/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 nBytes) override;
    size_t Write(const void *pBuffer, size_t nBytes) 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 nByteToRead)

{
    if (nByteToRead == 0)
        return 0;

    size_t nRet = 0;
    if (nSubregionSize == 0)
    {
        nRet = fp->Read(pBuffer, nByteToRead);
    }
    else
    {
        const vsi_l_offset nCurOffset = fp->Tell();
        if (nCurOffset >= nSubregionOffset + nSubregionSize)
        {
            bAtEOF = true;
            return 0;
        }

        if (nCurOffset + nByteToRead > nSubregionOffset + nSubregionSize)
        {
            nRet = fp->Read(pBuffer,
                            static_cast<size_t>(nSubregionOffset +
                                                nSubregionSize - nCurOffset));
        }
        else
        {
            nRet = fp->Read(pBuffer, nByteToRead);
        }
    }

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

    return nRet;
}

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

size_t VSISubFileHandle::Write(const void *pBuffer, size_t nBytes)

{
    bAtEOF = false;

    if (nBytes == 0)
        return 0;

    if (nSubregionSize == 0)
        return fp->Write(pBuffer, nBytes);

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

    if (nCurOffset + nBytes > nSubregionOffset + nSubregionSize)
    {
        return fp->Write(pBuffer,
                         static_cast<size_t>(nSubregionOffset + nSubregionSize -
                                             nCurOffset));
    }

    return fp->Write(pBuffer, nBytes);
}

/************************************************************************/
/*                              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/", std::make_shared<VSISubFileFilesystemHandler>());
}

