/src/gdal/port/cpl_vsil_subfile.cpp

Source
/******************************************************************************
 *
 * Project:  VSI Virtual File System
 * Purpose:  Implementation of subfile virtual IO functions.
 * Author:   Frank Warmerdam, warmerdam@pobox.com
 *
 ******************************************************************************
 * Copyright (c) 2005, Frank Warmerdam <warmerdam@pobox.com>
 * Copyright (c) 2009-2014, Even Rouault <even dot rouault at spatialys.com>
 *
 * SPDX-License-Identifier: MIT
 ****************************************************************************/

#include "cpl_port.h"
#include "cpl_vsi.h"

#include <cerrno>
#include <cstddef>
#include <cstring>
#include <limits>

#include "cpl_conv.h"
#include "cpl_multiproc.h"
#include "cpl_string.h"
#include "cpl_vsi_virtual.h"

/************************************************************************/
/* ==================================================================== */
/*                           VSISubFileHandle                           */
/* ==================================================================== */
/************************************************************************/

class VSISubFileHandle final : public VSIVirtualHandle
{
    CPL_DISALLOW_COPY_ASSIGN(VSISubFileHandle)

  public:
    VSILFILE *fp = nullptr;
    vsi_l_offset nSubregionOffset = 0;
    vsi_l_offset nSubregionSize = 0;
    bool bAtEOF = false;
    bool bError = false;

    VSISubFileHandle() = default;
    ~VSISubFileHandle() override;

    int Seek(vsi_l_offset nOffset, int nWhence) override;
    vsi_l_offset Tell() override;
    size_t Read(void *pBuffer, size_t nSize, size_t nMemb) override;
    size_t Write(const void *pBuffer, size_t nSize, size_t nMemb) override;
    void ClearErr() override;
    int Eof() override;
    int Error() override;
    int Close() override;
};

/************************************************************************/
/* ==================================================================== */
/*                   VSISubFileFilesystemHandler                        */
/* ==================================================================== */
/************************************************************************/

class VSISubFileFilesystemHandler final : public VSIFilesystemHandler
{
    CPL_DISALLOW_COPY_ASSIGN(VSISubFileFilesystemHandler)

  public:
    VSISubFileFilesystemHandler() = default;
    ~VSISubFileFilesystemHandler() override = default;

    static int DecomposePath(const char *pszPath, CPLString &osFilename,
                             vsi_l_offset &nSubFileOffset,
                             vsi_l_offset &nSubFileSize);

    VSIVirtualHandleUniquePtr Open(const char *pszFilename,
                                   const char *pszAccess, bool bSetError,
                                   CSLConstList /* papszOptions */) override;
    int Stat(const char *pszFilename, VSIStatBufL *pStatBuf,
             int nFlags) override;
    int Unlink(const char *pszFilename) override;
    int Mkdir(const char *pszDirname, long nMode) override;
    int Rmdir(const char *pszDirname) override;
    char **ReadDirEx(const char *pszDirname, int nMaxFiles) override;
};

/************************************************************************/
/* ==================================================================== */
/*                             VSISubFileHandle                         */
/* ==================================================================== */
/************************************************************************/

VSISubFileHandle::~VSISubFileHandle()
{
    VSISubFileHandle::Close();
}

/************************************************************************/
/*                               Close()                                */
/************************************************************************/

int VSISubFileHandle::Close()

{
    if (fp == nullptr)
        return -1;
    int nRet = VSIFCloseL(fp);
    fp = nullptr;

    return nRet;
}

/************************************************************************/
/*                                Seek()                                */
/************************************************************************/

int VSISubFileHandle::Seek(vsi_l_offset nOffset, int nWhence)

