From 9fe693343fa3efd0caa34a5dda68326e1a75eee3 Mon Sep 17 00:00:00 2001
From: Luiz Felipe <silva97@freedev.com.br>
Date: Sun, 19 Jan 2025 15:06:51 -0300
Subject: [PATCH] feat: add stack implementation

---
 src/include/stack.h       | 48 +++++++++++++++++++++++++++++++++++++++
 src/include/types/stack.h | 14 ++++++++++++
 src/types/stack.c         | 44 +++++++++++++++++++++++++++++++++++
 3 files changed, 106 insertions(+)
 create mode 100644 src/include/stack.h
 create mode 100644 src/include/types/stack.h
 create mode 100644 src/types/stack.c

diff --git a/src/include/stack.h b/src/include/stack.h
new file mode 100644
index 0000000..aa12188
--- /dev/null
+++ b/src/include/stack.h
@@ -0,0 +1,48 @@
+#pragma once
+
+#include <stdbool.h>
+
+#include "types/err.h"
+#include "types/stack.h"
+
+/**
+ * Initializes the given stack.
+ *
+ * @param stack  The stack to be initialized.
+ */
+void
+stack_init(stack_t* stack);
+
+/**
+ * Push a new value on the stack.
+ *
+ * @param stack  The stack where tbe value will be pushed.
+ * @param value  The value to push on the stack.
+ *
+ * @return  The index of the new value inside the stack.
+ */
+unsigned int
+stack_push(stack_t* stack, void* value);
+
+/**
+ * Pop a value from the stack.
+ *
+ * @param stack  The stack from where the value will be poped.
+ * @param value  Pointer for where the poped value will be saved.
+ *
+ * @return  ERR_EMPTY on stack is empty.
+ * @return  ERR_OK on value is poped successful.
+ */
+error_code_t
+stack_pop(stack_t* stack, void** value);
+
+/**
+ * Check if the given stack is empty.
+ *
+ * @param stack  The stack to check.
+ *
+ * @return  true on stack is empty.
+ * @return  false if stack has values.
+ */
+bool
+stack_isempty(stack_t* stack);
diff --git a/src/include/types/stack.h b/src/include/types/stack.h
new file mode 100644
index 0000000..875f32c
--- /dev/null
+++ b/src/include/types/stack.h
@@ -0,0 +1,14 @@
+#pragma once
+
+#define STACK_INITIAL_LENGTH   20
+#define STACK_LENGTH_INCREMENT 50
+
+/**
+ * A struct representing a dynamic stack. Each value on the stack is a `void *`.
+ */
+typedef struct stack
+{
+  void** values;        ///< Array of values on the stack.
+  unsigned int length;  ///< Number of elements on the stack.
+  unsigned int _size;   ///< Current number of elements that fits on the stack.
+} stack_t;
diff --git a/src/types/stack.c b/src/types/stack.c
new file mode 100644
index 0000000..2929fba
--- /dev/null
+++ b/src/types/stack.c
@@ -0,0 +1,44 @@
+#include <stdlib.h>
+
+#include "stack.h"
+#include "types/err.h"
+
+void
+stack_init(stack_t* stack)
+{
+  stack->length = 0;
+
+  stack->values = malloc(sizeof(void*) * STACK_INITIAL_LENGTH);
+  stack->_size = STACK_INITIAL_LENGTH;
+}
+
+unsigned int
+stack_push(stack_t* stack, void* value)
+{
+  if (stack->length >= stack->_size) {
+    stack->_size += STACK_LENGTH_INCREMENT;
+    stack->values = realloc(stack->values, sizeof(void*) * stack->_size);
+  }
+
+  stack->values[stack->length] = value;
+
+  return stack->length++;
+}
+
+error_code_t
+stack_pop(stack_t* stack, void** value)
+{
+  if (stack_isempty(stack)) {
+    return ERR_EMPTY;
+  }
+
+  *value = stack->values[--stack->length];
+
+  return ERR_OK;
+}
+
+bool
+stack_isempty(stack_t* stack)
+{
+  return stack->length == 0;
+}