/src/gdal/port/cpl_vsil_subfile.cpp

Source (jump to first uncovered line)
/******************************************************************************
 *
 * 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>
#if HAVE_FCNTL_H
#include <fcntl.h>
#endif
#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);

    VSIVirtualHandle *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()                                */
/************************************************************************/

VSIVirtualHandle *
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.                                       */
    /* -------------------------------------------------------------------- */
    VSILFILE *fp = VSIFOpenL(osSubFilePath, pszAccess);

    if (fp == nullptr)
        return nullptr;

    /* -------------------------------------------------------------------- */
    /*      Setup the file handle on this file.                             */
    /* -------------------------------------------------------------------- */
    VSISubFileHandle *poHandle = new VSISubFileHandle;

    poHandle->fp = fp;
    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(fp, 0, SEEK_END) != 0)
        {
            poHandle->Close();
            delete poHandle;
            return nullptr;
        }
        vsi_l_offset nFpSize = VSIFTellL(fp);
        // For a directory, the size will be max(vsi_l_offset) / 2
        if (nFpSize == ~(static_cast<vsi_l_offset>(0)) / 2 || nOff > nFpSize)
        {
            poHandle->Close();
            delete poHandle;
            return nullptr;
        }
        if (nOff + nSize > nFpSize)
        {
            nSize = nFpSize - nOff;
            poHandle->nSubregionSize = nSize;
        }
    }

    if (VSIFSeekL(fp, nOff, SEEK_SET) != 0)
    {
        poHandle->Close();
        delete poHandle;
        poHandle = nullptr;
    }

    return poHandle;
}

/************************************************************************/
/*                                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: 2025-06-13 06:18

