[jffi-next] 09/24: Add PageManager, a thin wrapper around mmap/munmap/mprotect, and the windows equivalents

[Tim Potter]

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tpot-guest pushed a commit to tag 0.6.5
in repository jffi-next.

commit 5d09f619cbdacf10fd47b5b2ea3de743bda51762
Author: Wayne Meissner <wmeissner at gmail.com>
Date:   Thu Dec 31 13:14:51 2009 +1000

    Add PageManager, a thin wrapper around mmap/munmap/mprotect, and the windows equivalents
---
 src/com/kenai/jffi/PageManager.java | 129 ++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)

diff --git a/src/com/kenai/jffi/PageManager.java b/src/com/kenai/jffi/PageManager.java
new file mode 100644
index 0000000..2ba61cf
--- /dev/null
+++ b/src/com/kenai/jffi/PageManager.java
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2009 Wayne Meissner
+ *
+ * This file is part of jffi.
+ *
+ * This code is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License version 3 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
+ * version 3 for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * version 3 along with this work.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.kenai.jffi;
+
+/**
+ * Manages allocation, disposal and protection of native memory pages
+ */
+abstract public class PageManager {
+    /** The memory should be executable */
+    public static final int PROT_EXEC = Foreign.PROT_EXEC;
+
+    /** The memory should be readable */
+    public static final int PROT_READ = Foreign.PROT_READ;
+
+    /** The memory should be writable */
+    public static final int PROT_WRITE = Foreign.PROT_WRITE;
+
+    private static final class SingletonHolder {
+        public static final PageManager INSTANCE = Platform.getPlatform().getOS() == Platform.OS.WINDOWS
+                ? new Windows() : new Unix();
+    }
+
+    /**
+     * Gets the page manager for the current platform.
+     *
+     * @return An instance of <tt>PageManager</tt>
+     */
+    public static final PageManager getInstance() {
+        return SingletonHolder.INSTANCE;
+    }
+
+    /**
+     * Gets the system page size.
+     *
+     * @return The size of a page on the current system, in bytes.
+     */
+    public final long pageSize() {
+        return Foreign.getInstance().pageSize();
+    }
+
+    /**
+     * Allocates native memory pages.
+     *
+     * The memory allocated is aligned on a page boundary, and the size of the
+     * allocated memory is <tt>npages</tt> * {@link #pageSize}.
+     *
+     * @param npages The number of pages to allocate.
+     * @param protection The initial protection for the page.  This must be a
+     *   bitmask of {@link #PROT_READ}, {@link #PROT_WRITE} and {@link #PROT_EXEC}.
+     *
+     * @return The native address of the allocated memory.
+     */
+    public abstract long allocatePages(int npages, int protection);
+
+    /**
+     * Free pages allocated via {@link #allocatePages }
+     *
+     * @param address The memory address as returned from {@link #allocatePages}
+     * @param npages The number of pages to free.
+     */
+    public abstract void freePages(long address, int npages);
+
+    /**
+     * Sets the protection mask on a memory region.
+     *
+     * @param address The start of the memory region.
+     * @param npages The number of pages to protect.
+     * @param protection The protection mask.
+     */
+    public abstract void protectPages(long address, int npages, int protection);
+
+    static final class Unix extends PageManager {
+
+        @Override
+        public long allocatePages(int npages, int protection) {
+            long sz = npages * pageSize();
+            return Foreign.getInstance().mmap(0, sz, protection,
+                    Foreign.MAP_ANON | Foreign.MAP_PRIVATE, 0, 0);
+
+        }
+
+        @Override
+        public void freePages(long address, int npages) {
+            Foreign.getInstance().munmap(address, npages * pageSize());
+        }
+
+        @Override
+        public void protectPages(long address, int npages, int protection) {
+            Foreign.getInstance().mprotect(address, npages * pageSize(), protection);
+        }
+    }
+
+    static final class Windows extends PageManager {
+
+        public Windows() {
+        }
+
+        @Override
+        public long allocatePages(int npages, int protection) {
+            throw new UnsupportedOperationException("Not supported yet.");
+        }
+
+        @Override
+        public void freePages(long address, int npages) {
+            throw new UnsupportedOperationException("Not supported yet.");
+        }
+
+        @Override
+        public void protectPages(long address, int npages, int protection) {
+            throw new UnsupportedOperationException("Not supported yet.");
+        }
+    }
+}

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