[英]fallocate() command equivalent in OS X?
Is there a fallocate()
equivalent in OS X? OS X 中是否有
fallocate()
等价物?
I would like to aggregate all of those equivalent in OS X questions into some doc/table or whatever for everyone.我想将 OS X 问题中的所有等价物汇总到一些文档/表格或任何适合每个人的内容中。 Anybody knows something familiar?
有人知道熟悉的东西吗?
What about using:怎么用:
mkfile -n 1m test.tmp
It's not the same command but serves the same purpose.这不是相同的命令,但具有相同的目的。
Note that fallocate
uses decimal multipliers, whereas mkfile
uses binary multipliers.注意
fallocate
使用十进制乘数,而mkfile
使用二进制乘数。
fallocate()
doesn't exist on OSX. fallocate()
在 OSX 上不存在。 You can "fake" it though;你可以“伪造”它; Mozilla fakes it in their FileUtils class.
Mozilla 在他们的 FileUtils 类中伪造了它。 See this file:
看到这个文件:
http://hg.mozilla.org/mozilla-central/file/3d846420a907/xpcom/glue/FileUtils.cpp#l61 http://hg.mozilla.org/mozilla-central/file/3d846420a907/xpcom/glue/FileUtils.cpp#l61
Here's the code, in case that link goes stale:这是代码,以防链接失效:
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla code.
*
* The Initial Developer of the Original Code is
* Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2010
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Taras Glek <tglek@mozilla.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#if defined(XP_UNIX)
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#elif defined(XP_WIN)
#include <windows.h>
#endif
#include "nscore.h"
#include "private/pprio.h"
#include "mozilla/FileUtils.h"
bool
mozilla::fallocate(PRFileDesc *aFD, PRInt64 aLength)
{
#if defined(HAVE_POSIX_FALLOCATE)
return posix_fallocate(PR_FileDesc2NativeHandle(aFD), 0, aLength) == 0;
#elif defined(XP_WIN)
return PR_Seek64(aFD, aLength, PR_SEEK_SET) == aLength
&& 0 != SetEndOfFile((HANDLE)PR_FileDesc2NativeHandle(aFD));
#elif defined(XP_MACOSX)
int fd = PR_FileDesc2NativeHandle(aFD);
fstore_t store = {F_ALLOCATECONTIG, F_PEOFPOSMODE, 0, aLength};
// Try to get a continous chunk of disk space
int ret = fcntl(fd, F_PREALLOCATE, &store);
if(-1 == ret){
// OK, perhaps we are too fragmented, allocate non-continuous
store.fst_flags = F_ALLOCATEALL;
ret = fcntl(fd, F_PREALLOCATE, &store);
if (-1 == ret)
return false;
}
return 0 == ftruncate(fd, aLength);
#elif defined(XP_UNIX)
// The following is copied from fcntlSizeHint in sqlite
/* If the OS does not have posix_fallocate(), fake it. First use
** ftruncate() to set the file size, then write a single byte to
** the last byte in each block within the extended region. This
** is the same technique used by glibc to implement posix_fallocate()
** on systems that do not have a real fallocate() system call.
*/
struct stat buf;
int fd = PR_FileDesc2NativeHandle(aFD);
if (fstat(fd, &buf))
return false;
if (buf.st_size >= aLength)
return false;
const int nBlk = buf.st_blksize;
if (!nBlk)
return false;
if (ftruncate(fd, aLength))
return false;
int nWrite; // Return value from write()
PRInt64 iWrite = ((buf.st_size + 2 * nBlk - 1) / nBlk) * nBlk - 1; // Next offset to write to
do {
nWrite = 0;
if (PR_Seek64(aFD, iWrite, PR_SEEK_SET) == iWrite)
nWrite = PR_Write(aFD, "", 1);
iWrite += nBlk;
} while (nWrite == 1 && iWrite < aLength);
return nWrite == 1;
#endif
return false;
}
For those wanting to create fake data files for testing, mkfile
is pretty elegant.对于那些想要创建虚假数据文件进行测试的人来说,
mkfile
非常优雅。 An alternative is to use dd
:另一种方法是使用
dd
:
dd if=/dev/zero of=zfile count=1024 bs=1024
As you can see with od -b zfile
, it's full of zeros.正如您在
od -b zfile
看到的od -b zfile
,它充满了零。 If you want random data (which you may want for testing workflows with data compression, for example), then use "/dev/random" in place of "/dev/zero":如果您需要随机数据(例如,您可能需要使用数据压缩测试工作流),请使用“/dev/random”代替“/dev/zero”:
dd if=/dev/random of=randfile count=1024 bs=1024
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