On Wed, Nov 27, 2013 at 4:48 PM, David Herrmann <dh.herrm...@gmail.com> wrote: > This adds a very straightforward ring-buffer implementation to > libsystemd-shared. Ring-buffers allow pushing data to, and pulling data > from, both ends of a buffer without modifying existing/remaining buffer > content. This is very useful for network buffers and asynchronous writes. > > This implementation only contains the most basic functions to push data > onto the end of the buffer and pull data from the front. More helpers may > be added once needed. > --- > Makefile.am | 2 + > src/shared/ring.c | 213 > ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > src/shared/ring.h | 54 ++++++++++++++ > 3 files changed, 269 insertions(+) > create mode 100644 src/shared/ring.c > create mode 100644 src/shared/ring.h > > diff --git a/Makefile.am b/Makefile.am > index 0119751..4aa2bdf 100644 > --- a/Makefile.am > +++ b/Makefile.am > @@ -768,6 +768,8 @@ libsystemd_shared_la_SOURCES = \ > src/shared/net-util.h \ > src/shared/errno-list.c \ > src/shared/errno-list.h \ > + src/shared/ring.h \ > + src/shared/ring.c \ > src/shared/syscall-list.c \ > src/shared/syscall-list.h > > diff --git a/src/shared/ring.c b/src/shared/ring.c > new file mode 100644 > index 0000000..f60f098 > --- /dev/null > +++ b/src/shared/ring.c > @@ -0,0 +1,213 @@ > +/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ > + > +/*** > + This file is part of systemd. > + > + Copyright 2013 David Herrmann <dh.herrm...@gmail.com> > + > + systemd is free software; you can redistribute it and/or modify it > + under the terms of the GNU Lesser General Public License as published by > + the Free Software Foundation; either version 2.1 of the License, or > + (at your option) any later version. > + > + systemd is distributed in the hope that it will be useful, but > + WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + Lesser General Public License for more details. > + > + You should have received a copy of the GNU Lesser General Public License > + along with systemd; If not, see <http://www.gnu.org/licenses/>. > +***/ > + > +#include <errno.h> > +#include <stdlib.h> > +#include <string.h> > +#include <sys/uio.h> > + > +#include "ring.h" > +#include "util.h" > + > +#define RING_MASK(_r, _v) ((_v) & ((_r)->size - 1)) > + > +void ring_flush(Ring *r) { > + r->start = 0; > + r->end = 0; > +} > + > +void ring_clear(Ring *r) { > + free(r->buf); > + memset(r, 0, sizeof(*r)); > +} > + > +/* > + * Resize ring-buffer to size @nsize. @nsize must be a power-of-2, otherwise > + * ring operations will behave incorrectly. > + */ > +static int ring_resize(Ring *r, size_t nsize) { > + char *buf; > + > + buf = malloc(nsize); > + if (!buf) > + return -ENOMEM; > + > + if (r->end == r->start) { > + r->end = 0; > + r->start = 0; > + } else if (r->end > r->start) { > + memcpy(buf, &r->buf[r->start], r->end - r->start); > + > + r->end -= r->start; > + r->start = 0; > + } else { > + memcpy(buf, &r->buf[r->start], r->size - r->start); > + memcpy(&buf[r->size - r->start], r->buf, r->end); > + > + r->end += r->size - r->start; > + r->start = 0; > + } > + > + free(r->buf); > + r->buf = buf; > + r->size = nsize; > + > + return 0; > +} > + > +/* Compute next higher power-of-2 of @v. Returns 4096 in case v is 0. */ > +static size_t ring_pow2(size_t v) { > + size_t i; > + > + if (!v) > + return 4096; > + > + --v; > + > + for (i = 1; i < 8 * sizeof(size_t); i *= 2) > + v |= v >> i; > + > + return ++v;
If you are interested, take a look in https://git.kernel.org/cgit/utils/kernel/kmod/kmod.git/commit/?id=3ba7f59e84857eb4dbe56a68fc7a3ffe8a650393 for a shorter and faster version of this. Lucas De Marchi _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
