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last update Jan 2, 2002 (hackie@prohost.org/ilia@prohost.org)
Shared Memory Operations Extension to PHP
While developing a search deamon we needed a php based front end
to communicate the deamon via SHM. PHP already had a shared memory
extension (sysvshm) written by Christian Cartus <cartus@atrior.de>,
unfortunately this extension was designed with PHP only in mind and
offers high level features which are extremely bothersome for basic SHM
we had in mind. After spending a day trying to reverse engineer and figure
out the format of sysvshm we decided that it would be much easier to
add our own extension to php for simple SHM operations, we were right :)).
the functions are:
int shmop_open(int key, string flags, int mode, int size)
key - the key of/for the shared memory block
flags - 4 flags are avalible
a for read only access (sets SHM_RDONLY)
w for read & write access
c create or open an existing segment (sets IPC_CREATE)
n create a new segment and fail if one already exists under same name (sets IPC_CREATE|IPC_EXCL)
(the n flag is mostly useful for security perpouses, so that you don't end up opening a faked segment
if someone guesses your key)
mode - acsess mode same as for a file (0644) for example
size - size of the block in bytes
returns an indentifier
char shmop_read(int shmid, int start, int count)
shmid - shmid from which to read
start - offset from which to start reading
count - how many bytes to read
returns the data read
int shmop_write(int shmid, string data, int offset)
shmid - shmid from which to read
data - string to put into shared memory
offset - offset in shm to write from
returns bytes written
int shmop_size(int shmid)
shmid - shmid for which to return the size
returns the size in bytes of the shm segment
int shmop_delete(int shmid)
marks the segment for deletion, the segment will be deleted when all processes mapping it will detach
shmid - shmid which to mark for deletion
returns 1 if all ok, zero on failure
int shmop_close(int shmid)
shmid - shmid which to close
returns zero
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