Runtime/r3/fileio.cpp

/* $Id$ */
/** @file
 * IPRT - File I/O.
 */

/*
 * Copyright (C) 2006-2011 Oracle Corporation
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
 * VirtualBox OSE distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 */

/*******************************************************************************
*   Header Files                                                               *
*******************************************************************************/
#include "internal/iprt.h"
#include <iprt/file.h>

#include <iprt/mem.h>
#include <iprt/assert.h>
#include <iprt/alloca.h>
#include <iprt/string.h>
#include <iprt/err.h>
#include "internal/file.h"


/*******************************************************************************
*   Global Variables                                                           *
*******************************************************************************/
/** Set of forced set open flags for files opened read-only. */
static unsigned g_fOpenReadSet = 0;

/** Set of forced cleared open flags for files opened read-only. */
static unsigned g_fOpenReadMask = 0;

/** Set of forced set open flags for files opened write-only. */
static unsigned g_fOpenWriteSet = 0;

/** Set of forced cleared open flags for files opened write-only. */
static unsigned g_fOpenWriteMask = 0;

/** Set of forced set open flags for files opened read-write. */
static unsigned g_fOpenReadWriteSet = 0;

/** Set of forced cleared open flags for files opened read-write. */
static unsigned g_fOpenReadWriteMask = 0;


/**
 * Force the use of open flags for all files opened after the setting is
 * changed. The caller is responsible for not causing races with RTFileOpen().
 *
 * @returns iprt status code.
 * @param   fOpenForAccess  Access mode to which the set/mask settings apply.
 * @param   fSet            Open flags to be forced set.
 * @param   fMask           Open flags to be masked out.
 */
RTR3DECL(int)  RTFileSetForceFlags(unsigned fOpenForAccess, unsigned fSet, unsigned fMask)
{
    /*
     * For now allow only RTFILE_O_WRITE_THROUGH. The other flags either
     * make no sense in this context or are not useful to apply to all files.
     */
    if ((fSet | fMask) & ~RTFILE_O_WRITE_THROUGH)
        return VERR_INVALID_PARAMETER;
    switch (fOpenForAccess)
    {
        case RTFILE_O_READ:
            g_fOpenReadSet = fSet;
            g_fOpenReadMask = fMask;
            break;
        case RTFILE_O_WRITE:
            g_fOpenWriteSet = fSet;
            g_fOpenWriteMask = fMask;
            break;
        case RTFILE_O_READWRITE:
            g_fOpenReadWriteSet = fSet;
            g_fOpenReadWriteMask = fMask;
            break;
        default:
            AssertMsgFailed(("Invalid access mode %d\n", fOpenForAccess));
            return VERR_INVALID_PARAMETER;
    }
    return VINF_SUCCESS;
}


/**
 * Adjusts and validates the flags.
 *
 * The adjustments are made according to the wishes specified using the RTFileSetForceFlags API.
 *
 * @returns IPRT status code.
 * @param   pfOpen      Pointer to the user specified flags on input.
 *                      Updated on successful return.
 * @internal
 */
int rtFileRecalcAndValidateFlags(uint64_t *pfOpen)
{
    /*
     * Recalc.
     */
    uint32_t fOpen = *pfOpen;
    switch (fOpen & RTFILE_O_ACCESS_MASK)
    {
        case RTFILE_O_READ:
            fOpen |= g_fOpenReadSet;
            fOpen &= ~g_fOpenReadMask;
            break;
        case RTFILE_O_WRITE:
            fOpen |= g_fOpenWriteSet;
            fOpen &= ~g_fOpenWriteMask;
            break;
        case RTFILE_O_READWRITE:
            fOpen |= g_fOpenReadWriteSet;
            fOpen &= ~g_fOpenReadWriteMask;
            break;
        default:
            AssertMsgFailed(("Invalid RW value, fOpen=%#llx\n", fOpen));
            return VERR_INVALID_PARAMETER;
    }

