Exercise 5.17 - Sorting with options#
Question#
Add a field-searching capability, so sorting may bee done on fields within lines, each field sorted according to an independent set of options. (The index for this book was sorted with -df for the index category and -n for the page numbers.)
/* Add a field handling capablity, so sorting may be done on the fields within lines,
each field sorted according to an independent set of options. ( The index for the KnR Book was sorted with -df for the index category and -n for page number */
#include<stdio.h>
#include<ctype.h>
#define NUMERIC 1 /* numeric sort */
#define DECR 2 /* sort in decreasing order */
#define FOLD 4 /* fold upper and lower case */
#define MDIR 8 /* directory order */
#define LINES 100 /* maximum number of lines to be sorted */
int charcmp(char *,char *);
void error(char *);
int numcmp(char *,char *);
void readargs(int argc,char *argv[]);
int readlines(char *lineptr[],int maxlines);
void mqsort(void *v[],int left,int right,int (*comp)(void *,void *));
void writelines(char *lineptr[],int nlines,int order);
int option = 0;
int pos1 = 0; /* field begining with pos 1 */
int pos2 = 0; /* ending just before pos 2 */
/* Sort input line */
int main(int argc,char *argv[])
{
char *lineptr[LINES]; /* pointer to text lines */
int nlines; /* number of input lines read */
int rc = 0;
readargs(argc,argv);
if((nlines = readlines(lineptr,LINES))>0)
{
if(option & NUMERIC)
myqsort((void **)lineptr,0,nlines-1,(int (*)(void *,void *))numcmp);
else
myqsort((void **)lineptr,0,nlines-1,(int (*)(void *,void *))charcmp);
writelines(lineptr,nlines,option & DECR);
}
else
{
printf("input too big to sort \n");
rc = -1;
}
return rc;
}
/* readargs: read programs argument */
void readargs(int argc,char *argv[])
{
int c;
int atoi(char *);
while(--argc > 0 && (c=(*++argv)[0])=='-' || c == '+')
{
if( c == '-' && !isdigit(*(argv[0]+1)))
while( c = *++argv[0])
switch(c)
{
case 'd': /* directory order */
option |= MDIR;
break;
case 'f':
/* fold upper and lower */
option |= FOLD;
break;
case 'n':
/* numeric sort */
option |= NUMERIC;
break;
case 'r':
option |= DECR;
break;
default:
printf("sort: illegal option %c \n",c);
error("Usage: sort -dfnr [+pos1] [-pos2]");
break;
}
else if( c == '-')
pos2 = atoi(argv[0]+1);
else if((pos1 = atoi(argv[0]+1))<0)
error("Usage: sort -dfnr [+pos1][-pos2]");
}
if(argc || pos1 > pos2)
error("Usage: sort -dfnr [+pos1] [-pos2]");
}
/* The source file numcmp.c */
#include<math.h>
#include<ctype.h>
#include<string.h>
#define MAXSTR 100
void substr(char *s,char *t,int maxstr);
/* numcmp: compare s1 and s2 numerically */
int numcmp(char *s1,char *s2)
{
double v1,v2;
char str[MAXSTR];
substr(s1,str,MAXSTR);
v1 = atof(str);
substr(s2,str,MAXSTR);
v2 = atof(str);
if(v1 < v2)
return -1;
else if ( v1 > v2)
return 1;
else
return 0;
}
#define FOLD 4 /* fold upper and lower cases */
#define MDIR 8 /* directory order */
/* charcmp: return < 0 if s < t, 0 if s =t, >0 if s > t */
int charcmp(char *s,char *t)
{
char a,b;
int i,j,endpos;
extern int option,pos1,pos2;
int fold = (option & FOLD) ? 1 : 0;
int dir = (option & MDIR) ? 1 : 0;
i=j=pos1;
if (pos2 > 0)
endpos = pos2;
else if ((endpos = strlen(s)) > strlen(t))
endpos = strlen(t);
do
{
if(dir)
{
while(i < endpos && !isalnum(s[i]) && s[i] != ' ' && s[i] !='\0')
s[i] != ' ' && s[i] != '\0';
i++;
while(j < endpos && !isalnum(t[j]) && t[j] != ' ' && t[j] != '\0')
t[j] != ' ' && t[j] != '\0';
j++;
}
if(i < endpos && j < endpos)
{
a = fold ? tolower(s[i]):s[i];
i++;
b = fold ? tolower(t[j]):t[j];
j++;
if(a==b && a == '\0')
return 0;
}
}while(a == b && i < endpos && j < endpos);
return a - b;
}
/* The source file substr.c */
#include<string.h>
void error(char *);
/* substr: get a substring of S and put in str */
void substr(char *s,char *str)
{
int i,j,len;
extern int pos1,pos2;
len = strlen(s);
if( pos2 > 0 && len > pos2)
len = pos2;
else if ( pos2 > 0 && len < pos2)
error("substr: string too short");
for( j =0, i = pos1; i< len;i++,j++)
str[j] = str[i];
str[j] = '\0';
}
/* error: print error message and exit */
void error(char *s)
{
printf("%s \n",s);
exit(1);
}
void swap(void *v[],int i,int j)
{
void *temp;
temp = v[i];
v[i] = v[j];
v[j] = temp;
}
/* myqsort: sort v[left] ... v[right] into increasing order */
void myqsort(void *v[],int left,int right,int (*comp)(void *,void *))
{
int i,last;
void swap(void *v[],int,int);
if(left >= right) /* do nothing if array contains */
return;
swap(v,left,(left+right)/2);
last = left;
for(i = left + 1; i <=right; i++)
if((*comp)(v[i],v[left])<0)
swap(v,++last,i);
swap(v,left,last);
myqsort(v,left,last-1,comp);
myqsort(v,last+1,right,comp);
}
#define MAXLEN 1000 /* max length of any input line */
int mgetline(char *,int);
char *alloc(int);
/* readlines: read input lines */
int readlines(char *lineptr[],int maxlines)
{
int len,nlines;
char *p,line[MAXLEN];
nlines=0;
while((len=mgetline(line,MAXLEN))>0)
if(nlines >= maxlines || (p = alloc(len)) == NULL)
return -1;
else
{
line[len-1] = '\0'; /* delete newline */
strcpy(p,line);
lineptr[nlines++]=p;
}
return nlines;
}
/* writelines: write output lines */
void writelines(char *lineptr[],int nlines)
{
int i;
for(i = 0;i <nlines;i++)
printf("%s\n",lineptr[i]);
}
#define ALLOCSIZE 10000 /* size of available space */
static char allocbuf[ALLOCSIZE]; /* storage for alloc */
static char *allocp = allocbuf; /* next free position */
char *alloc(int n) /* return pointer to n characters */
{
if ( allocbuf + ALLOCSIZE - allocp >= n)
{
allocp += n;
return allocp - n; /* old p */
}
else /* not enough room */
return 0;
}
void afree(char *p) /* free storage pointed to by p */
{
if(p >= allocbuf && p < allocbuf + ALLOCSIZE)
allocp = p;
}
/* mgetline: read a line into s,return length */
int mgetline(char s[],int lim)
{
int c,i;
for(i=0;i<lim-1 && (c=getchar())!=EOF c!='\n';++i)
s[i] = c;
if(c == '\n')
{
s[i] = c;
++i;
}
s[i] = '\0';
return i;
}