在c中制作共享数据结构
Making a shared data structure in c
我在我的 C 程序中创建了一个数据结构，如下所示，
typedef struct {
int *array;
size_t used;
size_t size;
} Array;
void initArray(Array *a, size_t initialSize) {
a->array = (int *)malloc(initialSize * sizeof(int));
a->used = 0;
a->size = initialSize;
}
void insertArray(Array *a, int element) {
if (a->used == a->size) {
a->size *= 2;
a->array = (int *)realloc(a->array, a->size * sizeof(int));
}
a->array[a->used++] = element;
}
void freeArray(Array *a) {
free(a->array);
a->array = NULL;
a->used = a->size = 0;
}
然后我使用以下方法从外部文本文件向该数据结构添加一些数据，
Array read_ints (const char* file_name)
{
Array numbers;
initArray(&numbers,5);
FILE* file = fopen (file_name, "r");
int i = 0;
int count = 0;
fscanf (file, "%d,", &i);
insertArray(&numbers,i);
while (!feof (file))
{
//printf ("%d ", i);
fscanf (file, "%d,", &i);
insertArray(&numbers,i);
}
fclose (file);
return numbers;
}
现在我需要做的是，我需要使 'Array' 数据结构成为共享内存部分，以便我程序中的子进程和父进程都可以访问该数据结构。我不知道如何使它成为共享内存。我知道 shmget() 系统调用可用于在 UNIX 环境中获取共享内存。但我看不到如何在这种情况下使用该系统调用。请帮助我。
主要代码 — shm-master.c
#include "posixver.h"
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <unistd.h>
#include "so-stderr.h"
enum { DEFAULT_SHM_SIZE = 65536 };
enum { DEFAULT_FTOK_ID = 0 };
static const char default_filename[] = "/etc/passwd";
static const char usestr[] = "[-adx][-f file][-s size][-i id]";
static const char optstr[] = "adf:s:x";
int main(int argc, char **argv)
{
int aflag = 0;
int xflag = 0;
int dflag = 0;
int id = DEFAULT_FTOK_ID;
size_t size = DEFAULT_SHM_SIZE;
const char *file = default_filename;
int opt;
err_setarg0(argv[0]);
while ((opt = getopt(argc, argv, optstr)) != -1)
{
switch (opt)
{
case 'a':
aflag = 1;
break;
case 'd':
dflag = 1;
break;
case 'f':
file = optarg;
break;
case 'i':
id = atoi(optarg);
break;
case 's':
size = strtoull(optarg, 0, 0);
if (size == 0)
err_error("Invalid size (%s) evaluates to zero\n", optarg);
break;
case 'x':
xflag = 1;
break;
default:
err_usage(usestr);
}
}
if (aflag + dflag + xflag > 1)
err_error("%d of 3 mutually exclusive options -a, -d and -x specified\n", aflag + dflag + xflag);
printf("ID: %d, File: %s\n", id, file);
key_t key = ftok(file, id);
printf("Key: 0x%.8" PRIX64 "\n", (uint64_t)key);
int shmflg = S_IRUSR | S_IWUSR;
if (!aflag && !dflag)
shmflg |= IPC_CREAT;
if (xflag)
shmflg |= IPC_EXCL;
int shmid = shmget(key, size, shmflg);
if (shmid < 0)
err_syserr("Failed to get shared memory ID: ");
printf("ShmID: %d\n", shmid);
if (dflag)
{
struct shmid_ds buf;
int rc = shmctl(shmid, IPC_RMID, &buf);
if (rc < 0)
err_syserr("Failed to delete shared memory: ");
printf("Shared memory removed\n");
}
else
{
void *space = shmat(shmid, 0, 0);
if (space == (void *)-1)
err_syserr("Failed to attach to shared memory: ");
printf("Shared memory allocated at 0x%" PRIXPTR "\n", (uintptr_t)space);
memset(space, '[=10=]', size);
int rc = shmdt(space);
if (rc != 0)
err_syserr("Failed to detach from shared memory: ");
printf("Detached from shared memory\n");
}
return 0;
}
图书馆代码 — so-stderr.h
#ifndef SO_STDERR_H_INCLUDED
#define SO_STDERR_H_INCLUDED
extern void err_setarg0(const char *arg0);
extern void err_error(const char *fmt, ...);
extern void err_syserr(const char *fmt, ...);
#endif /* SO_STDERR_H_INCLUDED */
图书馆代码 — so-stderr.c
#include "so-stderr.h"
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static const char *argv0 = "**undefined**";
void err_setarg0(const char *arg0)
{
argv0 = arg0;
}
void err_error(const char *fmt, ...)
