From a6f125eae289a00dec324e139d64002fae14bcfb Mon Sep 17 00:00:00 2001
From: JP Appel <jeanpierre.appel01@gmail.com>
Date: Sat, 20 Apr 2024 01:53:34 -0400
Subject: functions for working with grids

---
 src/grids.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/grids.h | 18 ++++++++++++++
 2 files changed, 99 insertions(+)
 create mode 100644 src/grids.c
 create mode 100644 src/grids.h

diff --git a/src/grids.c b/src/grids.c
new file mode 100644
index 0000000..10a934e
--- /dev/null
+++ b/src/grids.c
@@ -0,0 +1,81 @@
+#include <stdlib.h>
+#include <string.h>
+#include "grids.h"
+
+/*
+ * Creates a grid for storing the results of the escape algorithm
+ */
+grid_t* create_grid(const size_t x, const size_t y){
+    if(x <= 0 || y <= 0) return NULL;
+
+    const size_t size = x * y;
+    size_t* data = malloc(size * sizeof(size_t));
+    if(!data) return NULL;
+
+    grid_t* grid = malloc(sizeof(grid_t));
+    if(!grid){
+        free(data);
+        return NULL;
+    }
+
+    grid->x = x;
+    grid->y = y;
+    grid->size = size;
+    grid->data = data;
+
+    return grid;
+}
+
+/*
+ * Sets all entries of a grid to the value val
+ */
+void set_grid(grid_t* grid, const double val){
+    if(!grid || !grid->data) return;
+    memset(grid->data, val, grid->size);
+}
+
+/*
+ * Creates a copy of a grid
+ */
+grid_t* copy_grid(const grid_t* grid){
+    if(!grid || !grid->data) return NULL;
+
+    grid_t* grid_copy = create_grid(grid->x, grid->y);
+    if(!grid_copy) return NULL;
+
+    memcpy(grid_copy->data, grid->data, grid->size);
+
+    return grid_copy;
+}
+
+/*
+ * Frees a grid and its members
+ */
+void free_grid(grid_t* grid){
+    if(!grid) return;
+
+    free(grid->data);
+    free(grid);
+}
+
+/*
+ * Checks if two grids are exactly equal
+ * This may return incorrect values due to floating point arrithmetic errors 
+ * that occur while the grid is being filled
+ */
+bool grid_equal(const grid_t* grid1, const grid_t* grid2){
+    return grid1->x == grid2->x && grid1->y == grid2->y &&
+        memcmp(grid1->data, grid2->data, grid1->size) == 0;
+}
+
+/*
+ * Checks if two grids have a given maximum difference
+ */
+bool grid_allclose(const grid_t *grid1, const grid_t *grid2, const size_t max_error){
+    if(grid1->x != grid2->x || grid1->y != grid2->y) return false;
+    const size_t size = grid1->size;
+    for(size_t i = 0; i < size; i++){
+        if(abs(grid1->data[i] - grid2->data[i]) >= max_error) return false;
+    }
+    return true;
+}
diff --git a/src/grids.h b/src/grids.h
new file mode 100644
index 0000000..8de6375
--- /dev/null
+++ b/src/grids.h
@@ -0,0 +1,18 @@
+#include <stddef.h>
+#include <stdbool.h>
+
+#pragma once
+
+typedef struct {
+    size_t x;
+    size_t y;
+    size_t size;
+    size_t* data;
+} grid_t;
+
+grid_t* create_grid(const size_t x, const size_t y);
+void set_grid(grid_t* grid, const double val);
+grid_t* copy_grid(const grid_t* grid);
+void free_grid(grid_t* grid);
+bool grid_equal(const grid_t* grid1, const grid_t* grid2);
+bool grid_allclose(const grid_t* grid1, const grid_t* grid2, const size_t max_error);
-- 
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