    /*
     * Validate                                                                                                                                       .
     */
    AssertMsgReturn(fOpen & RTFILE_O_ACCESS_MASK, ("Missing RTFILE_O_READ/WRITE: fOpen=%#llx\n", fOpen), VERR_INVALID_PARAMETER);
#if defined(RT_OS_WINDOWS) || defined(RT_OS_OS2)
    AssertMsgReturn(!(fOpen & (~(uint64_t)RTFILE_O_VALID_MASK | RTFILE_O_NON_BLOCK)), ("%#llx\n", fOpen), VERR_INVALID_PARAMETER);
#else
    AssertMsgReturn(!(fOpen & ~(uint64_t)RTFILE_O_VALID_MASK), ("%#llx\n", fOpen), VERR_INVALID_PARAMETER);
#endif
    AssertMsgReturn((fOpen & (RTFILE_O_TRUNCATE | RTFILE_O_WRITE)) != RTFILE_O_TRUNCATE, ("%#llx\n", fOpen), VERR_INVALID_PARAMETER);

    switch (fOpen & RTFILE_O_ACTION_MASK)
    {
        case 0: /* temporarily */
            AssertMsgFailed(("Missing RTFILE_O_OPEN/CREATE*! (continuable assertion)\n"));
            fOpen |= RTFILE_O_OPEN;
            break;
        case RTFILE_O_OPEN:
            AssertMsgReturn(!(RTFILE_O_NOT_CONTENT_INDEXED & fOpen), ("%#llx\n", fOpen), VERR_INVALID_PARAMETER);
        case RTFILE_O_OPEN_CREATE:
        case RTFILE_O_CREATE:
        case RTFILE_O_CREATE_REPLACE:
            break;
        default:
            AssertMsgFailed(("Invalid action value: fOpen=%#llx\n", fOpen));
            return VERR_INVALID_PARAMETER;
    }

    switch (fOpen & RTFILE_O_DENY_MASK)
    {
        case 0: /* temporarily */
            AssertMsgFailed(("Missing RTFILE_O_DENY_*! (continuable assertion)\n"));
            fOpen |= RTFILE_O_DENY_NONE;
            break;
        case RTFILE_O_DENY_NONE:
        case RTFILE_O_DENY_READ:
        case RTFILE_O_DENY_WRITE:
        case RTFILE_O_DENY_WRITE | RTFILE_O_DENY_READ:
        case RTFILE_O_DENY_NOT_DELETE:
        case RTFILE_O_DENY_NOT_DELETE | RTFILE_O_DENY_READ:
        case RTFILE_O_DENY_NOT_DELETE | RTFILE_O_DENY_WRITE:
        case RTFILE_O_DENY_NOT_DELETE | RTFILE_O_DENY_WRITE | RTFILE_O_DENY_READ:
            break;
        default:
            AssertMsgFailed(("Invalid deny value: fOpen=%#llx\n", fOpen));
            return VERR_INVALID_PARAMETER;
    }

    /* done */
    *pfOpen = fOpen;
    return VINF_SUCCESS;
}


/**
 * Read bytes from a file at a given offset.
 * This function may modify the file position.
 *
 * @returns iprt status code.
 * @param   File        Handle to the file.
 * @param   off         Where to read.
 * @param   pvBuf       Where to put the bytes we read.
 * @param   cbToRead    How much to read.
 * @param   *pcbRead    How much we actually read.
 *                      If NULL an error will be returned for a partial read.
 */
RTR3DECL(int)  RTFileReadAt(RTFILE File, RTFOFF off, void *pvBuf, size_t cbToRead, size_t *pcbRead)
{
    int rc = RTFileSeek(File, off, RTFILE_SEEK_BEGIN, NULL);
    if (RT_SUCCESS(rc))
        rc = RTFileRead(File, pvBuf, cbToRead, pcbRead);
    return rc;
}


/**
 * Read bytes from a file at a given offset into a S/G buffer.
 * This function may modify the file position.
 *
 * @returns iprt status code.
 * @param   hFile       Handle to the file.
 * @param   off         Where to read.
 * @param   pSgBuf      Pointer to the S/G buffer to read into.
 * @param   cbToRead    How much to read.
 * @param   pcbRead     How much we actually read.
 *                      If NULL an error will be returned for a partial read.
 */
RTR3DECL(int)  RTFileSgReadAt(RTFILE hFile, RTFOFF off, PRTSGBUF pSgBuf, size_t cbToRead, size_t *pcbRead)
{
    int rc = VINF_SUCCESS;
    size_t cbRead = 0;

    while (cbToRead)
    {
        size_t cbThisRead = 0;
        size_t cbBuf = cbToRead;
        void *pvBuf = RTSgBufGetNextSegment(pSgBuf, &cbBuf);

        rc = RTFileReadAt(hFile, off, pvBuf, cbBuf, pcbRead ? &cbThisRead : NULL);
        if (RT_SUCCESS(rc))
            cbRead += cbThisRead;

