《CSAPP》(第3版)答案(第八章)
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2022-07-04 15:04:12
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《CSAPP》(第3版)答案(第八章)
P9
process pair | cocurrent? |
---|---|
AB | No |
AC | Yes |
AD | Yes |
BC | Yes |
BD | Yes |
CD | Yes |
P10
A. call once, return twice
fork
B. call once, never return
longjmp, execve
C. call once, return 1 or more times
setjmp
P11
4行
c
+-------+
| "hello"
|
c | p
+-------+-------+
| fork "hello"
|
| c
| +-------+
| | "hello"
| |
| p | p
+------+-------+-------+
main fork fork "hello"
P12
8行
c
+-------+---------+
| "hello" "hello"
|
c | p
+-------+-------+---------+
| fork "hello" "hello"
|
| c
| +-------+---------+
| | "hello" "hello"
| |
| p | p
+------+-------+-------+---------+
main fork fork "hello" "hello"
P13
P14
3行
c
+-------+
| "hello"
|
c | p
+-------+-------+
| fork "hello"
|
| p
+------+-------+-------+
main fork return "hello"
P15
5行
c
+-------+---------+
| "hello" "hello"
|
c | p
+-------+-------+---------+
| fork "hello" "hello"
|
|
| p
+------+-------+-------+
main fork return "hello"
P16
注意子进程有自己的计数器。
P17
hello 0 1 Bye 2 Bye
hello 1 0 Bye 2 Bye
hello 1 Bye 0 2 Bye
P18
c
+-------+---------+
| "0" exit "2"
|
c | p
+-------+-------+---------+
| fork "1" exit "2"
| (atexit)
| c
| +-------+---------+
| | "0" exit
| |
| p | p
+------+-------+-------+---------+
main fork fork "1" exit
2一定在0/1后面,所以是B、D
P19
P20
#include <stdio.h>
#include "csapp.h"
int main(int argc, char* argv[], char* env[]) {
if (execve("/bin/ls", argv, env) == -1) {
fprintf(stderr, "execve error: %s\n", strerror(errno));
exit(1);
}
}
P21
abc或bac
P22
#include <stdio.h>
#include "csapp.h"
int mysystem(char* command) {
pid_t pid;
int status;
if ((pid = Fork()) == 0) {
char* argv[4] = { "", "-c", command, NULL };
execve("/bin/sh", argv, environ);
}
printf("child pid: %d\n", pid);
if (Waitpid(pid, &status, 0) > 0) {
if (WIFEXITED(status))
return WEXITSTATUS(status);
if (WIFSIGNALED(status))
return WTERMSIG(status);
}
}
int main(int argc, char* argv[]) {
int code;
code = mysystem("./exit-code");
printf("normally exit, code: %d\n", code); fflush(stdout);
code = mysystem("./wait-sig");
printf("exit caused by signal, code: %d\n", code); fflush(stdout);
return 0;
}
csapp.h
#ifndef __CSAPP_H__
#define __CSAPP_H__
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <setjmp.h>
#include <signal.h>
#include <dirent.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <errno.h>
#include <math.h>
#include <pthread.h>
#include <semaphore.h>
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
/* Default file permissions are DEF_MODE & ~DEF_UMASK */
/* $begin createmasks */
#define DEF_MODE S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH
#define DEF_UMASK S_IWGRP|S_IWOTH
/* $end createmasks */
/* Simplifies calls to bind(), connect(), and accept() */
/* $begin sockaddrdef */
typedef struct sockaddr SA;
/* $end sockaddrdef */
/* Persistent state for the robust I/O (Rio) package */
/* $begin rio_t */
#define RIO_BUFSIZE 8192
typedef struct {
int rio_fd; /* Descriptor for this internal buf */
int rio_cnt; /* Unread bytes in internal buf */
char *rio_bufptr; /* Next unread byte in internal buf */
char rio_buf[RIO_BUFSIZE]; /* Internal buffer */
} rio_t;
/* $end rio_t */
/* External variables */
extern int h_errno; /* Defined by BIND for DNS errors */
extern char **environ; /* Defined by libc */
/* Misc constants */
#define MAXLINE 8192 /* Max text line length */
#define MAXBUF 8192 /* Max I/O buffer size */
#define LISTENQ 1024 /* Second argument to listen() */
/* Our own error-handling functions */
void unix_error(char *msg);
void posix_error(int code, char *msg);
void dns_error(char *msg);
void gai_error(int code, char *msg);
void app_error(char *msg);
/* Process control wrappers */
pid_t Fork(void);
void Execve(const char *filename, char *const argv[], char *const envp[]);
pid_t Wait(int *status);
pid_t Waitpid(pid_t pid, int *iptr, int options);
void Kill(pid_t pid, int signum);
unsigned int Sleep(unsigned int secs);
