添加以前的作业

exp0.5/task53.c

@@ -0,0 +1,197 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <time.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#define INTERVAL_SEC 10
+#define LOG_FILE "log"
+
+static unsigned int compute_hash(const char *data, size_t len)
+{
+    unsigned int hash =0;
+    const unsigned char *p = (const unsigned char *)data;
+    size_t i,n = len /4;
+
+    for ( i = 0; i < n; i++)
+    {
+        unsigned int val = (unsigned int)p[i * 4] | ((unsigned int)p[i * 4 + 1] << 8) 
+                         | ((unsigned int)p[i * 4 + 2] << 16) | ((unsigned int)p[i * 4 + 3] << 24);
+        hash += val;    
+    }
+    
+    size_t rem = len % 4,base = n*4;
+    for ( i = 0; i < rem; i++)
+    {
+        hash += (unsigned int)p[base + i];
+    }
+    return hash;
+}
+
+
+static char *read_file(const char *path,size_t *out_len)
+{
+    int fd = open(path,O_RDONLY);
+    if (fd < 0)
+    {
+        return NULL;
+    }
+    
+    off_t size = lseek(fd,0,SEEK_END);
+    if (size < 0)
+    {
+        close(fd);
+        return NULL;
+    }
+    lseek(fd,0,SEEK_SET);
+
+    char *buf = malloc((size_t)size + 1);
+    if (!buf)
+    {
+        close(fd);
+        return NULL;
+    }
+    
+    ssize_t n = read(fd,buf,(size_t)size);
+    if (n < 0)
+    {
+        free(buf);
+        close(fd);
+        return NULL;
+    }
+
+    buf[n] = '\0';
+    *out_len = (size_t)n;
+    close(fd);
+    return buf;   
+}
+
+static void write_log(unsigned int hash)
+{
+    FILE *fp = fopen(LOG_FILE,"a");
+    if (!fp)
+    {
+        return;
+    }
+    
+    time_t now = time(NULL);
+    struct tm *tm_info = localtime(&now);
+    char time_str[20];
+    strftime(time_str,sizeof(time_str),"%Y-%m-%d %H:%M:%S",tm_info);
+
+    fprintf(fp,"%s  hash=%u\n",time_str,hash);
+    fclose(fp);
+}
+
+static void daemonize(void)
+{
+    pid_t pid = fork();
+    if (pid < 0)
+    {
+        exit(1);
+    }
+    if (pid > 0)
+    {
+        exit(0);
+    }
+
+    setsid();
+    umask(0);
+
+    close(STDIN_FILENO);
+    close(STDOUT_FILENO);
+    close(STDERR_FILENO);
+}
+
+
+int main(int argc,char *argv[])
+{
+    //自检模式
+    if (argc > 1 && strcmp(argv[1],"test") == 0)
+    {
+        /* 测试1: 不同内容应产生不同hash值 */
+        printf("自检模式\n");
+
+        const char *test_str = "Hello, World!";
+        unsigned int h1 = compute_hash(test_str,strlen(test_str));
+        
+        const char *test_str2 = "Hello, world!"; // 注意 'W' 和 'w'
+        unsigned int h2 = compute_hash(test_str2,strlen(test_str2));
+
+        printf("测试1: hash1=%u, hash2=%u\n",h1,h2);
+        if (h1 != h2)
+            printf("通过: 不同内容 -> 不同hash值\n");
+        else
+            printf("失败: 不同内容应产生不同的hash值\n");
+
+        
+            /* 测试2: 相同内容应产生相同hash值 */
+        unsigned int h3 = compute_hash(test_str,strlen(test_str));
+        printf("测试2: hash3=%u\n",h3);
+        if (h1 == h3)
+            printf("通过: 相同内容 -> 相同hash值\n");
+        else
+            printf("失败: 相同内容应产生相同的hash值\n");
+
+        /* 测试3: 读取自身并计算hash */
+        size_t len;
+        char *self = read_file("task53.c",&len);
+        if (self)
+        {
+            unsigned int hself = compute_hash(self,len);
+            printf("测试3: 自身hash=%u, 文件大小=%zu字节\n",hself,len);
+            free(self);
+        }
+        return 0;
+    }
+
+    /*
+     * 守护进程模式
+     * -f 表示前台运行(不调用daemonize), 便于测试
+     * 第二个参数可指定检查间隔秒数
+     */
+    int foreground = (argc > 1 && strcmp(argv[1],"-f") == 0);
+    int interval = INTERVAL_SEC;
+    if (argc > 2) interval = atoi(argv[2]);
+    if (interval <= 0) interval = INTERVAL_SEC;
+
+    if (!foreground) 
+    {
+        daemonize();
+    }
+
+    size_t len;
+    char *prev_data = read_file("test.log",&len);
+    if (!prev_data) return 1;
+    unsigned int prev_hash = compute_hash(prev_data,len);
+    
+    while (1)
+    {
+        sleep(interval);
+
+        size_t cur_len;
+        char *cur_data = read_file("test.log",&cur_len);
+        if (!cur_data)
+        {
+            continue;
+        }
+
+        unsigned int cur_hash = compute_hash(cur_data,cur_len);
+        if (cur_hash != prev_hash)
+        {
+            write_log(cur_hash);
+            free(prev_data);
+            prev_data = cur_data;
+            prev_hash = cur_hash;
+        }
+        else
+        {
+            free(cur_data);
+        }
+    }
+    free(prev_data);
+    return 0;
+}