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/*

    File: file_mkv.c

    Copyright (C) 1998-2007,2011 Christophe GRENIER <grenier@cgsecurity.org>
    Copyright (C) 2011 Nick Schrader <nick.schrader@iserv-gis.de>
  
    This software 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 the Free Software Foundation, Inc., 51
    Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 */

#if !defined(SINGLE_FORMAT) || defined(SINGLE_FORMAT_mkv)
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#include <stdio.h>
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#include "types.h"
#include "filegen.h"
#include "common.h"
#ifdef DEBUG_MKV
#include "log.h"
#endif

/*@
  @ requires \valid(file_stat);
  @*/
static void register_header_check_mkv(file_stat_t *file_stat);

const file_hint_t file_hint_mkv= {
  .extension="mkv",
  .description="Matroska",
  .max_filesize=PHOTOREC_MAX_FILE_SIZE,
  .recover=1,
  .enable_by_default=1,
  .register_header_check=&register_header_check_mkv
};

/*@
  @ requires \valid_read(p + (0 .. p_size-1));
  @ requires \valid(uint64);
  @ requires \separated(p + (..), uint64);
  @ ensures -1 == \result || (1 <= \result <= 8);
  @ ensures -1 != \result ==> \initialized(uint64);
  @ ensures -1 != \result ==> *uint64 <= 0xfeffffffffffffff;
  @ assigns *uint64;
  @*/
static int EBML_read_unsigned(const unsigned char *p, const unsigned int p_size, uint64_t *uint64)
{
  unsigned char test_bit = 0x80;
  unsigned int i, bytes = 1;
  const unsigned char c=*p;
  uint64_t val;
  if(p_size==0 || c== 0x00)
    return -1;
  /*@ assert c != 0; */
  /*@
    @ loop invariant test_bit > 0;
    @ loop invariant test_bit == (0x100 >> bytes);
    @ loop assigns test_bit, bytes;
    @ loop unroll 8;
    @*/
  while((c & test_bit) != test_bit)
  {
    /*@ assert c < test_bit; */
    test_bit >>= 1;
    bytes++;
  }
  /*@ assert (c & test_bit) == test_bit; */
  /*@ assert 1 <= bytes <= 8; */
  /*@ assert c >= test_bit; */
  if(p_size < bytes)
    return -1;
  /*@ assert bytes <= p_size; */
  val = c - test_bit; //eliminate first bit, val < 0x80
  /*@ assert val <= 0xfe; */
  /*@
    @ loop assigns i, val;
    @ loop unroll 8;
    @ loop variant bytes-i;
    @*/
  for(i=1; i<bytes; i++)
  {
    val <<= 8;
    val += p[i];
  }
  /*@ assert val <= 0xfeffffffffffffff; */
  *uint64 = val;
  return bytes;
}

/*@
  @ requires EBML_size > 0;
  @ requires \valid_read(buffer + (0 .. buffer_size-1));
  @ requires \valid_read(EBML_Header + (0 .. EBML_size-1));
  @ assigns \result;
  @*/
static int EBML_find(const unsigned char *buffer, const unsigned int buffer_size, const unsigned char *EBML_Header, const unsigned int EBML_size)
{
  unsigned int offset=0;
  /*@
    @ loop assigns offset;
    @*/
  while(offset < buffer_size)
  {
    uint64_t uint64=0;
    int bytes;
    bytes = EBML_read_unsigned(&buffer[offset], buffer_size-offset, &uint64);
#ifdef DEBUG_MKV
    log_info("EBML_find %02x%02x bytes=%d\n", buffer[offset], buffer[offset+1], bytes);
#endif
    if(bytes <= 0)
      return -1;
    if((unsigned int)bytes == EBML_size && memcmp(&buffer[offset], EBML_Header, EBML_size)==0)
    {
      return offset+bytes;
    }
    offset += bytes;
    if(offset >= buffer_size)
      return -1;
    bytes = EBML_read_unsigned(&buffer[offset], buffer_size-offset, &uint64);
    if(bytes <= 0 || uint64 > buffer_size)
      return -1;
    offset += bytes;
    offset += uint64;
  }
  return -1;
}

