1 files changed, 53 insertions, 2 deletions

diff --git a/source/kit/string_builder.h b/source/kit/string_builder.h
index 322f6e2..5cc12ee 100644
--- a/source/kit/string_builder.h
+++ b/source/kit/string_builder.h
@@ -23,7 +23,11 @@ typedef KIT_DA(char) kit_str_builder_t;
 
 static kit_str_builder_t kit_str_build(kit_str_t        s,
                                        kit_allocator_t *alloc) {
+  assert(s.size >= 0 && (s.size == 0 || s.values != NULL));
   kit_str_builder_t builder;
+  memset(&builder, 0, sizeof builder);
+  if (s.size < 0 || (s.size != 0 && s.values == NULL))
+    return builder;
   KIT_DA_INIT(builder, s.size, alloc);
   assert(builder.size == s.size);
   if (builder.size == s.size)
@@ -31,8 +35,19 @@ static kit_str_builder_t kit_str_build(kit_str_t        s,
   return builder;
 }
 
-static kit_status_t kit_str_append(kit_str_builder_t *a,
-                                   kit_str_t          b) {
+static kit_str_builder_t kit_substr_build(kit_str_t s, i64 index,
+                                          i64              size,
+                                          kit_allocator_t *alloc) {
+  assert(index + size <= s.size);
+  if (index + size > s.size) {
+    kit_str_builder_t builder;
+    memset(&builder, 0, sizeof builder);
+    return builder;
+  }
+  return kit_str_build(kit_str(size, s.values + index), alloc);
+}
+
+static s32 kit_str_append(kit_str_builder_t *a, kit_str_t b) {
   assert(a != NULL);
   if (a == NULL)
     return KIT_ERROR_INVALID_ARGUMENT;
@@ -46,6 +61,38 @@ static kit_status_t kit_str_append(kit_str_builder_t *a,
   return KIT_OK;
 }
 
+static s32 kit_str_insert(kit_str_builder_t *a, i64 index,
+                          kit_str_t b) {
+  assert(a != NULL && index >= 0 && index <= a->size);
+  if (a == NULL || index < 0 || index > a->size)
+    return KIT_ERROR_INVALID_ARGUMENT;
+  if (b.size <= 0)
+    return KIT_OK;
+  i64 n = a->size;
+  KIT_DA_RESIZE(*a, n + b.size);
+  if (a->size != n + b.size)
+    return KIT_ERROR_BAD_ALLOC;
+  if (index < n)
+    memmove(a->values + (index + b.size), a->values + index,
+            n - index);
+  memcpy(a->values + index, b.values, b.size);
+  return KIT_OK;
+}
+
+static s32 kit_str_erase(kit_str_builder_t *a, i64 index, i64 size) {
+  assert(a != NULL && index >= 0 && size >= 0 &&
+         index + size <= a->size);
+  if (a == NULL || index < 0 || size < 0 || index + size > a->size)
+    return KIT_ERROR_INVALID_ARGUMENT;
+  if (size <= 0)
+    return KIT_OK;
+  if (index + size < a->size)
+    memmove(a->values + index, a->values + (index + size),
+            a->size - index - size);
+  KIT_DA_RESIZE(*a, a->size - size);
+  return KIT_OK;
+}
+
 #ifdef __GNUC__
 #  pragma GCC            pop_options
 #  pragma GCC diagnostic pop
@@ -57,7 +104,11 @@ static kit_status_t kit_str_append(kit_str_builder_t *a,
 
 #ifndef KIT_DISABLE_SHORT_NAMES
 #  define str_builder_t kit_str_builder_t
+#  define str_build kit_str_build
+#  define substr_build kit_substr_build
 #  define str_append kit_str_append
+#  define str_insert kit_str_insert
+#  define str_erase kit_str_erase
 #endif
 
 #endif