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Revert binary database block position encoding

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This reverts commits a2003b0d553c7223a61c75e5dad79ea68e058ba2 and 54ffe2e5de9ce44129f84f4748743f893b75fda7.

These weren't correct.  Add a black magic warning instead.
This commit is contained in:
ShadowNinja 2014-04-22 12:52:48 -04:00
parent 9ec281c712
commit 41bc24477b
2 changed files with 31 additions and 10 deletions
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37
src/database.cpp
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@ -20,6 +20,14 @@ with this program; if not, write to the Free Software Foundation, Inc.,
#include "database.h"
#include "irrlichttypes.h"
/****************
* Black magic! *
****************
* The position hashing is very messed up.
* It's a lot more complicated than it looks.
*/
static inline s16 unsigned_to_signed(u16 i, u16 max_positive)
{
if (i < max_positive) {
@ -30,19 +38,32 @@ static inline s16 unsigned_to_signed(u16 i, u16 max_positive)
}
s64 Database::getBlockAsInteger(const v3s16 pos) const
// Modulo of a negative number does not work consistently in C
static inline s64 pythonmodulo(s64 i, s16 mod)
{
return (((u64) pos.Z) << 24) +
(((u64) pos.Y) << 12) +
((u64) pos.X);
if (i >= 0) {
return i % mod;
}
return mod - ((-i) % mod);
}
v3s16 Database::getIntegerAsBlock(const s64 i) const
s64 Database::getBlockAsInteger(const v3s16 pos) const
{
return (u64) pos.Z * 0x1000000 +
(u64) pos.Y * 0x1000 +
(u64) pos.X;
}
v3s16 Database::getIntegerAsBlock(s64 i) const
{
v3s16 pos;
pos.Z = unsigned_to_signed((i >> 24) & 0xFFF, 0x1000 / 2);
pos.Y = unsigned_to_signed((i >> 12) & 0xFFF, 0x1000 / 2);
pos.X = unsigned_to_signed((i ) & 0xFFF, 0x1000 / 2);
pos.X = unsigned_to_signed(pythonmodulo(i, 4096), 2048);
i = (i - pos.X) / 4096;
pos.Y = unsigned_to_signed(pythonmodulo(i, 4096), 2048);
i = (i - pos.Y) / 4096;
pos.Z = unsigned_to_signed(pythonmodulo(i, 4096), 2048);
return pos;
}

2
src/database.h
View File

@ -35,7 +35,7 @@ public:
virtual void saveBlock(MapBlock *block)=0;
virtual MapBlock* loadBlock(v3s16 blockpos)=0;
s64 getBlockAsInteger(const v3s16 pos) const;
v3s16 getIntegerAsBlock(const s64 i) const;
v3s16 getIntegerAsBlock(s64 i) const;
virtual void listAllLoadableBlocks(std::list<v3s16> &dst)=0;
virtual int Initialized(void)=0;
virtual ~Database() {};