add mmaping of exact blocks

namely file headers needs to be accessed unaligned and exactly as given,
this adds mmap functions to create mmap objects to do this.

src/backend/mmap.c

@@ -214,6 +214,70 @@ lumiera_mmap_init (LumieraMMap self, LumieraFile file, off_t start, size_t size)
   return NULL;
 }
 
+
+LumieraMMap
+lumiera_mmap_init_exact (LumieraMMap self, LumieraFile file, off_t start, size_t size)
+{
+  TRACE (mmap_dbg);
+
+  REQUIRE (self);
+  REQUIRE (file);
+  REQUIRE (start >= 0);
+  REQUIRE (size);
+
+  LumieraFiledescriptor descriptor = file->descriptor;
+
+  int fd = lumiera_file_handle_acquire (file);
+  TRACE (mmap_dbg, "got fd %d", fd);
+  if (fd == -1)
+    goto efile;
+
+  if ((off_t)(start + size) > descriptor->stat.st_size)
+    {
+      /* request past the end */
+      if ((descriptor->flags & O_ACCMODE) == O_RDWR)
+        {
+          /* extend file (writable) */
+          if (ftruncate (fd, start+size) == -1)
+            {
+              LUMIERA_ERROR_SET (mmap, ERRNO, lumiera_filedescriptor_name (file->descriptor));
+              goto etruncate;
+            };
+          descriptor->stat.st_size = descriptor->realsize = start+size;
+        }
+    }
+
+  TODO ("use resourcecllector here");
+  void* addr = mmap (NULL,
+                     size,
+                     (descriptor->flags & O_ACCMODE) == O_RDONLY ? PROT_READ : PROT_READ|PROT_WRITE,
+                     MAP_SHARED,
+                     fd,
+                     start);
+
+  INFO_IF (addr==(void*)-1, mmap_dbg, "mmap failed %s", strerror (errno));
+  ENSURE (errno == 0 || errno == ENOMEM, "unexpected mmap error %s", strerror (errno));
+
+  llist_init (&self->cachenode);
+  llist_init (&self->searchnode);
+
+  self->start = start;
+  self->size = size;
+  self->address = addr;
+  self->refmap = NULL;
+  self->refcnt = 1;
+  lumiera_mmapcache_announce (self);
+
+  lumiera_file_handle_release (file);
+  return self;
+
+ etruncate:
+ efile:
+  lumiera_file_handle_release (file);
+  return NULL;
+}
+
+
 LumieraMMap
 lumiera_mmap_new (LumieraFile file, off_t start, size_t size)
 {
@@ -231,6 +295,23 @@ lumiera_mmap_new (LumieraFile file, off_t start, size_t size)
 }
 
 
+LumieraMMap
+lumiera_mmap_new_exact (LumieraFile file, off_t start, size_t size)
+{
+  TRACE (mmap_dbg);
+
+  LumieraMMap self = lumiera_mmapcache_mmap_acquire ();
+
+  if (lumiera_mmap_init_exact (self, file, start, size))
+    return self;
+  else
+    {
+      lumiera_free (self);
+      return NULL;
+    }
+}
+
+
 void
 lumiera_mmap_delete (LumieraMMap self)
 {

src/backend/mmap.h

@@ -69,14 +69,37 @@ struct lumiera_mmap_struct
   short* refmap;       // TODO flexible array?
 };
 
-
+/**
+ * Initialize a MMap object.
+ * The mmap objects are aligned and shifted by the chunksize and bias defined for the file
+ * @param self the mmap object to be initialized
+ * @param file file from which to map
+ * @param start offset in file which must be part of the mmaped region
+ * @param size minimum size after start to map
+ * @return self on success or NULL on error
+ */
 LumieraMMap
 lumiera_mmap_init (LumieraMMap self, LumieraFile file, off_t start, size_t size);
 
+/**
+ * Initialize a MMap object.
+ * Maps exactly the given range
+ * @param self the mmap object to be initialized
+ * @param file file from which to map
+ * @param start offset in file which must be part of the mmaped region
+ * @param size minimum size after start to map
+ * @return self on success or NULL on error
+ */
+LumieraMMap
+lumiera_mmap_init_exact (LumieraMMap self, LumieraFile file, off_t start, size_t size);
+
 
 LumieraMMap
 lumiera_mmap_new (LumieraFile file, off_t start, size_t size);
 
+LumieraMMap
+lumiera_mmap_new_exact (LumieraFile file, off_t start, size_t size);
+
 
 /**
  * Translate a 'external' offset to a address in memory

tests/30mmap.tests

@@ -40,6 +40,10 @@ TEST "accessing file" file_access <<END
 return: 0
 END
 
+TEST "exact mmap" exact_mmap <<END
+return: 0
+END
+
 TEST "mmaped secion" mmap_section <<END
 return: 0
 END

tests/backend/test-filemmap.c

@@ -294,6 +294,25 @@ TEST (file_access)
 
 
 
+TEST (exact_mmap)
+{
+  lumiera_backend_init ();
+  LumieraFile file = lumiera_file_new (",tmp-filemmap", LUMIERA_FILE_RECREATE);
+
+  LumieraMMap map = lumiera_mmap_new_exact (file, 0, 6);
+
+  char* addr = lumiera_mmap_address (map, 1);
+
+  strcpy (addr, "test");
+
+  lumiera_mmap_delete (map);
+
+  lumiera_file_delete (file);
+  lumiera_backend_destroy ();
+}
+
+
+
 TEST (mmap_section)
 {
   lumiera_backend_init ();