{
fprintf(stderr, "%s: ", argv0);
va_list args;
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
exit(EXIT_FAILURE);
}
void err_syserr(const char *fmt, ...)
{
int errnum = errno;
fprintf(stderr, "%s: ", argv0);
va_list args;
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
if (errnum != 0)
fprintf(stderr, "(%d: %s)", errnum, strerror(errnum));
putc('\n', stderr);
exit(EXIT_FAILURE);
}
配置header — posixver.h
您可以在许多系统上将较高版本号调整为 700（对于 POSIX 2008/2013），但在 Mac [=48= 上可能不是一个好主意] X，即使是 10.10.3 Yosemite.
#ifndef JLSS_ID_POSIXVER_H
#define JLSS_ID_POSIXVER_H
#if !defined(_XOPEN_SOURCE) && !defined(_POSIX_C_SOURCE)
#if __STDC_VERSION__ >= 199901L
#define _XOPEN_SOURCE 600
#else
#define _XOPEN_SOURCE 500
#endif
#endif
在所有情况下，'real' 代码都包含（一些）注释和对正在发生的事情的其他解释。生产 stderr.h 和 stderr.c 比显示的最小版本更复杂，但对于许多用途，显示的内容等同于生产版本。
示例运行
$ ./shm-master -H
./shm-master: invalid option -- 'H'
Usage: ./shm-master [-adx][-f file][-s size][-i id]
$ ./shm-master -ax
./shm-master: 2 of 3 mutually exclusive options -a, -d and -x specified
$ ./shm-master -dx
./shm-master: 2 of 3 mutually exclusive options -a, -d and -x specified
$ ./shm-master -da
./shm-master: 2 of 3 mutually exclusive options -a, -d and -x specified
$ ./shm-master -dax
./shm-master: 3 of 3 mutually exclusive options -a, -d and -x specified
$ ipcs -m | grep -v '^0x00000000 '
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x620010f7 0 root 660 557920 4
0x63002725 32769 root 666 82164 3
$ ./shm-master -x
ID: 0, File: /etc/passwd
Key: 0x0000009F
ShmID: 44793901
Shared memory allocated at 0x7F29AC43A000
Detached from shared memory
$ ipcs -m | grep -v '^0x00000000 '
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x620010f7 0 root 660 557920 4
0x63002725 32769 root 666 82164 3
0x0000009f 44793901 jleffler 600 65536 0
$ ./shm-master -d
ID: 0, File: /etc/passwd
Key: 0x0000009F
ShmID: 44793901
Shared memory removed
$ ipcs -m
$ grep -v '^0x00000000 '
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x620010f7 0 root 660 557920 4
0x63002725 32769 root 666 82164 3
$ ./shm-master -f /home/jleffler/soq/shm-master -a
./shm-master: Failed to get shared memory ID: (2: No such file or directory)
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
$ ./shm-master -f /home/jleffler/soq/shm-master -d
./shm-master: Failed to get shared memory ID: (2: No such file or directory)
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
$ ./shm-master -f /home/jleffler/soq/shm-master -x
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
ShmID: 44826669
Shared memory allocated at 0x7FA1488CA000
Detached from shared memory
$ ./shm-master -f /home/jleffler/soq/shm-master -d
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
ShmID: 44826669
Shared memory removed
$ ./shm-master -f /home/jleffler/soq/shm-master -x
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
ShmID: 44859437
Shared memory allocated at 0x7F93005EC000
Detached from shared memory
$ shmid=$(./shm-master -f /home/jleffler/soq/shm-master -a sed -n '/ShmID: /s///p')
$ ipcs -m -i $shmid
Shared memory Segment shmid=44859437
uid=199484 gid=5000 cuid=199484 cgid=5000
mode=0600 access_perms=0600
bytes=65536 lpid=31202 cpid=31200 nattch=0
att_time=Fri Apr 17 11:37:06 2015
det_time=Fri Apr 17 11:37:06 2015
change_time=Fri Apr 17 11:37:06 2015
$ ./shm-master -f /home/jleffler/soq/shm-master -d
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
ShmID: 44859437
Shared memory removed
$