void Pause(void);
unsigned int Alarm(unsigned int seconds);
void Setpgid(pid_t pid, pid_t pgid);
pid_t Getpgrp();
/* Signal wrappers */
typedef void handler_t(int);
handler_t *Signal(int signum, handler_t *handler);
void Sigprocmask(int how, const sigset_t *set, sigset_t *oldset);
void Sigemptyset(sigset_t *set);
void Sigfillset(sigset_t *set);
void Sigaddset(sigset_t *set, int signum);
void Sigdelset(sigset_t *set, int signum);
int Sigismember(const sigset_t *set, int signum);
int Sigsuspend(const sigset_t *set);
/* Sio (Signal-safe I/O) routines */
ssize_t sio_puts(char s[]);
ssize_t sio_putl(long v);
void sio_error(char s[]);
/* Sio wrappers */
ssize_t Sio_puts(char s[]);
ssize_t Sio_putl(long v);
void Sio_error(char s[]);
/* Unix I/O wrappers */
int Open(const char *pathname, int flags, mode_t mode);
ssize_t Read(int fd, void *buf, size_t count);
ssize_t Write(int fd, const void *buf, size_t count);
off_t Lseek(int fildes, off_t offset, int whence);
void Close(int fd);
int Select(int n, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
struct timeval *timeout);
int Dup2(int fd1, int fd2);
void Stat(const char *filename, struct stat *buf);
void Fstat(int fd, struct stat *buf) ;
/* Directory wrappers */
DIR *Opendir(const char *name);
struct dirent *Readdir(DIR *dirp);
int Closedir(DIR *dirp);
/* Memory mapping wrappers */
void *Mmap(void *addr, size_t len, int prot, int flags, int fd, off_t offset);
void Munmap(void *start, size_t length);
/* Standard I/O wrappers */
void Fclose(FILE *fp);
FILE *Fdopen(int fd, const char *type);
char *Fgets(char *ptr, int n, FILE *stream);
FILE *Fopen(const char *filename, const char *mode);
void Fputs(const char *ptr, FILE *stream);
size_t Fread(void *ptr, size_t size, size_t nmemb, FILE *stream);
void Fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream);
/* Dynamic storage allocation wrappers */
void *Malloc(size_t size);
void *Realloc(void *ptr, size_t size);
void *Calloc(size_t nmemb, size_t size);
void Free(void *ptr);
/* Sockets interface wrappers */
int Socket(int domain, int type, int protocol);
void Setsockopt(int s, int level, int optname, const void *optval, int optlen);
void Bind(int sockfd, struct sockaddr *my_addr, int addrlen);
void Listen(int s, int backlog);
int Accept(int s, struct sockaddr *addr, socklen_t *addrlen);
void Connect(int sockfd, struct sockaddr *serv_addr, int addrlen);
/* Protocol independent wrappers */
void Getaddrinfo(const char *node, const char *service,
const struct addrinfo *hints, struct addrinfo **res);
void Getnameinfo(const struct sockaddr *sa, socklen_t salen, char *host,
size_t hostlen, char *serv, size_t servlen, int flags);
void Freeaddrinfo(struct addrinfo *res);
void Inet_ntop(int af, const void *src, char *dst, socklen_t size);
void Inet_pton(int af, const char *src, void *dst);
/* DNS wrappers */
struct hostent *Gethostbyname(const char *name);
struct hostent *Gethostbyaddr(const char *addr, int len, int type);
/* Pthreads thread control wrappers */
void Pthread_create(pthread_t *tidp, pthread_attr_t *attrp,
void * (*routine)(void *), void *argp);
void Pthread_join(pthread_t tid, void **thread_return);
void Pthread_cancel(pthread_t tid);
void Pthread_detach(pthread_t tid);
void Pthread_exit(void *retval);
pthread_t Pthread_self(void);
void Pthread_once(pthread_once_t *once_control, void (*init_function)());
/* POSIX semaphore wrappers */
void Sem_init(sem_t *sem, int pshared, unsigned int value);
void P(sem_t *sem);
void V(sem_t *sem);
/* Rio (Robust I/O) package */
ssize_t rio_readn(int fd, void *usrbuf, size_t n);
ssize_t rio_writen(int fd, void *usrbuf, size_t n);
void rio_readinitb(rio_t *rp, int fd);
ssize_t rio_readnb(rio_t *rp, void *usrbuf, size_t n);
ssize_t rio_readlineb(rio_t *rp, void *usrbuf, size_t maxlen);
/* Wrappers for Rio package */
ssize_t Rio_readn(int fd, void *usrbuf, size_t n);
void Rio_writen(int fd, void *usrbuf, size_t n);
void Rio_readinitb(rio_t *rp, int fd);
ssize_t Rio_readnb(rio_t *rp, void *usrbuf, size_t n);
