byte math
ASSERT(m_BufferSize >= m_ReadPos);
size_t BytesToEndOfBuffer = m_BufferSize - m_ReadPos;
if (BytesToEndOfBuffer <= a_Count)
{
// Reading across the ringbuffer end, read the first part and adjust parameters:
if (BytesToEndOfBuffer > 0)
{
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):
if (a_Count > 0)
{
memcpy(Dst, m_Buffer + m_ReadPos, a_Count);
m_ReadPos += a_Count;
}
return true;
}
bool cByteBuffer::WriteBuf(const void * a_Buffer, size_t a_Count)
{
CHECK_THREAD
CheckValid();
PUTBYTES(a_Count);
char * Src = reinterpret_cast<char *>(const_cast<void*>(a_Buffer)); // So that we can do byte math
ASSERT(m_BufferSize >= m_ReadPos);
size_t BytesToEndOfBuffer = m_BufferSize - m_WritePos;
if (BytesToEndOfBuffer <= a_Count)
{
// Reading across the ringbuffer end, read the first part and adjust parameters:
memcpy(m_Buffer + m_WritePos, Src, BytesToEndOfBuffer);
Src += BytesToEndOfBuffer;
a_Count -= BytesToEndOfBuffer;
m_WritePos = 0;
}
// Read the rest of the bytes in a single read (guaranteed to fit):
if (a_Count > 0)
{
memcpy(m_Buffer + m_WritePos, Src, a_Count);
m_WritePos += a_Count;
}
return true;
}
bool cByteBuffer::ReadString(AString & a_String, size_t a_Count)
{
CHECK_THREAD
CheckValid();
NEEDBYTES(a_Count);
a_String.clear();
a_String.reserve(a_Count);
ASSERT(m_BufferSize >= m_ReadPos);
size_t BytesToEndOfBuffer = m_BufferSize - m_ReadPos;
if (BytesToEndOfBuffer <= a_Count)
{
// Reading across the ringbuffer end, read the first part and adjust parameters:
if (BytesToEndOfBuffer > 0)
{
a_String.assign(m_Buffer + m_ReadPos, BytesToEndOfBuffer);
ASSERT(a_Count >= BytesToEndOfBuffer);
a_Count -= BytesToEndOfBuffer;
}
m_ReadPos = 0;
}
// Read the rest of the bytes in a single read (guaranteed to fit):
if (a_Count > 0)
{
a_String.append(m_Buffer + m_ReadPos, a_Count);
m_ReadPos += a_Count;
}
return true;
}
bool cByteBuffer::SkipRead(size_t a_Count)
{
CHECK_THREAD
CheckValid();
if (!CanReadBytes(a_Count))
{
return false;
}
AdvanceReadPos(a_Count);
return true;
}
void cByteBuffer::ReadAll(AString & a_Data)
{
CHECK_THREAD
CheckValid();
ReadString(a_Data, GetReadableSpace());
}
bool cByteBuffer::ReadToByteBuffer(cByteBuffer & a_Dst, size_t a_NumBytes)
{
CHECK_THREAD
if (!a_Dst.CanWriteBytes(a_NumBytes) || !CanReadBytes(a_NumBytes))
{
// There's not enough source bytes or space in the dest BB
return false;
}
char buf[1024];
// > 0 without generating warnings about unsigned comparisons where size_t is unsigned
while (a_NumBytes != 0)
{
size_t num = (a_NumBytes > sizeof(buf)) ? sizeof(buf) : a_NumBytes;
VERIFY(ReadBuf(buf, num));
VERIFY(a_Dst.Write(buf, num));
ASSERT(a_NumBytes >= num);
a_NumBytes -= num;
}
return true;
}
void cByteBuffer::CommitRead(void)
{
CHECK_THREAD
CheckValid();
m_DataStart = m_ReadPos;
}
void cByteBuffer::ResetRead(void)
{
CHECK_THREAD
CheckValid();
m_ReadPos = m_DataStart;
}
void cByteBuffer::ReadAgain(AString & a_Out)
{
// Return the data between m_DataStart and m_ReadPos (the data that has been read but not committed)
// Used by ProtoProxy to repeat communication twice, once for parsing and the other time for the remote party
CHECK_THREAD
CheckValid();
size_t DataStart = m_DataStart;
if (m_ReadPos < m_DataStart)
{
// Across the ringbuffer end, read the first part and adjust next part's start:
ASSERT(m_BufferSize >= m_DataStart);
a_Out.append(m_Buffer + m_DataStart, m_BufferSize - m_DataStart);
DataStart = 0;
}
ASSERT(m_ReadPos >= DataStart);
a_Out.append(m_Buffer + DataStart, m_ReadPos - DataStart);
}
void cByteBuffer::AdvanceReadPos(size_t a_Count)
{
CHECK_THREAD
CheckValid();
m_ReadPos += a_Count;
if (m_ReadPos >= m_BufferSize)
{
m_ReadPos -= m_BufferSize;
}
}
void cByteBuffer::CheckValid(void) const
{
ASSERT(m_ReadPos < m_BufferSize);
ASSERT(m_WritePos < m_BufferSize);
}
size_t cByteBuffer::GetVarIntSize(UInt32 a_Value)
{
size_t Count = 0;
do
{
// If the value cannot be expressed in 7 bits, it needs to take up another byte
Count++;
a_Value >>= 7;
} while (a_Value != 0);
return Count;
}
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