Jan 30, 2012

K & R C Programs Exercise 5-7.

K and R C, Solution to Exercise 5-7:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
C Program to rewrite the readline function to store lines in the arraysupplied by main, rather than calling alloc to maintain storage. How much faster is the program?
The readlile function is slightly faster than the original version in the book K and R C Program page 109. Read more about C Programming Language .


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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>

#define TRUE     1
#define FALSE    0

#define MAXLINES 5000       /* maximum number of lines */
#define MAXLEN   1000       /* maximum length of a line */
char *lineptr[MAXLINES];
char lines[MAXLINES][MAXLEN];


int getline(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;   
 }
 s[i] = '\0';
 return i;
}


int readlines(char *lineptr[], int maxlines)
{
 int len, nlines;
 char *p, line[MAXLEN];

 nlines = 0;
 while ((len = getline(line, MAXLEN)) > 0)
  if (nlines >= maxlines || (p = malloc(len)) == NULL)
   return -1;
  else {
   line[len - 1] = '\0';  /* delete the newline */
   strcpy(p, line);
   lineptr[nlines++] = p;
  }                       
 return nlines;  
}

int readlines2(char lines[][MAXLEN], int maxlines)
{
 int len, nlines;

 nlines = 0;
 while ((len = getline(lines[nlines], MAXLEN)) > 0)
  if (nlines >= maxlines)                         
   return -1;           
  else
   lines[nlines++][len - 1] = '\0';  
 return nlines;
}

int main(int argc, char *argv[])
{

 readlines2(lines, MAXLINES);

 if (argc > 1 && *argv[1] == '2') {
  puts("readlines2()");           
  readlines2(lines, MAXLINES);
 } else {
  puts("readlines()");
  readlines(lineptr, MAXLINES);
 }

 return 0;
}

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