Line	Count	Source (jump to first uncovered line)
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		#if HAVE_FCNTL_H
21		#include <fcntl.h>
22		#endif
23		#include <limits>
24
25		#include "cpl_conv.h"
26		#include "cpl_multiproc.h"
27		#include "cpl_string.h"
28		#include "cpl_vsi_virtual.h"
29
30		/************************************************************************/
31		/* ==================================================================== */
32		/* VSISubFileHandle */
33		/* ==================================================================== */
34		/************************************************************************/
35
36		class VSISubFileHandle final : public VSIVirtualHandle
37		{
38		CPL_DISALLOW_COPY_ASSIGN(VSISubFileHandle)
39
40		public:
41		VSILFILE *fp = nullptr;
42		vsi_l_offset nSubregionOffset = 0;
43		vsi_l_offset nSubregionSize = 0;
44		bool bAtEOF = false;
45		bool bError = false;
46
47	0	VSISubFileHandle() = default;
48		~VSISubFileHandle() override;
49
50		int Seek(vsi_l_offset nOffset, int nWhence) override;
51		vsi_l_offset Tell() override;
52		size_t Read(void *pBuffer, size_t nSize, size_t nMemb) override;
53		size_t Write(const void *pBuffer, size_t nSize, size_t nMemb) override;
54		void ClearErr() override;
55		int Eof() override;
56		int Error() override;
57		int Close() override;
58		};
59
60		/************************************************************************/
61		/* ==================================================================== */
62		/* VSISubFileFilesystemHandler */
63		/* ==================================================================== */
64		/************************************************************************/
65
66		class VSISubFileFilesystemHandler final : public VSIFilesystemHandler
67		{
68		CPL_DISALLOW_COPY_ASSIGN(VSISubFileFilesystemHandler)
69
70		public:
71	1	VSISubFileFilesystemHandler() = default;
72		~VSISubFileFilesystemHandler() override = default;
73
74		static int DecomposePath(const char *pszPath, CPLString &osFilename,
75		vsi_l_offset &nSubFileOffset,
76		vsi_l_offset &nSubFileSize);
77
78		VSIVirtualHandle Open(const char pszFilename, const char *pszAccess,
79		bool bSetError,
80		CSLConstList /* papszOptions */) override;
81		int Stat(const char pszFilename, VSIStatBufL pStatBuf,
82		int nFlags) override;
83		int Unlink(const char *pszFilename) override;
84		int Mkdir(const char *pszDirname, long nMode) override;
85		int Rmdir(const char *pszDirname) override;
86		char *ReadDirEx(const char pszDirname, int nMaxFiles) override;
87		};
88
89		/************************************************************************/
90		/* ==================================================================== */
91		/* VSISubFileHandle */
92		/* ==================================================================== */
93		/************************************************************************/
94
95		VSISubFileHandle::~VSISubFileHandle()
96	0	{
97	0	VSISubFileHandle::Close();
98	0	}
99
100		/************************************************************************/
101		/* Close() */
102		/************************************************************************/
103
104		int VSISubFileHandle::Close()
105
106	0	{
107	0	if (fp == nullptr)
108	0	return -1;
109	0	int nRet = VSIFCloseL(fp);
110	0	fp = nullptr;
111
112	0	return nRet;
113	0	}
114
115		/************************************************************************/
116		/* Seek() */
117		/************************************************************************/
118
119		int VSISubFileHandle::Seek(vsi_l_offset nOffset, int nWhence)
120
121	0	{
122	0	bAtEOF = false;
123
124	0	if (nWhence == SEEK_SET)
125	0	{
126	0	if (nOffset >
127	0	std::numeric_limits<vsi_l_offset>::max() - nSubregionOffset)
128	0	return -1;
129	0	nOffset += nSubregionOffset;
130	0	}
131	0	else if (nWhence == SEEK_CUR)
132	0	{
133		// handle normally.
134	0	}
135	0	else if (nWhence == SEEK_END)
136	0	{
137	0	if (nSubregionSize != 0)
138	0	{
139	0	nOffset = nSubregionOffset + nSubregionSize;
140	0	nWhence = SEEK_SET;
141	0	}
142	0	}
143	0	else
144	0	{
145	0	errno = EINVAL;
146	0	return -1;
147	0	}
148
149	0	return VSIFSeekL(fp, nOffset, nWhence);
150	0	}
151
152		/************************************************************************/
153		/* Tell() */
154		/************************************************************************/
155
156		vsi_l_offset VSISubFileHandle::Tell()
157
158	0	{
159	0	vsi_l_offset nBasePos = VSIFTellL(fp);
160	0	if (nBasePos >= nSubregionOffset)
161	0	return nBasePos - nSubregionOffset;
162	0	return 0;
163	0	}
164
165		/************************************************************************/
166		/* Read() */
167		/************************************************************************/
168
169		size_t VSISubFileHandle::Read(void *pBuffer, size_t nSize, size_t nCount)
170
171	0	{
172	0	size_t nRet = 0;
173	0	if (nSubregionSize == 0)
174	0	{
175	0	nRet = VSIFReadL(pBuffer, nSize, nCount, fp);
176	0	}
177	0	else
178	0	{
