Initial append

CMakeLists.txt

@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.16 FATAL_ERROR)
+project(dynarr
+    VERSION 0
+    DESCRIPTION "Simple Dynamic Arrays"
+    HOMEPAGE_URL "https://git.warwick-new.co.uk/"
+    LANGUAGES C
+)
+
+set(CMAKE_C_STANDARD 17)
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
+# Executables
+file(GLOB_RECURSE SOURCE_FILES
+    ${CMAKE_SOURCE_DIR}/src/*.c)
+file(GLOB_RECURSE HEADER_FILES
+    ${CMAKE_SOURCE_DIR}/src/*.h)
+add_executable(${PROJECT_NAME} ${HEADER_FILES} ${SOURCE_FILES})

src/dyn_arr.c

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+// Special thanks to https://bytesbeneath.com/p/dynamic-arrays-in-c
+#include "dyn_arr.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#define ARRAY_GROWTH_MULTIPLIER 1.3
+
+void *dyn_arr_init(size_t item_size, size_t capacity) {
+  void *dyna_ptr = NULL;
+  size_t size = item_size * capacity + sizeof(dyna_header);
+  dyna_header *header = malloc(size);
+
+  if (header) {
+    header->capacity = capacity;
+    header->length = 0;
+    dyna_ptr = header + 1;
+  }
+
+  return dyna_ptr;
+}
+
+void *dyna_ensure_capacity(void *array, size_t item_count, size_t item_size) {
+  dyna_header *header = dyna_get_header(array);
+  size_t minimum_capacity = header->length + item_count;
+
+  if (header->capacity > minimum_capacity) {
+    return header + 1;
+  }
+
+  size_t new_capacity = header->capacity * ARRAY_GROWTH_MULTIPLIER;
+  while (new_capacity < minimum_capacity) {
+    new_capacity *= ARRAY_GROWTH_MULTIPLIER;
+  }
+
+  size_t new_size = sizeof(dyna_header) + new_capacity * item_size;
+  header = realloc(header, new_size);
+  header->capacity = new_capacity;
+  return header + 1;
+}

src/dyn_arr.h

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+#pragma once
+
+#include <stdlib.h>
+
+#define ARRAY_INITIAL_CAPACITY 4
+
+typedef struct dyna_header {
+  size_t capacity;
+  size_t length;
+} dyna_header;
+
+#define dyna_init(T) (T *)dyn_arr_init(sizeof(T), ARRAY_INITIAL_CAPACITY)
+void *dyn_arr_init(size_t item_size, size_t capacity);
+
+#define dyna_append(array, value)                                              \
+  ((array) = dyna_ensure_capacity(array, 1, sizeof(value)),                    \
+   (array)[dyna_get_header(array)->length] = (value),                          \
+   &(array)[dyna_get_header(array)->length++])
+
+#define dyna_get_header(array) ((dyna_header *)(array) - 1)
+#define dyna_length(array) (array_header(array)->length)
+#define dyna_capacity(array) (array_header(array)->capacity)
+
+void *dyna_ensure_capacity(void *array, size_t item_count, size_t item_size);

src/main.c

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+#include "dyn_arr.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+int main() {
+  int *dyna_array = dyna_init(int);
+
+  for (int i = 0; i < 999999999; i++) {
+    dyna_append(dyna_array, i);
+  }
+    printf("capacity %zu\n",  dyna_get_header(dyna_array)->capacity);
+
+  return EXIT_SUCCESS;
+}