Add support for setting read/write map functions

include/vm_segment.h

@@ -58,5 +58,7 @@ extern vm_segment *vm_segment_create(size_t);
 extern void vm_segment_free(vm_segment *);
 extern vm_8bit vm_segment_get(vm_segment *, size_t);
 extern int vm_segment_set(vm_segment *, size_t, vm_8bit);
+extern int vm_segment_read_map(vm_segment *, size_t, vm_segment_read_fn);
+extern int vm_segment_write_map(vm_segment *, size_t, vm_segment_write_fn);
 
 #endif

src/vm_segment.c

@@ -157,3 +157,29 @@ vm_segment_copy(vm_segment *dest,
 
     return OK;
 }
+
+int
+vm_segment_read_map(vm_segment *segment, 
+                    size_t addr, 
+                    vm_segment_read_fn fn)
+{
+    if (addr >= segment->size) {
+        return ERR_OOB;
+    }
+
+    segment->read_table[addr] = fn;
+    return OK;
+}
+
+int
+vm_segment_write_map(vm_segment *segment,
+                     size_t addr,
+                     vm_segment_write_fn fn)
+{
+    if (addr >= segment->size) {
+        return ERR_OOB;
+    }
+
+    segment->write_table[addr] = fn;
+    return OK;
+}

tests/vm_segment.c

@@ -72,3 +72,24 @@ Test(vm_segment, copy) {
     vm_segment_free(src);
     vm_segment_free(dest);
 }
+
+Test(vm_segment, read_map)
+{
+    // We use some trickery here; I don't want to go to the trouble of
+    // defining a function for this test, so I am just passing in an
+    // arbitrary pointer to junk. As long as the garbage-in, garbage-out
+    // principle holds, we're golden.
+    cr_assert_eq(vm_segment_read_map(segment, 123, (vm_segment_read_fn)456), OK);
+    cr_assert_eq(vm_segment_read_map(segment, 321, (vm_segment_read_fn)456), ERR_OOB);
+
+    cr_assert_eq(segment->read_table[123], (vm_segment_read_fn)456);
+}
+
+Test(vm_segment, write_map)
+{
+    // See the read_map test for more details on the following trickery
+    cr_assert_eq(vm_segment_write_map(segment, 123, (vm_segment_write_fn)456), OK);
+    cr_assert_eq(vm_segment_write_map(segment, 321, (vm_segment_write_fn)456), ERR_OOB);
+
+    cr_assert_eq(segment->write_table[123], (vm_segment_write_fn)456);
+}