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Module Netmcore_buffer

module Netmcore_buffer: sig .. end
Shared buffer

One can add more data to the end of the buffer, and one can remove data from the beginning of the buffer.

Additions and deletions of data are atomic, and are strictly serialized. Read accesses can occur in parallel, and can even overlap with modifications (to some degree). It is, however, ensured that reads do not see the parallel modification, i.e. reads always base on the state from the beginning of the read operation.

It is not excluded that additions can be executed in parallel. If done this way, it is guaranteed that the effects of parallel additions are the same as if they were executed in a serial way. In particular, if an addition operation returns, this addition and all parallel additions affecting preceding index positions must be done. (The current implementation does not attempt this optimization.)

Index positions are "eternal", i.e. the index position of a byte does not change when preceding bytes are deleted. Instead, a deletion merely advances the start index of the valid data (which is not necessarily 0). This model is more consistent with parallel modifications.

On 32 bit platforms it can happen that index positions wrap around (at 1G). The position following max_int is 0. The length is restricted to max_int-bsize on these platforms.

type 'h buffer 
A buffer with a header of type 'h
type 'h buffer_descr 
The marshallable buffer descriptor
val create : Netmcore.res_id -> int -> 'h -> 'h buffer
create pool bsize h: Creates a buffer in pool with a block size of bsize. The block size can be an arbitrary positive integer which is always rounded up to the next multiple of the page size of the operating system. Blocks are the units of allocation of memory.
val destroy : 'h buffer -> unit
Destroys the buffer

The valid index positions (e.g. for sub) are start to start+length-1:
val start : 'h buffer -> int
Returns the start index
val length : 'h buffer -> int
Returns the length
val contents : 'h buffer -> string
Returns the full contents
val sub : 'h buffer -> int -> int -> string
Returns a substring
val blit_to_string : 'h buffer -> int -> string -> int -> int -> unit
Blits contents to a string
val blit_to_memory : 'h buffer -> int -> Netsys_mem.memory -> int -> int -> unit
Blits contents to a memory buffer
val access : 'h buffer -> int -> (string -> int -> int -> 'a) -> 'a
access b pos f: Gets access to the internal string backing the byte at position pos. The function f is called as f s k n so that s.[k] is the requested byte at pos. The number n is the number of valid bytes in the string.

During the execution of f the string s is pinned and cannot be deleted by the garbage collector.

val add_string : 'h buffer -> string -> unit
Adds a string to the end of the buffer
val add_sub_string : 'h buffer -> string -> int -> int -> unit
Adds a sub string to the end of the buffer
val add_sub_memory : 'h buffer -> Netsys_mem.memory -> int -> int -> unit
Adds a sub memory buffer to the end of the buffer
val delete_hd : 'h buffer -> int -> unit
delete_hd b n: Deletes n bytes from the beginning of the buffer. This means that the start index is increased by n.
val clear : 'h buffer -> unit
Deletes all contents of the buffer
val header : 'h buffer -> 'h
Returns the header
val descr_of_buffer : 'h buffer -> 'h buffer_descr
Returns the descriptor
val buffer_of_descr : Netmcore.res_id ->
'h buffer_descr -> 'h buffer
Look up the buffer for this descriptor
val heap : 'a buffer -> Obj.t Netmcore_heap.heap
Returns the underlying heap
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