        if (   RT_FAILURE(rc)
            || (   cbThisRead < cbBuf
                && pcbRead))
            break;

        cbToRead -= cbBuf;
        off += cbBuf;
    }

    if (pcbRead)
        *pcbRead = cbRead;

    return rc;
}


/**
 * Write bytes to a file at a given offset.
 * This function may modify the file position.
 *
 * @returns iprt status code.
 * @param   File        Handle to the file.
 * @param   off         Where to write.
 * @param   pvBuf       What to write.
 * @param   cbToWrite   How much to write.
 * @param   *pcbWritten How much we actually wrote.
 *                      If NULL an error will be returned for a partial write.
 */
RTR3DECL(int)  RTFileWriteAt(RTFILE File, RTFOFF off, const void *pvBuf, size_t cbToWrite, size_t *pcbWritten)
{
    int rc = RTFileSeek(File, off, RTFILE_SEEK_BEGIN, NULL);
    if (RT_SUCCESS(rc))
        rc = RTFileWrite(File, pvBuf, cbToWrite, pcbWritten);
    return rc;
}


/**
 * Write bytes from a S/G buffer to a file at a given offset.
 * This function may modify the file position.
 *
 * @returns iprt status code.
 * @param   hFile       Handle to the file.
 * @param   off         Where to write.
 * @param   pSgBuf      What to write.
 * @param   cbToWrite   How much to write.
 * @param   pcbWritten  How much we actually wrote.
 *                      If NULL an error will be returned for a partial write.
 */
RTR3DECL(int)  RTFileSgWriteAt(RTFILE hFile, RTFOFF off, PRTSGBUF pSgBuf, size_t cbToWrite, size_t *pcbWritten)
{
    int rc = VINF_SUCCESS;
    size_t cbWritten = 0;

    while (cbToWrite)
    {
        size_t cbThisWritten = 0;
        size_t cbBuf = cbToWrite;
        void *pvBuf = RTSgBufGetNextSegment(pSgBuf, &cbBuf);

        rc = RTFileWriteAt(hFile, off, pvBuf, cbBuf, pcbWritten ? &cbThisWritten : NULL);
        if (RT_SUCCESS(rc))
            cbWritten += cbThisWritten;

        if (   RT_FAILURE(rc)
            || (   cbThisWritten < cbBuf
                && pcbWritten))
            break;

        cbToWrite -= cbBuf;
        off += cbBuf;
    }

    if (pcbWritten)
        *pcbWritten = cbWritten;

    return rc;
}


/**
 * Gets the current file position.
 *
 * @returns File offset.
 * @returns ~0UUL on failure.
 * @param   File        File handle.
 */
RTR3DECL(uint64_t)  RTFileTell(RTFILE File)
{
    /*
     * Call the seek api to query the stuff.
     */
    uint64_t off = 0;
    int rc = RTFileSeek(File, 0, RTFILE_SEEK_CURRENT, &off);
    if (RT_SUCCESS(rc))
        return off;
    AssertMsgFailed(("RTFileSeek(%d) -> %d\n", File, rc));
    return ~0ULL;
}


/**
 * Determine the maximum file size.
 *
 * @returns The max size of the file.
 *          -1 on failure, the file position is undefined.
 * @param   File        Handle to the file.
 * @see     RTFileGetMaxSizeEx.
 */
RTR3DECL(RTFOFF) RTFileGetMaxSize(RTFILE File)
{
    RTFOFF cbMax;
    int rc = RTFileGetMaxSizeEx(File, &cbMax);
    return RT_SUCCESS(rc) ? cbMax : -1;
}


RTDECL(int) RTFileCopyByHandles(RTFILE FileSrc, RTFILE FileDst)
{
    return RTFileCopyByHandlesEx(FileSrc, FileDst, NULL, NULL);
}


RTDECL(int) RTFileCopyEx(const char *pszSrc, const char *pszDst, uint32_t fFlags, PFNRTPROGRESS pfnProgress, void *pvUser)
{
    /*
     * Validate input.
     */
    AssertMsgReturn(VALID_PTR(pszSrc), ("pszSrc=%p\n", pszSrc), VERR_INVALID_PARAMETER);
    AssertMsgReturn(*pszSrc, ("pszSrc=%p\n", pszSrc), VERR_INVALID_PARAMETER);
    AssertMsgReturn(VALID_PTR(pszDst), ("pszDst=%p\n", pszDst), VERR_INVALID_PARAMETER);
    AssertMsgReturn(*pszDst, ("pszDst=%p\n", pszDst), VERR_INVALID_PARAMETER);
    AssertMsgReturn(!pfnProgress || VALID_PTR(pfnProgress), ("pfnProgress=%p\n", pfnProgress), VERR_INVALID_PARAMETER);
    AssertMsgReturn(!(fFlags & ~RTFILECOPY_FLAGS_MASK), ("%#x\n", fFlags), VERR_INVALID_PARAMETER);