ssize_t Rio_readlineb(rio_t *rp, void *usrbuf, size_t maxlen);
/* Reentrant protocol-independent client/server helpers */
int open_clientfd(char *hostname, char *port);
int open_listenfd(char *port);
/* Wrappers for reentrant protocol-independent client/server helpers */
int Open_clientfd(char *hostname, char *port);
int Open_listenfd(char *port);
#endif /* __CSAPP_H__ */
/* $end csapp.h */
csapp.c
#include "csapp.h"
/**************************
* Error-handling functions
**************************/
/* $begin errorfuns */
/* $begin unixerror */
void unix_error(char *msg) /* Unix-style error */
{
fprintf(stderr, "%s: %s\n", msg, strerror(errno));
exit(0);
}
/* $end unixerror */
void posix_error(int code, char *msg) /* Posix-style error */
{
fprintf(stderr, "%s: %s\n", msg, strerror(code));
exit(0);
}
void gai_error(int code, char *msg) /* Getaddrinfo-style error */
{
fprintf(stderr, "%s: %s\n", msg, gai_strerror(code));
exit(0);
}
void app_error(char *msg) /* Application error */
{
fprintf(stderr, "%s\n", msg);
exit(0);
}
/* $end errorfuns */
void dns_error(char *msg) /* Obsolete gethostbyname error */
{
fprintf(stderr, "%s\n", msg);
exit(0);
}
/*********************************************
* Wrappers for Unix process control functions
********************************************/
/* $begin forkwrapper */
pid_t Fork(void)
{
pid_t pid;
if ((pid = fork()) < 0)
unix_error("Fork error");
return pid;
}
/* $end forkwrapper */
void Execve(const char *filename, char *const argv[], char *const envp[])
{
if (execve(filename, argv, envp) < 0)
unix_error("Execve error");
}
/* $begin wait */
pid_t Wait(int *status)
{
pid_t pid;
if ((pid = wait(status)) < 0)
unix_error("Wait error");
return pid;
}
/* $end wait */
pid_t Waitpid(pid_t pid, int *iptr, int options)
{
pid_t retpid;
if ((retpid = waitpid(pid, iptr, options)) < 0)
unix_error("Waitpid error");
return(retpid);
}
/* $begin kill */
void Kill(pid_t pid, int signum)
{
int rc;
if ((rc = kill(pid, signum)) < 0)
unix_error("Kill error");
}
/* $end kill */
void Pause()
{
(void)pause();
return;
}
unsigned int Sleep(unsigned int secs)
{
unsigned int rc;
if ((rc = sleep(secs)) < 0)
unix_error("Sleep error");
return rc;
}
unsigned int Alarm(unsigned int seconds) {
return alarm(seconds);
}
void Setpgid(pid_t pid, pid_t pgid) {
int rc;
if ((rc = setpgid(pid, pgid)) < 0)
unix_error("Setpgid error");
return;
}
pid_t Getpgrp(void) {
return getpgrp();
}
/************************************
* Wrappers for Unix signal functions
***********************************/
/* $begin sigaction */
handler_t *Signal(int signum, handler_t *handler)
{
struct sigaction action, old_action;
action.sa_handler = handler;
sigemptyset(&action.sa_mask); /* Block sigs of type being handled */
action.sa_flags = SA_RESTART; /* Restart syscalls if possible */
if (sigaction(signum, &action, &old_action) < 0)
unix_error("Signal error");
return (old_action.sa_handler);
}
/* $end sigaction */
void Sigprocmask(int how, const sigset_t *set, sigset_t *oldset)
{
if (sigprocmask(how, set, oldset) < 0)
unix_error("Sigprocmask error");
return;
}
void Sigemptyset(sigset_t *set)
{
if (sigemptyset(set) < 0)
unix_error("Sigemptyset error");
return;
}
void Sigfillset(sigset_t *set)
{
if (sigfillset(set) < 0)
unix_error("Sigfillset error");
return;
}
void Sigaddset(sigset_t *set, int signum)
{
if (sigaddset(set, signum) < 0)
unix_error("Sigaddset error");
return;
}
void Sigdelset(sigset_t *set, int signum)
{
if (sigdelset(set, signum) < 0)
unix_error("Sigdelset error");
return;
}
int Sigismember(const sigset_t *set, int signum)
{
int rc;
if ((rc = sigismember(set, signum)) < 0)
unix_error("Sigismember error");
return rc;
}
int Sigsuspend(const sigset_t *set)
{
int rc = sigsuspend(set); /* always returns -1 */
if (errno != EINTR)
unix_error("Sigsuspend error");
return rc;
}
/*************************************************************
* The Sio (Signal-safe I/O) package - simple reentrant output
* functions that are safe for signal handlers.