{
    bAtEOF = false;

    if (nWhence == SEEK_SET)
    {
        if (nOffset >
            std::numeric_limits<vsi_l_offset>::max() - nSubregionOffset)
            return -1;
        nOffset += nSubregionOffset;
    }
    else if (nWhence == SEEK_CUR)
    {
        // handle normally.
    }
    else if (nWhence == SEEK_END)
    {
        if (nSubregionSize != 0)
        {
            nOffset = nSubregionOffset + nSubregionSize;
            nWhence = SEEK_SET;
        }
    }
    else
    {
        errno = EINVAL;
        return -1;
    }

    return VSIFSeekL(fp, nOffset, nWhence);
}

/************************************************************************/
/*                                Tell()                                */
/************************************************************************/

vsi_l_offset VSISubFileHandle::Tell()

{
    vsi_l_offset nBasePos = VSIFTellL(fp);
    if (nBasePos >= nSubregionOffset)
        return nBasePos - nSubregionOffset;
    return 0;
}

/************************************************************************/
/*                                Read()                                */
/************************************************************************/

size_t VSISubFileHandle::Read(void *pBuffer, size_t nSize, size_t nCount)

{
    size_t nRet = 0;
    if (nSubregionSize == 0)
    {
        nRet = VSIFReadL(pBuffer, nSize, nCount, fp);
    }
    else
    {
        if (nSize == 0)
            return 0;

        const vsi_l_offset nCurOffset = VSIFTellL(fp);
        if (nCurOffset >= nSubregionOffset + nSubregionSize)
        {
            bAtEOF = true;
            return 0;
        }

        const size_t nByteToRead = nSize * nCount;
        if (nCurOffset + nByteToRead > nSubregionOffset + nSubregionSize)
        {
            const int nRead = static_cast<int>(
                VSIFReadL(pBuffer, 1,
                          static_cast<size_t>(nSubregionOffset +
                                              nSubregionSize - nCurOffset),
                          fp));
            nRet = nRead / nSize;
        }
        else
        {
            nRet = VSIFReadL(pBuffer, nSize, nCount, fp);
        }
    }

    if (nRet < nCount)
    {
        if (fp->Eof())
            bAtEOF = true;
        else /* if (fp->Error()) */
            bError = true;
    }

    return nRet;
}

/************************************************************************/
/*                               Write()                                */
/************************************************************************/

size_t VSISubFileHandle::Write(const void *pBuffer, size_t nSize, size_t nCount)

{
    bAtEOF = false;

    if (nSubregionSize == 0)
        return VSIFWriteL(pBuffer, nSize, nCount, fp);

    if (nSize == 0)
        return 0;

    const vsi_l_offset nCurOffset = VSIFTellL(fp);
    if (nCurOffset >= nSubregionOffset + nSubregionSize)
        return 0;

    const size_t nByteToWrite = nSize * nCount;
    if (nCurOffset + nByteToWrite > nSubregionOffset + nSubregionSize)
    {
        const int nWritten = static_cast<int>(VSIFWriteL(
            pBuffer, 1,
            static_cast<size_t>(nSubregionOffset + nSubregionSize - nCurOffset),
            fp));
        return nWritten / nSize;
    }

    return VSIFWriteL(pBuffer, nSize, nCount, fp);
}

/************************************************************************/
/*                             ClearErr()                               */
/************************************************************************/

void VSISubFileHandle::ClearErr()

{
    fp->ClearErr();
    bAtEOF = false;
    bError = false;
}

/************************************************************************/
/*                              Error()                                 */
/************************************************************************/

int VSISubFileHandle::Error()

{
    return bError;
}

/************************************************************************/
/*                                Eof()                                 */
/************************************************************************/

int VSISubFileHandle::Eof()

{
    return bAtEOF;
}

/************************************************************************/
/* ==================================================================== */
/*                       VSISubFileFilesystemHandler                    */
/* ==================================================================== */
/************************************************************************/

/************************************************************************/
/*                           DecomposePath()                            */
/*                                                                      */
/*      Parse a path like /vsisubfile/1000_2000,data/abc.tif into an    */
/*      offset (1000), a size (2000) and a path (data/abc.tif).         */
/************************************************************************/

int VSISubFileFilesystemHandler::DecomposePath(const char *pszPath,
                                               CPLString &osFilename,
                                               vsi_l_offset &nSubFileOffset,
                                               vsi_l_offset &nSubFileSize)

