sscoding.cpp

本程序实现了数据压缩中“算术编码”的全过程。执行环境为 TC 3.0。

#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
//----------Initialization.
begin:  FILE    *f_str;
	char	*f_path;
	int	array_length,el_number=1;
	int	tmp_length2=1,ch_tmp_flag=1,ch_counter,order_num;
	char	str_array[20],str_element[20],Dec_str_array[20],ch_temp_str,ch_temp_el,ch_exit;
	char	*str_exit={"System is trying to Quit...Byebye!"};
	double  ch_rates[20][2],ch_area[20][2],Code_area[1][2],Decode_area[1][2];
	double  P_acum_rate=0,P_temp=0,p_get_rate=1,p_temp=1,C_codes=0,C_temp=0,Area_length=1,Area_temp=1,Dec_code;
	printf("Please input the file PATH:");
	gets(f_path);
	f_str=fopen(f_path,"r");
	fgets(str_array,20,f_str);
	array_length=strlen(str_array);
//----------Input error?
	if(array_length>20)
		{printf("The file string OVERFLOW!\n");goto exit;}
	if(f_str==NULL)
		{printf("The file is not exist or is empty!\n");goto again;}
	else if(array_length>0&&array_length<=20)
	{
		printf("The CODING string of the file is:\n");
		printf("%s\n",str_array);
		printf("The total character number of the string is: %d.\n",array_length);
		printf("Character--Amount----p(x)------P(x)---------Area---------\n");
//----------Get single-characters.
		str_element[0]=str_array[0];
		for(int i=0;i<array_length;i++)
		{
			ch_temp_str=str_array[i];
			for(int i1=0;i1<el_number;i1++)
			{
				if(ch_temp_str==str_element[i1])
					{ch_tmp_flag=0;break;}
				else	{ch_tmp_flag=1;}
			}
			if(ch_tmp_flag==1)
			{
				str_element[el_number]=ch_temp_str;
				tmp_length2=tmp_length2+1;
				el_number=tmp_length2;
			}
		}
//----------Get the rates and the areas.
		ch_rates[0][1]=0;
		for(i=0;i<el_number;i++)
		{
			ch_counter=0;
			ch_temp_el=str_element[i];
			for(int j=0;j<array_length;j++)
			{
				ch_temp_str=str_array[j];
				if(ch_temp_str==ch_temp_el)
					{ch_counter=ch_counter+1;}
			}
			ch_rates[i][0]=(double)ch_counter/(double)array_length;
			if(i<el_number-1)
				{ch_rates[i+1][1]=ch_rates[i][1]+ch_rates[i][0];}
			ch_area[i][0]=ch_rates[i][1];
			ch_area[i][1]=ch_rates[i][1]+ch_rates[i][0];
			printf("     %c       ",ch_temp_el);
			printf("%d     ",ch_counter);
			printf("%lf  %lf  ",ch_rates[i][0],ch_rates[i][1]);
			printf("[%lf,%lf)\n",ch_area[i][0],ch_area[i][1]);
		}
//----------Get the coding area.
		for(i=0;i<array_length;i++)
		{
			ch_temp_str=str_array[i];
			for(int j=0;j<el_number;j++)
			{
				if(ch_temp_str==str_element[j])
					{order_num=j; break;}
			}
			P_acum_rate=ch_rates[order_num][1];
			p_get_rate=ch_rates[order_num][0];
			C_codes=C_codes+P_acum_rate*Area_length;
			Area_length=p_get_rate*Area_length;
		}
		Code_area[0][0]=C_codes;
		Code_area[0][1]=C_codes+Area_length;
		printf("The last Coding/Decoding-Area is:  [%g,%g)\n",Code_area[0][0],Code_area[0][1]);
//----------Decoding start here.
		Dec_code=(Code_area[0][0]+Code_area[0][1])/2;
		P_acum_rate=0,p_get_rate=1,C_codes=0,Area_length=1;
//----------Get the first character and its rate information.
		for(i=0;i<el_number;i++)
		{
			if(Dec_code>=ch_area[i][0]&&Dec_code<ch_area[i][1])
			{
				Dec_str_array[0]=str_element[i];
				Decode_area[0][0]=ch_area[i][0];
				Decode_area[0][1]=ch_area[i][1];
				P_acum_rate=ch_rates[i][1];
				p_get_rate=ch_rates[i][0];
				C_codes=C_codes+P_acum_rate*Area_length;
				Area_length=p_get_rate*Area_length;
				break;
			}
		}
//----------Resume the string with computing and comparing circularly.
		for(i=1;i<array_length;i++)
		{
			P_temp=P_acum_rate;
			p_temp=p_get_rate;
			C_temp=C_codes;
			Area_temp=Area_length;
			ch_temp_str=str_array[i];
			for(int j=0;j<el_number;j++)
			{
				if(ch_temp_str==str_element[j])
				{
					P_temp=ch_rates[j][1];
					p_temp=ch_rates[j][0];
					C_temp=C_temp+P_temp*Area_temp;
					Area_temp=p_temp*Area_temp;
					if(Dec_code>=C_temp&&Dec_code<C_temp+Area_temp)
					{
						P_acum_rate=P_temp;
						p_get_rate=p_temp;
						C_codes=C_temp;
						Area_length=Area_temp;
						Dec_str_array[i]=str_element[j];
					}
					break;
				}
			}
		}
		printf("The DECODED string is as follow:\n");
		for(i=0;i<array_length;i++)
			{printf("%c",Dec_str_array[i]);}
		printf("\n");
	}
again:  printf("\nTry again?(Enter to Continue;Any key for Quit.)\n");
	ch_exit=getch();
	if(ch_exit==13)
	{
//free valiables here
		printf("\n");
		goto begin;
	}

exit:   for(long i=0;i<7000000;i++)
		{if(i%200000==0)printf("%c",str_exit[i/200000]);}
	for(i=0;i<100000000;i++){;}
	printf("\n\n");
}