SQLite

static int pagesize = 1024;     /* Size of a database page */
static int fd = -1;             /* File descriptor for reading the WAL file */
static int mxFrame = 0;         /* Last frame */
static int perLine = 16;        /* HEX elements to print per line */

typedef long long int i64;      /* Datatype for 64-bit integers */

/* Information for computing the checksum */
typedef struct Cksum Cksum;
struct Cksum {
  int bSwap;           /* True to do byte swapping on 32-bit words */
  unsigned s0, s1;     /* Current checksum value */
};

/*
** extract a 32-bit big-endian integer
*/
static unsigned int getInt32(const unsigned char *a){
  unsigned int x = (a[0]<<24) + (a[1]<<16) + (a[2]<<8) + a[3];
  return x;
}

/*
** Swap bytes on a 32-bit unsigned integer
*/
static unsigned int swab32(unsigned int x){
  return (((x)&0x000000FF)<<24) + (((x)&0x0000FF00)<<8)
         + (((x)&0x00FF0000)>>8)  + (((x)&0xFF000000)>>24);
}

/* Extend the checksum.  Reinitialize the checksum if bInit is true.
*/
static void extendCksum(
  Cksum *pCksum,
  unsigned char *aData,
  unsigned int nByte,
  int bInit
){
  unsigned int *a32;
  if( bInit ){
    int a = 0;
    *((char*)&a) = 1;
    if( a==1 ){
      /* Host is little-endian */
      pCksum->bSwap = getInt32(aData)!=0x377f0682;
    }else{
      /* Host is big-endian */
      pCksum->bSwap = getInt32(aData)!=0x377f0683;
    }
    pCksum->s0 = 0;
    pCksum->s1 = 0;
  }
  a32 = (unsigned int*)aData;
  while( nByte>0 ){
    unsigned int x0 = a32[0];
    unsigned int x1 = a32[1];
    if( pCksum->bSwap ){
      x0 = swab32(x0);
      x1 = swab32(x1);
    }
    pCksum->s0 += x0 + pCksum->s1;
    pCksum->s1 += x1 + pCksum->s0;
    nByte -= 8;
    a32 += 2;
  }
}

/*
** Convert the var-int format into i64.  Return the number of bytes
** in the var-int.  Write the var-int value into *pVal.
*/
static int decodeVarint(const unsigned char *z, i64 *pVal){
  i64 v = 0;

  print_decode_line(aData,16, 4, 1, "Checksum-1");
  print_decode_line(aData,20, 4, 1, "Checksum-2");
  print_byte_range(iStart+24, pagesize, aData+24, 0);
  free(aData);
}

/*






** Summarize a single frame on a single line.


*/
static void print_oneline_frame(int iFrame, Cksum *pCksum){
  int iStart;
  unsigned char *aData;
  unsigned int s0, s1;
  iStart = 32 + (iFrame-1)*(pagesize+24);
  aData = getContent(iStart, 24);
  extendCksum(pCksum, aData, 8, 0);
  extendCksum(pCksum, getContent(iStart+24, pagesize), pagesize, 0);
  s0 = getInt32(aData+16);
  s1 = getInt32(aData+20);
  fprintf(stdout, "Frame %4d: %6d %6d 0x%08x,%08x 0x%08x,%08x %s\n",
          iFrame, 
          getInt32(aData),
          getInt32(aData+4),
          getInt32(aData+8),
          getInt32(aData+12),

          s0,
          s1,
          (s0==pCksum->s0 && s1==pCksum->s1) ? "cksum-ok" : "cksum-fail"
  );
  free(aData);
}

/*
** Decode the WAL header.
*/
static void print_wal_header(Cksum *pCksum){
  unsigned char *aData;
  aData = getContent(0, 32);
  if( pCksum ){
    extendCksum(pCksum, aData, 24, 1);
    printf("Checksum byte order: %s\n", pCksum->bSwap ? "swapped" : "native");
  }
  printf("WAL Header:\n");
  print_decode_line(aData, 0, 4,1,"Magic.  0x377f0682 (le) or 0x377f0683 (be)");
  print_decode_line(aData, 4, 4, 0, "File format");
  print_decode_line(aData, 8, 4, 0, "Database page size");
  print_decode_line(aData, 12,4, 0, "Checkpoint sequence number");
  print_decode_line(aData, 16,4, 1, "Salt-1");
  print_decode_line(aData, 20,4, 1, "Salt-2");
  print_decode_line(aData, 24,4, 1, "Checksum-1");
  print_decode_line(aData, 28,4, 1, "Checksum-2");
  if( pCksum ){
    if( pCksum->s0!=getInt32(aData+24) ){
      printf("**** cksum-1 mismatch: 0x%08x\n", pCksum->s0);
    }
    if( pCksum->s1!=getInt32(aData+28) ){
      printf("**** cksum-2 mismatch: 0x%08x\n", pCksum->s1);
    }
  }
  free(aData);
}

/*
** Create a description for a single cell.
*/
static int describeCell(unsigned char cType, unsigned char *a, char **pzDesc){

    printf("file too small to be a WAL\n");
    return 0;
  }
  mxFrame = (sbuf.st_size - 32)/(pagesize + 24);
  printf("Available pages: 1..%d\n", mxFrame);
  if( argc==2 ){
    int i;
    Cksum x;
    print_wal_header(&x);
    for(i=1; i<=mxFrame; i++){
      print_oneline_frame(i, &x);
    }
  }else{
    int i;
    for(i=2; i<argc; i++){
      int iStart, iEnd;
      char *zLeft;
      if( strcmp(argv[i], "header")==0 ){
        print_wal_header(0);
        continue;
      }
      if( !isdigit(argv[i][0]) ){
        fprintf(stderr, "%s: unknown option: [%s]\n", argv[0], argv[i]);
        continue;
      }
      iStart = strtol(argv[i], &zLeft, 0);