/*
 *  pass.c: Routines that read and write patterns to block devices.
 *
 *  Copyright Darik Horn <dajhorn-dban@vanadac.com>.
 *
 *  Modifications to original dwipe Copyright Andy Beverley <andy@andybev.com>
 *
 *  This program is free software; you can redistribute it and/or modify it under
 *  the terms of the GNU General Public License as published by the Free Software
 *  Foundation, version 2.
 *
 *  This program is distributed in the hope that it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 *  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 *  details.
 *
 *  You should have received a copy of the GNU General Public License along with
 *  this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

#define _POSIX_C_SOURCE 200809L

#include <stdint.h>
#include "nwipe.h"
#include "context.h"
#include "method.h"
#include "prng.h"
#include "options.h"
#include "pass.h"
#include "logging.h"
#include "gui.h"

int nwipe_random_verify( nwipe_context_t* c )
{
    /**
     * Verifies that a random pass was correctly written to the device.
     *
     */

    /* The result holder. */
    int r;

    /* The IO size. */
    size_t blocksize;

    /* The result buffer for calls to lseek. */
    off64_t offset;

    /* The input buffer. */
    char* b;

    /* The pattern buffer that is used to check the input buffer. */
    char* d;

    /* The number of bytes remaining in the pass. */
    u64 z = c->device_size;

    if( c->prng_seed.s == NULL )
    {
        nwipe_log( NWIPE_LOG_SANITY, "Null seed pointer." );
        return -1;
    }

    if( c->prng_seed.length <= 0 )
    {
        nwipe_log( NWIPE_LOG_SANITY, "The entropy length member is %i.", c->prng_seed.length );
        return -1;
    }

    /* Create the input buffer. */
    b = malloc( c->device_stat.st_blksize );

    /* Check the memory allocation. */
    if( !b )
    {
        nwipe_perror( errno, __FUNCTION__, "malloc" );
        nwipe_log( NWIPE_LOG_FATAL, "Unable to allocate memory for the input buffer." );
        return -1;
    }

    /* Create the pattern buffer */
    d = malloc( c->device_stat.st_blksize );

    /* Check the memory allocation. */
    if( !d )
    {
        nwipe_perror( errno, __FUNCTION__, "malloc" );
        nwipe_log( NWIPE_LOG_FATAL, "Unable to allocate memory for the pattern buffer." );
        free( b );
        return -1;
    }

    /* Reset the file pointer. */
    offset = lseek( c->device_fd, 0, SEEK_SET );

    /* Reset the pass byte counter. */
    c->pass_done = 0;

    if( offset == (off64_t) -1 )
    {
        nwipe_perror( errno, __FUNCTION__, "lseek" );
        nwipe_log( NWIPE_LOG_FATAL, "Unable to reset the '%s' file offset.", c->device_name );
        free( b );
        free( d );
        return -1;
    }

    if( offset != 0 )
    {
        /* This is system insanity. */
        nwipe_log( NWIPE_LOG_SANITY, "lseek() returned a bogus offset on '%s'.", c->device_name );
        free( b );
        free( d );
        return -1;
    }

    /* Tell our parent that we are syncing the device. */
    c->sync_status = 1;

    /* Sync the device. */
    r = fdatasync( c->device_fd );

    /* Tell our parent that we have finished syncing the device. */
    c->sync_status = 0;

    if( r != 0 )
    {
        nwipe_perror( errno, __FUNCTION__, "fdatasync" );
        nwipe_log( NWIPE_LOG_WARNING, "Buffer flush failure on '%s'.", c->device_name );
        c->fsyncdata_errors++;
    }

    /* Reseed the PRNG. */
    c->prng->init( &c->prng_state, &c->prng_seed );

    while( z > 0 )
    {
        if( c->device_stat.st_blksize <= z )
        {
            blocksize = c->device_stat.st_blksize;
        }
        else
        {
            /* This is a seatbelt for buggy drivers and programming errors because */
            /* the device size should always be an even multiple of its blocksize. */
            blocksize = z;
            nwipe_log( NWIPE_LOG_WARNING,
                       "%s: The size of '%s' is not a multiple of its block size %i.",
                       __FUNCTION__,
                       c->device_name,
                       c->device_stat.st_blksize );
        }

        /* Fill the output buffer with the random pattern. */
        c->prng->read( &c->prng_state, d, blocksize );

