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** Copyright 2007, The Android Open Source Project
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** Redistribution and use in source and binary forms, with or without
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** modification, are permitted provided that the following conditions are met:
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** * Redistributions of source code must retain the above copyright
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** notice, this list of conditions and the following disclaimer.
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** * Redistributions in binary form must reproduce the above copyright
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** notice, this list of conditions and the following disclaimer in the
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** documentation and/or other materials provided with the distribution.
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** * Neither the name of Google Inc. nor the names of its contributors may
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** be used to endorse or promote products derived from this software
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** without specific prior written permission.
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** THIS SOFTWARE IS PROVIDED BY Google Inc. ``AS IS'' AND ANY EXPRESS OR
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** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
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** EVENT SHALL Google Inc. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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** PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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** OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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** OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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** ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// A simple and portable piece of code used to generate a blank FAT32 image file.
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// Modified for Dolphin.
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#include "SDCardUtil.h"
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#include <unistd.h> // for unlink()
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/* Believe me, you *don't* want to change these constants !! */
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#define BYTES_PER_SECTOR 512
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#define RESERVED_SECTORS 32
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#define BACKUP_BOOT_SECTOR 6
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#define BYTE_(p,i) (((u8*)(p))[(i)])
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#define POKEB(p,v) BYTE_(p,0) = (u8)(v)
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#define POKES(p,v) ( BYTE_(p,0) = (u8)(v), BYTE_(p,1) = (u8)((v) >> 8) )
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#define POKEW(p,v) ( BYTE_(p,0) = (u8)(v), BYTE_(p,1) = (u8)((v) >> 8), BYTE_(p,2) = (u8)((v) >> 16), BYTE_(p,3) = (u8)((v) >> 24) )
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static u8 s_boot_sector [ BYTES_PER_SECTOR ]; /* Boot sector */
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static u8 s_fsinfo_sector [ BYTES_PER_SECTOR ]; /* FS Info sector */
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static u8 s_fat_head [ BYTES_PER_SECTOR ]; /* First FAT sector */
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/* This is the date and time when creating the disk */
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static unsigned int get_serial_id()
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time_t now = time(nullptr);
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struct tm tm = gmtime( &now )[0];
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lo = (u16)(tm.tm_mday + ((tm.tm_mon+1) << 8) + (tm.tm_sec << 8));
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hi = (u16)(tm.tm_min + (tm.tm_hour << 8) + (tm.tm_year + 1900));
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return lo + (hi << 16);
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static unsigned int get_sectors_per_cluster(u64 disk_size)
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u64 disk_MB = disk_size/(1024*1024);
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static unsigned int get_sectors_per_fat(u64 disk_size, u32 sectors_per_cluster)
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/* Weird computation from MS - see fatgen103.doc for details */
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disk_size -= RESERVED_SECTORS * BYTES_PER_SECTOR; /* Don't count 32 reserved sectors */
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disk_size /= BYTES_PER_SECTOR; /* Disk size in sectors */
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divider = ((256 * sectors_per_cluster) + NUM_FATS) / 2;
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return (u32)( (disk_size + (divider-1)) / divider );
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static void boot_sector_init(u8* boot, u8* info, u64 disk_size, const char* label)
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u32 sectors_per_cluster = get_sectors_per_cluster(disk_size);
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u32 sectors_per_fat = get_sectors_per_fat(disk_size, sectors_per_cluster);
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u32 sectors_per_disk = (u32)(disk_size / BYTES_PER_SECTOR);
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u32 serial_id = get_serial_id();
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if (label == nullptr)
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strcpy( (char*)boot + 3, "MSWIN4.1" );
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POKES( boot + 0x0b, BYTES_PER_SECTOR ); /* Sector size */
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POKEB( boot + 0xd, sectors_per_cluster ); /* Sectors per cluster */
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POKES( boot + 0xe, RESERVED_SECTORS ); /* Reserved sectors before first FAT */
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POKEB( boot + 0x10, NUM_FATS ); /* Number of FATs */
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POKES( boot + 0x11, 0 ); /* Max root directory entries for FAT12/FAT16, 0 for FAT32 */
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POKES( boot + 0x13, 0 ); /* Total sectors, 0 to use 32-bit value at offset 0x20 */
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POKEB( boot + 0x15, 0xF8 ); /* Media descriptor, 0xF8 == hard disk */
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POKES( boot + 0x16, 0 ); /* Sectors per FAT for FAT12/16, 0 for FAT32 */