Coverage Report

Created: 2026-02-14 06:52

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	700	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 nBytes) override;
50		size_t Write(const void *pBuffer, size_t nBytes) 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	700	{
94	700	VSISubFileHandle::Close();
95	700	}
96
97		/************************************************************************/
98		/* Close() */
99		/************************************************************************/
100
101		int VSISubFileHandle::Close()
102
103	1.36k	{
104	1.36k	if (fp == nullptr)
105	667	return -1;
106	700	int nRet = VSIFCloseL(fp);
107	700	fp = nullptr;
108
109	700	return nRet;
110	1.36k	}
111
112		/************************************************************************/
113		/* Seek() */
114		/************************************************************************/
115
116		int VSISubFileHandle::Seek(vsi_l_offset nOffset, int nWhence)
117
118	5.32k	{
119	5.32k	bAtEOF = false;
120
121	5.32k	if (nWhence == SEEK_SET)
122	3.29k	{
123	3.29k	if (nOffset >
124	3.29k	std::numeric_limits<vsi_l_offset>::max() - nSubregionOffset)
125	0	return -1;
126	3.29k	nOffset += nSubregionOffset;
127	3.29k	}
128	2.03k	else if (nWhence == SEEK_CUR)
129	0	{
130		// handle normally.
131	0	}
132	2.03k	else if (nWhence == SEEK_END)
133	2.03k	{
134	2.03k	if (nSubregionSize != 0)
135	0	{
136	0	nOffset = nSubregionOffset + nSubregionSize;
137	0	nWhence = SEEK_SET;
138	0	}
139	2.03k	}
140	0	else
141	0	{
142	0	errno = EINVAL;
143	0	return -1;
144	0	}
145
146	5.32k	return VSIFSeekL(fp, nOffset, nWhence);
147	5.32k	}
148
149		/************************************************************************/
150		/* Tell() */
151		/************************************************************************/
152
153		vsi_l_offset VSISubFileHandle::Tell()
154
155	2.03k	{
156	2.03k	vsi_l_offset nBasePos = VSIFTellL(fp);
157	2.03k	if (nBasePos >= nSubregionOffset)
158	2.03k	return nBasePos - nSubregionOffset;
159	0	return 0;
160	2.03k	}
161
162		/************************************************************************/
163		/* Read() */
164		/************************************************************************/
165
166		size_t VSISubFileHandle::Read(void *pBuffer, size_t nByteToRead)
167
168	1.28k	{
169	1.28k	if (nByteToRead == 0)
170	0	return 0;
171
172	1.28k	size_t nRet = 0;
173	1.28k	if (nSubregionSize == 0)
174	1.28k	{
175	1.28k	nRet = fp->Read(pBuffer, nByteToRead);
176	1.28k	}
177	0	else
178	0	{
179	0	const vsi_l_offset nCurOffset = fp->Tell();
180	0	if (nCurOffset >= nSubregionOffset + nSubregionSize)
181	0	{
182	0	bAtEOF = true;
183	0	return 0;
184	0	}
185
186	0	if (nCurOffset + nByteToRead > nSubregionOffset + nSubregionSize)
187	0	{
188	0	nRet = fp->Read(pBuffer,
189	0	static_cast<size_t>(nSubregionOffset +
190	0	nSubregionSize - nCurOffset));
191	0	}
192	0	else
193	0	{
194	0	nRet = fp->Read(pBuffer, nByteToRead);
195	0	}
196	0	}
197
198	1.28k	if (nRet < nByteToRead)
199	1.28k	{
200	1.28k	if (fp->Eof())
201	1.28k	bAtEOF = true;
202	0	else /* if (fp->Error()) */
203	0	bError = true;
204	1.28k	}
205
206	1.28k	return nRet;
207	1.28k	}
208
209		/************************************************************************/
210		/* Write() */
211		/************************************************************************/
212
213		size_t VSISubFileHandle::Write(const void *pBuffer, size_t nBytes)
214
215	0	{
216	0	bAtEOF = false;
217
218	0	if (nBytes == 0)
219	0	return 0;
220
221	0	if (nSubregionSize == 0)
222	0	return fp->Write(pBuffer, nBytes);
223
224	0	const vsi_l_offset nCurOffset = VSIFTellL(fp);
225	0	if (nCurOffset >= nSubregionOffset + nSubregionSize)
226	0	return 0;
227
228	0	if (nCurOffset + nBytes > nSubregionOffset + nSubregionSize)
229	0	{
230	0	return fp->Write(pBuffer,
231	0	static_cast<size_t>(nSubregionOffset + nSubregionSize -
232	0	nCurOffset));
233	0	}
234
235	0	return fp->Write(pBuffer, nBytes);
236	0	}
237
238		/************************************************************************/
239		/* ClearErr() */
240		/************************************************************************/
241
242		void VSISubFileHandle::ClearErr()
