reverse_string.c

linux下多线程程序设计,包括signals,mutex,simple_once

/********************************************************
 * An example source module to accompany...
 *
 * "Using POSIX Threads: Programming with Pthreads"
 *     by Brad nichols, Dick Buttlar, Jackie Farrell
 *     O'Reilly & Associates, Inc.
 *
 ********************************************************
 * reverse_string --
 * 
 * Example showing thread-safe versus thread-unsafe ways to write 
 * a string reversal routine.
 */
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>

#include <pthread.h>

void reverse_string(char*);
void reverse_string_r(char *); 


pthread_mutex_t reverse_string_lock = PTHREAD_MUTEX_INITIALIZER;

#define safe_reverse_string(x) \
pthread_mutex_lock(&reverse_string_lock); \
reverse_string(x); \
pthread_mutex_unlock(&reverse_string_lock);


static char my_buffer[100];

void reverse_string(char *in_str)
{
	int size = 0, i = 0, j = 0;	
	
	/* Find the end of the in_str */
	while ( (in_str[size] != '\0') && (size != 100)) 
	{
		size++;
	}	
	
	/* Copy from in_str into buffer, reversing it */
	for (i = size-1; i > -1; i--) 
		my_buffer[j++] = in_str[i];
	
	my_buffer[j+1] = '\0';	
	
	/* Copy back from buffer to in_str */
	for (i = 0; i < size+1; i++)
		in_str[i] = my_buffer[i];
}


void reverse_string_r(char *in_str)
{
	int size = 0, i = 0, j = 0;
	char my_auto_buffer[100];
	
	/* Find the end of the in_str */
	while ( (in_str[size] != '\0') && (size != 100)) 
	{
		size++;
	}
	
	/* Copy from in_str into buffer, reversing it */
	for (i = size-1; i > -1; i--) 
		my_auto_buffer[j++] = in_str[i];

	my_auto_buffer[j+1] = '\0';	
	
	/* Copy back from buffer to in_str */
	for (i = 0; i < size+1; i++)
		in_str[i] = my_auto_buffer[i];
}

extern int	main(void)
{
	char s1[25], s2[25];
	
	sprintf(s1,"%s", "This is a string");
	sprintf(s2,"%s", "This is another string");
	
	printf("%s\n",s1);
	reverse_string(s1);
	printf("%s\n\n",s1);
	
	
	printf("%s\n",s2);
	reverse_string_r(s2);
	printf("%s\n\n",s2);
	
	printf("%s\n",s2);
	safe_reverse_string(s2);
	printf("%s\n",s2);
	
	return 0;
}