*************************************************************/
/* Private sio functions */
/* $begin sioprivate */
/* sio_reverse - Reverse a string (from K&R) */
static void sio_reverse(char s[])
{
int c, i, j;
for (i = 0, j = strlen(s)-1; i < j; i++, j--) {
c = s[i];
s[i] = s[j];
s[j] = c;
}
}
/* sio_ltoa - Convert long to base b string (from K&R) */
static void sio_ltoa(long v, char s[], int b)
{
int c, i = 0;
int neg = v < 0;
if (neg)
v = -v;
do {
s[i++] = ((c = (v % b)) < 10) ? c + '0' : c - 10 + 'a';
} while ((v /= b) > 0);
if (neg)
s[i++] = '-';
s[i] = '\0';
sio_reverse(s);
}
/* sio_strlen - Return length of string (from K&R) */
static size_t sio_strlen(char s[])
{
int i = 0;
while (s[i] != '\0')
++i;
return i;
}
/* $end sioprivate */
/* Public Sio functions */
/* $begin siopublic */
ssize_t sio_puts(char s[]) /* Put string */
{
return write(STDOUT_FILENO, s, sio_strlen(s)); //line:csapp:siostrlen
}
ssize_t sio_putl(long v) /* Put long */
{
char s[128];
sio_ltoa(v, s, 10); /* Based on K&R itoa() */ //line:csapp:sioltoa
return sio_puts(s);
}
void sio_error(char s[]) /* Put error message and exit */
{
sio_puts(s);
_exit(1); //line:csapp:sioexit
}
/* $end siopublic */
/*******************************
* Wrappers for the SIO routines
******************************/
ssize_t Sio_putl(long v)
{
ssize_t n;
if ((n = sio_putl(v)) < 0)
sio_error("Sio_putl error");
return n;
}
ssize_t Sio_puts(char s[])
{
ssize_t n;
if ((n = sio_puts(s)) < 0)
sio_error("Sio_puts error");
return n;
}
void Sio_error(char s[])
{
sio_error(s);
}
/********************************
* Wrappers for Unix I/O routines
********************************/
int Open(const char *pathname, int flags, mode_t mode)
{
int rc;
if ((rc = open(pathname, flags, mode)) < 0)
unix_error("Open error");
return rc;
}
ssize_t Read(int fd, void *buf, size_t count)
{
ssize_t rc;
if ((rc = read(fd, buf, count)) < 0)
unix_error("Read error");
return rc;
}
ssize_t Write(int fd, const void *buf, size_t count)
{
ssize_t rc;
if ((rc = write(fd, buf, count)) < 0)
unix_error("Write error");
return rc;
}
off_t Lseek(int fildes, off_t offset, int whence)
{
off_t rc;
if ((rc = lseek(fildes, offset, whence)) < 0)
unix_error("Lseek error");
return rc;
}
void Close(int fd)
{
int rc;
if ((rc = close(fd)) < 0)
unix_error("Close error");
}
int Select(int n, fd_set *readfds, fd_set *writefds,
fd_set *exceptfds, struct timeval *timeout)
{
int rc;
if ((rc = select(n, readfds, writefds, exceptfds, timeout)) < 0)
unix_error("Select error");
return rc;
}
int Dup2(int fd1, int fd2)
{
int rc;
if ((rc = dup2(fd1, fd2)) < 0)
unix_error("Dup2 error");
return rc;
}
void Stat(const char *filename, struct stat *buf)
{
if (stat(filename, buf) < 0)
unix_error("Stat error");
}
void Fstat(int fd, struct stat *buf)
{
if (fstat(fd, buf) < 0)
unix_error("Fstat error");
}
/*********************************
* Wrappers for directory function
*********************************/
DIR *Opendir(const char *name)
{
DIR *dirp = opendir(name);
if (!dirp)
unix_error("opendir error");
return dirp;
}
struct dirent *Readdir(DIR *dirp)
{
struct dirent *dep;
errno = 0;
dep = readdir(dirp);
if ((dep == NULL) && (errno != 0))
unix_error("readdir error");
return dep;
}
int Closedir(DIR *dirp)
{
int rc;
if ((rc = closedir(dirp)) < 0)
unix_error("closedir error");
return rc;
}
/***************************************
* Wrappers for memory mapping functions
***************************************/
void *Mmap(void *addr, size_t len, int prot, int flags, int fd, off_t offset)
{
void *ptr;
if ((ptr = mmap(addr, len, prot, flags, fd, offset)) == ((void *) -1))
unix_error("mmap error");
return(ptr);
}
void Munmap(void *start, size_t length)
{
if (munmap(start, length) < 0)
unix_error("munmap error");
}
/***************************************************
* Wrappers for dynamic storage allocation functions
***************************************************/
void *Malloc(size_t size)
{
void *p;
if ((p = malloc(size)) == NULL)
unix_error("Malloc error");
return p;
}
void *Realloc(void *ptr, size_t size)
{
void *p;
if ((p = realloc(ptr, size)) == NULL)
unix_error("Realloc error");
return p;
}
void *Calloc(size_t nmemb, size_t size)
{
void *p;
if ((p = calloc(nmemb, size)) == NULL)
unix_error("Calloc error");
return p;
}
void Free(void *ptr)
{
free(ptr);
}
/******************************************
* Wrappers for the Standard I/O functions.
