From 0e75b541df04d51fbe8cc94490b7aa30d1f12b19 Mon Sep 17 00:00:00 2001
From: Aryadev Chavali <aryadev@aryadevchavali.com>
Date: Fri, 13 Feb 2026 00:07:24 +0000
Subject: [PATCH] vec: vec_try_append

Essentially a method to attempt to append data but without doing any
reallocation - stay within the bounds of the capacity.
---
 include/alisp/vec.h |  3 +++
 src/vec.c           | 16 +++++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/include/alisp/vec.h b/include/alisp/vec.h
index 035021b..50cb4f9 100644
--- a/include/alisp/vec.h
+++ b/include/alisp/vec.h
@@ -36,7 +36,10 @@ void vec_init(vec_t *, u64);
 void vec_free(vec_t *);
 u8 *vec_data(vec_t *);
 
+// Append, possibly reallocating memory
 void vec_append(vec_t *, const void *const, u64);
+// Try to append without allocating memory
+bool vec_try_append(vec_t *, const void *const, u64);
 void vec_ensure_free(vec_t *, u64);
 void vec_clone(vec_t *, vec_t *);
 
diff --git a/src/vec.c b/src/vec.c
index e4b9d6f..c522f96 100644
--- a/src/vec.c
+++ b/src/vec.c
@@ -81,10 +81,24 @@ void vec_append(vec_t *vec, const void *const ptr, u64 size)
   if (!vec)
     return;
   vec_ensure_free(vec, size);
-  memcpy(vec_data(vec) + vec->size, ptr, size);
+  if (ptr)
+    memcpy(vec_data(vec) + vec->size, ptr, size);
   vec->size += size;
 }
 
+bool vec_try_append(vec_t *vec, const void *const ptr, u64 size)
+{
+  if (!vec || vec->capacity - vec->size < size)
+    return false;
+  if (ptr)
+  {
+    void *newptr = vec_data(vec) + vec->size;
+    memcpy(newptr, ptr, size);
+  }
+  vec->size += size;
+  return true;
+}
+
 void vec_clone(vec_t *dest, vec_t *src)
 {
   if (!src || !dest)