        /* Read the buffer in from the device. */
        r = read( c->device_fd, b, blocksize );

        /* Check the result. */
        if( r < 0 )
        {
            nwipe_perror( errno, __FUNCTION__, "read" );
            nwipe_log( NWIPE_LOG_ERROR, "Unable to read from '%s'.", c->device_name );
            return -1;
        }

        /* Check for a partial read. */
        if( r != blocksize )
        {
            /* TODO: Handle a partial read. */

            /* The number of bytes that were not read. */
            int s = blocksize - r;

            nwipe_log(
                NWIPE_LOG_WARNING, "%s: Partial read from '%s', %i bytes short.", __FUNCTION__, c->device_name, s );

            /* Increment the error count. */
            c->verify_errors += 1;

            /* Bump the file pointer to the next block. */
            offset = lseek( c->device_fd, s, SEEK_CUR );

            if( offset == (off64_t) -1 )
            {
                nwipe_perror( errno, __FUNCTION__, "lseek" );
                nwipe_log(
                    NWIPE_LOG_ERROR, "Unable to bump the '%s' file offset after a partial read.", c->device_name );
                return -1;
            }

        } /* partial read */

        /* Compare buffer contents. */
        if( memcmp( b, d, blocksize ) != 0 )
        {
            c->verify_errors += 1;
        }

        /* Decrement the bytes remaining in this pass. */
        z -= r;

        /* Increment the total progress counters. */
        c->pass_done += r;
        c->round_done += r;

        pthread_testcancel();

    } /* while bytes remaining */

    /* Release the buffers. */
    free( b );
    free( d );

    /* We're done. */
    return 0;

} /* nwipe_random_verify */

int nwipe_random_pass( NWIPE_METHOD_SIGNATURE )
{
    /**
     * Writes a random pattern to the device.
     *
     */

    /* The result holder. */
    int r;

    /* The IO size. */
    size_t blocksize;

    /* The result buffer for calls to lseek. */
    off64_t offset;

    /* The output buffer. */
    char* b;

    /* The number of bytes remaining in the pass. */
    u64 z = c->device_size;

    /* Number of writes to do before a fdatasync. */
    int syncRate = nwipe_options.sync;

    /* Counter to track when to do a fdatasync. */
    int i = 0;

    /* general index counter */
    int idx;

    if( c->prng_seed.s == NULL )
    {
        nwipe_log( NWIPE_LOG_SANITY, "__FUNCTION__: Null seed pointer." );
        return -1;
    }

    if( c->prng_seed.length <= 0 )
    {
        nwipe_log( NWIPE_LOG_SANITY, "__FUNCTION__: The entropy length member is %i.", c->prng_seed.length );
        return -1;
    }

    /* Create the initialised output buffer. Initialised because we don't want memory leaks
     * to disk in the event of some future undetected bug in a prng or its implementation. */
    b = calloc( c->device_stat.st_blksize, sizeof( char ) );

    /* Check the memory allocation. */
    if( !b )
    {
        nwipe_perror( errno, __FUNCTION__, "malloc" );
        nwipe_log( NWIPE_LOG_FATAL, "Unable to allocate memory for the output buffer." );
        return -1;
    }

    /* Seed the PRNG. */
    c->prng->init( &c->prng_state, &c->prng_seed );

    /* Reset the file pointer. */
    offset = lseek( c->device_fd, 0, SEEK_SET );

    /* Reset the pass byte counter. */
    c->pass_done = 0;

    if( offset == (off64_t) -1 )
    {
        nwipe_perror( errno, __FUNCTION__, "lseek" );
        nwipe_log( NWIPE_LOG_FATAL, "Unable to reset the '%s' file offset.", c->device_name );
        free( b );
        return -1;
    }

    if( offset != 0 )
    {
        /* This is system insanity. */
        nwipe_log( NWIPE_LOG_SANITY, "__FUNCTION__: lseek() returned a bogus offset on '%s'.", c->device_name );
        free( b );
        return -1;
    }

    while( z > 0 )
    {
        if( c->device_stat.st_blksize <= z )
        {
            blocksize = c->device_stat.st_blksize;
        }
        else
        {
            /* This is a seatbelt for buggy drivers and programming errors because */
            /* the device size should always be an even multiple of its blocksize. */
            blocksize = z;
            nwipe_log( NWIPE_LOG_WARNING,
                       "%s: The size of '%s' is not a multiple of its block size %i.",
                       __FUNCTION__,
                       c->device_name,
                       c->device_stat.st_blksize );
        }