243
244	0	{
245	0	fp->ClearErr();
246	0	bAtEOF = false;
247	0	bError = false;
248	0	}
249
250		/************************************************************************/
251		/* Error() */
252		/************************************************************************/
253
254		int VSISubFileHandle::Error()
255
256	0	{
257	0	return bError;
258	0	}
259
260		/************************************************************************/
261		/* Eof() */
262		/************************************************************************/
263
264		int VSISubFileHandle::Eof()
265
266	1.03k	{
267	1.03k	return bAtEOF;
268	1.03k	}
269
270		/************************************************************************/
271		/* ==================================================================== */
272		/* VSISubFileFilesystemHandler */
273		/* ==================================================================== */
274		/************************************************************************/
275
276		/************************************************************************/
277		/* DecomposePath() */
278		/* */
279		/* Parse a path like /vsisubfile/1000_2000,data/abc.tif into an */
280		/* offset (1000), a size (2000) and a path (data/abc.tif). */
281		/************************************************************************/
282
283		int VSISubFileFilesystemHandler::DecomposePath(const char *pszPath,
284		CPLString &osFilename,
285		vsi_l_offset &nSubFileOffset,
286		vsi_l_offset &nSubFileSize)
287
288	3.20k	{
289	3.20k	if (!STARTS_WITH(pszPath, "/vsisubfile/"))
290	0	return FALSE;
291
292	3.20k	osFilename = "";
293	3.20k	nSubFileOffset = 0;
294	3.20k	nSubFileSize = 0;
295
296	3.20k	nSubFileOffset =
297	3.20k	CPLScanUIntBig(pszPath + 12, static_cast<int>(strlen(pszPath + 12)));
298	222k	for (int i = 12; pszPath[i] != '\0'; i++)
299	221k	{
300	221k	if (pszPath[i] == '_' && nSubFileSize == 0)
301	4.45k	{
302		// -1 is sometimes passed to mean that we don't know the file size
303		// for example when creating a JPEG2000 datastream in a NITF file
304		// Transform it into 0 for correct behavior of Read(), Write() and
305		// Eof().
306	4.45k	if (pszPath[i + 1] == '-')
307	253	nSubFileSize = 0;
308	4.19k	else
309	4.19k	nSubFileSize = CPLScanUIntBig(
310	4.19k	pszPath + i + 1, static_cast<int>(strlen(pszPath + i + 1)));
311	4.45k	}
312	217k	else if (pszPath[i] == ',')
313	2.78k	{
314	2.78k	osFilename = pszPath + i + 1;
315	2.78k	return TRUE;
316	2.78k	}
317	214k	else if (pszPath[i] == '/')
318	80	{
319		// Missing comma!
320	80	return FALSE;
321	80	}
322	221k	}
323
324	337	return FALSE;
325	3.20k	}
326
327		/************************************************************************/
328		/* Open() */
329		/************************************************************************/
330
331		VSIVirtualHandleUniquePtr
332		VSISubFileFilesystemHandler::Open(const char *pszFilename,
333		const char *pszAccess, bool bSetError,
334		CSLConstList papszOptions)
335
336	1.68k	{
337	1.68k	if (!STARTS_WITH_CI(pszFilename, "/vsisubfile/"))
338	2	return nullptr;
339
340	1.68k	CPLString osSubFilePath;
341	1.68k	vsi_l_offset nOff = 0;
342	1.68k	vsi_l_offset nSize = 0;
343
344	1.68k	if (!DecomposePath(pszFilename, osSubFilePath, nOff, nSize))
345	326	{
346	326	errno = ENOENT;
347	326	return nullptr;
348	326	}
349	1.36k	if (nOff > std::numeric_limits<vsi_l_offset>::max() - nSize)
350	73	{
351	73	return nullptr;
352	73	}
353
354		/* -------------------------------------------------------------------- */
355		/* We can't open the containing file with "w" access, so if */
356		/* that is requested use "r+" instead to update in place. */
357		/* -------------------------------------------------------------------- */
358	1.28k	if (pszAccess[0] == 'w')
359	0	pszAccess = "r+";
360
361		/* -------------------------------------------------------------------- */
362		/* Open the underlying file. */
363		/* -------------------------------------------------------------------- */
364	1.28k	auto fp = VSIFilesystemHandler::OpenStatic(osSubFilePath, pszAccess,
365	1.28k	bSetError, papszOptions);
366
367	1.28k	if (fp == nullptr)
368	588	return nullptr;
369