179	0	if (nSize == 0)
180	0	return 0;
181
182	0	const vsi_l_offset nCurOffset = VSIFTellL(fp);
183	0	if (nCurOffset >= nSubregionOffset + nSubregionSize)
184	0	{
185	0	bAtEOF = true;
186	0	return 0;
187	0	}
188
189	0	const size_t nByteToRead = nSize * nCount;
190	0	if (nCurOffset + nByteToRead > nSubregionOffset + nSubregionSize)
191	0	{
192	0	const int nRead = static_cast<int>(
193	0	VSIFReadL(pBuffer, 1,
194	0	static_cast<size_t>(nSubregionOffset +
195	0	nSubregionSize - nCurOffset),
196	0	fp));
197	0	nRet = nRead / nSize;
198	0	}
199	0	else
200	0	{
201	0	nRet = VSIFReadL(pBuffer, nSize, nCount, fp);
202	0	}
203	0	}
204
205	0	if (nRet < nCount)
206	0	{
207	0	if (fp->Eof())
208	0	bAtEOF = true;
209	0	else /* if (fp->Error()) */
210	0	bError = true;
211	0	}
212
213	0	return nRet;
214	0	}
215
216		/************************************************************************/
217		/* Write() */
218		/************************************************************************/
219
220		size_t VSISubFileHandle::Write(const void *pBuffer, size_t nSize, size_t nCount)
221
222	0	{
223	0	bAtEOF = false;
224
225	0	if (nSubregionSize == 0)
226	0	return VSIFWriteL(pBuffer, nSize, nCount, fp);
227
228	0	if (nSize == 0)
229	0	return 0;
230
231	0	const vsi_l_offset nCurOffset = VSIFTellL(fp);
232	0	if (nCurOffset >= nSubregionOffset + nSubregionSize)
233	0	return 0;
234
235	0	const size_t nByteToWrite = nSize * nCount;
236	0	if (nCurOffset + nByteToWrite > nSubregionOffset + nSubregionSize)
237	0	{
238	0	const int nWritten = static_cast<int>(VSIFWriteL(
239	0	pBuffer, 1,
240	0	static_cast<size_t>(nSubregionOffset + nSubregionSize - nCurOffset),
241	0	fp));
242	0	return nWritten / nSize;
243	0	}
244
245	0	return VSIFWriteL(pBuffer, nSize, nCount, fp);
246	0	}
247
248		/************************************************************************/
249		/* ClearErr() */
250		/************************************************************************/
251
252		void VSISubFileHandle::ClearErr()
253
254	0	{
255	0	fp->ClearErr();
256	0	bAtEOF = false;
257	0	bError = false;
258	0	}
259
260		/************************************************************************/
261		/* Error() */
262		/************************************************************************/
263
264		int VSISubFileHandle::Error()
265
266	0	{
267	0	return bError;
268	0	}
269
270		/************************************************************************/
271		/* Eof() */
272		/************************************************************************/
273
274		int VSISubFileHandle::Eof()
275
276	0	{
277	0	return bAtEOF;
278	0	}
279
280		/************************************************************************/
281		/* ==================================================================== */
282		/* VSISubFileFilesystemHandler */
283		/* ==================================================================== */
284		/************************************************************************/
285
286		/************************************************************************/
287		/* DecomposePath() */
288		/* */
289		/* Parse a path like /vsisubfile/1000_2000,data/abc.tif into an */
290		/* offset (1000), a size (2000) and a path (data/abc.tif). */
291		/************************************************************************/
292
293		int VSISubFileFilesystemHandler::DecomposePath(const char *pszPath,
294		CPLString &osFilename,
295		vsi_l_offset &nSubFileOffset,
296		vsi_l_offset &nSubFileSize)
297
298	0	{
299	0	if (!STARTS_WITH(pszPath, "/vsisubfile/"))
300	0	return FALSE;
301
302	0	osFilename = "";
303	0	nSubFileOffset = 0;
304	0	nSubFileSize = 0;
305
306	0	nSubFileOffset =
307	0	CPLScanUIntBig(pszPath + 12, static_cast<int>(strlen(pszPath + 12)));
308	0	for (int i = 12; pszPath[i] != '\0'; i++)
309	0	{
310	0	if (pszPath[i] == '_' && nSubFileSize == 0)
311	0	{
312		// -1 is sometimes passed to mean that we don't know the file size
313		// for example when creating a JPEG2000 datastream in a NITF file
314		// Transform it into 0 for correct behavior of Read(), Write() and
315		// Eof().
316	0	if (pszPath[i + 1] == '-')
317	0	nSubFileSize = 0;
318	0	else
319	0	nSubFileSize = CPLScanUIntBig(
320	0	pszPath + i + 1, static_cast<int>(strlen(pszPath + i + 1)));
321	0	}
322	0	else if (pszPath[i] == ',')
323	0	{
324	0	osFilename = pszPath + i + 1;
325	0	return TRUE;
326	0	}
327	0	else if (pszPath[i] == '/')
328	0	{
329		// Missing comma!
330	0	return FALSE;
331	0	}
332	0	}
333
334	0	return FALSE;
335	0	}
336
337		/************************************************************************/
338		/* Open() */
339		/************************************************************************/
340
341		VSIVirtualHandle *
342		VSISubFileFilesystemHandler::Open(const char *pszFilename,
343		const char pszAccess, bool / bSetError */,
344		CSLConstList /* papszOptions */)
345
346	0	{
347	0	if (!STARTS_WITH_CI(pszFilename, "/vsisubfile/"))
348	0	return nullptr;
349
350	0	CPLString osSubFilePath;
351	0	vsi_l_offset nOff = 0;
352	0	vsi_l_offset nSize = 0;
