Apache Portable Runtime
apr_mmap.h
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00001 /* Licensed to the Apache Software Foundation (ASF) under one or more
00002  * contributor license agreements.  See the NOTICE file distributed with
00003  * this work for additional information regarding copyright ownership.
00004  * The ASF licenses this file to You under the Apache License, Version 2.0
00005  * (the "License"); you may not use this file except in compliance with
00006  * the License.  You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 
00017 #ifndef APR_MMAP_H
00018 #define APR_MMAP_H
00019 
00020 /**
00021  * @file apr_mmap.h
00022  * @brief APR MMAP routines
00023  */
00024 
00025 #include "apr.h"
00026 #include "apr_pools.h"
00027 #include "apr_errno.h"
00028 #include "apr_ring.h"
00029 #include "apr_file_io.h"        /* for apr_file_t */
00030 
00031 #ifdef BEOS
00032 #include <kernel/OS.h>
00033 #endif
00034 
00035 #ifdef __cplusplus
00036 extern "C" {
00037 #endif /* __cplusplus */
00038 
00039 /**
00040  * @defgroup apr_mmap MMAP (Memory Map) Routines
00041  * @ingroup APR 
00042  * @{
00043  */
00044 
00045 /** MMap opened for reading */
00046 #define APR_MMAP_READ    1
00047 /** MMap opened for writing */
00048 #define APR_MMAP_WRITE   2
00049 
00050 /** @see apr_mmap_t */
00051 typedef struct apr_mmap_t            apr_mmap_t;
00052 
00053 /**
00054  * @remark
00055  * As far as I can tell the only really sane way to store an MMAP is as a
00056  * void * and a length.  BeOS requires this area_id, but that's just a little
00057  * something extra.  I am exposing this type, because it doesn't make much
00058  * sense to keep it private, and opening it up makes some stuff easier in
00059  * Apache.
00060  */
00061 /** The MMAP structure */
00062 struct apr_mmap_t {
00063     /** The pool the mmap structure was allocated out of. */
00064     apr_pool_t *cntxt;
00065 #ifdef BEOS
00066     /** An area ID.  Only valid on BeOS */
00067     area_id area;
00068 #endif
00069 #ifdef WIN32
00070     /** The handle of the file mapping */
00071     HANDLE mhandle;
00072     /** The start of the real memory page area (mapped view) */
00073     void *mv;
00074     /** The physical start, size and offset */
00075     apr_off_t  pstart;
00076     apr_size_t psize;
00077     apr_off_t  poffset;
00078 #endif
00079     /** The start of the memory mapped area */
00080     void *mm;
00081     /** The amount of data in the mmap */
00082     apr_size_t size;
00083     /** ring of apr_mmap_t's that reference the same
00084      * mmap'ed region; acts in place of a reference count */
00085     APR_RING_ENTRY(apr_mmap_t) link;
00086 };
00087 
00088 #if APR_HAS_MMAP || defined(DOXYGEN)
00089 
00090 /** @def APR_MMAP_THRESHOLD 
00091  * Files have to be at least this big before they're mmap()d.  This is to deal
00092  * with systems where the expense of doing an mmap() and an munmap() outweighs
00093  * the benefit for small files.  It shouldn't be set lower than 1.
00094  */
00095 #ifdef MMAP_THRESHOLD
00096 #  define APR_MMAP_THRESHOLD              MMAP_THRESHOLD
00097 #else
00098 #  ifdef SUNOS4
00099 #    define APR_MMAP_THRESHOLD            (8*1024)
00100 #  else
00101 #    define APR_MMAP_THRESHOLD            1
00102 #  endif /* SUNOS4 */
00103 #endif /* MMAP_THRESHOLD */
00104 
00105 /** @def APR_MMAP_LIMIT
00106  * Maximum size of MMap region
00107  */
00108 #ifdef MMAP_LIMIT
00109 #  define APR_MMAP_LIMIT                  MMAP_LIMIT
00110 #else
00111 #  define APR_MMAP_LIMIT                  (4*1024*1024)
00112 #endif /* MMAP_LIMIT */
00113 
00114 /** Can this file be MMaped */
00115 #define APR_MMAP_CANDIDATE(filelength) \
00116     ((filelength >= APR_MMAP_THRESHOLD) && (filelength < APR_MMAP_LIMIT))
00117 
00118 /*   Function definitions */
00119 
00120 /** 
00121  * Create a new mmap'ed file out of an existing APR file.
00122  * @param newmmap The newly created mmap'ed file.
00123  * @param file The file turn into an mmap.
00124  * @param offset The offset into the file to start the data pointer at.
00125  * @param size The size of the file
00126  * @param flag bit-wise or of:
00127  * <PRE>
00128  *          APR_MMAP_READ       MMap opened for reading
00129  *          APR_MMAP_WRITE      MMap opened for writing
00130  * </PRE>
00131  * @param cntxt The pool to use when creating the mmap.
00132  */
00133 APR_DECLARE(apr_status_t) apr_mmap_create(apr_mmap_t **newmmap, 
00134                                           apr_file_t *file, apr_off_t offset,
00135                                           apr_size_t size, apr_int32_t flag,
00136                                           apr_pool_t *cntxt);
00137 
00138 /**
00139  * Duplicate the specified MMAP.
00140  * @param new_mmap The structure to duplicate into. 
00141  * @param old_mmap The mmap to duplicate.
00142  * @param p The pool to use for new_mmap.
00143  */         
00144 APR_DECLARE(apr_status_t) apr_mmap_dup(apr_mmap_t **new_mmap,
00145                                        apr_mmap_t *old_mmap,
00146                                        apr_pool_t *p);
00147 
00148 /**
00149  * Remove a mmap'ed.
00150  * @param mm The mmap'ed file.
00151  */
00152 APR_DECLARE(apr_status_t) apr_mmap_delete(apr_mmap_t *mm);
00153 
00154 /** 
00155  * Move the pointer into the mmap'ed file to the specified offset.
00156  * @param addr The pointer to the offset specified.
00157  * @param mm The mmap'ed file.
00158  * @param offset The offset to move to.
00159  */
00160 APR_DECLARE(apr_status_t) apr_mmap_offset(void **addr, apr_mmap_t *mm, 
00161                                           apr_off_t offset);
00162 
00163 #endif /* APR_HAS_MMAP */
00164 
00165 /** @} */
00166 
00167 #ifdef __cplusplus
00168 }
00169 #endif
00170 
00171 #endif  /* ! APR_MMAP_H */
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