        /* Fill the output buffer with the random pattern. */
        c->prng->read( &c->prng_state, b, blocksize );

        /* For the first block only, check the prng actually wrote something to the buffer */
        if( z == c->device_size )
        {
            idx = c->device_stat.st_blksize - 1;
            while( idx > 0 )
            {
                if( b[idx] != 0 )
                {
                    nwipe_log( NWIPE_LOG_NOTICE, "prng stream is active" );
                    break;
                }
                idx--;
            }
            if( idx == 0 )
            {
                nwipe_log( NWIPE_LOG_FATAL, "ERROR, prng wrote nothing to the buffer" );
                if( c->bytes_erased < ( c->device_size - z ) )  // How much of the device has been erased?
                {
                    c->bytes_erased = c->device_size - z;
                }
                return -1;
            }
        }

        /* Write the next block out to the device. */
        r = write( c->device_fd, b, blocksize );

        /* Check the result for a fatal error. */
        if( r < 0 )
        {
            nwipe_perror( errno, __FUNCTION__, "write" );
            nwipe_log( NWIPE_LOG_FATAL, "Unable to read from '%s'.", c->device_name );
            if( c->bytes_erased < ( c->device_size - z ) )  // How much of the device has been erased?
            {
                c->bytes_erased = c->device_size - z;
            }
            return -1;
        }

        /* Check for a partial write. */
        if( r != blocksize )
        {
            /* TODO: Handle a partial write. */

            /* The number of bytes that were not written. */
            int s = blocksize - r;

            /* Increment the error count by the number of bytes that were not written. */
            c->pass_errors += s;

            nwipe_log( NWIPE_LOG_WARNING, "Partial write on '%s', %i bytes short.", c->device_name, s );

            /* Bump the file pointer to the next block. */
            offset = lseek( c->device_fd, s, SEEK_CUR );

            if( offset == (off64_t) -1 )
            {
                nwipe_perror( errno, __FUNCTION__, "lseek" );
                nwipe_log(
                    NWIPE_LOG_ERROR, "Unable to bump the '%s' file offset after a partial write.", c->device_name );
                if( c->bytes_erased < ( c->device_size - z ) )  // How much of the device has been erased?
                {
                    c->bytes_erased = c->device_size - z;
                }
                return -1;
            }

        } /* partial write */

        /* Decrement the bytes remaining in this pass. */
        z -= r;

        /* Increment the total progress counters. */
        c->pass_done += r;
        c->round_done += r;

        /* Perodic Sync */
        if( syncRate > 0 )
        {
            i++;

            if( i >= syncRate )
            {
                /* Tell our parent that we are syncing the device. */
                c->sync_status = 1;

                /* Sync the device. */
                r = fdatasync( c->device_fd );

                /* Tell our parent that we have finished syncing the device. */
                c->sync_status = 0;

                if( r != 0 )
                {
                    nwipe_perror( errno, __FUNCTION__, "fdatasync" );
                    nwipe_log( NWIPE_LOG_WARNING, "Buffer flush failure on '%s'.", c->device_name );
                    nwipe_log( NWIPE_LOG_WARNING, "Wrote %llu bytes on '%s'.", c->pass_done, c->device_name );
                    c->fsyncdata_errors++;
                    free( b );
                    if( c->bytes_erased < ( c->device_size - z ) )  // How much of the device has been erased?
                    {
                        c->bytes_erased = c->device_size - z;
                    }
                    return -1;
                }

                i = 0;
            }
        }

        pthread_testcancel();

        /* If statement required so that it does not reset on subsequent passes */
        if( c->bytes_erased < ( c->device_size - z ) )  // How much of the device has been erased?
        {
            c->bytes_erased = c->device_size - z;
        }

    } /* /remaining bytes */

    /* Release the output buffer. */
    free( b );

    /* Tell our parent that we are syncing the device. */
    c->sync_status = 1;

    /* Sync the device. */
    r = fdatasync( c->device_fd );

