Declare Function encode_rs Lib "dllstring.dll" (ByRef RecdEncode As Long, ByVal DataEncode As Long)Private Sub Form_Load()
Dim Data(0 To 10) As Long
Dim Recd(0 To 20) As Long
Dim a As Boolean
Data(0) = 8
Data(1) = 6
Data(2) = 8
Data(3) = 1
Data(4) = 2
Data(5) = 4
Data(6) = 15
Data(7) = 6
Data(8) = 6
a = decode_rs(Data(0), Recd(0))End Sub
Dim Data(0 To 10) As Long
Dim Recd(0 To 20) As Long
Dim a As Boolean
Data(0) = 8
Data(1) = 6
Data(2) = 8
Data(3) = 1
Data(4) = 2
Data(5) = 4
Data(6) = 15
Data(7) = 6
Data(8) = 6
a = decode_rs(Data(0), Recd(0))End Sub
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默认 As VariantDeclare Function encode_rs Lib "dllstring.dll" (ByRef RecdEncode As Long, ByVal DataEncode As Long) As Integer建议给出C函数原型,不然不好回答
//#include "stdafx.h"
#include <shlwapi.h>BOOL APIENTRY DllMain( HANDLE hModule,
DWORD ul_reason_for_call,
LPVOID lpReserved
)
{
return TRUE;
}
/* rs.c */
/* This program is an encoder/decoder for Reed-Solomon codes. Encoding is in
systematic form, decoding via the Berlekamp iterative algorithm.
In the present form , the constants mm, nn, tt, and kk=nn-2tt must be
specified (the double letters are used simply to avoid clashes with
other n,k,t used in other programs into which this was incorporated!)
Also, the irreducible polynomial used to generate GF(2**mm) must also be
entered -- these can be found in Lin and Costello, and also Clark and Cain. The representation of the elements of GF(2**m) is either in index form,
where the number is the power of the primitive element alpha, which is
convenient for multiplication (add the powers modulo 2**m-1) or in
polynomial form, where the bits represent the coefficients of the
polynomial representation of the number, which is the most convenient form
for addition. The two forms are swapped between via lookup tables.
This leads to fairly messy looking expressions, but unfortunately, there
is no easy alternative when working with Galois arithmetic. The code is not written in the most elegant way, but to the best
of my knowledge, (no absolute guarantees!), it works.
However, when including it into a simulation program, you may want to do
some conversion of global variables (used here because I am lazy!) to
local variables where appropriate, and passing parameters (eg array
addresses) to the functions may be a sensible move to reduce the number
of global variables and thus decrease the chance of a bug being introduced. This program does not handle erasures at present, but should not be hard
to adapt to do this, as it is just an adjustment to the Berlekamp-Massey
algorithm. It also does not attempt to decode past the BCH bound -- see
Blahut "Theory and practice of error control codes" for how to do this. Simon Rockliff, University of Adelaide 21/9/89 26/6/91 Slight modifications to remove a compiler dependent bug which hadn't
previously surfaced. A few extra comments added for clarity.
Appears to all work fine, ready for posting to net! Notice
--------
This program may be freely modified and/or given to whoever wants it.
A condition of such distribution is that the author's contribution be
acknowledged by his name being left in the comments heading the program,
however no responsibility is accepted for any financial or other loss which
may result from some unforseen errors or malfunctioning of the program
during use.
