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diff --git a/libdex/SysUtil.h b/libdex/SysUtil.h
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+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * System utilities.
+ */
+#ifndef LIBDEX_SYSUTIL_H_
+#define LIBDEX_SYSUTIL_H_
+
+#include <sys/types.h>
+
+/*
+ * System page size.  Normally you're expected to get this from
+ * sysconf(_SC_PAGESIZE) or some system-specific define (usually PAGESIZE
+ * or PAGE_SIZE).  If we use a simple #define the compiler can generate
+ * appropriate masks directly, so we define it here and verify it as the
+ * VM is starting up.
+ *
+ * Must be a power of 2.
+ */
+#define SYSTEM_PAGE_SIZE        4096
+
+/*
+ * Use this to keep track of mapped segments.
+ */
+struct MemMapping {
+    void*   addr;           /* start of data */
+    size_t  length;         /* length of data */
+
+    void*   baseAddr;       /* page-aligned base address */
+    size_t  baseLength;     /* length of mapping */
+};
+
+/*
+ * Copy a map.
+ */
+void sysCopyMap(MemMapping* dst, const MemMapping* src);
+
+/*
+ * Load a file into a new shared memory segment.  All data from the current
+ * offset to the end of the file is pulled in.
+ *
+ * The segment is read-write, allowing VM fixups.  (It should be modified
+ * to support .gz/.zip compressed data.)
+ *
+ * On success, "pMap" is filled in, and zero is returned.
+ */
+int sysLoadFileInShmem(int fd, MemMapping* pMap);
+
+/*
+ * Map a file (from fd's current offset) into a shared,
+ * read-only memory segment.
+ *
+ * On success, "pMap" is filled in, and zero is returned.
+ */
+int sysMapFileInShmemReadOnly(int fd, MemMapping* pMap);
+
+/*
+ * Map a file (from fd's current offset) into a shared, read-only memory
+ * segment that can be made writable.  (In some cases, such as when
+ * mapping a file on a FAT filesystem, the result may be fully writable.)
+ *
+ * On success, "pMap" is filled in, and zero is returned.
+ */
+int sysMapFileInShmemWritableReadOnly(int fd, MemMapping* pMap);
+
+/*
+ * Like sysMapFileInShmemReadOnly, but on only part of a file.
+ */
+int sysMapFileSegmentInShmem(int fd, off_t start, size_t length,
+    MemMapping* pMap);
+
+/*
+ * Create a private anonymous mapping, useful for large allocations.
+ *
+ * On success, "pMap" is filled in, and zero is returned.
+ */
+int sysCreatePrivateMap(size_t length, MemMapping* pMap);
+
+/*
+ * Change the access rights on one or more pages.  If "wantReadWrite" is
+ * zero, the pages will be made read-only; otherwise they will be read-write.
+ *
+ * Returns 0 on success.
+ */
+int sysChangeMapAccess(void* addr, size_t length, int wantReadWrite,
+    MemMapping* pmap);
+
+/*
+ * Release the pages associated with a shared memory segment.
+ *
+ * This does not free "pMap"; it just releases the memory.
+ */
+void sysReleaseShmem(MemMapping* pMap);
+
+/*
+ * Write until all bytes have been written.
+ *
+ * Returns 0 on success, or an errno value on failure.
+ */
+int sysWriteFully(int fd, const void* buf, size_t count, const char* logMsg);
+
+/*
+ * Copy the given number of bytes from one fd to another. Returns
+ * 0 on success, -1 on failure.
+ */
+int sysCopyFileToFile(int outFd, int inFd, size_t count);
+
+#endif  // LIBDEX_SYSUTIL_H_