◆ magic()

int datrw::util::magic ( const char *const cmagic )

function to create the magic number

Create a magic number from a character string. ,

If $x_{i}=(\vec{x})_{i}$ represents the input character sequence cmagic and $N=4$ is the value of sizeof(int), then the return value will be

$\textrm{magic}(\vec{x}) =\sum\limits_{i=0}^{N-1} x_{i}\; 2^{8\; (N-1-i)} =x_{3}+256\; (x_{2}+256\; (x_{1}+256\; x_{0})).$

.

Parameters

cmagic 4-byte character sequence representing magic number (most restrictive: pass a const pointer to a const char) is pointer to character array of size sizeof(int)

Returns: The magic number representing the 4-byte character sequence on your system

Definition at line 52 of file bytesex.cc.

Referenced by cpu(), file_magic_test(), and file_magic_write().

     {
       union {
         unsigned int uival;
         int ival;
       } out;
       union {
         char chr[sizeof(int)];
         unsigned char uchr[sizeof(int)];
       } in;
       const int& intsize=sizeof(int);
       for (int i=0; i<intsize; i++)
       { in.chr[i]=cmagic[i]; }
       out.uival=0;
       for (int i=0; i<intsize; i++)
       { out.uival=out.uival*256+in.uchr[i]; }
       return(out.ival);
     } // magic()

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