add numerical recipes library

lib/nr/ansi/examples/xhuffman.c

@@ -0,0 +1,82 @@
+
+/* Driver for routines hufmak, hufenc, hufdec */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define MC 512
+#define MQ (2*MC-1)
+
+#define MAXLINE 256
+
+int main(void)
+{
+	int k;
+	unsigned long i,j,ilong,n,nb,nh,nlong,nt,lcode=MAXLINE,nch,nfreq[257];
+	unsigned char *code,mess[MAXLINE],ness[MAXLINE];
+	huffcode hcode;
+	FILE *fp;
+
+	code=cvector(0,MAXLINE);
+	hcode.icod=lvector(1,MQ);
+	hcode.ncod=lvector(1,MQ);
+	hcode.left=lvector(1,MQ);
+	hcode.right=lvector(1,MQ);
+	for (j=1;j<=MQ;j++) hcode.icod[j]=hcode.ncod[j]=0;
+	/* construct a letter frequency table from the file text.dat */
+	if ((fp = fopen("text.dat","r")) == NULL)
+		nrerror("Input file text.dat not found.\n");
+	for (j=1;j<=256;j++) nfreq[j]=0;
+	while ((k=getc(fp)) != EOF) {
+		if ((k -= 31) >= 1) nfreq[k]++;
+	}
+	fclose(fp);
+	nch=96;
+	/* here is the initialization that constructs the code */
+	hufmak(nfreq,nch,&ilong,&nlong,&hcode);
+	printf("ind char  nfreq  ncod  icod\n");
+	for (j=1;j<=nch;j++)
+		if (nfreq[j]) printf("%3lu %c %6lu %6lu %6lu\n",
+			j,(char)(j+31),nfreq[j],hcode.ncod[j],hcode.icod[j]);
+	for (;;) {
+		/* now ready to prompt for lines to encode */
+		printf("Enter a line:\n");
+		if (gets((char *)&mess[1]) == NULL) break;
+		n=strlen((char *)&mess[1]);
+		/* shift from 256 character alphabet to 96 printing characters */
+		for (j=1;j<=n;j++) mess[j] -= 32;
+		/* here we Huffman encode mess[1..n] */
+		nb=0;
+		for (j=1;j<=n;j++) hufenc((unsigned long)mess[j],&code,&lcode,&nb,&hcode);
+		nh=(nb>>3)+1;
+		/* message termination (encode a single long character) */
+		hufenc(ilong,&code,&lcode,&nb,&hcode);
+		/* here we decode the message, hopefully to get the original back */
+		nb=0;
+		for (j=1;j<=MAXLINE;j++) {
+			hufdec(&i,code,nh,&nb,&hcode);
+			if (i == nch) break;
+			else ness[j]=(unsigned char)i;
+		}
+		if (j > lcode) nrerror("Huffman coding: Never get here");
+		nt=j-1;
+		printf("Length of line input,coded= %lu %lu\n",n,nh);
+		printf("Decoded output:\n");
+		for (j=1;j<=nt;j++) printf("%c",(char)(ness[j]+32));
+		printf("\n");
+		if (nt != n) printf("Error! :  n decoded != n input\n");
+		if (nt-n == 1) printf("May be harmless spurious character.\n");
+	}
+	free_cvector(code,0,MAXLINE);
+	free_lvector(hcode.right,1,MQ);
+	free_lvector(hcode.left,1,MQ);
+	free_lvector(hcode.ncod,1,MQ);
+	free_lvector(hcode.icod,1,MQ);
+	printf("Normal completion\n");
+	return 0;
+}
+#undef NRANSI