{
    if (!STARTS_WITH(pszPath, "/vsisubfile/"))
        return FALSE;

    osFilename = "";
    nSubFileOffset = 0;
    nSubFileSize = 0;

    nSubFileOffset =
        CPLScanUIntBig(pszPath + 12, static_cast<int>(strlen(pszPath + 12)));
    for (int i = 12; pszPath[i] != '\0'; i++)
    {
        if (pszPath[i] == '_' && nSubFileSize == 0)
        {
            // -1 is sometimes passed to mean that we don't know the file size
            // for example when creating a JPEG2000 datastream in a NITF file
            // Transform it into 0 for correct behavior of Read(), Write() and
            // Eof().
            if (pszPath[i + 1] == '-')
                nSubFileSize = 0;
            else
                nSubFileSize = CPLScanUIntBig(
                    pszPath + i + 1, static_cast<int>(strlen(pszPath + i + 1)));
        }
        else if (pszPath[i] == ',')
        {
            osFilename = pszPath + i + 1;
            return TRUE;
        }
        else if (pszPath[i] == '/')
        {
            // Missing comma!
            return FALSE;
        }
    }

    return FALSE;
}

/************************************************************************/
/*                                Open()                                */
/************************************************************************/

VSIVirtualHandleUniquePtr
VSISubFileFilesystemHandler::Open(const char *pszFilename,
                                  const char *pszAccess, bool bSetError,
                                  CSLConstList papszOptions)

{
    if (!STARTS_WITH_CI(pszFilename, "/vsisubfile/"))
        return nullptr;

    CPLString osSubFilePath;
    vsi_l_offset nOff = 0;
    vsi_l_offset nSize = 0;

    if (!DecomposePath(pszFilename, osSubFilePath, nOff, nSize))
    {
        errno = ENOENT;
        return nullptr;
    }
    if (nOff > std::numeric_limits<vsi_l_offset>::max() - nSize)
    {
        return nullptr;
    }

    /* -------------------------------------------------------------------- */
    /*      We can't open the containing file with "w" access, so if        */
    /*      that is requested use "r+" instead to update in place.          */
    /* -------------------------------------------------------------------- */
    if (pszAccess[0] == 'w')
        pszAccess = "r+";

    /* -------------------------------------------------------------------- */
    /*      Open the underlying file.                                       */
    /* -------------------------------------------------------------------- */
    auto fp = VSIFilesystemHandler::OpenStatic(osSubFilePath, pszAccess,
                                               bSetError, papszOptions);

    if (fp == nullptr)
        return nullptr;

    /* -------------------------------------------------------------------- */
    /*      Setup the file handle on this file.                             */
    /* -------------------------------------------------------------------- */
    auto poHandle = std::make_unique<VSISubFileHandle>();

    poHandle->fp = fp.release();
    poHandle->nSubregionOffset = nOff;
    poHandle->nSubregionSize = nSize;

    // In read-only mode validate (offset, size) against underlying file size
    if (strchr(pszAccess, 'r') != nullptr && strchr(pszAccess, '+') == nullptr)
    {
        if (VSIFSeekL(poHandle->fp, 0, SEEK_END) != 0)
        {
            return nullptr;
        }
        vsi_l_offset nFpSize = VSIFTellL(poHandle->fp);
        // For a directory, the size will be max(vsi_l_offset) / 2
        if (nFpSize == ~(static_cast<vsi_l_offset>(0)) / 2 || nOff > nFpSize)
        {
            return nullptr;
        }
        if (nOff + nSize > nFpSize)
        {
            nSize = nFpSize - nOff;
            poHandle->nSubregionSize = nSize;
        }
    }

    if (VSIFSeekL(poHandle->fp, nOff, SEEK_SET) != 0)
    {
        poHandle.reset();
    }

    return VSIVirtualHandleUniquePtr(poHandle.release());
}

/************************************************************************/
/*                                Stat()                                */
/************************************************************************/

int VSISubFileFilesystemHandler::Stat(const char *pszFilename,
                                      VSIStatBufL *psStatBuf, int nFlags)

