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utils.c
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utils.c
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/*
* vsfat - virtual synthetic FAT filesystem on network block device from local folder
* Copyright (C) 2017 Sean Mollet
*
* 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; either version 2 of the License, or
* (at your option) any later version.
*
* 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.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dirent.h>
#include <sys/stat.h>
#include <ctype.h>
#include "utils.h"
int32_t min(int32_t left, int32_t right)
{
if (left < right)
{
return left;
}
return right;
}
//Compare two arrays up to "length" bytes for equality
int8_t arrays_equal(uint8_t *left, uint8_t *right, int8_t length)
{
for (length--; length >= 0; length--)
{
if (left[length] != right[length])
{
return 0;
}
}
return 1;
}
//Utility function for division that always returns a rounded up value
uint32_t ceil_div(uint32_t x, uint32_t y)
{
if (x == 0)
{
return 0;
}
return (x % y) ? x / y + 1 : x / y; //Ceiling division
}
//Check if a file exists in the given directory
int8_t file_exists(Fat_Directory *current_dir, uint8_t *filename, uint8_t *extension)
{
FileEntry *testFile = current_dir->files;
while (testFile != 0)
{
if (arrays_equal(testFile->Filename, filename, 8) && arrays_equal(testFile->Ext, extension, 3))
{
return 1;
}
testFile = testFile->next;
}
return 0;
}
//Add the ~ and the number (given in iterator) to the given filename
int updateSFN(uint8_t *filename, int *tildePos, int iterator)
{
//First time with a two digit iterator, so we move the tilde
if (iterator == 10)
{
//If the tildePos is lower than this, there's no need to move it
if (*tildePos > 5)
{
(*tildePos)--;
}
}
filename[*tildePos] = '~';
if (iterator > 10)
{
int tensPlace = iterator / 10;
filename[*tildePos + 1] = tensPlace + 48; //Convert int to ascii number
int onesPlace = iterator % 10;
filename[*tildePos + 2] = onesPlace + 48; //Convert into to ascii number
if (iterator > 99)
{
fprintf(stderr, "Too many file collisions for %s\n", filename);
return -1;
}
}
else
{
filename[*tildePos + 1] = iterator + 48;
}
return 0;
}
//Convert filename to FAT32 8.3 format and generate an lfn string in proper format
void format_name_83(Fat_Directory *current_dir, unsigned char *input, uint32_t length, unsigned char *filename,
unsigned char *ext, unsigned char *lfn, unsigned int *lfnlength)
{
unsigned char *adjusted = malloc(length);
//If none of the lfn_required things exist in this filename, we don't build one
int8_t lfn_required = 0;
int32_t period = -1;
*lfnlength = 0;
//First we take out things we know don't belong
for (int a = 0; a < (int32_t)length; a++)
{
adjusted[a] = input[a];
if (input[a] == 0x20)
{ // Space
adjusted[a] = 0x5F; // _
lfn_required = 1;
}
if (input[a] == 0xe5)
{
adjusted[a] = 0x05;
lfn_required = 1;
}
unsigned char test = toupper(input[a]); //This does nothing if there isn't an upper case form
if (test != input[a])
{
adjusted[a] = test;
lfn_required = 1;
}
//Check if this is a period
if (input[a] == 46)
{
period = a;
}
}
//Finally, check if the length exceeds the allowed amount
if (length > 11 //Overall length is too long
|| (length > 8 && period < 0) //Length is too long without an extension
|| (length - period) > 4 //The extension is longer than 3 characters
)
{
lfn_required = 1;
}
//If we didn't get a period, just run to the length
if (period < 0)
{
period = length;
}
for (int a = 0; a < 3; a++)
{
//Note: the +1 is needed because period= the actual period, not the extension
if (period + a + 1 < (int32_t)length)
{
ext[a] = adjusted[period + a + 1];
}
else
{
ext[a] = 0x20;
}
}
for (int a = 0; a < 8; a++)
{
if (a < period)
{
filename[a] = adjusted[a];
}
else
{
filename[a] = 0x20;
}
}
if (lfn_required)
{
int iterator = 1; //Ascii 1
int tildePos = 6;
//If we have a file that requires LFN, but is shorter than 8
if (period == 7)
{
tildePos = 6;
}
if (period < 7)
{
tildePos = period;
}
//Test until we find a usable name
do
{
updateSFN(filename, &tildePos, iterator);
iterator++;
} while (file_exists(current_dir, filename, ext));
//We have a usable name, so now we copy the given name into the lfn field, padding with 0x00 to fake UCS-2.
