Patchwork [3/5] libpayload: Implement ffs()

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Submitter Patrick Georgi
Date 2011-02-25 12:11:19
Message ID <1298640300.2470.15.camel@linux-0a8x.site>
Download mbox | patch
Permalink /patch/2699/
State Accepted
Headers show

Comments

Patrick Georgi - 2011-02-25 12:11:19
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
---
 payloads/libpayload/include/strings.h |   35 ++++++++++++++++++++++++++++
 payloads/libpayload/libc/Makefile.inc |    2 +-
 payloads/libpayload/libc/strings.c    |   40 +++++++++++++++++++++++++++++++++
 3 files changed, 76 insertions(+), 1 deletions(-)
 create mode 100644 payloads/libpayload/include/strings.h
 create mode 100644 payloads/libpayload/libc/strings.c
Stefan Reinauer - 2011-02-25 20:43:56
* Patrick Georgi <Patrick.Georgi@secunet.com> [110225 13:11]:
> Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
> ---
>  payloads/libpayload/include/strings.h |   35 ++++++++++++++++++++++++++++
>  payloads/libpayload/libc/Makefile.inc |    2 +-
>  payloads/libpayload/libc/strings.c    |   40 +++++++++++++++++++++++++++++++++
>  3 files changed, 76 insertions(+), 1 deletions(-)
>  create mode 100644 payloads/libpayload/include/strings.h
>  create mode 100644 payloads/libpayload/libc/strings.c
> 
> diff --git a/payloads/libpayload/include/strings.h b/payloads/libpayload/include/strings.h
> new file mode 100644
> index 0000000..ce7fe93
> --- /dev/null
> +++ b/payloads/libpayload/include/strings.h
> @@ -0,0 +1,35 @@
> +#ifndef _STRING_H
> +#define _STRING_H

This should be _STRINGS_H otherwise it can/will conflict.

Otherwise

Acked-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Peter Stuge - 2011-02-25 20:48:27
Patrick Georgi wrote:
> +int ffs(int i);

Wording in my ffs(3) page suggests that int can be 64 bit. We don't
care?


//Peter
Stefan Reinauer - 2011-02-25 21:19:29
* Peter Stuge <peter@stuge.se> [110225 21:48]:
> Patrick Georgi wrote:
> > +int ffs(int i);
> 
> Wording in my ffs(3) page suggests that int can be 64 bit. We don't
> care?

So far the only compiler I know where this could happen is MSVC. Since
we have an endless amount of GNUisms in all of our code that basically
limits us to gcc/llvm/sun compiler/intel compiler/... it will never be a
problem for us.

We might want to consider a slightly bigger but non-looping and faster
implementation

int ffs(int i)
{
        int count = 1;

        if (i == 0)
                return 0;

        if (!(i & 0xffff)) {
                i >>= 16;
                count += 16;
        }

        if (!(i & 0xff)) {
                i >>= 8;
                count += 8;
        }

        if (!(i & 0xf)) {
                i >>= 4;
                count += 4;
        }

        if (!(i & 3)) {
                i >>= 2;
                count += 2;
        }

        if (!(i & 1)) {
                i >>= 1;
                count += 1;
        }

        return count;
}


Stefan

Patch

diff --git a/payloads/libpayload/include/strings.h b/payloads/libpayload/include/strings.h
new file mode 100644
index 0000000..ce7fe93
--- /dev/null
+++ b/payloads/libpayload/include/strings.h
@@ -0,0 +1,35 @@ 
+/*
+ * This file is part of the libpayload project.
+ *
+ * Copyright (C) 2011 secunet Security Networks AG
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 THE AUTHOR 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 _STRING_H
+#define _STRING_H
+
+int ffs(int i);
+
+#endif
diff --git a/payloads/libpayload/libc/Makefile.inc b/payloads/libpayload/libc/Makefile.inc
index 3cd98c9..d629ccc 100644
--- a/payloads/libpayload/libc/Makefile.inc
+++ b/payloads/libpayload/libc/Makefile.inc
@@ -32,7 +32,7 @@  TARGETS-$(CONFIG_LIBC) += libc/malloc.o libc/printf.o libc/console.o libc/string
 TARGETS-$(CONFIG_LIBC) += libc/memory.o libc/ctype.o libc/ipchecksum.o libc/lib.o
 TARGETS-$(CONFIG_LIBC) += libc/rand.o libc/time.o libc/exec.o
 TARGETS-$(CONFIG_LIBC) += libc/readline.o libc/getopt_long.o libc/sysinfo.o
-TARGETS-$(CONFIG_LIBC) += libc/args.o
+TARGETS-$(CONFIG_LIBC) += libc/args.o libc/strings.o
 
 # should be moved to coreboot directory
 TARGETS-$(CONFIG_LAR) += libc/lar.o
diff --git a/payloads/libpayload/libc/strings.c b/payloads/libpayload/libc/strings.c
new file mode 100644
index 0000000..9a56ba1
--- /dev/null
+++ b/payloads/libpayload/libc/strings.c
@@ -0,0 +1,40 @@ 
+/*
+ * This file is part of the libpayload project.
+ *
+ * Copyright (C) 2011 secunet Security Networks AG
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 THE AUTHOR 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.
+ */
+
+int ffs(int i)
+{
+	int count = 1;
+	if (i == 0) return 0;
+
+	while ((i & 1) != 1) {
+		i>>=1;
+		count++;
+	}
+	return count;
+}