83 lines
2.4 KiB
C
83 lines
2.4 KiB
C
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/* Driver for routines hufmak, hufenc, hufdec */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#define NRANSI
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#include "nr.h"
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#include "nrutil.h"
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#define MC 512
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#define MQ (2*MC-1)
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#define MAXLINE 256
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int main(void)
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{
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int k;
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unsigned long i,j,ilong,n,nb,nh,nlong,nt,lcode=MAXLINE,nch,nfreq[257];
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unsigned char *code,mess[MAXLINE],ness[MAXLINE];
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huffcode hcode;
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FILE *fp;
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code=cvector(0,MAXLINE);
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hcode.icod=lvector(1,MQ);
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hcode.ncod=lvector(1,MQ);
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hcode.left=lvector(1,MQ);
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hcode.right=lvector(1,MQ);
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for (j=1;j<=MQ;j++) hcode.icod[j]=hcode.ncod[j]=0;
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/* construct a letter frequency table from the file text.dat */
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if ((fp = fopen("text.dat","r")) == NULL)
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nrerror("Input file text.dat not found.\n");
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for (j=1;j<=256;j++) nfreq[j]=0;
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while ((k=getc(fp)) != EOF) {
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if ((k -= 31) >= 1) nfreq[k]++;
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}
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fclose(fp);
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nch=96;
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/* here is the initialization that constructs the code */
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hufmak(nfreq,nch,&ilong,&nlong,&hcode);
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printf("ind char nfreq ncod icod\n");
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for (j=1;j<=nch;j++)
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if (nfreq[j]) printf("%3lu %c %6lu %6lu %6lu\n",
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j,(char)(j+31),nfreq[j],hcode.ncod[j],hcode.icod[j]);
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for (;;) {
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/* now ready to prompt for lines to encode */
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printf("Enter a line:\n");
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if (gets((char *)&mess[1]) == NULL) break;
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n=strlen((char *)&mess[1]);
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/* shift from 256 character alphabet to 96 printing characters */
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for (j=1;j<=n;j++) mess[j] -= 32;
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/* here we Huffman encode mess[1..n] */
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nb=0;
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for (j=1;j<=n;j++) hufenc((unsigned long)mess[j],&code,&lcode,&nb,&hcode);
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nh=(nb>>3)+1;
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/* message termination (encode a single long character) */
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hufenc(ilong,&code,&lcode,&nb,&hcode);
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/* here we decode the message, hopefully to get the original back */
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nb=0;
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for (j=1;j<=MAXLINE;j++) {
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hufdec(&i,code,nh,&nb,&hcode);
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if (i == nch) break;
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else ness[j]=(unsigned char)i;
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}
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if (j > lcode) nrerror("Huffman coding: Never get here");
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nt=j-1;
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printf("Length of line input,coded= %lu %lu\n",n,nh);
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printf("Decoded output:\n");
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for (j=1;j<=nt;j++) printf("%c",(char)(ness[j]+32));
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printf("\n");
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if (nt != n) printf("Error! : n decoded != n input\n");
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if (nt-n == 1) printf("May be harmless spurious character.\n");
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}
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free_cvector(code,0,MAXLINE);
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free_lvector(hcode.right,1,MQ);
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free_lvector(hcode.left,1,MQ);
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free_lvector(hcode.ncod,1,MQ);
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free_lvector(hcode.icod,1,MQ);
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printf("Normal completion\n");
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return 0;
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}
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#undef NRANSI
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