    /*
     * Open the files.
     */
    RTFILE FileSrc;
    int rc = RTFileOpen(&FileSrc, pszSrc,
                        RTFILE_O_READ | RTFILE_O_OPEN
                        | (fFlags & RTFILECOPY_FLAGS_NO_SRC_DENY_WRITE ? RTFILE_O_DENY_NONE : RTFILE_O_DENY_WRITE));
    if (RT_SUCCESS(rc))
    {
        RTFILE FileDst;
        rc = RTFileOpen(&FileDst, pszDst,
                        RTFILE_O_WRITE | RTFILE_O_CREATE
                        | (fFlags & RTFILECOPY_FLAGS_NO_DST_DENY_WRITE ? RTFILE_O_DENY_NONE : RTFILE_O_DENY_WRITE));
        if (RT_SUCCESS(rc))
        {
            /*
             * Call the ByHandles version and let it do the job.
             */
            rc = RTFileCopyByHandlesEx(FileSrc, FileDst, pfnProgress, pvUser);

            /*
             * Close the files regardless of the result.
             * Don't bother cleaning up or anything like that.
             */
            int rc2 = RTFileClose(FileDst);
            AssertRC(rc2);
            if (RT_FAILURE(rc2) && RT_SUCCESS(rc))
                rc = rc2;
        }

        int rc2 = RTFileClose(FileSrc);
        AssertRC(rc2);
        if (RT_FAILURE(rc2) && RT_SUCCESS(rc))
            rc = rc2;
    }
    return rc;
}


RTDECL(int) RTFileCopyByHandlesEx(RTFILE FileSrc, RTFILE FileDst, PFNRTPROGRESS pfnProgress, void *pvUser)
{
    /*
     * Validate input.
     */
    AssertMsgReturn(RTFileIsValid(FileSrc), ("FileSrc=%RTfile\n", FileSrc), VERR_INVALID_PARAMETER);
    AssertMsgReturn(RTFileIsValid(FileDst), ("FileDst=%RTfile\n", FileDst), VERR_INVALID_PARAMETER);
    AssertMsgReturn(!pfnProgress || VALID_PTR(pfnProgress), ("pfnProgress=%p\n", pfnProgress), VERR_INVALID_PARAMETER);

    /*
     * Save file offset.
     */
    RTFOFF offSrcSaved;
    int rc = RTFileSeek(FileSrc, 0, RTFILE_SEEK_CURRENT, (uint64_t *)&offSrcSaved);
    if (RT_FAILURE(rc))
        return rc;

    /*
     * Get the file size.
     */
    RTFOFF cbSrc;
    rc = RTFileSeek(FileSrc, 0, RTFILE_SEEK_END, (uint64_t *)&cbSrc);
    if (RT_FAILURE(rc))
        return rc;

    /*
     * Allocate buffer.
     */
    size_t      cbBuf;
    uint8_t    *pbBufFree = NULL;
    uint8_t    *pbBuf;
    if (cbSrc < _512K)
    {
        cbBuf = 8*_1K;
        pbBuf = (uint8_t *)alloca(cbBuf);
    }
    else
    {
        cbBuf = _128K;
        pbBuf = pbBufFree = (uint8_t *)RTMemTmpAlloc(cbBuf);
    }
    if (pbBuf)
    {
        /*
         * Seek to the start of each file
         * and set the size of the destination file.
         */
        rc = RTFileSeek(FileSrc, 0, RTFILE_SEEK_BEGIN, NULL);
        if (RT_SUCCESS(rc))
        {
            rc = RTFileSeek(FileDst, 0, RTFILE_SEEK_BEGIN, NULL);
            if (RT_SUCCESS(rc))
                rc = RTFileSetSize(FileDst, cbSrc);
            if (RT_SUCCESS(rc) && pfnProgress)
                rc = pfnProgress(0, pvUser);
            if (RT_SUCCESS(rc))
            {
                /*
                 * Copy loop.
                 */
                unsigned    uPercentage = 0;
                RTFOFF      off = 0;
                RTFOFF      cbPercent = cbSrc / 100;
                RTFOFF      offNextPercent = cbPercent;
                while (off < cbSrc)
                {
                    /* copy block */
                    RTFOFF cbLeft = cbSrc - off;
                    size_t cbBlock = cbLeft >= (RTFOFF)cbBuf ? cbBuf : (size_t)cbLeft;
                    rc = RTFileRead(FileSrc, pbBuf, cbBlock, NULL);
                    if (RT_FAILURE(rc))
                        break;
                    rc = RTFileWrite(FileDst, pbBuf, cbBlock, NULL);
                    if (RT_FAILURE(rc))
                        break;

