libdex/SysUtil.h

/*
 * 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.
 */
#ifdef PAGE_SHIFT
#define SYSTEM_PAGE_SIZE        (1<<PAGE_SHIFT)
#else
#define SYSTEM_PAGE_SIZE        4096
#endif

/*
 * 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);

/*
 * 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);

/*
 * Map part of a file into a shared, read-only memory segment.
 *
 * On success, "pMap" is filled in, and zero is returned.
 */
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_