Now with static-vectors support!
(deftype octet '(unsigned-byte 8)) (deftype octet-vector '(simple-array octet (*)))
Fast-io is about improving performance to octet-vectors and octet streams (though primarily the former, while wrapping the latter). Imagine we're creating messages for the network. If we try and fill an octet-vector with 50 bytes, 50000 times, here are the results (SBCL 1.0.57):
t/benchmarks.lisp for the exact code used.)
It should be surprising that it takes a nontrivial effort to achieve relatively decent performance to octet-vectors, but probably isn't. However, fast-io provides a relatively straightforward interface for reading and writing either a stream or a vector:
;;; Write a byte or sequence, optionally to a stream: (with-fast-output (buffer [STREAM | :vector | :static]) (fast-write-byte BYTE buffer)) (with-fast-output (buffer [STREAM | :vector | :static]) (fast-write-sequence OCTET-VECTOR buffer [START [END]])) ;;; Read from a vector or stream: (with-fast-input (buffer VECTOR [STREAM]) (fast-read-byte buffer)) (with-fast-input (buffer VECTOR [STREAM]) (let ((vec (make-octet-vector N))) (fast-read-sequence vec buffer [START [END]])))
Multi-byte and Endianness
Fast-io provides a host of read and write functions for big- and little-endian reads, in the following forms:
(write32-be VALUE BUFFER)will write the specified 32-bit value to the specified buffer with a big-endian layout. Likewise,
(writeu16-le VALUE BUFFER)will write an unsigned 16-bit value in little-endian layout.
(read64-le BUFFER)will read a 64-bit value from the buffer with little-endian layout.
You may now specify
:static instead of a stream to
WITH-OUTPUT-BUFFER. This returns an octet-vector created with
which means that passing the buffered data directly to a foreign
function is now that much more efficient:
(let ((data (with-fast-output (buffer :static) (buffer-some-data buffer)))) (foreign-send (static-vectors:static-vector-pointer data)) (static-vectors:free-static-vector data))
Note that the restriction for manually freeing the result remains. This avoids multiple inefficient (i.e., byte-by-byte) copies to foreign memory.
Obviously, the above API isn't built around Lisp streams, or even
gray-streams. However, fast-io provides a small wrapper using
trivial-gray-streams, and supports
(let ((stream (make-instance 'fast-io:fast-output-stream))) (write-sequence (fast-io:octets-from '(1 2 3 4)) stream))
fast-output-stream support backing a
stream, much like using the plain fast-io buffers. However, using the
gray-streams interface is a 3-4x as slow as using the buffers alone.
Simple benchmarks show the gray-streams interface writing 1M 50-byte
vectors in about 1.7s, whereas simply using buffers is about 0.8s.
Consing remains similar between the two.