{
    if (!STARTS_WITH_CI(pszFilename, "/vsisubfile/"))
        return -1;

    CPLString osSubFilePath;
    vsi_l_offset nOff = 0;
    vsi_l_offset nSize = 0;

    memset(psStatBuf, 0, sizeof(VSIStatBufL));

    if (!DecomposePath(pszFilename, osSubFilePath, nOff, nSize))
    {
        errno = ENOENT;
        return -1;
    }

    const int nResult = VSIStatExL(osSubFilePath, psStatBuf, nFlags);

    if (nResult == 0)
    {
        if (nSize != 0)
            psStatBuf->st_size = nSize;
        else if (static_cast<vsi_l_offset>(psStatBuf->st_size) >= nOff)
            psStatBuf->st_size -= nOff;
        else
            psStatBuf->st_size = 0;
    }

    return nResult;
}

/************************************************************************/
/*                               Unlink()                               */
/************************************************************************/

int VSISubFileFilesystemHandler::Unlink(const char * /* pszFilename */)
{
    errno = EACCES;
    return -1;
}

/************************************************************************/
/*                               Mkdir()                                */
/************************************************************************/

int VSISubFileFilesystemHandler::Mkdir(const char * /* pszPathname */,
                                       long /* nMode */)
{
    errno = EACCES;
    return -1;
}

/************************************************************************/
/*                               Rmdir()                                */
/************************************************************************/

int VSISubFileFilesystemHandler::Rmdir(const char * /* pszPathname */)

{
    errno = EACCES;
    return -1;
}

/************************************************************************/
/*                             ReadDirEx()                              */
/************************************************************************/

char **VSISubFileFilesystemHandler::ReadDirEx(const char * /* pszPath */,
                                              int /* nMaxFiles */)
{
    errno = EACCES;
    return nullptr;
}

/************************************************************************/
/*                 VSIInstallSubFileFilesystemHandler()                 */
/************************************************************************/

/*!
 \brief Install /vsisubfile/ virtual file handler.

 \verbatim embed:rst
 See :ref:`/vsisubfile/ documentation <vsisubfile>`
 \endverbatim
 */

void VSIInstallSubFileHandler()
{
    VSIFileManager::InstallHandler("/vsisubfile/",
                                   new VSISubFileFilesystemHandler);
}