******************************************/
void Fclose(FILE *fp)
{
if (fclose(fp) != 0)
unix_error("Fclose error");
}
FILE *Fdopen(int fd, const char *type)
{
FILE *fp;
if ((fp = fdopen(fd, type)) == NULL)
unix_error("Fdopen error");
return fp;
}
char *Fgets(char *ptr, int n, FILE *stream)
{
char *rptr;
if (((rptr = fgets(ptr, n, stream)) == NULL) && ferror(stream))
app_error("Fgets error");
return rptr;
}
FILE *Fopen(const char *filename, const char *mode)
{
FILE *fp;
if ((fp = fopen(filename, mode)) == NULL)
unix_error("Fopen error");
return fp;
}
void Fputs(const char *ptr, FILE *stream)
{
if (fputs(ptr, stream) == EOF)
unix_error("Fputs error");
}
size_t Fread(void *ptr, size_t size, size_t nmemb, FILE *stream)
{
size_t n;
if (((n = fread(ptr, size, nmemb, stream)) < nmemb) && ferror(stream))
unix_error("Fread error");
return n;
}
void Fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream)
{
if (fwrite(ptr, size, nmemb, stream) < nmemb)
unix_error("Fwrite error");
}
/****************************
* Sockets interface wrappers
****************************/
int Socket(int domain, int type, int protocol)
{
int rc;
if ((rc = socket(domain, type, protocol)) < 0)
unix_error("Socket error");
return rc;
}
void Setsockopt(int s, int level, int optname, const void *optval, int optlen)
{
int rc;
if ((rc = setsockopt(s, level, optname, optval, optlen)) < 0)
unix_error("Setsockopt error");
}
void Bind(int sockfd, struct sockaddr *my_addr, int addrlen)
{
int rc;
if ((rc = bind(sockfd, my_addr, addrlen)) < 0)
unix_error("Bind error");
}
void Listen(int s, int backlog)
{
int rc;
if ((rc = listen(s, backlog)) < 0)
unix_error("Listen error");
}
int Accept(int s, struct sockaddr *addr, socklen_t *addrlen)
{
int rc;
if ((rc = accept(s, addr, addrlen)) < 0)
unix_error("Accept error");
return rc;
}
void Connect(int sockfd, struct sockaddr *serv_addr, int addrlen)
{
int rc;
if ((rc = connect(sockfd, serv_addr, addrlen)) < 0)
unix_error("Connect error");
}
/*******************************
* Protocol-independent wrappers
*******************************/
/* $begin getaddrinfo */
void Getaddrinfo(const char *node, const char *service,
const struct addrinfo *hints, struct addrinfo **res)
{
int rc;
if ((rc = getaddrinfo(node, service, hints, res)) != 0)
gai_error(rc, "Getaddrinfo error");
}
/* $end getaddrinfo */
void Getnameinfo(const struct sockaddr *sa, socklen_t salen, char *host,
size_t hostlen, char *serv, size_t servlen, int flags)
{
int rc;
if ((rc = getnameinfo(sa, salen, host, hostlen, serv,
servlen, flags)) != 0)
gai_error(rc, "Getnameinfo error");
}
void Freeaddrinfo(struct addrinfo *res)
{
freeaddrinfo(res);
}
void Inet_ntop(int af, const void *src, char *dst, socklen_t size)
{
if (!inet_ntop(af, src, dst, size))
unix_error("Inet_ntop error");
}
void Inet_pton(int af, const char *src, void *dst)
{
int rc;
rc = inet_pton(af, src, dst);
if (rc == 0)
app_error("inet_pton error: invalid dotted-decimal address");
else if (rc < 0)
unix_error("Inet_pton error");
}
/*******************************************
* DNS interface wrappers.
