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cuberite-2a/source/WorldStorage/FastNBT.cpp

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// FastNBT.cpp
// Implements the fast NBT parser and writer
#include "Globals.h"
#include "FastNBT.h"
// The number of NBT tags that are reserved when an NBT parsing is started.
// You can override this by using a cmdline define
#ifndef NBT_RESERVE_SIZE
#define NBT_RESERVE_SIZE 200
#endif // NBT_RESERVE_SIZE
#define RETURN_FALSE_IF_FALSE(X) do { if (!X) return false; } while (0)
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// cParsedNBT:
#define NEEDBYTES(N) \
if (m_Length - m_Pos < N) \
{ \
return false; \
}
cParsedNBT::cParsedNBT(const char * a_Data, int a_Length) :
m_Data(a_Data),
m_Length(a_Length),
m_Pos(0)
{
m_IsValid = Parse();
}
bool cParsedNBT::Parse(void)
{
if (m_Length < 3)
{
// Data too short
return false;
}
if (m_Data[0] != TAG_Compound)
{
// The top-level tag must be a Compound
return false;
}
m_Tags.reserve(NBT_RESERVE_SIZE);
m_Tags.push_back(cFastNBTTag(TAG_Compound, -1));
m_Pos = 1;
RETURN_FALSE_IF_FALSE(ReadString(m_Tags.back().m_NameStart, m_Tags.back().m_NameLength));
RETURN_FALSE_IF_FALSE(ReadCompound());
return true;
}
bool cParsedNBT::ReadString(int & a_StringStart, int & a_StringLen)
{
NEEDBYTES(2);
a_StringStart = m_Pos + 2;
a_StringLen = ntohs(*((short *)(m_Data + m_Pos)));
if (a_StringLen < 0)
{
// Invalid string length
return false;
}
m_Pos += 2 + a_StringLen;
return true;
}
bool cParsedNBT::ReadCompound(void)
{
// Reads the latest tag as a compound
int ParentIdx = m_Tags.size() - 1;
int PrevSibling = -1;
while (true)
{
NEEDBYTES(1);
eTagType TagType = (eTagType)(m_Data[m_Pos]);
m_Pos++;
if (TagType == TAG_End)
{
break;
}
m_Tags.push_back(cFastNBTTag(TagType, ParentIdx, PrevSibling));
if (PrevSibling >= 0)
{
m_Tags[PrevSibling].m_NextSibling = m_Tags.size() - 1;
}
else
{
m_Tags[ParentIdx].m_FirstChild = m_Tags.size() - 1;
}
PrevSibling = m_Tags.size() - 1;
RETURN_FALSE_IF_FALSE(ReadString(m_Tags.back().m_NameStart, m_Tags.back().m_NameLength));
RETURN_FALSE_IF_FALSE(ReadTag());
} // while (true)
m_Tags[ParentIdx].m_LastChild = PrevSibling;
return true;
}
bool cParsedNBT::ReadList(eTagType a_ChildrenType)
{
// Reads the latest tag as a list of items of type a_ChildrenType
// Read the count:
NEEDBYTES(4);
int Count = ntohl(*((int *)(m_Data + m_Pos)));
m_Pos += 4;
if (Count < 0)
{
return false;
}
// Read items:
int ParentIdx = m_Tags.size() - 1;
int PrevSibling = -1;
for (int i = 0; i < Count; i++)
{
m_Tags.push_back(cFastNBTTag(a_ChildrenType, ParentIdx, PrevSibling));
if (PrevSibling >= 0)
{
m_Tags[PrevSibling].m_NextSibling = m_Tags.size() - 1;
}
else
{
m_Tags[ParentIdx].m_FirstChild = m_Tags.size() - 1;
}
PrevSibling = m_Tags.size() - 1;
RETURN_FALSE_IF_FALSE(ReadTag());
} // for (i)
m_Tags[ParentIdx].m_LastChild = PrevSibling;
return true;
}
#define CASE_SIMPLE_TAG(TAGTYPE, LEN) \
case TAG_##TAGTYPE: \
{ \
NEEDBYTES(LEN); \
Tag.m_DataStart = m_Pos; \
Tag.m_DataLength = LEN; \
m_Pos += LEN; \
