Hi On Thu, Nov 28, 2013 at 1:27 AM, Lucas De Marchi <lucas.de.mar...@gmail.com> wrote: > 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.
Yepp, that one looks good. Didn't know there was a builtin to count leading zeros. Thanks David _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