*
* NOTE: These are obsolete because they are not thread safe. Use
* getaddrinfo and getnameinfo instead
***********************************/
/* $begin gethostbyname */
struct hostent *Gethostbyname(const char *name)
{
struct hostent *p;
if ((p = gethostbyname(name)) == NULL)
dns_error("Gethostbyname error");
return p;
}
/* $end gethostbyname */
struct hostent *Gethostbyaddr(const char *addr, int len, int type)
{
struct hostent *p;
if ((p = gethostbyaddr(addr, len, type)) == NULL)
dns_error("Gethostbyaddr error");
return p;
}
/************************************************
* Wrappers for Pthreads thread control functions
************************************************/
void Pthread_create(pthread_t *tidp, pthread_attr_t *attrp,
void * (*routine)(void *), void *argp)
{
int rc;
if ((rc = pthread_create(tidp, attrp, routine, argp)) != 0)
posix_error(rc, "Pthread_create error");
}
void Pthread_cancel(pthread_t tid) {
int rc;
if ((rc = pthread_cancel(tid)) != 0)
posix_error(rc, "Pthread_cancel error");
}
void Pthread_join(pthread_t tid, void **thread_return) {
int rc;
if ((rc = pthread_join(tid, thread_return)) != 0)
posix_error(rc, "Pthread_join error");
}
/* $begin detach */
void Pthread_detach(pthread_t tid) {
int rc;
if ((rc = pthread_detach(tid)) != 0)
posix_error(rc, "Pthread_detach error");
}
/* $end detach */
void Pthread_exit(void *retval) {
pthread_exit(retval);
}
pthread_t Pthread_self(void) {
return pthread_self();
}
void Pthread_once(pthread_once_t *once_control, void (*init_function)()) {
pthread_once(once_control, init_function);
}
/*******************************
* Wrappers for Posix semaphores
*******************************/
void Sem_init(sem_t *sem, int pshared, unsigned int value)
{
if (sem_init(sem, pshared, value) < 0)
unix_error("Sem_init error");
}
void P(sem_t *sem)
{
if (sem_wait(sem) < 0)
unix_error("P error");
}
void V(sem_t *sem)
{
if (sem_post(sem) < 0)
unix_error("V error");
}
/****************************************
* The Rio package - Robust I/O functions
****************************************/
/*
* rio_readn - Robustly read n bytes (unbuffered)
*/
/* $begin rio_readn */
ssize_t rio_readn(int fd, void *usrbuf, size_t n)
{
size_t nleft = n;
ssize_t nread;
char *bufp = usrbuf;
while (nleft > 0) {
if ((nread = read(fd, bufp, nleft)) < 0) {
if (errno == EINTR) /* Interrupted by sig handler return */
nread = 0; /* and call read() again */
else
return -1; /* errno set by read() */
}
else if (nread == 0)
break; /* EOF */
nleft -= nread;
bufp += nread;
}
return (n - nleft); /* Return >= 0 */
}
/* $end rio_readn */
/*
* rio_writen - Robustly write n bytes (unbuffered)
*/
/* $begin rio_writen */
ssize_t rio_writen(int fd, void *usrbuf, size_t n)
{
size_t nleft = n;
ssize_t nwritten;
char *bufp = usrbuf;
while (nleft > 0) {
if ((nwritten = write(fd, bufp, nleft)) <= 0) {
if (errno == EINTR) /* Interrupted by sig handler return */
nwritten = 0; /* and call write() again */
else
return -1; /* errno set by write() */
}
nleft -= nwritten;
bufp += nwritten;
}
return n;
}
/* $end rio_writen */
/*
* rio_read - This is a wrapper for the Unix read() function that
* transfers min(n, rio_cnt) bytes from an internal buffer to a user
* buffer, where n is the number of bytes requested by the user and
* rio_cnt is the number of unread bytes in the internal buffer. On
* entry, rio_read() refills the internal buffer via a call to
* read() if the internal buffer is empty.