                    /* advance */
                    off += cbBlock;
                    if (pfnProgress && offNextPercent < off)
                    {
                        while (offNextPercent < off)
                        {
                            uPercentage++;
                            offNextPercent += cbPercent;
                        }
                        rc = pfnProgress(uPercentage, pvUser);
                        if (RT_FAILURE(rc))
                            break;
                    }
                }

#if 0
                /*
                 * Copy OS specific data (EAs and stuff).
                 */
                rtFileCopyOSStuff(FileSrc, FileDst);
#endif

                /* 100% */
                if (pfnProgress && uPercentage < 100 && RT_SUCCESS(rc))
                    rc = pfnProgress(100, pvUser);
            }
        }
        RTMemTmpFree(pbBufFree);
    }
    else
        rc = VERR_NO_MEMORY;

    /*
     * Restore source position.
     */
    RTFileSeek(FileSrc, offSrcSaved, RTFILE_SEEK_BEGIN, NULL);

    return rc;
}


RTDECL(int) RTFileCompare(const char *pszFile1, const char *pszFile2)
{
    return RTFileCompareEx(pszFile1, pszFile2, 0 /*fFlags*/, NULL, NULL);
}


RTDECL(int) RTFileCompareByHandles(RTFILE hFile1, RTFILE hFile2)
{
    return RTFileCompareByHandlesEx(hFile1, hFile2, 0 /*fFlags*/, NULL, NULL);
}


RTDECL(int) RTFileCompareEx(const char *pszFile1, const char *pszFile2, uint32_t fFlags, PFNRTPROGRESS pfnProgress, void *pvUser)
{
    /*
     * Validate input.
     */
    AssertPtrReturn(pszFile1, VERR_INVALID_POINTER);
    AssertReturn(*pszFile1, VERR_INVALID_PARAMETER);
    AssertPtrReturn(pszFile2, VERR_INVALID_POINTER);
    AssertReturn(*pszFile2, VERR_INVALID_PARAMETER);
    AssertMsgReturn(!pfnProgress || VALID_PTR(pfnProgress), ("pfnProgress=%p\n", pfnProgress), VERR_INVALID_PARAMETER);
    AssertMsgReturn(!(fFlags & ~RTFILECOMP_FLAGS_MASK), ("%#x\n", fFlags), VERR_INVALID_PARAMETER);

    /*
     * Open the files.
     */
    RTFILE hFile1;
    int rc = RTFileOpen(&hFile1, pszFile1,
                        RTFILE_O_READ | RTFILE_O_OPEN
                        | (fFlags & RTFILECOMP_FLAGS_NO_DENY_WRITE_FILE1 ? RTFILE_O_DENY_NONE : RTFILE_O_DENY_WRITE));
    if (RT_SUCCESS(rc))
    {
        RTFILE hFile2;
        rc = RTFileOpen(&hFile2, pszFile2,
                        RTFILE_O_READ | RTFILE_O_OPEN
                        | (fFlags & RTFILECOMP_FLAGS_NO_DENY_WRITE_FILE2 ? RTFILE_O_DENY_NONE : RTFILE_O_DENY_WRITE));
        if (RT_SUCCESS(rc))
        {
            /*
             * Call the ByHandles version and let it do the job.
             */
            rc = RTFileCompareByHandlesEx(hFile1, hFile2, fFlags,  pfnProgress, pvUser);

            /* Clean up */
            int rc2 = RTFileClose(hFile2);
            AssertRC(rc2);
            if (RT_FAILURE(rc2) && RT_SUCCESS(rc))
                rc = rc2;
        }

        int rc2 = RTFileClose(hFile1);
        AssertRC(rc2);
        if (RT_FAILURE(rc2) && RT_SUCCESS(rc))
            rc = rc2;
    }
    return rc;
}