顺便说一句，ipcs 选项 -i id 是对 ipcs 的 POSIX 规范的 Linux 扩展，并且该选项不可用例如，Mac OS X (BSD)。最接近的等价物是 ipcs -m -a | grep "$shmid"，这并不完美。 grep -v '^0x00000000 ' 操作消除了私有共享内存段（在我进行测试的机器上使用了很多）。
我在我的 C 程序中创建了一个数据结构，如下所示，
typedef struct {
int *array;
size_t used;
size_t size;
} Array;
void initArray(Array *a, size_t initialSize) {
a->array = (int *)malloc(initialSize * sizeof(int));
a->used = 0;
a->size = initialSize;
}
void insertArray(Array *a, int element) {
if (a->used == a->size) {
a->size *= 2;
a->array = (int *)realloc(a->array, a->size * sizeof(int));
}
a->array[a->used++] = element;
}
void freeArray(Array *a) {
free(a->array);
a->array = NULL;
a->used = a->size = 0;
}
然后我使用以下方法从外部文本文件向该数据结构添加一些数据，
Array read_ints (const char* file_name)
{
Array numbers;
initArray(&numbers,5);
FILE* file = fopen (file_name, "r");
int i = 0;
int count = 0;
fscanf (file, "%d,", &i);
insertArray(&numbers,i);
while (!feof (file))
{
//printf ("%d ", i);
fscanf (file, "%d,", &i);
insertArray(&numbers,i);
}
fclose (file);
return numbers;
}
现在我需要做的是，我需要使 'Array' 数据结构成为共享内存部分，以便我程序中的子进程和父进程都可以访问该数据结构。我不知道如何使它成为共享内存。我知道 shmget() 系统调用可用于在 UNIX 环境中获取共享内存。但我看不到如何在这种情况下使用该系统调用。请帮助我。
主要代码 — shm-master.c
#include "posixver.h"
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <unistd.h>
#include "so-stderr.h"
enum { DEFAULT_SHM_SIZE = 65536 };
enum { DEFAULT_FTOK_ID = 0 };
static const char default_filename[] = "/etc/passwd";
static const char usestr[] = "[-adx][-f file][-s size][-i id]";
static const char optstr[] = "adf:s:x";
int main(int argc, char **argv)
{
int aflag = 0;
int xflag = 0;
int dflag = 0;
int id = DEFAULT_FTOK_ID;
size_t size = DEFAULT_SHM_SIZE;
const char *file = default_filename;
int opt;
err_setarg0(argv[0]);
while ((opt = getopt(argc, argv, optstr)) != -1)
{
switch (opt)
{
case 'a':
aflag = 1;
break;
case 'd':
dflag = 1;
break;
case 'f':
file = optarg;
break;
case 'i':
id = atoi(optarg);
break;
case 's':
size = strtoull(optarg, 0, 0);
if (size == 0)
err_error("Invalid size (%s) evaluates to zero\n", optarg);
break;
case 'x':
xflag = 1;
break;
default:
err_usage(usestr);
}
}
if (aflag + dflag + xflag > 1)
err_error("%d of 3 mutually exclusive options -a, -d and -x specified\n", aflag + dflag + xflag);
printf("ID: %d, File: %s\n", id, file);
key_t key = ftok(file, id);
printf("Key: 0x%.8" PRIX64 "\n", (uint64_t)key);
int shmflg = S_IRUSR | S_IWUSR;
if (!aflag && !dflag)
shmflg |= IPC_CREAT;
if (xflag)
shmflg |= IPC_EXCL;
int shmid = shmget(key, size, shmflg);
if (shmid < 0)
err_syserr("Failed to get shared memory ID: ");
printf("ShmID: %d\n", shmid);
if (dflag)
{
struct shmid_ds buf;
int rc = shmctl(shmid, IPC_RMID, &buf);
if (rc < 0)
err_syserr("Failed to delete shared memory: ");
printf("Shared memory removed\n");
}
else
{
void *space = shmat(shmid, 0, 0);
if (space == (void *)-1)
err_syserr("Failed to attach to shared memory: ");
printf("Shared memory allocated at 0x%" PRIXPTR "\n", (uintptr_t)space);
memset(space, '[=10=]', size);
int rc = shmdt(space);
if (rc != 0)
err_syserr("Failed to detach from shared memory: ");
printf("Detached from shared memory\n");
}
return 0;
}
图书馆代码 — so-stderr.h
#ifndef SO_STDERR_H_INCLUDED
#define SO_STDERR_H_INCLUDED
extern void err_setarg0(const char *arg0);
extern void err_error(const char *fmt, ...);
extern void err_syserr(const char *fmt, ...);
#endif /* SO_STDERR_H_INCLUDED */
图书馆代码 — so-stderr.c
#include "so-stderr.h"
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static const char *argv0 = "**undefined**";
void err_setarg0(const char *arg0)
{
argv0 = arg0;
}
void err_error(const char *fmt, ...)