353
354	0	if (!DecomposePath(pszFilename, osSubFilePath, nOff, nSize))
355	0	{
356	0	errno = ENOENT;
357	0	return nullptr;
358	0	}
359	0	if (nOff > std::numeric_limits<vsi_l_offset>::max() - nSize)
360	0	{
361	0	return nullptr;
362	0	}
363
364		/* -------------------------------------------------------------------- */
365		/* We can't open the containing file with "w" access, so if */
366		/* that is requested use "r+" instead to update in place. */
367		/* -------------------------------------------------------------------- */
368	0	if (pszAccess[0] == 'w')
369	0	pszAccess = "r+";
370
371		/* -------------------------------------------------------------------- */
372		/* Open the underlying file. */
373		/* -------------------------------------------------------------------- */
374	0	VSILFILE *fp = VSIFOpenL(osSubFilePath, pszAccess);
375
376	0	if (fp == nullptr)
377	0	return nullptr;
378
379		/* -------------------------------------------------------------------- */
380		/* Setup the file handle on this file. */
381		/* -------------------------------------------------------------------- */
382	0	VSISubFileHandle *poHandle = new VSISubFileHandle;
383
384	0	poHandle->fp = fp;
385	0	poHandle->nSubregionOffset = nOff;
386	0	poHandle->nSubregionSize = nSize;
387
388		// In read-only mode validate (offset, size) against underlying file size
389	0	if (strchr(pszAccess, 'r') != nullptr && strchr(pszAccess, '+') == nullptr)
390	0	{
391	0	if (VSIFSeekL(fp, 0, SEEK_END) != 0)
392	0	{
393	0	poHandle->Close();
394	0	delete poHandle;
395	0	return nullptr;
396	0	}
397	0	vsi_l_offset nFpSize = VSIFTellL(fp);
398		// For a directory, the size will be max(vsi_l_offset) / 2
399	0	if (nFpSize == ~(static_cast<vsi_l_offset>(0)) / 2 \|\| nOff > nFpSize)
400	0	{
401	0	poHandle->Close();
402	0	delete poHandle;
403	0	return nullptr;
404	0	}
405	0	if (nOff + nSize > nFpSize)
406	0	{
407	0	nSize = nFpSize - nOff;
408	0	poHandle->nSubregionSize = nSize;
409	0	}
410	0	}
411
412	0	if (VSIFSeekL(fp, nOff, SEEK_SET) != 0)
413	0	{
414	0	poHandle->Close();
415	0	delete poHandle;
416	0	poHandle = nullptr;
417	0	}
418
419	0	return poHandle;
420	0	}
421
422		/************************************************************************/
423		/* Stat() */
424		/************************************************************************/
425
426		int VSISubFileFilesystemHandler::Stat(const char *pszFilename,
427		VSIStatBufL *psStatBuf, int nFlags)
428
429	0	{
430	0	if (!STARTS_WITH_CI(pszFilename, "/vsisubfile/"))
431	0	return -1;
432
433	0	CPLString osSubFilePath;
434	0	vsi_l_offset nOff = 0;
435	0	vsi_l_offset nSize = 0;
436
437	0	memset(psStatBuf, 0, sizeof(VSIStatBufL));
438
439	0	if (!DecomposePath(pszFilename, osSubFilePath, nOff, nSize))
440	0	{
441	0	errno = ENOENT;
442	0	return -1;
443	0	}
444
445	0	const int nResult = VSIStatExL(osSubFilePath, psStatBuf, nFlags);
446
447	0	if (nResult == 0)
448	0	{
449	0	if (nSize != 0)
450	0	psStatBuf->st_size = nSize;
451	0	else if (static_cast<vsi_l_offset>(psStatBuf->st_size) >= nOff)
452	0	psStatBuf->st_size -= nOff;
453	0	else
454	0	psStatBuf->st_size = 0;
455	0	}
456
457	0	return nResult;
458	0	}
459
460		/************************************************************************/
461		/* Unlink() */
462		/************************************************************************/
463
464		int VSISubFileFilesystemHandler::Unlink(const char * /* pszFilename */)
465	0	{
466	0	errno = EACCES;
467	0	return -1;
468	0	}
469
470		/************************************************************************/
471		/* Mkdir() */
472		/************************************************************************/
473
474		int VSISubFileFilesystemHandler::Mkdir(const char * /* pszPathname */,
475		long /* nMode */)
476	0	{
477	0	errno = EACCES;
478	0	return -1;
479	0	}
480
481		/************************************************************************/
482		/* Rmdir() */
483		/************************************************************************/
484
485		int VSISubFileFilesystemHandler::Rmdir(const char * /* pszPathname */)
486
487	0	{
488	0	errno = EACCES;
489	0	return -1;
490	0	}
491
492		/************************************************************************/
493		/* ReadDirEx() */
494		/************************************************************************/
495
496		char *VSISubFileFilesystemHandler::ReadDirEx(const char /* pszPath */,
497		int /* nMaxFiles */)
498	0	{
499	0	errno = EACCES;
500	0	return nullptr;
501	0	}
502
503		/************************************************************************/
504		/* VSIInstallSubFileFilesystemHandler() */
505		/************************************************************************/
506
507		/*!
508		\brief Install /vsisubfile/ virtual file handler.
509
510		\verbatim embed:rst
511		See :ref:`/vsisubfile/ documentation <vsisubfile>`
512		\endverbatim
513		*/
514
515		void VSIInstallSubFileHandler()
516	1	{
517	1	VSIFileManager::InstallHandler("/vsisubfile/",
518	1	new VSISubFileFilesystemHandler);
519	1	}