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POKES( boot + 0x18, 9 ); /* Sectors per track (whatever) */
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POKES( boot + 0x1a, 2 ); /* Number of heads (whatever) */
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POKEW( boot + 0x1c, 0 ); /* Hidden sectors */
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POKEW( boot + 0x20, sectors_per_disk ); /* Total sectors */
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POKEW( boot + 0x24, sectors_per_fat ); /* Sectors per FAT */
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POKES( boot + 0x28, 0 ); /* FAT flags */
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POKES( boot + 0x2a, 0 ); /* Version */
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POKEW( boot + 0x2c, 2 ); /* Cluster number of root directory start */
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POKES( boot + 0x30, 1 ); /* Sector number of FS information sector */
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POKES( boot + 0x32, BACKUP_BOOT_SECTOR ); /* Sector number of a copy of this boot sector */
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POKEB( boot + 0x40, 0x80 ); /* Physical drive number */
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POKEB( boot + 0x42, 0x29 ); /* Extended boot signature ?? */
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POKEW( boot + 0x43, serial_id ); /* Serial ID */
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strncpy( (char*)boot + 0x47, label, 11 ); /* Volume Label */
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memcpy( boot + 0x52, "FAT32 ", 8 ); /* FAT system type, padded with 0x20 */
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POKEB( boot + BYTES_PER_SECTOR-2, 0x55 ); /* Boot sector signature */
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POKEB( boot + BYTES_PER_SECTOR-1, 0xAA );
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free_count = sectors_per_disk - 32 - 2*sectors_per_fat;
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POKEW( info + 0, 0x41615252 );
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POKEW( info + 484, 0x61417272 );
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POKEW( info + 488, free_count ); /* Number of free clusters */
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POKEW( info + 492, 3 ); /* Next free clusters, 0-1 reserved, 2 is used for the root dir */
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POKEW( info + 508, 0xAA550000 );
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static void fat_init(u8* fat)
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POKEW( fat, 0x0ffffff8 ); /* Reserve cluster 1, media id in low byte */
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POKEW( fat + 4, 0x0fffffff ); /* Reserve cluster 2 */
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POKEW( fat + 8, 0x0fffffff ); /* End of cluster chain for root dir */
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static unsigned int write_sector(FILE* file, u8* sector)
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return fwrite(sector, 1, 512, file) != 512;
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static unsigned int write_empty(FILE* file, u64 count)
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static u8 empty[64*1024];
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u64 len = sizeof(empty);
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if ( fwrite(empty, 1, (size_t)len, file) != (size_t)len )
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bool SDCardCreate(u64 disk_size /*in MB*/, const char* filename)
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u32 sectors_per_disk;
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// Convert MB to bytes
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disk_size *= 1024 * 1024;
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if (disk_size < 0x800000 || disk_size > 0x800000000ULL) {
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ERROR_LOG(COMMON, "Trying to create SD Card image of size %lliMB is out of range (8MB-32GB)", disk_size/(1024*1024));
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// Pretty unlikely to overflow.
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sectors_per_disk = (u32)(disk_size / 512);
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sectors_per_fat = get_sectors_per_fat(disk_size, get_sectors_per_cluster(disk_size));
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boot_sector_init(s_boot_sector, s_fsinfo_sector, disk_size, nullptr);
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fat_init(s_fat_head);
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File::IOFile file(filename, "wb");
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FILE* const f = file.GetHandle();
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ERROR_LOG(COMMON, "Could not create file '%s', aborting...\n", filename);
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/* Here's the layout:
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* backup fsinfo sector
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* RESERVED_SECTORS - 4 empty sectors (if backup sectors), or RESERVED_SECTORS - 2 (if no backup)
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if (write_sector(f, s_boot_sector)) goto FailWrite;
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if (write_sector(f, s_fsinfo_sector)) goto FailWrite;
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if (BACKUP_BOOT_SECTOR > 0)
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if (write_empty(f, BACKUP_BOOT_SECTOR - 2)) goto FailWrite;
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if (write_sector(f, s_boot_sector)) goto FailWrite;
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if (write_sector(f, s_fsinfo_sector)) goto FailWrite;
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if (write_empty(f, RESERVED_SECTORS - 2 - BACKUP_BOOT_SECTOR)) goto FailWrite;
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if (write_empty(f, RESERVED_SECTORS - 2)) goto FailWrite;
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if (write_sector(f, s_fat_head)) goto FailWrite;
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if (write_empty(f, sectors_per_fat-1)) goto FailWrite;
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if (write_sector(f, s_fat_head)) goto FailWrite;
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if (write_empty(f, sectors_per_fat-1)) goto FailWrite;
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if (write_empty(f, sectors_per_disk - RESERVED_SECTORS - 2*sectors_per_fat)) goto FailWrite;
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ERROR_LOG(COMMON, "Could not write to '%s', aborting...\n", filename);
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if (unlink(filename) < 0)
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ERROR_LOG(COMMON, "unlink(%s) failed\n%s", filename, GetLastErrorMsg());