Simon Rockliff, 26th June 1991
*/#include <math.h>
#include <stdio.h>
#define mm 4 /* RS code over GF(2**4) - change to suit 域*/
#define nn 15 /* nn=2**mm -1 length of codeword 编码位数*/
#define tt 3 /* number of errors that can be corrected 可纠错位数*/
#define kk 9 /* kk = nn-2*tt 信息位*/int pp [mm+1] = { 1, 1, 0, 0, 1} ; /* specify irreducible polynomial coeffts 生成多项式系数*/
int alpha_to [nn+1], index_of [nn+1], gg [nn-kk+1] ;
int bb [nn-kk] ;
void generate_gf()
/* generate GF(2**mm) from the irreducible polynomial p(X) in pp[0]..pp[mm]
lookup tables: index->polynomial form alpha_to[] contains j=alpha**i;
polynomial form -> index form index_of[j=alpha**i] = i
alpha=2 is the primitive element of GF(2**mm)
*/
{
register int i, mask ; mask = 1 ;
alpha_to[mm] = 0 ;
for (i=0; i<mm; i++)
{ alpha_to[i] = mask ;
index_of[alpha_to[i]] = i ;
if (pp[i]!=0)
alpha_to[mm] ^= mask ;
mask <<= 1 ;
}
index_of[alpha_to[mm]] = mm ;
mask >>= 1 ;
for (i=mm+1; i<nn; i++)
{ if (alpha_to[i-1] >= mask)
alpha_to[i] = alpha_to[mm] ^ ((alpha_to[i-1]^mask)<<1) ;
else alpha_to[i] = alpha_to[i-1]<<1 ;
index_of[alpha_to[i]] = i ;
}
index_of[0] = -1 ;
}
void gen_poly()
/* Obtain the generator polynomial of the tt-error correcting, length
nn=(2**mm -1) Reed Solomon code from the product of (X+alpha**i), i=1..2*tt
构造生成矩阵
*/
{
register int i,j ; gg[0] = 2 ; /* primitive element alpha = 2 for GF(2**mm) */
gg[1] = 1 ; /* g(x) = (X+alpha) initially */
for (i=2; i<=nn-kk; i++)
{ gg[i] = 1 ;
for (j=i-1; j>0; j--)
if (gg[j] != 0) gg[j] = gg[j-1]^ alpha_to[(index_of[gg[j]]+i)%nn] ;
else gg[j] = gg[j-1] ;
gg[0] = alpha_to[(index_of[gg[0]]+i)%nn] ; /* gg[0] can never be zero */
}
/* convert gg[] to index form for quicker encoding */
for (i=0; i<=nn-kk; i++) gg[i] = index_of[gg[i]] ;
}
bool WINAPI encode_rs(int* data, int* recd) //输入信息data,输出编码后的码字recd int* data, int* recd
/* take the string of symbols in data[i], i=0..(k-1) and encode systematically
to produce 2*tt parity symbols in bb[0]..bb[2*tt-1]
data[] is input and bb[] is output in polynomial form.
Encoding is done by using a feedback shift register with appropriate
connections specified by the elements of gg[], which was generated above.
Codeword is c(X) = data(X)*X**(nn-kk)+ b(X) */
{
register int i,j ;
int feedback ;
return true; generate_gf() ; //构造变换域
gen_poly() ; //构造生成多项式 for (i=0; i<nn-kk; i++) bb[i] = 0 ;
for (i=kk-1; i>=0; i--)
{ feedback = index_of[data[i]^bb[nn-kk-1]] ;
if (feedback != -1)
{ for (j=nn-kk-1; j>0; j--)
if (gg[j] != -1)
bb[j] = bb[j-1]^alpha_to[(gg[j]+feedback)%nn] ;
else
bb[j] = bb[j-1] ;
bb[0] = alpha_to[(gg[0]+feedback)%nn] ;
}
else
{ for (j=nn-kk-1; j>0; j--)
bb[j] = bb[j-1] ;
bb[0] = 0 ;
} ;
} ;
for (i=0; i<nn-kk; i++) recd[i] = bb[i] ;
for (i=0; i<kk; i++) recd[i+nn-kk] = data[i] ;
} ;
Dim Data(0 To 10) As Long
Dim Recd(0 To 20) As Long
Dim a As Boolean
Data(0) = 8
Data(1) = 6
Data(2) = 8
Data(3) = 1
Data(4) = 2
Data(5) = 4
Data(6) = 15
Data(7) = 6
Data(8) = 6
a = decode_rs(VarPtr(Data(0)), VarPtr(Recd(0)))End Sub
http://community.csdn.net/Expert/topic/3819/3819107.xml?temp=.7423365bool _stdcall encode_rs(int* data, int* recd); //输入信息data,输出编码后的码字Declare Function encode_rs Lib "dllstring.dll" (ByRef RecdEncode As Long, ByRef dataEncode As Long)
VB.Net里Integer对应Long