lib/vec: vec_reset and vec_pop

include/arl/lib/vec.h

@@ -31,9 +31,13 @@ typedef struct
 
 static_assert(sizeof(vec_t) == 64, "Expected sizeof(vec_t) to be 64");
 
+// standard old appending methods
 void vec_append(vec_t *vec, const void *const ptr, u64 size);
 void vec_append_byte(vec_t *vec, u8 byte);
 
+// vector-as-a-stack
+u8 *vec_pop(vec_t *vec, u64 size);
+
 // Returns pointer to the start of the buffer VEC is currently using to store
 // data (either its inline buffer or the heap buffer).
 void *vec_data(vec_t *vec);
@@ -43,8 +47,13 @@ void vec_ensure_capacity(vec_t *vec, u64 capacity);
 
 // Ensure VEC has at least SIZE bytes free
 void vec_ensure_free(vec_t *vec, u64 size);
+
+// Free the memory associated with the vector
 void vec_free(vec_t *vec);
 
+// Reset a vector while preserving any allocations
+void vec_reset(vec_t *vec);
+
 // Copy all data from V1 into V2.
 void vec_clone(vec_t *v2, vec_t *v1);
 

src/lib/vec.c

@@ -31,6 +31,14 @@ void vec_append_byte(vec_t *vec, u8 byte)
   ++vec->size;
 }
 
+u8 *vec_pop(vec_t *vec, u64 size)
+{
+  if (!vec || vec->size < size)
+    return NULL;
+  vec->size -= size;
+  return (u8 *)vec_data(vec) + vec->size;
+}
+
 void *vec_data(vec_t *vec)
 {
   if (!vec)
@@ -89,6 +97,14 @@ void vec_free(vec_t *vec)
   memset(vec, 1, sizeof(*vec));
 }
 
+void vec_reset(vec_t *vec)
+{
+  if (!vec)
+    return;
+  memset(vec_data(vec), 0, vec->capacity);
+  vec->size = 0;
+}
+
 void vec_clone(vec_t *v2, vec_t *v1)
 {
   if (!v1 || !v2)