X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Fdatabase.cpp;h=26f6992fcb47e7e84b5fad70707857fcaa1cd857;hb=b97c9c65777b0389f4cc9a6e3257506f29761e03;hp=cf208be8dc0708212ca3444154ac6467368af43f;hpb=54ffe2e5de9ce44129f84f4748743f893b75fda7;p=oweals%2Fminetest.git

diff --git a/src/database.cpp b/src/database.cpp
index cf208be8d..26f6992fc 100644
--- a/src/database.cpp
+++ b/src/database.cpp
@@ -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) {
@@ -30,6 +38,16 @@ static inline s16 unsigned_to_signed(u16 i, u16 max_positive)
 }
 
 
+// Modulo of a negative number does not work consistently in C
+static inline s64 pythonmodulo(s64 i, s16 mod)
+{
+	if (i >= 0) {
+		return i % mod;
+	}
+	return mod - ((-i) % mod);
+}
+
+
 s64 Database::getBlockAsInteger(const v3s16 pos) const
 {
 	return (u64) pos.Z * 0x1000000 +
@@ -37,12 +55,15 @@ s64 Database::getBlockAsInteger(const v3s16 pos) const
 		(u64) pos.X;
 }
 
-v3s16 Database::getIntegerAsBlock(const s64 i) const
+
+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);
-        return pos;
+	v3s16 pos;
+	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;
 }