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package sun.nio.fs;

import jdk.internal.misc.Unsafe;

Factory for native buffers.
/** * Factory for native buffers. */
class NativeBuffers { private NativeBuffers() { } private static final Unsafe unsafe = Unsafe.getUnsafe(); private static final int TEMP_BUF_POOL_SIZE = 3; private static ThreadLocal<NativeBuffer[]> threadLocal = new ThreadLocal<NativeBuffer[]>();
Allocates a native buffer, of at least the given size, from the heap.
/** * Allocates a native buffer, of at least the given size, from the heap. */
static NativeBuffer allocNativeBuffer(int size) { // Make a new one of at least 2k if (size < 2048) size = 2048; return new NativeBuffer(size); }
Returns a native buffer, of at least the given size, from the thread local cache.
/** * Returns a native buffer, of at least the given size, from the thread * local cache. */
static NativeBuffer getNativeBufferFromCache(int size) { // return from cache if possible NativeBuffer[] buffers = threadLocal.get(); if (buffers != null) { for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) { NativeBuffer buffer = buffers[i]; if (buffer != null && buffer.size() >= size) { buffers[i] = null; return buffer; } } } return null; }
Returns a native buffer, of at least the given size. The native buffer is taken from the thread local cache if possible; otherwise it is allocated from the heap.
/** * Returns a native buffer, of at least the given size. The native buffer * is taken from the thread local cache if possible; otherwise it is * allocated from the heap. */
static NativeBuffer getNativeBuffer(int size) { NativeBuffer buffer = getNativeBufferFromCache(size); if (buffer != null) { buffer.setOwner(null); return buffer; } else { return allocNativeBuffer(size); } }
Releases the given buffer. If there is space in the thread local cache then the buffer goes into the cache; otherwise the memory is deallocated.
/** * Releases the given buffer. If there is space in the thread local cache * then the buffer goes into the cache; otherwise the memory is deallocated. */
static void releaseNativeBuffer(NativeBuffer buffer) { // create cache if it doesn't exist NativeBuffer[] buffers = threadLocal.get(); if (buffers == null) { buffers = new NativeBuffer[TEMP_BUF_POOL_SIZE]; buffers[0] = buffer; threadLocal.set(buffers); return; } // Put it in an empty slot if such exists for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) { if (buffers[i] == null) { buffers[i] = buffer; return; } } // Otherwise replace a smaller one in the cache if such exists for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) { NativeBuffer existing = buffers[i]; if (existing.size() < buffer.size()) { existing.free(); buffers[i] = buffer; return; } } // free it buffer.free(); }
Copies a byte array and zero terminator into a given native buffer.
/** * Copies a byte array and zero terminator into a given native buffer. */
static void copyCStringToNativeBuffer(byte[] cstr, NativeBuffer buffer) { long offset = Unsafe.ARRAY_BYTE_BASE_OFFSET; long len = cstr.length; assert buffer.size() >= (len + 1); unsafe.copyMemory(cstr, offset, null, buffer.address(), len); unsafe.putByte(buffer.address() + len, (byte)0); }
Copies a byte array and zero terminator into a native buffer, returning the buffer.
/** * Copies a byte array and zero terminator into a native buffer, returning * the buffer. */
static NativeBuffer asNativeBuffer(byte[] cstr) { NativeBuffer buffer = getNativeBuffer(cstr.length+1); copyCStringToNativeBuffer(cstr, buffer); return buffer; } }