读书笔记：第6章 System V消息队列 (7)
《UNIX网络编程：卷2》P122：图6-26
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#include <stdio.h>
#include <stdlib.h>
#include <sys/msg.h>
#include <sys/ipc.h>
#include <string.h>
#include <errno.h>
#define MSG_R 0400
#define MSG_W 0200
#define SVMSG_MODE (MSG_R | MSG_W | MSG_R>>3 | MSG_R>>6)
#define MAX_DATA 64 * 1024
#define MAX_NMESG 4096
#define MAX_NIDS 4096
int max_mesg;
struct mymesg {
long type;
char data[MAX_DATA];
}mesg;
int main(int argc, char *argv[])
{
int i, j, msqid, qid[MAX_NIDS];
// 创建一个消息队列
if ((msqid = msgget(IPC_PRIVATE, SVMSG_MODE | IPC_CREAT)) < 0) {
fprintf(stderr, "msgget error: %s\n", strerror(errno));
exit(1);
}
// 确定最大消息大小，从65536字节开始测试
mesg.type = 1;
for (i = MAX_DATA; i > 0; i -= 128) {
if (msgsnd(msqid, &mesg, i, 0) == 0) {
fprintf(stderr, "maximum amount of data per message = %4d\n", i);
max_mesg = i;
break;
}
if (errno != EINVAL) // 无错时输出结果
fprintf(stderr, "msgsnd error for length %d\n", i);
}
if (i == 0) {
fprintf(stderr, "i == 0\n");
exit(1);
}
msgctl(msqid, IPC_RMID, NULL); // 删除消息队列
// 确定一个队列中可放置多少不同大小的消息
mesg.type = 1;
for (i = 8; i <= max_mesg; i *= 2) { // 消息大小
// 创建一个消息队列
if ((msqid = msgget(IPC_PRIVATE, SVMSG_MODE | IPC_CREAT)) < 0) {
fprintf(stderr, "msgget error: %s\n", strerror(errno));
exit(1);
}
for (j = 0; j < MAX_NMESG; j++) { // 消息数
// 在指定消息队列中放置消息
if (msgsnd(msqid, &mesg, i, IPC_NOWAIT) != 0) {
if (errno == EAGAIN)
break;
fprintf(stderr, "msgsnd error, i = %4d, j = %4d\n", j, i);
break;
}
}
printf("%4d %4d-byte message were placed noto queue, ", j, i);
printf(" %4d bytes total\n", i * j);
msgctl(msqid, IPC_RMID, NULL); // 删除消息队列
}
// 确定同时可打开多少标识符
mesg.type = 1;
for (i = 0; i <= MAX_NIDS; i++) {
// 创建一个消息队列
if ((qid[i] = msgget(IPC_PRIVATE, SVMSG_MODE | IPC_CREAT)) == -1) {
printf("%4d identifiers open at once\n", i);
break;
}
}
for (j = 0; j < i; j++)
msgctl(qid[j], IPC_RMID, NULL); // 移出消息队列
exit(0);
}
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本人的测试平台为：
$ uname -a Linux user 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
运行程序：
$ ./limits maximum amount of data per message = 8192 2048 8-byte message were placed noto queue, 16384 bytes total 1024 16-byte message were placed noto queue, 16384 bytes total 512 32-byte message were placed noto queue, 16384 bytes total 256 64-byte message were placed noto queue, 16384 bytes total 128 128-byte message were placed noto queue, 16384 bytes total 64 256-byte message were placed noto queue, 16384 bytes total 32 512-byte message were placed noto queue, 16384 bytes total 16 1024-byte message were placed noto queue, 16384 bytes total 8 2048-byte message were placed noto queue, 16384 bytes total 4 4096-byte message were placed noto queue, 16384 bytes total 2 8192-byte message were placed noto queue, 16384 bytes total 3997 identifiers open at once