refactor(ltm): remove some code duplication

ltm/src/_include/ltm/template_internal.h

@@ -96,6 +96,12 @@ typedef struct ltm_instance_block {
 
 ltm_err ltm_instance_block_init(ltm_instance_block **out);
 
+/**
+ * Add a new block to the instance with the given type.
+ */
+ltm_err ltm_instance_block_add(ltm_instance_block **out, ltm_instance *instance,
+                               const char *name, ltm_instance_block_type type);
+
 struct ltm_instance {
   const ltm_template *template;
   struct {

ltm/src/ltm_instance.c

@@ -106,7 +106,9 @@ ltm_err ltm_template_instantiate(ltm_instance **out,
     } break;
     case ltm_template_block_type_var:
     case ltm_template_block_type_nested:
-      *vars = &instance->blocks.tail->next;
+      // Account for the possibility a template starts with a placeholder
+      *vars = instance->blocks.tail != NULL ? &instance->blocks.tail->next
+                                            : &instance->blocks.head;
       vars++;
       break;
     }
@@ -117,20 +119,21 @@ ltm_err ltm_template_instantiate(ltm_instance **out,
   return ltm_err_ok;
 }
 
-ltm_err ltm_instance_block_add_var(ltm_instance *instance, const char *name,
+ltm_err ltm_instance_block_add(ltm_instance_block **out, ltm_instance *instance,
-                                   ltm_instance_block_type type, void *data,
+                               const char *name, ltm_instance_block_type type) {
-                                   size_t len) {
   const ltm_template *template = instance->template;
 
   ltm_template_block_name *block_name = NULL;
   size_t i = 0;
 
-  for (i = 0; i < template->names.len; i++) {
+  while (i < template->names.len) {
     block_name = &template->names.arr[i];
 
     if (strncmp(name, block_name->name.s, block_name->name.len) == 0) {
       break;
     }
+
+    i++;
   }
 
   if (i == template->names.len) {
@@ -138,8 +141,22 @@ ltm_err ltm_instance_block_add_var(ltm_instance *instance, const char *name,
   }
 
   ltm_template_block *template_block = &template->blocks.arr[block_name->index];
+  bool correct_type = false;
 
-  if (template_block->type != ltm_template_block_type_var) {
+  switch (type) {
+  case ltm_instance_block_type_nested:
+    correct_type = template_block->type == ltm_template_block_type_nested;
+    break;
+  case ltm_instance_block_type_buf:
+  case ltm_instance_block_type_buf_owned:
+  case ltm_instance_block_type_file:
+  case ltm_instance_block_type_file_owned:
+  case ltm_instance_block_type_fn:
+    correct_type = template_block->type == ltm_template_block_type_var;
+    break;
+  }
+
+  if (!correct_type) {
     return ltm_err_wrong_block_type;
   }
 
@@ -147,57 +164,39 @@ ltm_err ltm_instance_block_add_var(ltm_instance *instance, const char *name,
   LTM_RES(ltm_instance_block_init(&block));
 
   block->type = type;
-  block->data.ptr = data;
-  block->data.len = len;
 
-  // We insert the block in the linked list and replace its next pointer as the
+  // Insert the block in the linked list
-  // new attachment point for this variable
   block->next = *instance->vars[i];
   *instance->vars[i] = block;
   instance->vars[i] = &block->next;
 
+  *out = block;
+
+  return ltm_err_ok;
+}
+
+ltm_err ltm_instance_block_add_var(ltm_instance *instance, const char *name,
+                                   ltm_instance_block_type type, void *data,
+                                   size_t len) {
+  ltm_instance_block *block;
+  LTM_RES(ltm_instance_block_add(&block, instance, name, type));
+
+  block->data.ptr = data;
+  block->data.len = len;
+
   return ltm_err_ok;
 }
 
 ltm_err ltm_instance_block_add_var_fn(ltm_instance *instance, const char *name,
                                       ltm_data_fn fn, void *data, size_t len) {
-  const ltm_template *template = instance->template;
-
-  ltm_template_block_name *block_name = NULL;
-  size_t i = 0;
-
-  for (i = 0; i < template->names.len; i++) {
-    block_name = &template->names.arr[i];
-
-    if (strncmp(name, block_name->name.s, block_name->name.len) == 0) {
-      break;
-    }
-  }
-
-  if (i == template->names.len) {
-    return ltm_err_not_found;
-  }
-
-  ltm_template_block *template_block = &template->blocks.arr[block_name->index];
-
-  if (template_block->type != ltm_template_block_type_var) {
-    return ltm_err_wrong_block_type;
-  }
-
   ltm_instance_block *block;
-  LTM_RES(ltm_instance_block_init(&block));
+  LTM_RES(ltm_instance_block_add(&block, instance, name,
+                                 ltm_instance_block_type_fn));
 
-  block->type = ltm_instance_block_type_fn;
   block->fn = fn;
   block->data.ptr = data;
   block->data.len = len;
 
-  // We insert the block in the linked list and replace its next pointer as the
-  // new attachment point for this variable
-  block->next = *instance->vars[i];
-  *instance->vars[i] = block;
-  instance->vars[i] = &block->next;
-
   return ltm_err_ok;
 }
 
@@ -205,19 +204,25 @@ ltm_err ltm_instance_block_add_nested(ltm_instance **out,
                                       ltm_instance *instance,
                                       const char *name) {
   const ltm_template *template = instance->template;
-  bool matched = false;
 
+  ltm_template_block_name *block_name = NULL;
   size_t i = 0;
-  for (i = 0; i < template->names.len && !matched; i++) {
+
-    ltm_template_block_name *block_name = &template->names.arr[i];
+  while (i < template->names.len) {
-    matched = strncmp(name, block_name->name.s, block_name->name.len) == 0;
+    block_name = &template->names.arr[i];
+
+    if (strncmp(name, block_name->name.s, block_name->name.len) == 0) {
+      break;
+    }
+
+    i++;
   }
 
-  if (!matched) {
+  if (i == template->names.len) {
     return ltm_err_not_found;
   }
 
-  ltm_template_block *template_block = &template->blocks.arr[i];
+  ltm_template_block *template_block = &template->blocks.arr[block_name->index];
 
   if (template_block->type != ltm_template_block_type_nested) {
     return ltm_err_wrong_block_type;