Coverage Report

Created: 2025-11-16 06:25

Line	Count	Source
1		/******************************************************************************
2		*
3		* Project: VSI Virtual File System
4		* Purpose: Implementation of subfile virtual IO functions.
5		* Author: Frank Warmerdam, warmerdam@pobox.com
6		*
7		******************************************************************************
8		* Copyright (c) 2005, Frank Warmerdam <warmerdam@pobox.com>
9		* Copyright (c) 2009-2014, Even Rouault <even dot rouault at spatialys.com>
10		*
11		* SPDX-License-Identifier: MIT
12		****************************************************************************/
13
14		#include "cpl_port.h"
15		#include "cpl_vsi.h"
16
17		#include <cerrno>
18		#include <cstddef>
19		#include <cstring>
20		#include <limits>
21
22		#include "cpl_conv.h"
23		#include "cpl_multiproc.h"
24		#include "cpl_string.h"
25		#include "cpl_vsi_virtual.h"
26
27		/************************************************************************/
28		/* ==================================================================== */
29		/* VSISubFileHandle */
30		/* ==================================================================== */
31		/************************************************************************/
32
33		class VSISubFileHandle final : public VSIVirtualHandle
34		{
35		CPL_DISALLOW_COPY_ASSIGN(VSISubFileHandle)
36
37		public:
38		VSILFILE *fp = nullptr;
39		vsi_l_offset nSubregionOffset = 0;
40		vsi_l_offset nSubregionSize = 0;
41		bool bAtEOF = false;
42		bool bError = false;
43
44	303	VSISubFileHandle() = default;
45		~VSISubFileHandle() override;
46
47		int Seek(vsi_l_offset nOffset, int nWhence) override;
48		vsi_l_offset Tell() override;
49		size_t Read(void *pBuffer, size_t nSize, size_t nMemb) override;
50		size_t Write(const void *pBuffer, size_t nSize, size_t nMemb) override;
51		void ClearErr() override;
52		int Eof() override;
53		int Error() override;
54		int Close() override;
55		};
56
57		/************************************************************************/
58		/* ==================================================================== */
59		/* VSISubFileFilesystemHandler */
60		/* ==================================================================== */
61		/************************************************************************/
62
63		class VSISubFileFilesystemHandler final : public VSIFilesystemHandler
64		{
65		CPL_DISALLOW_COPY_ASSIGN(VSISubFileFilesystemHandler)
66
67		public:
68	3	VSISubFileFilesystemHandler() = default;
69		~VSISubFileFilesystemHandler() override = default;
70
71		static int DecomposePath(const char *pszPath, CPLString &osFilename,
72		vsi_l_offset &nSubFileOffset,
73		vsi_l_offset &nSubFileSize);
74
75		VSIVirtualHandleUniquePtr Open(const char *pszFilename,
76		const char *pszAccess, bool bSetError,
77		CSLConstList /* papszOptions */) override;
78		int Stat(const char pszFilename, VSIStatBufL pStatBuf,
79		int nFlags) override;
80		int Unlink(const char *pszFilename) override;
81		int Mkdir(const char *pszDirname, long nMode) override;
82		int Rmdir(const char *pszDirname) override;
83		char *ReadDirEx(const char pszDirname, int nMaxFiles) override;
84		};
85
86		/************************************************************************/
87		/* ==================================================================== */
88		/* VSISubFileHandle */
89		/* ==================================================================== */
90		/************************************************************************/
91
92		VSISubFileHandle::~VSISubFileHandle()
93	303	{
94	303	VSISubFileHandle::Close();
95	303	}
96
97		/************************************************************************/
98		/* Close() */
99		/************************************************************************/
100
101		int VSISubFileHandle::Close()
102
103	453	{
104	453	if (fp == nullptr)
105	150	return -1;
106	303	int nRet = VSIFCloseL(fp);
107	303	fp = nullptr;
108
109	303	return nRet;