    /* Tell our parent that we have finished syncing the device. */
    c->sync_status = 0;

    if( r != 0 )
    {
        nwipe_perror( errno, __FUNCTION__, "fdatasync" );
        nwipe_log( NWIPE_LOG_WARNING, "Buffer flush failure on '%s'.", c->device_name );
        c->fsyncdata_errors++;
        if( c->bytes_erased < ( c->device_size - z - blocksize ) )  // How much of the device has been erased?
        {
            c->bytes_erased = c->device_size - z - blocksize;
        }
        return -1;
    }

    /* We're done. */
    return 0;

} /* nwipe_random_pass */

int nwipe_static_verify( NWIPE_METHOD_SIGNATURE, nwipe_pattern_t* pattern )
{
    /**
     * Verifies that a static pass was correctly written to the device.
     */

    /* The result holder. */
    int r;

    /* The IO size. */
    size_t blocksize;

    /* The result buffer for calls to lseek. */
    off64_t offset;

    /* The input buffer. */
    char* b;

    /* The pattern buffer that is used to check the input buffer. */
    char* d;

    /* A pointer into the pattern buffer. */
    char* q;

    /* The pattern buffer window offset. */
    int w = 0;

    /* The number of bytes remaining in the pass. */
    u64 z = c->device_size;

    if( pattern == NULL )
    {
        /* Caught insanity. */
        nwipe_log( NWIPE_LOG_SANITY, "nwipe_static_verify: Null entropy pointer." );
        return -1;
    }

    if( pattern->length <= 0 )
    {
        /* Caught insanity. */
        nwipe_log( NWIPE_LOG_SANITY, "nwipe_static_verify: The pattern length member is %i.", pattern->length );
        return -1;
    }

    /* Create the input buffer. */
    b = malloc( c->device_stat.st_blksize );

    /* Check the memory allocation. */
    if( !b )
    {
        nwipe_perror( errno, __FUNCTION__, "malloc" );
        nwipe_log( NWIPE_LOG_FATAL, "Unable to allocate memory for the input buffer." );
        return -1;
    }

    /* Create the pattern buffer */
    d = malloc( c->device_stat.st_blksize + pattern->length * 2 );

    /* Check the memory allocation. */
    if( !d )
    {
        nwipe_perror( errno, __FUNCTION__, "malloc" );
        nwipe_log( NWIPE_LOG_FATAL, "Unable to allocate memory for the pattern buffer." );
        free( b );
        return -1;
    }

    for( q = d; q < d + c->device_stat.st_blksize + pattern->length; q += pattern->length )
    {
        /* Fill the pattern buffer with the pattern. */
        memcpy( q, pattern->s, pattern->length );
    }

    /* Tell our parent that we are syncing the device. */
    c->sync_status = 1;

    /* Sync the device. */
    r = fdatasync( c->device_fd );

    /* Tell our parent that we have finished syncing the device. */
    c->sync_status = 0;

    if( r != 0 )
    {
        nwipe_perror( errno, __FUNCTION__, "fdatasync" );
        nwipe_log( NWIPE_LOG_WARNING, "Buffer flush failure on '%s'.", c->device_name );
        c->fsyncdata_errors++;
    }

    /* Reset the file pointer. */
    offset = lseek( c->device_fd, 0, SEEK_SET );

    /* Reset the pass byte counter. */
    c->pass_done = 0;

    if( offset == (off64_t) -1 )
    {
        nwipe_perror( errno, __FUNCTION__, "lseek" );
        nwipe_log( NWIPE_LOG_FATAL, "Unable to reset the '%s' file offset.", c->device_name );
        free( b );
        return -1;
    }

    if( offset != 0 )
    {
        /* This is system insanity. */
        nwipe_log( NWIPE_LOG_SANITY, "nwipe_static_verify: lseek() returned a bogus offset on '%s'.", c->device_name );
        free( b );
        free( d );
        return -1;
    }

    while( z > 0 )
    {
        if( c->device_stat.st_blksize <= z )
        {
            blocksize = c->device_stat.st_blksize;
        }
        else
        {
            /* This is a seatbelt for buggy drivers and programming errors because */
            /* the device size should always be an even multiple of its blocksize. */
            blocksize = z;
            nwipe_log( NWIPE_LOG_WARNING,
                       "%s: The size of '%s' is not a multiple of its block size %i.",
                       __FUNCTION__,
                       c->device_name,
                       c->device_stat.st_blksize );
        }

        /* Fill the output buffer with the random pattern. */
        /* Read the buffer in from the device. */
        r = read( c->device_fd, b, blocksize );