RTDECL(int) RTFileCompareByHandlesEx(RTFILE hFile1, RTFILE hFile2, uint32_t fFlags, PFNRTPROGRESS pfnProgress, void *pvUser)
{
    /*
     * Validate input.
     */
    AssertReturn(RTFileIsValid(hFile1), VERR_INVALID_HANDLE);
    AssertReturn(RTFileIsValid(hFile1), VERR_INVALID_HANDLE);
    AssertMsgReturn(!pfnProgress || VALID_PTR(pfnProgress), ("pfnProgress=%p\n", pfnProgress), VERR_INVALID_PARAMETER);
    AssertMsgReturn(!(fFlags & ~RTFILECOMP_FLAGS_MASK), ("%#x\n", fFlags), VERR_INVALID_PARAMETER);

    /*
     * Compare the file sizes first.
     */
    uint64_t cbFile1;
    int rc = RTFileGetSize(hFile1, &cbFile1);
    if (RT_FAILURE(rc))
        return rc;

    uint64_t cbFile2;
    rc = RTFileGetSize(hFile1, &cbFile2);
    if (RT_FAILURE(rc))
        return rc;

    if (cbFile1 != cbFile2)
        return VERR_NOT_EQUAL;


    /*
     * Allocate buffer.
     */
    size_t      cbBuf;
    uint8_t    *pbBuf1Free = NULL;
    uint8_t    *pbBuf1;
    uint8_t    *pbBuf2Free = NULL;
    uint8_t    *pbBuf2;
    if (cbFile1 < _512K)
    {
        cbBuf  = 8*_1K;
        pbBuf1 = (uint8_t *)alloca(cbBuf);
        pbBuf2 = (uint8_t *)alloca(cbBuf);
    }
    else
    {
        cbBuf = _128K;
        pbBuf1 = pbBuf1Free = (uint8_t *)RTMemTmpAlloc(cbBuf);
        pbBuf2 = pbBuf2Free = (uint8_t *)RTMemTmpAlloc(cbBuf);
    }
    if (pbBuf1 && pbBuf2)
    {
        /*
         * Seek to the start of each file
         * and set the size of the destination file.
         */
        rc = RTFileSeek(hFile1, 0, RTFILE_SEEK_BEGIN, NULL);
        if (RT_SUCCESS(rc))
        {
            rc = RTFileSeek(hFile2, 0, RTFILE_SEEK_BEGIN, NULL);
            if (RT_SUCCESS(rc) && pfnProgress)
                rc = pfnProgress(0, pvUser);
            if (RT_SUCCESS(rc))
            {
                /*
                 * Compare loop.
                 */
                unsigned    uPercentage    = 0;
                RTFOFF      off            = 0;
                RTFOFF      cbPercent      = cbFile1 / 100;
                RTFOFF      offNextPercent = cbPercent;
                while (off < (RTFOFF)cbFile1)
                {
                    /* read the blocks */
                    RTFOFF cbLeft = cbFile1 - off;
                    size_t cbBlock = cbLeft >= (RTFOFF)cbBuf ? cbBuf : (size_t)cbLeft;
                    rc = RTFileRead(hFile1, pbBuf1, cbBlock, NULL);
                    if (RT_FAILURE(rc))
                        break;
                    rc = RTFileRead(hFile2, pbBuf2, cbBlock, NULL);
                    if (RT_FAILURE(rc))
                        break;

                    /* compare */
                    if (memcmp(pbBuf1, pbBuf2, cbBlock))
                    {
                        rc = VERR_NOT_EQUAL;
                        break;
                    }

                    /* advance */
                    off += cbBlock;
                    if (pfnProgress && offNextPercent < off)
                    {
                        while (offNextPercent < off)
                        {
                            uPercentage++;
                            offNextPercent += cbPercent;
                        }
                        rc = pfnProgress(uPercentage, pvUser);
                        if (RT_FAILURE(rc))
                            break;
                    }
                }

#if 0
                /*
                 * Compare OS specific data (EAs and stuff).
                 */
                if (RT_SUCCESS(rc))
                    rc = rtFileCompareOSStuff(hFile1, hFile2);
#endif

                /* 100% */
                if (pfnProgress && uPercentage < 100 && RT_SUCCESS(rc))
                    rc = pfnProgress(100, pvUser);
            }
        }
    }
    else
        rc = VERR_NO_MEMORY;
    RTMemTmpFree(pbBuf2Free);
    RTMemTmpFree(pbBuf1Free);

    return rc;
}