370		/* -------------------------------------------------------------------- */
371		/* Setup the file handle on this file. */
372		/* -------------------------------------------------------------------- */
373	700	auto poHandle = std::make_unique<VSISubFileHandle>();
374
375	700	poHandle->fp = fp.release();
376	700	poHandle->nSubregionOffset = nOff;
377	700	poHandle->nSubregionSize = nSize;
378
379		// In read-only mode validate (offset, size) against underlying file size
380	700	if (strchr(pszAccess, 'r') != nullptr && strchr(pszAccess, '+') == nullptr)
381	700	{
382	700	if (VSIFSeekL(poHandle->fp, 0, SEEK_END) != 0)
383	0	{
384	0	return nullptr;
385	0	}
386	700	vsi_l_offset nFpSize = VSIFTellL(poHandle->fp);
387		// For a directory, the size will be max(vsi_l_offset) / 2
388	700	if (nFpSize == ~(static_cast<vsi_l_offset>(0)) / 2 \|\| nOff > nFpSize)
389	33	{
390	33	return nullptr;
391	33	}
392	667	if (nOff + nSize > nFpSize)
393	131	{
394	131	nSize = nFpSize - nOff;
395	131	poHandle->nSubregionSize = nSize;
396	131	}
397	667	}
398
399	667	if (VSIFSeekL(poHandle->fp, nOff, SEEK_SET) != 0)
400	0	{
401	0	poHandle.reset();
402	0	}
403
404	667	return VSIVirtualHandleUniquePtr(poHandle.release());
405	700	}
406
407		/************************************************************************/
408		/* Stat() */
409		/************************************************************************/
410
411		int VSISubFileFilesystemHandler::Stat(const char *pszFilename,
412		VSIStatBufL *psStatBuf, int nFlags)
413
414	1.62k	{
415	1.62k	if (!STARTS_WITH_CI(pszFilename, "/vsisubfile/"))
416	109	return -1;
417
418	1.51k	CPLString osSubFilePath;
419	1.51k	vsi_l_offset nOff = 0;
420	1.51k	vsi_l_offset nSize = 0;
421
422	1.51k	memset(psStatBuf, 0, sizeof(VSIStatBufL));
423
424	1.51k	if (!DecomposePath(pszFilename, osSubFilePath, nOff, nSize))
425	91	{
426	91	errno = ENOENT;
427	91	return -1;
428	91	}
429
430	1.42k	const int nResult = VSIStatExL(osSubFilePath, psStatBuf, nFlags);
431
432	1.42k	if (nResult == 0)
433	693	{
434	693	if (nSize != 0)
435	133	psStatBuf->st_size = nSize;
436	560	else if (static_cast<vsi_l_offset>(psStatBuf->st_size) >= nOff)
437	543	psStatBuf->st_size -= nOff;
438	17	else
439	17	psStatBuf->st_size = 0;
440	693	}
441
442	1.42k	return nResult;
443	1.51k	}
444
445		/************************************************************************/
446		/* Unlink() */
447		/************************************************************************/
448
449		int VSISubFileFilesystemHandler::Unlink(const char * /* pszFilename */)
450	0	{
451	0	errno = EACCES;
452	0	return -1;
453	0	}
454
455		/************************************************************************/
456		/* Mkdir() */
457		/************************************************************************/
458
459		int VSISubFileFilesystemHandler::Mkdir(const char * /* pszPathname */,
460		long /* nMode */)
461	0	{
462	0	errno = EACCES;
463	0	return -1;
464	0	}
465
466		/************************************************************************/
467		/* Rmdir() */
468		/************************************************************************/
469
470		int VSISubFileFilesystemHandler::Rmdir(const char * /* pszPathname */)
471
472	0	{
473	0	errno = EACCES;
474	0	return -1;
475	0	}
476
477		/************************************************************************/
478		/* ReadDirEx() */
479		/************************************************************************/
480
481		char *VSISubFileFilesystemHandler::ReadDirEx(const char /* pszPath */,
482		int /* nMaxFiles */)
483	0	{
484	0	errno = EACCES;
485	0	return nullptr;
486	0	}
487
488		/************************************************************************/
489		/* VSIInstallSubFileFilesystemHandler() */
490		/************************************************************************/
491
492		/*!
493		\brief Install /vsisubfile/ virtual file handler.
494
495		\verbatim embed:rst
496		See :ref:`/vsisubfile/ documentation <vsisubfile>`
497		\endverbatim
498		*/
499
500		void VSIInstallSubFileHandler()
501	3	{
502	3	VSIFileManager::InstallHandler(
503	3	"/vsisubfile/", std::make_shared<VSISubFileFilesystemHandler>());
504	3	}