/*@
  @ requires \valid_read(p + (0 .. p_size-1));
  @ requires \valid(strlength);
  @ requires \separated(p + (..), strlength);
  @ ensures -1 == \result || (1 <= \result <= 8);
  @ ensures -1 != \result ==> \initialized(strlength);
  @ ensures -1 != \result ==> *strlength <= 0xfeffffffffffffff;
  @ ensures -1 != \result ==> \result + *strlength <= p_size;
  @ assigns *strlength, \result;
  @*/
static int EBML_read_string(const unsigned char *p, const unsigned int p_size, uint64_t *strlength)
{
  int bytes;
  *strlength = 0;
  bytes = EBML_read_unsigned(p, p_size, strlength);
#ifdef DEBUG_MKV
  log_info("EBML_read_string bytes=%d strlength=%llu\n", bytes, (long long unsigned)*strlength);
#endif
  if(bytes <= 0)
    return -1;
  /*@ assert 1 <= bytes <= 8; */
  /*@ assert *strlength <= 0xfeffffffffffffff; */
  if(bytes + *strlength > p_size)
    return -1;
  /*@ assert bytes + *strlength <= p_size; */
  return bytes;
}

static const unsigned char EBML_header[4]= { 0x1a,0x45,0xdf,0xa3};

static int header_check_mkv(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new)
{
  if(memcmp(buffer,EBML_header,sizeof(EBML_header))!=0)
    return 0;
  {
    const unsigned char EBML_DocType[2]= { 0x42,0x82};
    const unsigned char EBML_Segment[4]= { 0x18,0x53,0x80,0x67};
    uint64_t segment_size=0;
    uint64_t header_data_size=0;
    const unsigned char *p;
    unsigned int header_data_offset;
    unsigned int segment_offset;
    unsigned int segment_data_offset;
    uint64_t strlength = 0;
    int bytes;
    int len;
    int offset_doctype;

    if((len=EBML_read_unsigned(buffer+sizeof(EBML_header),
	  buffer_size-sizeof(EBML_header), &header_data_size)) < 0)
      return 0;
    header_data_offset = sizeof(EBML_header) + len;
    if(header_data_offset >= buffer_size)
      return 0;
#ifdef DEBUG_MKV
    log_info("header_data_offset %llu\n", (long long unsigned) header_data_offset);
    log_info("header_data_size   %llu\n", (long long unsigned) header_data_size);
#endif
    if(header_data_size >= buffer_size)
      return 0;
    segment_offset = header_data_offset + header_data_size;
#ifdef DEBUG_MKV
    log_info("segment_offset     %llu\n", (long long unsigned) segment_offset);
#endif
    if(segment_offset +sizeof(EBML_Segment) >= buffer_size)
      return 0;
    if(memcmp(&buffer[segment_offset], EBML_Segment, sizeof(EBML_Segment)) != 0)
      return 0;
    p=&buffer[segment_offset+sizeof(EBML_Segment)];
    if((len=EBML_read_unsigned(p, buffer_size-(p-buffer), &segment_size)) < 0)
      return 0;
    segment_data_offset=segment_offset+sizeof(EBML_Segment)+len;
    /* Check if size is unkown */
    if(segment_size == (1ULL << (7 * len)) - 1)
      segment_size=0;
#ifdef DEBUG_MKV
    log_info("segment_data_offset %llu\n", (long long unsigned) segment_data_offset);
    log_info("segment size %llu\n", (long long unsigned) segment_size);
#endif
    /* get EBML_DocType, it will be used to set the file extension */
    offset_doctype=EBML_find(&buffer[header_data_offset], header_data_size, EBML_DocType, sizeof(EBML_DocType));
#ifdef DEBUG_MKV
    log_info("offset_doctype = %u\n", offset_doctype);
#endif
    if(offset_doctype < 0 || header_data_size <= (uint64_t)offset_doctype)
      return 0;
    /*@ assert header_data_size > offset_doctype; */
    p = &buffer[header_data_offset+offset_doctype];
    bytes = EBML_read_string(&buffer[header_data_offset+offset_doctype], header_data_size-offset_doctype, &strlength);
    if (bytes < 0)
      return 0;
    reset_file_recovery(file_recovery_new);
    if( (strlength == 8 && memcmp(p+bytes,"matroska", 8)==0) ||
	(strlength == 9 && memcmp(p+bytes,"matroska", 9)==0))
      file_recovery_new->extension=file_hint_mkv.extension;
    else if((strlength == 4 && memcmp(p+bytes,"webm", 4)==0) ||
	(    strlength == 5 && memcmp(p+bytes,"webm", 5)==0))
      file_recovery_new->extension="webm";
    else
      file_recovery_new->extension="ebml";
    if(segment_size > 0)
    {
      file_recovery_new->calculated_file_size = segment_data_offset + segment_size;
#ifdef DEBUG_MKV
      log_info("file size    %llu\n", (long long unsigned) file_recovery_new->calculated_file_size);
#endif
      file_recovery_new->data_check=&data_check_size;
      file_recovery_new->file_check=&file_check_size;
    }
  }
  return 1;
}

static void register_header_check_mkv(file_stat_t *file_stat)
{
  register_header_check(0, EBML_header,sizeof(EBML_header), &header_check_mkv, file_stat);
}
#endif