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db_env_set_func_file_map
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#include &lt;db.h&gt;

int
db_env_set_func_file_map(int (*func_file_map)(DB_ENV *dbenv, char *path, size_t len, int is_rdonly, void **addr),
 int (*func_file_unmap)(DB_ENV *dbenv, void *addr));
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Description: db_env_set_func_file_map
The Berkeley DB library optionally uses the ability to map a file into memory.
The db_env_set_func_file_map method configures all operations performed by a process and
all of its threads of control, not operations confined to a single
database environment.
Although the db_env_set_func_file_map method may be called at any time during the life of
the application, it should normally be called before making calls to the
<a href="../../db4-devel-4.7.25/api_c/env_class.html">db_env_create</a> or <a href="../../db4-devel-4.7.25/api_c/db_class.html">db_create</a> methods.
The db_env_set_func_file_map method
returns a non-zero error value on failure
and 0 on success.

Parameters 
 func_file_map<ul compact><li>The func_file_map parameter is the function which maps a file
into memory. The function takes 5 parameters:
 
dbenv<ul compact><li>The dbenv parameter is the enclosing database environment handle.</ul>
path<ul compact><li>The path parameter is the name of file. Repeated requests for
the mapping of the same name should return a reference to the same
memory.</ul>
len<ul compact><li>The len parameter is the length, in bytes, of the file.</ul>
is_rdonly<ul compact><li>The is_rdonly parameter will be non-zero if the mapped file is
read-only.</ul>
addr<ul compact><li>The addr parameter is the memory location into which a pointer
to the mapped file is returned.</ul>
 
The func_file_map function must return the value of errno on
failure and 0 on success.</ul>
 func_file_unmap<ul compact><li>The func_file_unmap parameter is the function which unmaps a
file from memory. The function takes 2 parameters:
 
dbenv<ul compact><li>The dbenv parameter is the enclosing database environment handle.</ul>
addr<ul compact><li>The addr parameter is the value returned by the
func_file_map function when the file or region was mapped into
memory.</ul>
 
The func_file_unmap function must return the value of errno on
failure and 0 on success.</ul>
 
 See Also
<a href="../../db4-devel-4.7.25/ref/program/runtime.html">Run-time configuration</a>
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