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//
// aegis - project change supervisor
// Copyright (C) 2005, 2006, 2008 Peter Miller
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
//
// This program 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see
// <http://www.gnu.org/licenses/>.
//
#include <common/error.h> // for assert
#include <common/nstring.h>
nstring
nstring::substring(long start, long nbytes)
const
{
//
// If start is negative, measure from the end instead of the beginning.
//
if (start < 0)
{
start += size();
}
//
// If nbytes is negative, measure to the left instead of to the right.
//
if (nbytes < 0)
{
start += nbytes;
nbytes = -nbytes;
}
//
// If the start of the string is negative, pretend the negative part
// is empty.
//
if (start < 0)
{
nbytes += start;
start = 0;
}
//
// If, after all that, the substring is still to the left of the
// content, return the empty string.
//
assert(start >= 0);
if (start + nbytes < 0)
return "";
assert(nbytes >= 0);
//
// If the bumber of bytes would project beynd the end of the string,
// truncate them.
//
assert(start + nbytes >= 0);
if ((size_t)(start + nbytes) > size())
nbytes = size() - start;
//
// Build the substring.
//
return nstring(c_str() + start, nbytes);
}
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