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/*
* Copyright (C) 2013 Colin Walters <walters@verbum.org>
*
* SPDX-License-Identifier: LGPL-2.0+
*
* This library 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 of the License, or (at your option) any later version.
*
* This library 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 this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/* Significant code derived from protobuf: */
/*
* Protocol Buffers - Google's data interchange format
* Copyright 2008 Google Inc. All rights reserved.
* http: *code.google.com/p/protobuf/
*
* 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 Google Inc. 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 THE COPYRIGHT HOLDERS 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 COPYRIGHT
* OWNER 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 "config.h"
#include "ostree-varint.h"
static const int max_varint_bytes = 10;
/**
* _ostree_read_varuint64:
* @buf: (array length=buflen): Byte buffer
* @buflen: Length of bytes in @buf
* @out_value: (out): Value
* @bytes_read: (out): Number of bytes read
*
* Returns: %TRUE on success, %FALSE on end of stream
*/
gboolean
_ostree_read_varuint64 (const guint8 *buf,
gsize buflen,
guint64 *out_value,
gsize *bytes_read)
{
guint64 result = 0;
int count = 0;
guint8 b;
/* Adapted from CodedInputStream::ReadVarint64Slow */
do
{
if (count == max_varint_bytes)
return FALSE;
if (buflen == 0)
return FALSE;
b = *buf;
result |= ((guint64)(b & 0x7F)) << (7 * count);
buf++;
buflen--;
++count;
} while (b & 0x80);
*bytes_read = count;
*out_value = result;
return TRUE;
}
/**
* _ostree_write_varuint64:
* @buf: Target buffer (will contain binary data)
* @n: Integer to encode
*
* Append a varint-encoded version of @n to @buf.
*/
void
_ostree_write_varuint64 (GString *buf, guint64 n)
{
/* Splitting into 32-bit pieces gives better performance on 32-bit
* processors. */
guint32 part0 = (guint32)n;
guint32 part1 = (guint32)(n >> 28);
guint32 part2 = (guint32)(n >> 56);
guint8 target[10];
int i;
int size;
/*
* Here we can't really optimize for small numbers, since the value is
* split into three parts. Cheking for numbers < 128, for instance,
* would require three comparisons, since you'd have to make sure part1
* and part2 are zero. However, if the caller is using 64-bit integers,
* it is likely that they expect the numbers to often be very large, so
* we probably don't want to optimize for small numbers anyway. Thus,
* we end up with a hardcoded binary search tree...
*/
if (part2 == 0) {
if (part1 == 0) {
if (part0 < (1 << 14)) {
if (part0 < (1 << 7)) {
size = 1; goto size1;
} else {
size = 2; goto size2;
}
} else {
if (part0 < (1 << 21)) {
size = 3; goto size3;
} else {
size = 4; goto size4;
}
}
} else {
if (part1 < (1 << 14)) {
if (part1 < (1 << 7)) {
size = 5; goto size5;
} else {
size = 6; goto size6;
}
} else {
if (part1 < (1 << 21)) {
size = 7; goto size7;
} else {
size = 8; goto size8;
}
}
}
} else {
if (part2 < (1 << 7)) {
size = 9; goto size9;
} else {
size = 10; goto size10;
}
}
g_assert_not_reached ();
size10: target[9] = (guint8)((part2 >> 7) | 0x80);
size9 : target[8] = (guint8)((part2 ) | 0x80);
size8 : target[7] = (guint8)((part1 >> 21) | 0x80);
size7 : target[6] = (guint8)((part1 >> 14) | 0x80);
size6 : target[5] = (guint8)((part1 >> 7) | 0x80);
size5 : target[4] = (guint8)((part1 ) | 0x80);
size4 : target[3] = (guint8)((part0 >> 21) | 0x80);
size3 : target[2] = (guint8)((part0 >> 14) | 0x80);
size2 : target[1] = (guint8)((part0 >> 7) | 0x80);
size1 : target[0] = (guint8)((part0 ) | 0x80);
target[size-1] &= 0x7F;
for (i = 0; i < size; i++)
g_string_append_c (buf, target[i]);
}
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