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"





// #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

    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:
        std::thread::id * m_ThreadID;

        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 = static_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 = static_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);
    const char * Src = static_cast<const char *>(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;
}