{
fprintf(stderr, "%s: ", argv0);
va_list args;
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
exit(EXIT_FAILURE);
}
void err_syserr(const char *fmt, ...)
{
int errnum = errno;
fprintf(stderr, "%s: ", argv0);
va_list args;
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
if (errnum != 0)
fprintf(stderr, "(%d: %s)", errnum, strerror(errnum));
putc('\n', stderr);
exit(EXIT_FAILURE);
}
配置header — posixver.h
您可以在许多系统上将较高版本号调整为 700（对于 POSIX 2008/2013），但在 Mac [=48= 上可能不是一个好主意] X，即使是 10.10.3 Yosemite.
#ifndef JLSS_ID_POSIXVER_H
#define JLSS_ID_POSIXVER_H
#if !defined(_XOPEN_SOURCE) && !defined(_POSIX_C_SOURCE)
#if __STDC_VERSION__ >= 199901L
#define _XOPEN_SOURCE 600
#else
#define _XOPEN_SOURCE 500
#endif
#endif
在所有情况下，'real' 代码都包含（一些）注释和对正在发生的事情的其他解释。生产 stderr.h 和 stderr.c 比显示的最小版本更复杂，但对于许多用途，显示的内容等同于生产版本。
示例运行
$ ./shm-master -H
./shm-master: invalid option -- 'H'
Usage: ./shm-master [-adx][-f file][-s size][-i id]
$ ./shm-master -ax
./shm-master: 2 of 3 mutually exclusive options -a, -d and -x specified
$ ./shm-master -dx
./shm-master: 2 of 3 mutually exclusive options -a, -d and -x specified
$ ./shm-master -da
./shm-master: 2 of 3 mutually exclusive options -a, -d and -x specified
$ ./shm-master -dax
./shm-master: 3 of 3 mutually exclusive options -a, -d and -x specified
$ ipcs -m | grep -v '^0x00000000 '
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x620010f7 0 root 660 557920 4
0x63002725 32769 root 666 82164 3
$ ./shm-master -x
ID: 0, File: /etc/passwd
Key: 0x0000009F
ShmID: 44793901
Shared memory allocated at 0x7F29AC43A000
Detached from shared memory
$ ipcs -m | grep -v '^0x00000000 '
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x620010f7 0 root 660 557920 4
0x63002725 32769 root 666 82164 3
0x0000009f 44793901 jleffler 600 65536 0
$ ./shm-master -d
ID: 0, File: /etc/passwd
Key: 0x0000009F
ShmID: 44793901
Shared memory removed
$ ipcs -m
$ grep -v '^0x00000000 '
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x620010f7 0 root 660 557920 4
0x63002725 32769 root 666 82164 3
$ ./shm-master -f /home/jleffler/soq/shm-master -a
./shm-master: Failed to get shared memory ID: (2: No such file or directory)
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
$ ./shm-master -f /home/jleffler/soq/shm-master -d
./shm-master: Failed to get shared memory ID: (2: No such file or directory)
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
$ ./shm-master -f /home/jleffler/soq/shm-master -x
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
ShmID: 44826669
Shared memory allocated at 0x7FA1488CA000
Detached from shared memory
$ ./shm-master -f /home/jleffler/soq/shm-master -d
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
ShmID: 44826669
Shared memory removed
$ ./shm-master -f /home/jleffler/soq/shm-master -x
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
ShmID: 44859437
Shared memory allocated at 0x7F93005EC000
Detached from shared memory
$ shmid=$(./shm-master -f /home/jleffler/soq/shm-master -a sed -n '/ShmID: /s///p')
$ ipcs -m -i $shmid
Shared memory Segment shmid=44859437
uid=199484 gid=5000 cuid=199484 cgid=5000
mode=0600 access_perms=0600
bytes=65536 lpid=31202 cpid=31200 nattch=0
att_time=Fri Apr 17 11:37:06 2015
det_time=Fri Apr 17 11:37:06 2015
change_time=Fri Apr 17 11:37:06 2015
$ ./shm-master -f /home/jleffler/soq/shm-master -d
ID: 0, File: /home/jleffler/soq/shm-master
Key: 0x00010FB9
ShmID: 44859437
Shared memory removed
$
顺便说一句，ipcs 选项 -i id 是对 ipcs 的 POSIX 规范的 Linux 扩展，并且该选项不可用例如，Mac OS X (BSD)。最接近的等价物是 ipcs -m -a | grep "$shmid"，这并不完美。 grep -v '^0x00000000 ' 操作消除了私有共享内存段（在我进行测试的机器上使用了很多）。