return true; \
}
bool cParsedNBT::ReadTag(void)
{
cFastNBTTag & Tag = m_Tags.back();
switch (Tag.m_Type)
{
CASE_SIMPLE_TAG(Byte, 1)
CASE_SIMPLE_TAG(Short, 2)
CASE_SIMPLE_TAG(Int, 4)
CASE_SIMPLE_TAG(Long, 8)
CASE_SIMPLE_TAG(Float, 4)
CASE_SIMPLE_TAG(Double, 8)
case TAG_String:
{
return ReadString(Tag.m_DataStart, Tag.m_DataLength);
}
case TAG_ByteArray:
{
NEEDBYTES(4);
int len = ntohl(*((int *)(m_Data + m_Pos)));
m_Pos += 4;
if (len < 0)
{
// Invalid length
return false;
}
NEEDBYTES(len);
Tag.m_DataLength = len;
Tag.m_DataStart = m_Pos;
m_Pos += len;
return true;
}
case TAG_List:
{
NEEDBYTES(1);
eTagType ItemType = (eTagType)m_Data[m_Pos];
m_Pos++;
RETURN_FALSE_IF_FALSE(ReadList(ItemType));
return true;
}
case TAG_Compound:
{
RETURN_FALSE_IF_FALSE(ReadCompound());
return true;
}
case TAG_IntArray:
{
NEEDBYTES(4);
int len = ntohl(*((int *)(m_Data + m_Pos)));
m_Pos += 4;
if (len < 0)
{
// Invalid length
return false;
}
len *= 4;
NEEDBYTES(len);
Tag.m_DataLength = len;
Tag.m_DataStart = m_Pos;
m_Pos += len;
return true;
}
default:
{
ASSERT(!"Unhandled NBT tag type");
return false;
}
} // switch (iType)
}
#undef CASE_SIMPLE_TAG
int cParsedNBT::FindChildByName(int a_Tag, const char * a_Name, size_t a_NameLength) const
{
if (a_Tag < 0)
{
return -1;
}
if (m_Tags[a_Tag].m_Type != TAG_Compound)
{
return -1;
}
if (a_NameLength == 0)
{
a_NameLength = strlen(a_Name);
}
for (int Child = m_Tags[a_Tag].m_FirstChild; Child != -1; Child = m_Tags[Child].m_NextSibling)
{
if (
(m_Tags[Child].m_NameLength == a_NameLength) &&
(memcmp(m_Data + m_Tags[Child].m_NameStart, a_Name, a_NameLength) == 0)
)
{
return Child;
}
} // for Child - children of a_Tag
return -1;
}
int cParsedNBT::FindTagByPath(int a_Tag, const AString & a_Path) const
{
if (a_Tag < 0)
{
return -1;
}
size_t Begin = 0;
size_t Length = a_Path.length();
int Tag = a_Tag;
for (size_t i = 0; i < Length; i++)
{
if (a_Path[i] != '\\')
{
continue;
}
Tag = FindChildByName(Tag, a_Path.c_str() + Begin, i - Begin - 1);
if (Tag < 0)
{
return -1;
}
Begin = i + 1;
} // for i - a_Path[]
if (Begin < Length)
{
Tag = FindChildByName(Tag, a_Path.c_str() + Begin, Length - Begin);
}
return Tag;
}
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// cFastNBTWriter:
cFastNBTWriter::cFastNBTWriter(const AString & a_RootTagName) :
m_CurrentStack(0)
{
m_Stack[0].m_Type = TAG_Compound;
m_Result.reserve(100 * 1024);
m_Result.push_back(TAG_Compound);
WriteString(a_RootTagName.data(), a_RootTagName.size());
}
void cFastNBTWriter::BeginCompound(const AString & a_Name)
{
if (m_CurrentStack >= MAX_STACK)
{
ASSERT(!"Stack overflow");
return;
}
TagCommon(a_Name, TAG_Compound);
++m_CurrentStack;
m_Stack[m_CurrentStack].m_Type = TAG_Compound;
}
void cFastNBTWriter::EndCompound(void)
{
ASSERT(m_CurrentStack > 0);
ASSERT(IsStackTopCompound());
m_Result.push_back(TAG_End);
--m_CurrentStack;
}
void cFastNBTWriter::BeginList(const AString & a_Name, eTagType a_ChildrenType)
{
if (m_CurrentStack >= MAX_STACK)
{
ASSERT(!"Stack overflow");
return;
}
TagCommon(a_Name, TAG_List);
