Fix division and multiplication of page segments

kriszyp · Feb 26, 2024 · 4a86d2d · 4a86d2d
1 parent 5f00403
commit 4a86d2d
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Showing 2 changed files with 4 additions and 5 deletions.
diff --git a/package.json b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "lmdb",
   "author": "Kris Zyp",
-  "version": "3.0.0-beta.7-debug1",
+  "version": "3.0.0-beta.7-debug2",
   "description": "Simple, efficient, scalable, high-performance LMDB interface",
   "license": "MIT",
   "repository": {

diff --git a/src/env.cpp b/src/env.cpp
@@ -624,9 +624,8 @@ int32_t EnvWrap::toSharedBuffer(MDB_env* env, uint32_t* keyBuffer,  MDB_val data
     if (dataAddress > mapAddress && (dataAddress + data.mv_size) <= (mapAddress + stat.me_mapsize)) {
         // an address within the memory map
         int64_t mapOffset = dataAddress - mapAddress;
-        size_t bufferPosition = (mapOffset + (mapOffset >> 4)) >> 32;
-        bufferStart = bufferPosition << 32;
-        bufferStart += mapAddress - (bufferStart >> 4);
+        size_t bufferPosition = mapOffset / 0xf0000000ll; // we don't use the full 4GB because we want to have overlap so records avoid crossing boundaries
+        bufferStart = bufferPosition * 0xf0000000ll + mapAddress;
         end = bufferStart + 0xffffffffll;
         if (end > mapAddress + stat.me_mapsize)
             end = mapAddress + stat.me_mapsize;
@@ -641,7 +640,7 @@ int32_t EnvWrap::toSharedBuffer(MDB_env* env, uint32_t* keyBuffer,  MDB_val data
     if ((dataAddress + data.mv_size) > end) {
         int64_t mapOffset = dataAddress - mapAddress;
         size_t bufferPosition = (mapOffset + (mapOffset >> 4)) >> 32;
-		fprintf(stderr, "Shared address crosses boundaries, dataAddress: %p, data start: %p, data end: %p, buffer end: %p, mapAddress %p, mapOffset %p, bufferPosition %p, \n", dataAddress, dataAddress + data.mv_size, bufferStart, end, mapAddress, mapOffset, bufferPosition);
+		fprintf(stderr, "Shared address crosses boundaries, dataAddress: %p, data end: %p, buffer start: %p, buffer end: %p, mapAddress %p, mapOffset %p, bufferPosition %p, \n", dataAddress, dataAddress + data.mv_size, bufferStart, end, mapAddress, mapOffset, bufferPosition);
         // crosses boundaries, create one-off for this address
         bufferStart = dataAddress;
         end = bufferStart + 0xffffffffll;