        /* Check the result. */
        if( r < 0 )
        {
            nwipe_perror( errno, __FUNCTION__, "read" );
            nwipe_log( NWIPE_LOG_ERROR, "Unable to read from '%s'.", c->device_name );
            return -1;
        }

        /* Check for a partial read. */
        if( r == blocksize )
        {
            /* Check every byte in the buffer. */
            if( memcmp( b, &d[w], r ) != 0 )
            {
                c->verify_errors += 1;
            }
        }
        else
        {
            /* The number of bytes that were not read. */
            int s = blocksize - r;

            /* TODO: Handle a partial read. */

            /* Increment the error count. */
            c->verify_errors += 1;

            nwipe_log( NWIPE_LOG_WARNING, "Partial read on '%s', %i bytes short.", c->device_name, s );

            /* Bump the file pointer to the next block. */
            offset = lseek( c->device_fd, s, SEEK_CUR );

            if( offset == (off64_t) -1 )
            {
                nwipe_perror( errno, __FUNCTION__, "lseek" );
                nwipe_log(
                    NWIPE_LOG_ERROR, "Unable to bump the '%s' file offset after a partial read.", c->device_name );
                return -1;
            }

        } /* partial read */

        /* Adjust the window. */
        w = ( c->device_stat.st_blksize + w ) % pattern->length;

        /* Intuition check:
         *   If the pattern length evenly divides the block size
         *   then ( w == 0 ) always.
         */

        /* Decrement the bytes remaining in this pass. */
        z -= r;

        /* Increment the total progress counters. */
        c->pass_done += r;
        c->round_done += r;

        pthread_testcancel();

    } /* while bytes remaining */

    /* Release the buffers. */
    free( b );
    free( d );

    /* We're done. */
    return 0;

} /* nwipe_static_verify */

int nwipe_static_pass( NWIPE_METHOD_SIGNATURE, nwipe_pattern_t* pattern )
{
    /**
     * Writes a static pattern to the device.
     */

    /* The result holder. */
    int r;

    /* The IO size. */
    size_t blocksize;

    /* The result buffer for calls to lseek. */
    off64_t offset;

    /* The output buffer. */
    char* b;

    /* A pointer into the output buffer. */
    char* p;

    /* The output buffer window offset. */
    int w = 0;

    /* The number of bytes remaining in the pass. */
    u64 z = c->device_size;

    /* Number of writes to do before a fdatasync. */
    int syncRate = nwipe_options.sync;

    /* Counter to track when to do a fdatasync. */
    int i = 0;

    if( pattern == NULL )
    {
        /* Caught insanity. */
        nwipe_log( NWIPE_LOG_SANITY, "__FUNCTION__: Null pattern pointer." );
        return -1;
    }

    if( pattern->length <= 0 )
    {
        /* Caught insanity. */
        nwipe_log( NWIPE_LOG_SANITY, "__FUNCTION__: The pattern length member is %i.", pattern->length );
        return -1;
    }

    /* Create the output buffer. */
    b = malloc( c->device_stat.st_blksize + pattern->length * 2 );

    /* Check the memory allocation. */
    if( !b )
    {
        nwipe_perror( errno, __FUNCTION__, "malloc" );
        nwipe_log( NWIPE_LOG_FATAL, "Unable to allocate memory for the pattern buffer." );
        return -1;
    }

    for( p = b; p < b + c->device_stat.st_blksize + pattern->length; p += pattern->length )
    {
        /* Fill the output buffer with the pattern. */
        memcpy( p, pattern->s, pattern->length );
    }
    ///
    /* Reset the file pointer. */
    offset = lseek( c->device_fd, 0, SEEK_SET );

    /* Reset the pass byte counter. */
    c->pass_done = 0;

    if( offset == (off64_t) -1 )
    {
        nwipe_perror( errno, __FUNCTION__, "lseek" );
        nwipe_log( NWIPE_LOG_FATAL, "Unable to reset the '%s' file offset.", c->device_name );
        return -1;
    }

    if( offset != 0 )
    {
        /* This is system insanity. */
        nwipe_log( NWIPE_LOG_SANITY, "__FUNCTION__: lseek() returned a bogus offset on '%s'.", c->device_name );
        return -1;
    }

    while( z > 0 )
    {
        if( c->device_stat.st_blksize <= z )
        {
            blocksize = c->device_stat.st_blksize;
        }
        else
        {
            /* This is a seatbelt for buggy drivers and programming errors because */
            /* the device size should always be an even multiple of its blocksize. */
            blocksize = z;
            nwipe_log( NWIPE_LOG_WARNING,
                       "%s: The size of '%s' is not a multiple of its block size %i.",
                       __FUNCTION__,
                       c->device_name,
                       c->device_stat.st_blksize );
        }

