Sometimes when you need to allocate and construct a large,
interconnected complex of structures, it can be a bit of a pain to
release the associated memory again. For the structures describing the
Z39.50 PDUs and related structures, it is convenient to use the
memory-management system of the ODR subsystem (see
Section 2, “Using ODR”). However, in some circumstances
where you might otherwise benefit from using a simple nibble-memory
management system, it may be impractical to use
odr_malloc()
and odr_reset()
.
For this purpose, the memory manager which also supports the ODR
streams is made available in the NMEM module. The external interface
to this module is given in the nmem.h
file.
The following prototypes are given:
NMEM nmem_create(void); void nmem_destroy(NMEM n); void *nmem_malloc(NMEM n, size_t size); void nmem_reset(NMEM n); size_t nmem_total(NMEM n); void nmem_init(void); void nmem_exit(void);
The nmem_create()
function returns a pointer to a
memory control handle, which can be released again by
nmem_destroy()
when no longer needed.
The function nmem_malloc()
allocates a block of
memory of the requested size. A call to nmem_reset()
or nmem_destroy()
will release all memory allocated
on the handle since it was created (or since the last call to
nmem_reset()
. The function
nmem_total()
returns the number of bytes currently
allocated on the handle.
The nibble-memory pool is shared amongst threads. POSIX
mutexes and WIN32 Critical sections are introduced to keep the
module thread safe. Function nmem_init()
initializes the nibble-memory library and it is called automatically
the first time the YAZ.DLL
is loaded. YAZ uses
function DllMain
to achieve this. You should
not call nmem_init
or
nmem_exit
unless you're absolute sure what
you're doing. Note that in previous YAZ versions you'd have to call
nmem_init
yourself.