110	453	}
111
112		/************************************************************************/
113		/* Seek() */
114		/************************************************************************/
115
116		int VSISubFileHandle::Seek(vsi_l_offset nOffset, int nWhence)
117
118	565	{
119	565	bAtEOF = false;
120
121	565	if (nWhence == SEEK_SET)
122	401	{
123	401	if (nOffset >
124	401	std::numeric_limits<vsi_l_offset>::max() - nSubregionOffset)
125	0	return -1;
126	401	nOffset += nSubregionOffset;
127	401	}
128	164	else if (nWhence == SEEK_CUR)
129	0	{
130		// handle normally.
131	0	}
132	164	else if (nWhence == SEEK_END)
133	164	{
134	164	if (nSubregionSize != 0)
135	0	{
136	0	nOffset = nSubregionOffset + nSubregionSize;
137	0	nWhence = SEEK_SET;
138	0	}
139	164	}
140	0	else
141	0	{
142	0	errno = EINVAL;
143	0	return -1;
144	0	}
145
146	565	return VSIFSeekL(fp, nOffset, nWhence);
147	565	}
148
149		/************************************************************************/
150		/* Tell() */
151		/************************************************************************/
152
153		vsi_l_offset VSISubFileHandle::Tell()
154
155	164	{
156	164	vsi_l_offset nBasePos = VSIFTellL(fp);
157	164	if (nBasePos >= nSubregionOffset)
158	164	return nBasePos - nSubregionOffset;
159	0	return 0;
160	164	}
161
162		/************************************************************************/
163		/* Read() */
164		/************************************************************************/
165
166		size_t VSISubFileHandle::Read(void *pBuffer, size_t nSize, size_t nCount)
167
168	258	{
169	258	size_t nRet = 0;
170	258	if (nSubregionSize == 0)
171	258	{
172	258	nRet = VSIFReadL(pBuffer, nSize, nCount, fp);
173	258	}
174	0	else
175	0	{
176	0	if (nSize == 0)
177	0	return 0;
178
179	0	const vsi_l_offset nCurOffset = VSIFTellL(fp);
180	0	if (nCurOffset >= nSubregionOffset + nSubregionSize)
181	0	{
182	0	bAtEOF = true;
183	0	return 0;
184	0	}
185
186	0	const size_t nByteToRead = nSize * nCount;
187	0	if (nCurOffset + nByteToRead > nSubregionOffset + nSubregionSize)
188	0	{
189	0	const int nRead = static_cast<int>(
190	0	VSIFReadL(pBuffer, 1,
191	0	static_cast<size_t>(nSubregionOffset +
192	0	nSubregionSize - nCurOffset),
193	0	fp));
194	0	nRet = nRead / nSize;
195	0	}
196	0	else
197	0	{
198	0	nRet = VSIFReadL(pBuffer, nSize, nCount, fp);
199	0	}
200	0	}
201
202	258	if (nRet < nCount)
203	258	{
204	258	if (fp->Eof())
205	258	bAtEOF = true;
206	0	else /* if (fp->Error()) */
207	0	bError = true;
208	258	}
209
210	258	return nRet;
211	258	}
212
213		/************************************************************************/
214		/* Write() */
215		/************************************************************************/
216
217		size_t VSISubFileHandle::Write(const void *pBuffer, size_t nSize, size_t nCount)
218
219	0	{
220	0	bAtEOF = false;
221
222	0	if (nSubregionSize == 0)
223	0	return VSIFWriteL(pBuffer, nSize, nCount, fp);
224
225	0	if (nSize == 0)
226	0	return 0;
227
228	0	const vsi_l_offset nCurOffset = VSIFTellL(fp);
229	0	if (nCurOffset >= nSubregionOffset + nSubregionSize)
230	0	return 0;
231
232	0	const size_t nByteToWrite = nSize * nCount;
233	0	if (nCurOffset + nByteToWrite > nSubregionOffset + nSubregionSize)
234	0	{
235	0	const int nWritten = static_cast<int>(VSIFWriteL(
236	0	pBuffer, 1,
237	0	static_cast<size_t>(nSubregionOffset + nSubregionSize - nCurOffset),
238	0	fp));
239	0	return nWritten / nSize;
240	0	}
241
242	0	return VSIFWriteL(pBuffer, nSize, nCount, fp);
243	0	}
244
245		/************************************************************************/
246		/* ClearErr() */
247		/************************************************************************/
248
249		void VSISubFileHandle::ClearErr()
250
251	0	{
252	0	fp->ClearErr();
253	0	bAtEOF = false;
254	0	bError = false;
255	0	}
256
257		/************************************************************************/
258		/* Error() */
259		/************************************************************************/
260