*/
/* $begin rio_read */
static ssize_t rio_read(rio_t *rp, char *usrbuf, size_t n)
{
int cnt;
while (rp->rio_cnt <= 0) { /* Refill if buf is empty */
rp->rio_cnt = read(rp->rio_fd, rp->rio_buf,
sizeof(rp->rio_buf));
if (rp->rio_cnt < 0) {
if (errno != EINTR) /* Interrupted by sig handler return */
return -1;
}
else if (rp->rio_cnt == 0) /* EOF */
return 0;
else
rp->rio_bufptr = rp->rio_buf; /* Reset buffer ptr */
}
/* Copy min(n, rp->rio_cnt) bytes from internal buf to user buf */
cnt = n;
if (rp->rio_cnt < n)
cnt = rp->rio_cnt;
memcpy(usrbuf, rp->rio_bufptr, cnt);
rp->rio_bufptr += cnt;
rp->rio_cnt -= cnt;
return cnt;
}
/* $end rio_read */
/*
* rio_readinitb - Associate a descriptor with a read buffer and reset buffer
*/
/* $begin rio_readinitb */
void rio_readinitb(rio_t *rp, int fd)
{
rp->rio_fd = fd;
rp->rio_cnt = 0;
rp->rio_bufptr = rp->rio_buf;
}
/* $end rio_readinitb */
/*
* rio_readnb - Robustly read n bytes (buffered)
*/
/* $begin rio_readnb */
ssize_t rio_readnb(rio_t *rp, void *usrbuf, size_t n)
{
size_t nleft = n;
ssize_t nread;
char *bufp = usrbuf;
while (nleft > 0) {
if ((nread = rio_read(rp, bufp, nleft)) < 0)
return -1; /* errno set by read() */
else if (nread == 0)
break; /* EOF */
nleft -= nread;
bufp += nread;
}
return (n - nleft); /* return >= 0 */
}
/* $end rio_readnb */
/*
* rio_readlineb - Robustly read a text line (buffered)
*/
/* $begin rio_readlineb */
ssize_t rio_readlineb(rio_t *rp, void *usrbuf, size_t maxlen)
{
int n, rc;
char c, *bufp = usrbuf;
for (n = 1; n < maxlen; n++) {
if ((rc = rio_read(rp, &c, 1)) == 1) {
*bufp++ = c;
if (c == '\n') {
n++;
break;
}
} else if (rc == 0) {
if (n == 1)
return 0; /* EOF, no data read */
else
break; /* EOF, some data was read */
} else
return -1; /* Error */
}
*bufp = 0;
return n-1;
}
/* $end rio_readlineb */
/**********************************
* Wrappers for robust I/O routines
**********************************/
ssize_t Rio_readn(int fd, void *ptr, size_t nbytes)
{
ssize_t n;
if ((n = rio_readn(fd, ptr, nbytes)) < 0)
unix_error("Rio_readn error");
return n;
}
void Rio_writen(int fd, void *usrbuf, size_t n)
{
if (rio_writen(fd, usrbuf, n) != n)
unix_error("Rio_writen error");
}
void Rio_readinitb(rio_t *rp, int fd)
{
rio_readinitb(rp, fd);
}
ssize_t Rio_readnb(rio_t *rp, void *usrbuf, size_t n)
{
ssize_t rc;
if ((rc = rio_readnb(rp, usrbuf, n)) < 0)
unix_error("Rio_readnb error");
return rc;
}
ssize_t Rio_readlineb(rio_t *rp, void *usrbuf, size_t maxlen)
{
ssize_t rc;
if ((rc = rio_readlineb(rp, usrbuf, maxlen)) < 0)
unix_error("Rio_readlineb error");
return rc;
}
/********************************
* Client/server helper functions
********************************/
/*
* open_clientfd - Open connection to server at <hostname, port> and
* return a socket descriptor ready for reading and writing. This
* function is reentrant and protocol-independent.
*
* On error, returns:
* -2 for getaddrinfo error
* -1 with errno set for other errors.
*/
/* $begin open_clientfd */
int open_clientfd(char *hostname, char *port) {
int clientfd, rc;
struct addrinfo hints, *listp, *p;
/* Get a list of potential server addresses */
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_socktype = SOCK_STREAM; /* Open a connection */
hints.ai_flags = AI_NUMERICSERV; /* ... using a numeric port arg. */
hints.ai_flags |= AI_ADDRCONFIG; /* Recommended for connections */
if ((rc = getaddrinfo(hostname, port, &hints, &listp)) != 0) {
fprintf(stderr, "getaddrinfo failed (%s:%s): %s\n", hostname, port, gai_strerror(rc));
return -2;
}
/* Walk the list for one that we can successfully connect to */
for (p = listp; p; p = p->ai_next) {
/* Create a socket descriptor */
if ((clientfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) < 0)
continue; /* Socket failed, try the next */
/* Connect to the server */
if (connect(clientfd, p->ai_addr, p->ai_addrlen) != -1)
break; /* Success */
if (close(clientfd) < 0) { /* Connect failed, try another */ //line:netp:openclientfd:closefd
fprintf(stderr, "open_clientfd: close failed: %s\n", strerror(errno));
return -1;
}
}
/* Clean up */
freeaddrinfo(listp);
if (!p) /* All connects failed */
return -1;
else /* The last connect succeeded */
return clientfd;
}
/* $end open_clientfd */
/*
* open_listenfd - Open and return a listening socket on port. This
* function is reentrant and protocol-independent.
