Separate field iterator logic from pb_decode to pb_common.

1 files changed, 88 insertions, 0 deletions

diff --git a/pb_common.c b/pb_common.c
new file mode 100644
index 00000000..de217699
--- /dev/null
+++ b/pb_common.c
@@ -0,0 +1,88 @@
+/* pb_common.c: Common support functions for pb_encode.c and pb_decode.c.
+ *
+ * 2014 Petteri Aimonen <jpa@kapsi.fi>
+ */
+
+#include "pb_common.h"
+
+void pb_field_iter_begin(pb_field_iter_t *iter, const pb_field_t *fields, void *dest_struct)
+{
+    iter->start = fields;
+    iter->pos = fields;
+    iter->required_field_index = 0;
+    iter->dest_struct = dest_struct;
+    iter->pData = (char*)dest_struct + iter->pos->data_offset;
+    iter->pSize = (char*)iter->pData + iter->pos->size_offset;
+}
+
+bool pb_field_iter_next(pb_field_iter_t *iter)
+{
+    const pb_field_t *prev_field = iter->pos;
+
+    if (prev_field->tag == 0)
+    {
+        /* Handle empty message types, where the first field is already the terminator.
+         * In other cases, the iter->pos never points to the terminator. */
+        return false;
+    }
+    
+    iter->pos++;
+    
+    if (iter->pos->tag == 0)
+    {
+        /* Wrapped back to beginning, reinitialize */
+        pb_field_iter_begin(iter, iter->start, iter->dest_struct);
+        return false;
+    }
+    else
+    {
+        /* Increment the pointers based on previous field size */
+        size_t prev_size = prev_field->data_size;
+    
+        if (PB_ATYPE(prev_field->type) == PB_ATYPE_STATIC &&
+            PB_HTYPE(prev_field->type) == PB_HTYPE_REPEATED)
+        {
+            /* In static arrays, the data_size tells the size of a single entry and
+             * array_size is the number of entries */
+            prev_size *= prev_field->array_size;
+        }
+        else if (PB_ATYPE(prev_field->type) == PB_ATYPE_POINTER)
+        {
+            /* Pointer fields always have a constant size in the main structure.
+             * The data_size only applies to the dynamically allocated area. */
+            prev_size = sizeof(void*);
+        }
+        
+        if (PB_HTYPE(prev_field->type) == PB_HTYPE_REQUIRED)
+        {
+            /* Count the required fields, in order to check their presence in the
+             * decoder. */
+            iter->required_field_index++;
+        }
+    
+        iter->pData = (char*)iter->pData + prev_size + iter->pos->data_offset;
+        iter->pSize = (char*)iter->pData + iter->pos->size_offset;
+        return true;
+    }
+}
+
+bool pb_field_iter_find(pb_field_iter_t *iter, uint32_t tag)
+{
+    const pb_field_t *start = iter->pos;
+    
+    do {
+        if (iter->pos->tag == tag &&
+            PB_LTYPE(iter->pos->type) != PB_LTYPE_EXTENSION)
+        {
+            /* Found the wanted field */
+            return true;
+        }
+        
+        (void)pb_field_iter_next(iter);
+    } while (iter->pos != start);
+    
+    /* Searched all the way back to start, and found nothing. */
+    return false;
+}
+
+