Add prefixes to arrays

1 files changed, 22 insertions, 7 deletions

diff --git a/array.c b/array.c
index d436414..f8e9b82 100644
--- a/array.c
+++ b/array.c
@@ -39,6 +39,7 @@ struct array_t
     gssize     n_elements;	/* Number of elements in use, not including
 				 * the nul terminator
 				 */
+    gssize     n_prefix_bytes;	/* Number of data bytes used for the application prefix */
     align_t    data[1];
 };
 
@@ -65,7 +66,10 @@ array_free (void *data, const int *magic)
 static void
 nul_terminate (array_t *array)
 {
-    char *end = (char *)array->data + array->n_elements * array->element_size;
+    char *end = (char *)array->data;
+
+    end += array->n_prefix_bytes;
+    end += array->n_elements * array->element_size;
 
     memset (end, 0, array->element_size);
 }
@@ -78,6 +82,7 @@ realloc_array (array_t *array, int n_elements)
     /* FIXME: overflow? */
     n_bytes = NUL_STRUCT_OFFSET (array_t, data);
     n_bytes += (n_elements + 1) * array->element_size;
+    n_bytes += array->n_prefix_bytes;
     
     if (n_bytes > array->n_bytes)
     {
@@ -97,12 +102,13 @@ realloc_array (array_t *array, int n_elements)
 }
 
 static void *
-array_new (int element_size, const int *magic)
+array_new (int element_size, const int *magic, int n_prefix_bytes)
 {
     array_t *array = g_new (array_t, 1);
     
     array->magic = magic;
     array->element_size = element_size;
+    array->n_prefix_bytes = n_prefix_bytes;
     array->n_bytes = sizeof (array_t);
     array->n_elements = 0;
 
@@ -117,13 +123,16 @@ array_delete_head (void *data, const int *magic, gssize n_elements)
     array_t *array = get_array (data, magic);
     int n_bytes = n_elements * array->element_size;
     int n_total = array->n_elements * array->element_size;
+    char *first;
 
     if (n_elements < 0 || n_elements > array->n_elements)
 	n_bytes = n_total;
     
     /* FIXME: this should be done in constant time */
+
+    first = (char *)array->data + array->n_prefix_bytes;
     
-    memmove (array->data, (char *)array->data + n_bytes, n_total - n_bytes);
+    memmove (first, first + n_bytes, n_total - n_bytes);
     
     array->n_elements -= n_elements;
     
@@ -158,7 +167,7 @@ array_append_undefined (void *data,
     nul_terminate (array);
 
     if (tail)
-	*tail = (char *)array->data + array->element_size * (array->n_elements - n_elements);
+	*tail = (char *)array->data + array->n_prefix_bytes + array->element_size * (array->n_elements - n_elements);
 
     return array->data;
 }
@@ -205,7 +214,13 @@ static const int arr_t_magic;
 nul_ptr_t
 nul_array_new (int element_size)
 {
-    return array_new (element_size, &arr_t_magic);
+    return array_new (element_size, &arr_t_magic, 0);
+}
+
+nul_ptr_t
+nul_array_new_prefix (int element_size, int prefix_size)
+{
+    return array_new (element_size, &arr_t_magic, prefix_size);
 }
 
 nul_ptr_t
@@ -256,7 +271,7 @@ static const int parr_t_magic;
 void **
 nul_ptr_array_new (void)
 {
-    return array_new (sizeof (void *), &parr_t_magic);
+    return array_new (sizeof (void *), &parr_t_magic, 0);
 }
 
 void **
@@ -285,7 +300,7 @@ static const int string_t_magic;
 nul_string_t *
 nul_string_new (void)
 {
-    return array_new (sizeof (char), &string_t_magic);
+    return array_new (sizeof (char), &string_t_magic, 0);
 }
 
 void