evenson at panix.com
Thu Jun 4 10:27:38 UTC 2020
We are pleased to announce the immediate availablity of the [ABCL
After consuming a steady diet of java.nio.ByteBuffer objects over the
past month, the Bear has managed to incorporate the use of these
abstractions for arrays specialized on the commonly used unsigned-byte
types (or (unsigned-byte 8) (unsigned-byte 16) (unsigned-byte 32)).
This replacement of the use arrays of primitive bytes is denoted by
the presence of the :NIO keyword in CL:*FEATURES*.
With this :NIO overhaul, we have extended our implementation of ANSI
Common Lisp [CL:MAKE-ARRAY] with two additional keywords,
viz. :NIO-BUFFER and :NIO-DIRECT.
The :NIO-BUFFER keyword argument allows one to construct a vector
directly utilizing the contents of an already allocated
java.nio.ByteBuffer object. When combined with the ability of JNA to
allocate memory on the heap via a malloc() system call, we implemented
shareable byte vectors in [CFFI-SYS:MAKE-SHAREABLE-BYTE-VECTOR].
(let* ((length 16)
(byte-buffer (java:jstatic "allocate"
(make-array length :element-type ’(unsigned-byte 8)
When the :NIO-DIRECT keyword argument is called with a non-NIL value,
the implementation creates a byte vector with a "directly allocated"
java.nio.ByteBuffer object. Such direct buffers typically have
somewhat higher allocation and deallocation costs than non-direct
buffers. The contents of direct buffers may reside outside of the
normal garbage-collected heap, and so their impact upon the memory
footprint of an application might not be obvious. It is therefore
recommended that direct buffers be allocated primarily for large,
long-lived buffers that are subject to the underlying system’s native
I/O operations. In general it is best to allocate direct buffers only
when they yield a measureable gain in program performance. In the near
future, we intend to exploring the performance gains available CL:LOAD
by accessing direct buffers memory mapped to our on-disk fasl
representation. Our fasls, as zipped archives, currently require a
new seek() from the beginning of the fasl for each component they
contain. With a memory mapped direct buffer we should be able to
simply read from the appropiate byte offset for each component.
A complete overview of the accumulated fixes and changes since the
previous release may be viewed in [CHANGES].
[ABCL 1.7.0 release]: https://abcl.org/releases/1.7.0/
"A screaming comes across the sky. It has happened before but there is nothing
to compare to it now."
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