Mon 16 Mar 11:09:06 CET 2026

src/shm.c

@@ -0,0 +1,76 @@
+/*
+ * Shared Memory Control
+ */
+
+#include "config.h"
+
+#if  SHM>0
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <sys/mman.h>
+#include <sys/stat.h>        /* For mode constants */
+#include <fcntl.h>           /* For O_* constants */
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "shm.h"
+
+/*
+  Allocate entire SHM segment.
+  *buf must be either 0 or a valid vaddr
+  key must start with /
+*/
+int allocate_shm(char *key, int bufsize, void **buf) {
+  int oflags  = O_RDWR|O_CREAT;
+  int     fd  = shm_open(key, oflags, 0644 );
+  ftruncate(fd, bufsize);
+  *buf = mmap(*buf, bufsize, PROT_READ|PROT_WRITE, MAP_SHARED|(*buf?MAP_FIXED:0), fd, 0);
+  shm_header_entry_t *root = (shm_header_entry_t*)buf;
+  root->type=SMS_ROOT;
+  root->addr=0;
+  root->size=1;
+  return fd;
+}
+
+int free_shm(char *key) {
+  return shm_unlink(key);
+}
+/*
+  Open SHm segment
+  *buf must be either 0 or a valid vaddr
+*/
+int open_shm(char *key, int *bufsize, void **buf) {
+  int oflags  = O_RDWR;
+  int     fd  = shm_open(key, oflags, 0644 );
+  struct stat sb;
+	fstat(fd, &sb);
+	*bufsize = sb.st_size;
+  *buf = mmap(*buf, *bufsize, PROT_READ|PROT_WRITE, MAP_SHARED|(*buf?MAP_FIXED:0), fd, 0);
+  return fd;
+}
+
+void close_shm(int fd) {
+  close(fd);
+}
+
+/*
+  Allocate space for a structure or data segment from SHM buffer
+*/
+void *allocate_section(void *buf,shm_section_t type,int size) {
+  shm_header_entry_t *root = (shm_header_entry_t*)buf;  // size is next free entry index in the  header segment
+  shm_header_entry_t *top  = (shm_header_entry_t*)&((char*)buf)[root->size*sizeof(shm_header_entry_t)]; 
+  if (root->size==1) {
+    top->addr=sizeof(shm_header_entry_t);
+  } else {
+    shm_header_entry_t *last = (shm_header_entry_t*)(top-sizeof(shm_header_entry_t));
+    top->addr=last->addr+last->size;
+  }  
+  top->size=size;
+  root->size++;
+  return 0;
+}
+#endif /* SHM */