util: Implement dynamic vector array for storing AST children

Previously, we lacked a dynamic array for storing children elements in
our abstract syntax tree (AST). This commit introduces a new
implementation that dynamically adjusts its capacity as elements are
added, using a doubling strategy.

I considered two approaches for managing the vector's memory
allocation: allocating it on the heap, or providing a vector_init
function that allocates only the items array. Ultimately, I decided to
provide a vector_new function for instantiating the vector, as this
aligns with the expected usage pattern when there is a destroy function.

With this new implementation, we can efficiently store and manage AST
children, enabling more flexible and expressive tree structures.

Signed-off-by: Johnny Richard <johnny@johnnyrichard.com>

2 files changed, 118 insertions, 0 deletions

diff --git a/src/vector.c b/src/vector.c
new file mode 100644
index 0000000..99ebffc
--- /dev/null
+++ b/src/vector.c
@@ -0,0 +1,83 @@
+/*
+* Copyright (C) 2023 Johnny Richard
+*
+* This program is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation, either version 3 of the License, or
+* (at your option) any later version.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+#include "vector.h"
+#include <assert.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+vector_t*
+vector_new()
+{
+  vector_t *vector = (vector_t *) malloc(sizeof(vector_t));
+
+  if (vector == NULL) {
+    fprintf(stderr, "failed to create vector: %s\n", strerror(errno));
+    exit(EXIT_FAILURE);
+  }
+
+  vector->items = calloc(sizeof(void *), VECTOR_INITIAL_CAPACITY);
+
+  if (vector->items == NULL) {
+    free(vector);
+    fprintf(stderr, "failed to create vector items: %s\n", strerror(errno));
+    exit(EXIT_FAILURE);
+  }
+
+  vector->size = 0;
+  vector->capacity = VECTOR_INITIAL_CAPACITY;
+  return vector;
+}
+
+void
+vector_resize(vector_t *vector)
+{
+  vector->capacity = vector->capacity * 2;
+  vector->items = realloc(vector->items, sizeof(void *) * vector->capacity);
+  if (vector->items == NULL) {
+    vector_destroy(vector);
+    fprintf(stderr, "failed to reallocat memory for vector: %s\n", strerror(errno));
+    exit(EXIT_FAILURE);
+  }
+}
+
+void
+vector_push_back(vector_t *vector, void *item)
+{
+  assert(vector);
+  assert(item);
+  if (vector->size == vector->capacity) {
+    vector_resize(vector);
+  }
+  vector->items[vector->size++] = item;
+}
+
+void*
+vector_at(vector_t *vector, uint32_t index)
+{
+  assert(vector);
+  return vector->items[index];
+}
+
+void
+vector_destroy(vector_t * vector)
+{
+  assert(vector);
+  free(vector->items);
+  free(vector);
+}
diff --git a/src/vector.h b/src/vector.h
new file mode 100644
index 0000000..0f29085
--- /dev/null
+++ b/src/vector.h
@@ -0,0 +1,35 @@
+/*
+* Copyright (C) 2023 Johnny Richard
+*
+* This program is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation, either version 3 of the License, or
+* (at your option) any later version.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+#ifndef VECTOR_H
+#define VECTOR_H
+#include <stdint.h>
+#include <stdlib.h>
+
+#define VECTOR_INITIAL_CAPACITY 4
+
+typedef struct vector_t {
+  size_t   capacity;
+  size_t   size;
+  void   **items;
+} vector_t;
+
+vector_t* vector_new();
+void vector_push_back(vector_t *vector, void *item);
+void* vector_at(vector_t *vector, uint32_t index);
+void vector_destroy(vector_t * vector);
+
+#endif /* VECTOR_H */