m_Result.push_back((char)a_ChildrenType);
m_Result.append(4, (char)0);
++m_CurrentStack;
m_Stack[m_CurrentStack].m_Type = TAG_List;
m_Stack[m_CurrentStack].m_Pos = m_Result.size() - 4;
m_Stack[m_CurrentStack].m_Count = 0;
m_Stack[m_CurrentStack].m_ItemType = a_ChildrenType;
}
void cFastNBTWriter::EndList(void)
{
ASSERT(m_CurrentStack > 0);
ASSERT(m_Stack[m_CurrentStack].m_Type == TAG_List);
// Update the list count:
*((int *)(m_Result.c_str() + m_Stack[m_CurrentStack].m_Pos)) = htonl(m_Stack[m_CurrentStack].m_Count);
--m_CurrentStack;
}
void cFastNBTWriter::AddByte(const AString & a_Name, unsigned char a_Value)
{
TagCommon(a_Name, TAG_Byte);
m_Result.push_back(a_Value);
}
void cFastNBTWriter::AddShort(const AString & a_Name, Int16 a_Value)
{
TagCommon(a_Name, TAG_Short);
Int16 Value = htons(a_Value);
m_Result.append((const char *)&Value, 2);
}
void cFastNBTWriter::AddInt(const AString & a_Name, Int32 a_Value)
{
TagCommon(a_Name, TAG_Int);
Int32 Value = htonl(a_Value);
m_Result.append((const char *)&Value, 4);
}
void cFastNBTWriter::AddLong(const AString & a_Name, Int64 a_Value)
{
TagCommon(a_Name, TAG_Long);
Int64 Value = HostToNetwork8(&a_Value);
m_Result.append((const char *)&Value, 8);
}
void cFastNBTWriter::AddFloat(const AString & a_Name, float a_Value)
{
TagCommon(a_Name, TAG_Float);
Int32 Value = HostToNetwork4(&a_Value);
m_Result.append((const char *)&Value, 4);
}
void cFastNBTWriter::AddDouble(const AString & a_Name, double a_Value)
{
TagCommon(a_Name, TAG_Double);
Int64 Value = HostToNetwork8(&a_Value);
m_Result.append((const char *)&Value, 8);
}
void cFastNBTWriter::AddString(const AString & a_Name, const AString & a_Value)
{
TagCommon(a_Name, TAG_String);
Int16 len = htons((short)(a_Value.size()));
m_Result.append((const char *)&len, 2);
m_Result.append(a_Value.c_str(), a_Value.size());
}
void cFastNBTWriter::AddByteArray(const AString & a_Name, const char * a_Value, size_t a_NumElements)
{
TagCommon(a_Name, TAG_ByteArray);
Int32 len = htonl(a_NumElements);
m_Result.append((const char *)&len, 4);
m_Result.append(a_Value, a_NumElements);
}
void cFastNBTWriter::AddIntArray(const AString & a_Name, const int * a_Value, size_t a_NumElements)
{
TagCommon(a_Name, TAG_IntArray);
Int32 len = htonl(a_NumElements);
m_Result.append((const char *)&len, 4);
#if defined(ANDROID_NDK)
// Android has alignment issues - cannot byteswap (htonl) an int that is not 32-bit-aligned, which happens in the regular version
for (size_t i = 0; i < a_NumElements; i++)
{
int Element = htonl(a_Value[i]);
m_Result.append((const char *)&Element, 4);
}
#else
int * Elements = (int *)(m_Result.data() + m_Result.size());
m_Result.append(a_NumElements * 4, (char)0);
for (size_t i = 0; i < a_NumElements; i++)
{
Elements[i] = htonl(a_Value[i]);
}
#endif
}
void cFastNBTWriter::Finish(void)
{
ASSERT(m_CurrentStack == 0);
m_Result.push_back(TAG_End);
}
void cFastNBTWriter::WriteString(const char * a_Data, short a_Length)
{
Int16 Len = htons(a_Length);
m_Result.append((const char *)&Len, 2);
m_Result.append(a_Data, a_Length);
}