261		int VSISubFileHandle::Error()
262
263	0	{
264	0	return bError;
265	0	}
266
267		/************************************************************************/
268		/* Eof() */
269		/************************************************************************/
270
271		int VSISubFileHandle::Eof()
272
273	136	{
274	136	return bAtEOF;
275	136	}
276
277		/************************************************************************/
278		/* ==================================================================== */
279		/* VSISubFileFilesystemHandler */
280		/* ==================================================================== */
281		/************************************************************************/
282
283		/************************************************************************/
284		/* DecomposePath() */
285		/* */
286		/* Parse a path like /vsisubfile/1000_2000,data/abc.tif into an */
287		/* offset (1000), a size (2000) and a path (data/abc.tif). */
288		/************************************************************************/
289
290		int VSISubFileFilesystemHandler::DecomposePath(const char *pszPath,
291		CPLString &osFilename,
292		vsi_l_offset &nSubFileOffset,
293		vsi_l_offset &nSubFileSize)
294
295	1.95k	{
296	1.95k	if (!STARTS_WITH(pszPath, "/vsisubfile/"))
297	0	return FALSE;
298
299	1.95k	osFilename = "";
300	1.95k	nSubFileOffset = 0;
301	1.95k	nSubFileSize = 0;
302
303	1.95k	nSubFileOffset =
304	1.95k	CPLScanUIntBig(pszPath + 12, static_cast<int>(strlen(pszPath + 12)));
305	128k	for (int i = 12; pszPath[i] != '\0'; i++)
306	128k	{
307	128k	if (pszPath[i] == '_' && nSubFileSize == 0)
308	2.61k	{
309		// -1 is sometimes passed to mean that we don't know the file size
310		// for example when creating a JPEG2000 datastream in a NITF file
311		// Transform it into 0 for correct behavior of Read(), Write() and
312		// Eof().
313	2.61k	if (pszPath[i + 1] == '-')
314	63	nSubFileSize = 0;
315	2.55k	else
316	2.55k	nSubFileSize = CPLScanUIntBig(
317	2.55k	pszPath + i + 1, static_cast<int>(strlen(pszPath + i + 1)));
318	2.61k	}
319	125k	else if (pszPath[i] == ',')
320	1.62k	{
321	1.62k	osFilename = pszPath + i + 1;
322	1.62k	return TRUE;
323	1.62k	}
324	123k	else if (pszPath[i] == '/')
325	101	{
326		// Missing comma!
327	101	return FALSE;
328	101	}
329	128k	}
330
331	226	return FALSE;
332	1.95k	}
333
334		/************************************************************************/
335		/* Open() */
336		/************************************************************************/
337
338		VSIVirtualHandleUniquePtr
339		VSISubFileFilesystemHandler::Open(const char *pszFilename,
340		const char *pszAccess, bool bSetError,
341		CSLConstList papszOptions)
342
343	1.19k	{
344	1.19k	if (!STARTS_WITH_CI(pszFilename, "/vsisubfile/"))
345	1	return nullptr;
346
347	1.19k	CPLString osSubFilePath;
348	1.19k	vsi_l_offset nOff = 0;
349	1.19k	vsi_l_offset nSize = 0;
350
351	1.19k	if (!DecomposePath(pszFilename, osSubFilePath, nOff, nSize))
352	268	{
353	268	errno = ENOENT;
354	268	return nullptr;
355	268	}
356	928	if (nOff > std::numeric_limits<vsi_l_offset>::max() - nSize)
357	5	{
358	5	return nullptr;
359	5	}
360
361		/* -------------------------------------------------------------------- */
362		/* We can't open the containing file with "w" access, so if */
363		/* that is requested use "r+" instead to update in place. */
364		/* -------------------------------------------------------------------- */
365	923	if (pszAccess[0] == 'w')
366	0	pszAccess = "r+";
367
368		/* -------------------------------------------------------------------- */
369		/* Open the underlying file. */
370		/* -------------------------------------------------------------------- */
371	923	auto fp = VSIFilesystemHandler::OpenStatic(osSubFilePath, pszAccess,
372	923	bSetError, papszOptions);
373
374	923	if (fp == nullptr)
375	620	return nullptr;
376
377		/* -------------------------------------------------------------------- */
378		/* Setup the file handle on this file. */