        /* Fill the output buffer with the random pattern. */
        /* Write the next block out to the device. */
        r = write( c->device_fd, &b[w], blocksize );

        /* Check the result for a fatal error. */
        if( r < 0 )
        {
            nwipe_perror( errno, __FUNCTION__, "write" );
            nwipe_log( NWIPE_LOG_FATAL, "Unable to write to '%s'.", c->device_name );
            if( c->bytes_erased < ( c->device_size - z ) )  // How much of the device has been erased?
            {
                c->bytes_erased = c->device_size - z;
            }
            return -1;
        }

        /* Check for a partial write. */
        if( r != blocksize )
        {
            /* TODO: Handle a partial write. */

            /* The number of bytes that were not written. */
            int s = blocksize - r;

            /* Increment the error count. */
            c->pass_errors += s;

            nwipe_log( NWIPE_LOG_WARNING, "Partial write on '%s', %i bytes short.", c->device_name, s );

            /* Bump the file pointer to the next block. */
            offset = lseek( c->device_fd, s, SEEK_CUR );

            if( offset == (off64_t) -1 )
            {
                nwipe_perror( errno, __FUNCTION__, "lseek" );
                nwipe_log(
                    NWIPE_LOG_ERROR, "Unable to bump the '%s' file offset after a partial write.", c->device_name );
                if( c->bytes_erased < ( c->device_size - z ) )  // How much of the device has been erased?
                {
                    c->bytes_erased = c->device_size - z;
                }
                return -1;
            }

        } /* partial write */

        /* Adjust the window. */
        w = ( c->device_stat.st_blksize + w ) % pattern->length;

        /* Intuition check:
         *
         *   If the pattern length evenly divides the block size
         *   then ( w == 0 ) always.
         */

        /* Decrement the bytes remaining in this pass. */
        z -= r;

        /* Increment the total progress counterr. */
        c->pass_done += r;
        c->round_done += r;

        /* Perodic Sync */
        if( syncRate > 0 )
        {
            i++;

            if( i >= syncRate )
            {
                /* Tell our parent that we are syncing the device. */
                c->sync_status = 1;

                /* Sync the device. */
                r = fdatasync( c->device_fd );

                /* Tell our parent that we have finished syncing the device. */
                c->sync_status = 0;

                if( r != 0 )
                {
                    nwipe_perror( errno, __FUNCTION__, "fdatasync" );
                    nwipe_log( NWIPE_LOG_WARNING, "Buffer flush failure on '%s'.", c->device_name );
                    nwipe_log( NWIPE_LOG_WARNING, "Wrote %llu bytes on '%s'.", c->pass_done, c->device_name );
                    c->fsyncdata_errors++;
                    free( b );
                    if( c->bytes_erased < ( c->device_size - z ) )  // How much of the device has been erased?
                    {
                        c->bytes_erased = c->device_size - z;
                    }
                    return -1;
                }

                i = 0;
            }
        }

        pthread_testcancel();

        if( c->bytes_erased < ( c->device_size - z ) )  // How much of the device has been erased?
        {
            c->bytes_erased = c->device_size - z;
        }

    } /* /remaining bytes */

    /* Tell our parent that we are syncing the device. */
    c->sync_status = 1;

    /* Sync the device. */
    r = fdatasync( c->device_fd );

    /* Tell our parent that we have finished syncing the device. */
    c->sync_status = 0;

    if( r != 0 )
    {
        nwipe_perror( errno, __FUNCTION__, "fdatasync" );
        nwipe_log( NWIPE_LOG_WARNING, "Buffer flush failure on '%s'.", c->device_name );
        c->fsyncdata_errors++;
        if( c->bytes_erased < ( c->device_size - z - blocksize ) )  // How much of the device has been erased?
        {
            c->bytes_erased = c->device_size - z - blocksize;
        }
        return -1;
    }

    /* Release the output buffer. */
    free( b );

    /* We're done. */
    return 0;

} /* nwipe_static_pass */