*
* On error, returns:
* -2 for getaddrinfo error
* -1 with errno set for other errors.
*/
/* $begin open_listenfd */
int open_listenfd(char *port)
{
struct addrinfo hints, *listp, *p;
int listenfd, rc, optval=1;
/* Get a list of potential server addresses */
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_socktype = SOCK_STREAM; /* Accept connections */
hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG; /* ... on any IP address */
hints.ai_flags |= AI_NUMERICSERV; /* ... using port number */
if ((rc = getaddrinfo(NULL, port, &hints, &listp)) != 0) {
fprintf(stderr, "getaddrinfo failed (port %s): %s\n", port, gai_strerror(rc));
return -2;
}
/* Walk the list for one that we can bind to */
for (p = listp; p; p = p->ai_next) {
/* Create a socket descriptor */
if ((listenfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) < 0)
continue; /* Socket failed, try the next */
/* Eliminates "Address already in use" error from bind */
setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, //line:netp:csapp:setsockopt
(const void *)&optval , sizeof(int));
/* Bind the descriptor to the address */
if (bind(listenfd, p->ai_addr, p->ai_addrlen) == 0)
break; /* Success */
if (close(listenfd) < 0) { /* Bind failed, try the next */
fprintf(stderr, "open_listenfd close failed: %s\n", strerror(errno));
return -1;
}
}
/* Clean up */
freeaddrinfo(listp);
if (!p) /* No address worked */
return -1;
/* Make it a listening socket ready to accept connection requests */
if (listen(listenfd, LISTENQ) < 0) {
close(listenfd);
return -1;
}
return listenfd;
}
/* $end open_listenfd */
/****************************************************
* Wrappers for reentrant protocol-independent helpers
****************************************************/
int Open_clientfd(char *hostname, char *port)
{
int rc;
if ((rc = open_clientfd(hostname, port)) < 0)
unix_error("Open_clientfd error");
return rc;
}
int Open_listenfd(char *port)
{
int rc;
if ((rc = open_listenfd(port)) < 0)
unix_error("Open_listenfd error");
return rc;
}
/* $end csapp.c */
P23
SIGUSR2 SIGUSR2 SIGUSR2 SIGUSR2 SIGUSR2
| | | | |
being handled Pending Canceld Canceld Canceld
need 1 sec
在任何时刻只有一个信号处于等待状态,其他的都会被取消。
P24
#include "csapp.h"
#define N 2
#define LEN 100
int main() {
int status, i;
pid_t pid;
/* Parent creates N children */
for (i = 0; i < N; i++)
if ((pid = Fork()) == 0) {
/* access address 0, cause fault */
char* cptr = NULL;
*cptr = 'd';
}
/* Parent reaps N children in no particular order */
while ((pid = waitpid(-1, &status, 0)) > 0) {
if (WIFEXITED(status))
printf("child %d terminated normally with exit status=%d\n",
pid, WEXITSTATUS(status));
else if (WIFSIGNALED(status)) {
/* print signal that cause process exit */
char buf[LEN];
sprintf(buf, "child %d terminated by signal %d", pid, WTERMSIG(status));
psignal(WTERMSIG(status), buf);
}
else
printf("child %d terminated abnormally\n", pid);
}
/* The only normal termination is if there are no more children */
if (errno != ECHILD)
unix_error("waitpid error");
exit(0);
}
/* $end waitpid1 */
P25
#include <stdio.h>
#include "csapp.h"
sigjmp_buf buf;
void handler(int sig) {
/* jump */
siglongjmp(buf, 1);
}
char* tfgets(char* s, int size, FILE* stream) {
char* result;
if (!sigsetjmp(buf, 1)) {
alarm(5);
if (signal(SIGALRM, handler) == SIG_ERR)
unix_error("set alarm handler error");
return fgets(s, size, stream);
} else {
/* run out of time */
return NULL;
}
}
#define LEN 100
int main(int argc, char* argv[]) {
char buf[LEN];
char* input = tfgets(buf, LEN, stdin);
if (input == NULL) {
printf("nothing input: NULL\n");
} else {
printf("%s", input);
}
return 0;
}
P26
????
第八章 完
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