From: dje@google.com (Doug Evans)
To: gcc-patches@gcc.gnu.org, binutils@sourceware.org
Cc: gdb-patches@sourceware.org
Subject: Re: [RFA] leb128.h: New file.
Date: Thu, 17 May 2012 18:29:00 -0000 [thread overview]
Message-ID: <20120517182920.64FAE2461B2@ruffy.mtv.corp.google.com> (raw)
Hi.
This is a slightly modified version of my previous patch.
ref: http://gcc.gnu.org/ml/gcc-patches/2012-05/msg00962.html
The only change is to make the result of the functions an int
instead of a const pointer.
This lets them be used in places where the code is using
non-const pointers without having to apply ugly casts.
Ok to check in?
2012-05-17 Doug Evans <dje@google.com>
* leb128.h: New file.
Index: leb128.h
===================================================================
RCS file: leb128.h
diff -N leb128.h
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ leb128.h 17 May 2012 18:23:29 -0000
@@ -0,0 +1,130 @@
+/* Utilities for reading leb128 values.
+ Copyright (C) 2012 Free Software Foundation, Inc.
+
+This file is part of the libiberty library.
+Libiberty is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public
+License as published by the Free Software Foundation; either
+version 2 of the License, or (at your option) any later version.
+
+Libiberty 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
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with libiberty; see the file COPYING.LIB. If not, write
+to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
+Boston, MA 02110-1301, USA. */
+
+/* The functions defined here can be speed critical.
+ Since they are all pretty small we keep things simple and just define
+ them all as "static inline". */
+
+#ifndef LEB128_H
+#define LEB128_H
+
+#include "ansidecl.h"
+
+/* Get a definition for NULL. */
+#include <stdio.h>
+
+#ifdef HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#ifdef HAVE_INTTYPES_H
+#include <inttypes.h>
+#endif
+
+/* Decode the unsigned LEB128 constant at BUF into the variable pointed to
+ by R, and return the number of bytes read.
+ If we read off the end of the buffer, zero is returned,
+ and nothing is stored in R.
+
+ Note: The result is an int instead of a pointer to the next byte to be
+ read to avoid const-vs-non-const problems. */
+
+static inline int
+read_uleb128 (const unsigned char *buf, const unsigned char *buf_end,
+ uint64_t *r)
+{
+ const unsigned char *p = buf;
+ unsigned int shift = 0;
+ uint64_t result = 0;
+ unsigned char byte;
+
+ while (1)
+ {
+ if (p >= buf_end)
+ return 0;
+
+ byte = *p++;
+ result |= ((uint64_t) (byte & 0x7f)) << shift;
+ if ((byte & 0x80) == 0)
+ break;
+ shift += 7;
+ }
+
+ *r = result;
+ return p - buf;
+}
+
+/* Decode the signed LEB128 constant at BUF into the variable pointed to
+ by R, and return the number of bytes read.
+ If we read off the end of the buffer, zero is returned,
+ and nothing is stored in R.
+
+ Note: The result is an int instead of a pointer to the next byte to be
+ read to avoid const-vs-non-const problems. */
+
+static inline int
+read_sleb128 (const unsigned char *buf, const unsigned char *buf_end,
+ int64_t *r)
+{
+ const unsigned char *p = buf;
+ unsigned int shift = 0;
+ int64_t result = 0;
+ unsigned char byte;
+
+ while (1)
+ {
+ if (p >= buf_end)
+ return 0;
+
+ byte = *p++;
+ result |= ((uint64_t) (byte & 0x7f)) << shift;
+ shift += 7;
+ if ((byte & 0x80) == 0)
+ break;
+ }
+ if (shift < (sizeof (*r) * 8) && (byte & 0x40) != 0)
+ result |= -(((uint64_t) 1) << shift);
+
+ *r = result;
+ return p - buf;
+}
+
+/* Return the number of bytes to read to skip past an LEB128 number in BUF.
+ If the end isn't found before reaching BUF_END, return zero.
+
+ Note: The result is an int instead of a pointer to the next byte to be
+ read to avoid const-vs-non-const problems. */
+
+static inline int
+skip_leb128 (const unsigned char *buf, const unsigned char *buf_end)
+{
+ const unsigned char *p = buf;
+ unsigned char byte;
+
+ while (1)
+ {
+ if (p == buf_end)
+ return 0;
+
+ byte = *p++;
+ if ((byte & 128) == 0)
+ return p - buf;
+ }
+}
+
+#endif /* LEB128_H */
next reply other threads:[~2012-05-17 18:29 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-17 18:29 Doug Evans [this message]
2012-05-21 0:31 ` Doug Evans
2012-05-21 14:20 ` Jan Kratochvil
2012-05-21 17:09 ` Ian Lance Taylor
2012-05-21 17:36 ` Doug Evans
2012-05-21 18:22 ` Ian Lance Taylor
-- strict thread matches above, loose matches on Subject: below --
2012-05-15 5:02 Doug Evans
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