Re: [Libguestfs] [PATCH v2 nbdkit 4/6] common: Add a directory for common code shared by plugins and filters.

Currently this adds two useful header files containing functions which will be consumed by filters in later commits. --- Makefile.am | 5 +++- common/include/Makefile.am | 39 ++++++++++++++++++++++++ common/include/ispowerof2.h | 50 +++++++++++++++++++++++++++++++ common/include/iszero.h | 60 +++++++++++++++++++++++++++++++++++++ configure.ac | 1 + 5 files changed, 154 insertions(+), 1 deletion(-) diff --git a/Makefile.am b/Makefile.am index 6a3a377..09dbdb9 100644 --- a/Makefile.am +++ b/Makefile.am @@ -53,7 +53,10 @@ SUBDIRS = \ src if HAVE_PLUGINS -SUBDIRS += plugins filters +SUBDIRS += \ + common/include \ + plugins \ + filters endif SUBDIRS += tests diff --git a/common/include/Makefile.am b/common/include/Makefile.am new file mode 100644 index 0000000..4ce1723 --- /dev/null +++ b/common/include/Makefile.am @@ -0,0 +1,39 @@ +# nbdkit +# Copyright (C) 2018 Red Hat Inc. +# All rights reserved. +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions are +# met: +# +# * Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# +# * Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in the +# documentation and/or other materials provided with the distribution. +# +# * Neither the name of Red Hat nor the names of its contributors may be +# used to endorse or promote products derived from this software without +# specific prior written permission. +# +# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND +# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, +# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A +# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR +# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF +# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT +# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +# SUCH DAMAGE. + +include $(top_srcdir)/common-rules.mk + +# These headers contain only common code shared by plugins and +# filters. They are not installed. +EXTRA_DIST = \ + ispowerof2.h \ + iszero.h diff --git a/common/include/ispowerof2.h b/common/include/ispowerof2.h new file mode 100644 index 0000000..41844b3 --- /dev/null +++ b/common/include/ispowerof2.h @@ -0,0 +1,50 @@ +/* nbdkit + * Copyright (C) 2018 Red Hat Inc. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * * Neither the name of Red Hat nor the names of its contributors may be + * used to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef NBDKIT_ISPOWEROF2_H +#define NBDKIT_ISPOWEROF2_H + +#include <stdbool.h> + +/* Returns true if v is a power of 2. + * + * Uses the algorithm described at + * http://graphics.stanford.edu/~seander/bithacks.html#DetermineIfPowerOf2 + */ +static inline bool +is_power_of_2 (unsigned long v) +{ + return v && ((v & (v - 1)) == 0); +} + +#endif /* NBDKIT_ISPOWEROF2_H */ diff --git a/common/include/iszero.h b/common/include/iszero.h new file mode 100644 index 0000000..331614c --- /dev/null +++ b/common/include/iszero.h @@ -0,0 +1,60 @@ +/* nbdkit + * Copyright (C) 2018 Red Hat Inc. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * * Neither the name of Red Hat nor the names of its contributors may be + * used to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef NBDKIT_ISZERO_H +#define NBDKIT_ISZERO_H + +#include <string.h> +#include <stdbool.h> + +/* Return true iff the buffer is all zero bytes. + * + * The clever approach here was suggested by Eric Blake. See: + * https://www.redhat.com/archives/libguestfs/2017-April/msg00171.html

+ */ +static inline bool +is_zero (const char *buffer, size_t size) +{ + size_t i; + const size_t limit = size < 16 ? size : 16; + + for (i = 0; i < limit; ++i) + if (buffer[i]) + return false; + if (size != limit) + return ! memcmp (buffer, buffer + 16, size - 16); + + return true; +} + +#endif /* NBDKIT_ISZERO_H */ diff --git a/configure.ac b/configure.ac index b87efb9..774f290 100644 --- a/configure.ac +++ b/configure.ac @@ -538,6 +538,7 @@ AC_CONFIG_FILES([podwrapper.pl], [chmod +x,-w podwrapper.pl]) AC_CONFIG_FILES([Makefile bash/Makefile + common/include/Makefile docs/Makefile include/Makefile plugins/Makefile -- 2.18.0 _______________________________________________ Libguestfs mailing list Libguestfs(a)redhat.com https://www.redhat.com/mailman/listinfo/libguestfs