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7168505: (bf) MappedByteBuffer.load does not load buffer's content into memory

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Reviewed-by: mduigou, forax
This commit is contained in:
Alan Bateman 2012-05-16 12:43:27 +01:00
parent 5f43f7c289
commit 2a928a555d
1 changed files with 10 additions and 2 deletions
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12
jdk/src/share/classes/java/nio/MappedByteBuffer.java
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@ -139,6 +139,9 @@ public abstract class MappedByteBuffer
return isLoaded0(mappingAddress(offset), length, Bits.pageCount(length));
}
// not used, but a potential target for a store, see load() for details.
private static byte unused;
/**
* Loads this buffer's content into physical memory.
*
@ -157,15 +160,20 @@ public abstract class MappedByteBuffer
long length = mappingLength(offset);
load0(mappingAddress(offset), length);
// touch each page
// Read a byte from each page to bring it into memory. A checksum
// is computed as we go along to prevent the compiler from otherwise
// considering the loop as dead code.
Unsafe unsafe = Unsafe.getUnsafe();
int ps = Bits.pageSize();
int count = Bits.pageCount(length);
long a = mappingAddress(offset);
byte x = 0;
for (int i=0; i<count; i++) {
unsafe.getByte(a);
x ^= unsafe.getByte(a);
a += ps;
}
if (unused != 0)
unused = x;
return this;
}