//TODO: Properly support UTF-16/UCS-2
for (uint8_t i = 0; i < length; i++)
{
lfn[(i * 2)] = input[i];
lfn[(i * 2) + 1] = 0x00;
(*lfnlength)++;
}
}
}
//Long filename checksum of SFN
//Thanks to itisravi, https://gist.github.com/itisravi/4440535 for this algorithm
//Long filename checksum of SFN
//Thanks to itisravi, https://gist.github.com/itisravi/4440535 for this algorithm
unsigned char fn_checksum(unsigned char *filename, unsigned char *ext)
{
uint8_t filename_len;
unsigned char sum;
sum = 0;
for (filename_len = 8; filename_len != 0; filename_len--)
{
// NOTE: The operation is an unsigned char rotate right
sum = ((sum & 1) ? 0x80 : 0) + (sum >> 1) + *filename++;
}
for (filename_len = 3; filename_len != 0; filename_len--)
{
// NOTE: The operation is an unsigned char rotate right
sum = ((sum & 1) ? 0x80 : 0) + (sum >> 1) + *ext++;
}
return (sum);
}
//Output the contents of a boot struct
void printBootSect(BootEntry *bootentry)
{
fprintf(stderr, "BS_jmpBoot[3] %02x %02x %02x\n",
bootentry->BS_jmpBoot[0],
bootentry->BS_jmpBoot[1], bootentry->BS_jmpBoot[2]);
fprintf(stderr,
"BS_OEMName[8] %02x %02x %02x %02x %02x %02x %02x %02x %.8s\n",
bootentry->BS_OEMName[0], bootentry->BS_OEMName[1],
bootentry->BS_OEMName[2], bootentry->BS_OEMName[3],
bootentry->BS_OEMName[4], bootentry->BS_OEMName[5],
bootentry->BS_OEMName[6], bootentry->BS_OEMName[7],
bootentry->BS_OEMName);
fprintf(stderr, "BPB_BytsPerSec=%u\n", bootentry->BPB_BytsPerSec);
fprintf(stderr, "BPB_SecPerClus=%u\n", bootentry->BPB_SecPerClus);
fprintf(stderr, "BPB_RsvdSecCnt=%u\n", bootentry->BPB_RsvdSecCnt);
fprintf(stderr, "BPB_NumFATs=%u\n", bootentry->BPB_NumFATs);
fprintf(stderr, "BPB_RootEntCnt=%u\n", bootentry->BPB_RootEntCnt);
fprintf(stderr, "BPB_TotSec16=%u\n", bootentry->BPB_TotSec16);
fprintf(stderr, "BPB_Media=%u\n", bootentry->BPB_Media);
fprintf(stderr, "BPB_FATSz16=%u\n", bootentry->BPB_FATSz16);
fprintf(stderr, "BPB_SecPerTrk=%u\n", bootentry->BPB_SecPerTrk);
fprintf(stderr, "BPB_NumHeads=%u\n", bootentry->BPB_NumHeads);
fprintf(stderr, "BPB_HiddSec=%u\n", bootentry->BPB_HiddSec);
fprintf(stderr, "BPB_TotSec32=%u\n", bootentry->BPB_TotSec32);
fprintf(stderr, "BPB_FATSz32=%u\n", bootentry->BPB_FATSz32);
fprintf(stderr, "BPB_ExtFlags=%u\n", bootentry->BPB_ExtFlags);
fprintf(stderr, "BPB_FSVer=%u\n", bootentry->BPB_FSVer);
fprintf(stderr, "BPB_RootClus=%u\n", bootentry->BPB_RootClus);
fprintf(stderr, "BPB_FSInfo=%u\n", bootentry->BPB_FSInfo);
fprintf(stderr, "BPB_BkBootSec=%u\n", bootentry->BPB_BkBootSec);
fprintf(stderr, "BPB_Reserved[12] %02x\n", bootentry->BPB_Reserved);
fprintf(stderr, "BS_DrvNum=%u\n", bootentry->BS_DrvNum);
fprintf(stderr, "BS_Reserved1=%02x\n", bootentry->BS_Reserved1);
fprintf(stderr, "BS_BootSig=%02x\n", bootentry->BS_BootSig);
fprintf(stderr, "BS_VolID=%02x\n", bootentry->BS_VolID);
fprintf(stderr,
"BS_VolLab[11] %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %.11s\n",
bootentry->BS_VolLab[0], bootentry->BS_VolLab[1],
bootentry->BS_VolLab[2], bootentry->BS_VolLab[3],
bootentry->BS_VolLab[4], bootentry->BS_VolLab[5],
bootentry->BS_VolLab[6], bootentry->BS_VolLab[7],
bootentry->BS_VolLab[8], bootentry->BS_VolLab[9],
bootentry->BS_VolLab[10], bootentry->BS_VolLab);
fprintf(stderr,
"BS_FilSysType[8] %02x %02x %02x %02x %02x %02x %02x %02x %.8s\n",
bootentry->BS_FilSysType[0], bootentry->BS_FilSysType[1],
bootentry->BS_FilSysType[2], bootentry->BS_FilSysType[3],
bootentry->BS_FilSysType[4], bootentry->BS_FilSysType[5],
bootentry->BS_FilSysType[6], bootentry->BS_FilSysType[7],
bootentry->BS_FilSysType);
fprintf(stderr, "\n");
}