monocoque initial commit

tests/usesharedmemory.c

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+/**
+ * Simple program demonstrating shared memory in POSIX systems.
+ *
+ * This is the consumer process
+ *
+ * Figure 3.18
+ *
+ * @author Gagne, Galvin, Silberschatz
+ * Operating System Concepts - Ninth Edition
+ * Copyright John Wiley & Sons - 2013
+ *
+ * modifications by dheller@cse.psu.edu, 31 Jan. 2014
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/shm.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <errno.h>
+#include <string.h>
+
+void display(char* prog, char* bytes, int n);
+
+int main(void)
+{
+    const char* name = "/shm-example";    // file name
+    const int SIZE = 4096;        // file size
+
+    int shm_fd;       // file descriptor, from shm_open()
+    char* shm_base;   // base address, from mmap()
+
+    /* open the shared memory segment as if it was a file */
+    shm_fd = shm_open(name, O_RDONLY, 0666);
+    if (shm_fd == -1)
+    {
+        printf("cons: Shared memory failed: %s\n", strerror(errno));
+        exit(1);
+    }
+
+    /* map the shared memory segment to the address space of the process */
+    shm_base = mmap(0, SIZE, PROT_READ, MAP_SHARED, shm_fd, 0);
+    if (shm_base == MAP_FAILED)
+    {
+        printf("cons: Map failed: %s\n", strerror(errno));
+        // close and unlink?
+        exit(1);
+    }
+
+    /* read from the mapped shared memory segment */
+    display("cons", shm_base, 64);    // first as bytes, then as a string
+    printf("%s", shm_base);
+
+    /* remove the mapped shared memory segment from the address space of the process */
+    if (munmap(shm_base, SIZE) == -1)
+    {
+        printf("cons: Unmap failed: %s\n", strerror(errno));
+        exit(1);
+    }
+
+    /* close the shared memory segment as if it was a file */
+    if (close(shm_fd) == -1)
+    {
+        printf("cons: Close failed: %s\n", strerror(errno));
+        exit(1);
+    }
+
+    /* remove the shared memory segment from the file system */
+    if (shm_unlink(name) == -1)
+    {
+        printf("cons: Error removing %s: %s\n", name, strerror(errno));
+        exit(1);
+    }
+
+    return 0;
+}
+
+void display(char* prog, char* bytes, int n)
+{
+    printf("display: %s\n", prog);
+    for (int i = 0; i < n; i++)
+    {
+        printf("%02x%c", bytes[i], ((i+1)%16) ? ' ' : '\n');
+    }
+    printf("\n");
+}