379		/* -------------------------------------------------------------------- */
380	303	auto poHandle = std::make_unique<VSISubFileHandle>();
381
382	303	poHandle->fp = fp.release();
383	303	poHandle->nSubregionOffset = nOff;
384	303	poHandle->nSubregionSize = nSize;
385
386		// In read-only mode validate (offset, size) against underlying file size
387	303	if (strchr(pszAccess, 'r') != nullptr && strchr(pszAccess, '+') == nullptr)
388	303	{
389	303	if (VSIFSeekL(poHandle->fp, 0, SEEK_END) != 0)
390	99	{
391	99	return nullptr;
392	99	}
393	204	vsi_l_offset nFpSize = VSIFTellL(poHandle->fp);
394		// For a directory, the size will be max(vsi_l_offset) / 2
395	204	if (nFpSize == ~(static_cast<vsi_l_offset>(0)) / 2 \|\| nOff > nFpSize)
396	54	{
397	54	return nullptr;
398	54	}
399	150	if (nOff + nSize > nFpSize)
400	44	{
401	44	nSize = nFpSize - nOff;
402	44	poHandle->nSubregionSize = nSize;
403	44	}
404	150	}
405
406	150	if (VSIFSeekL(poHandle->fp, nOff, SEEK_SET) != 0)
407	0	{
408	0	poHandle.reset();
409	0	}
410
411	150	return VSIVirtualHandleUniquePtr(poHandle.release());
412	303	}
413
414		/************************************************************************/
415		/* Stat() */
416		/************************************************************************/
417
418		int VSISubFileFilesystemHandler::Stat(const char *pszFilename,
419		VSIStatBufL *psStatBuf, int nFlags)
420
421	828	{
422	828	if (!STARTS_WITH_CI(pszFilename, "/vsisubfile/"))
423	73	return -1;
424
425	755	CPLString osSubFilePath;
426	755	vsi_l_offset nOff = 0;
427	755	vsi_l_offset nSize = 0;
428
429	755	memset(psStatBuf, 0, sizeof(VSIStatBufL));
430
431	755	if (!DecomposePath(pszFilename, osSubFilePath, nOff, nSize))
432	59	{
433	59	errno = ENOENT;
434	59	return -1;
435	59	}
436
437	696	const int nResult = VSIStatExL(osSubFilePath, psStatBuf, nFlags);
438
439	696	if (nResult == 0)
440	223	{
441	223	if (nSize != 0)
442	48	psStatBuf->st_size = nSize;
443	175	else if (static_cast<vsi_l_offset>(psStatBuf->st_size) >= nOff)
444	139	psStatBuf->st_size -= nOff;
445	36	else
446	36	psStatBuf->st_size = 0;
447	223	}
448
449	696	return nResult;
450	755	}
451
452		/************************************************************************/
453		/* Unlink() */
454		/************************************************************************/
455
456		int VSISubFileFilesystemHandler::Unlink(const char * /* pszFilename */)
457	0	{
458	0	errno = EACCES;
459	0	return -1;
460	0	}
461
462		/************************************************************************/
463		/* Mkdir() */
464		/************************************************************************/
465
466		int VSISubFileFilesystemHandler::Mkdir(const char * /* pszPathname */,
467		long /* nMode */)
468	0	{
469	0	errno = EACCES;
470	0	return -1;
471	0	}
472
473		/************************************************************************/
474		/* Rmdir() */
475		/************************************************************************/
476
477		int VSISubFileFilesystemHandler::Rmdir(const char * /* pszPathname */)
478
479	0	{
480	0	errno = EACCES;
481	0	return -1;
482	0	}
483
484		/************************************************************************/
485		/* ReadDirEx() */
486		/************************************************************************/
487
488		char *VSISubFileFilesystemHandler::ReadDirEx(const char /* pszPath */,
489		int /* nMaxFiles */)
490	0	{
491	0	errno = EACCES;
492	0	return nullptr;
493	0	}
494
495		/************************************************************************/
496		/* VSIInstallSubFileFilesystemHandler() */
497		/************************************************************************/
498
499		/*!
500		\brief Install /vsisubfile/ virtual file handler.
501
502		\verbatim embed:rst
503		See :ref:`/vsisubfile/ documentation <vsisubfile>`
504		\endverbatim
505		*/
506
507		void VSIInstallSubFileHandler()
508	3	{
509	3	VSIFileManager::InstallHandler("/vsisubfile/",
510	3	new VSISubFileFilesystemHandler);
511	3	}