Add filesystem library.

3 files changed, 122 insertions, 0 deletions

diff --git a/filesystem/CMakeLists.txt b/filesystem/CMakeLists.txt
new file mode 100644
index 0000000..55430e6
--- /dev/null
+++ b/filesystem/CMakeLists.txt
@@ -0,0 +1,11 @@
+cmake_minimum_required(VERSION 3.0)
+
+project(filesystem)
+
+add_library(filesystem
+  src/filesystem.c)
+
+target_include_directories(filesystem PUBLIC
+  include)
+
+target_compile_options(filesystem PRIVATE -Wall -Wextra)
diff --git a/filesystem/include/filesystem.h b/filesystem/include/filesystem.h
new file mode 100644
index 0000000..62bd7f0
--- /dev/null
+++ b/filesystem/include/filesystem.h
@@ -0,0 +1,19 @@
+/*
+ * Various filesystem utilities.
+ */
+#pragma once
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+
+/// Get the file's size.
+size_t get_file_size(FILE* file);
+
+/// Read the entire contents of the file into memory.
+void* read_file(const char* filepath);
+
+/// Make a path relative to the parent directory of a file.
+bool make_relative_path(
+    size_t max_path_length, const char* filepath, const char* path,
+    char* relative);
diff --git a/filesystem/src/filesystem.c b/filesystem/src/filesystem.c
new file mode 100644
index 0000000..6c0dcfb
--- /dev/null
+++ b/filesystem/src/filesystem.c
@@ -0,0 +1,92 @@
+#include <filesystem.h>
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+size_t get_file_size(FILE* file) {
+  assert(file);
+  const long int starting_pos = ftell(file);
+  if (starting_pos == -1) {
+    return (size_t)-1;
+  }
+  if (fseek(file, 0, SEEK_END) != 0) {
+    return (size_t)-1;
+  }
+  const size_t file_size = ftell(file);
+  if (file_size == (size_t)-1) {
+    return (size_t)-1;
+  }
+  if (fseek(file, starting_pos, SEEK_SET) != 0) {
+    return (size_t)-1;
+  }
+  return file_size;
+}
+
+void* read_file(const char* filepath) {
+  assert(filepath);
+
+  void* data = 0;
+
+  FILE* file = fopen(filepath, "rb");
+  if (!file) {
+    return 0;
+  }
+  const size_t file_size = get_file_size(file);
+  if (file_size == (size_t)-1) {
+    goto cleanup;
+  }
+
+  data = calloc(1, file_size);
+  if (!data) {
+    goto cleanup;
+  }
+  if (fread(data, 1, file_size, file) != file_size) {
+    goto cleanup;
+  }
+
+  return data;
+
+cleanup:
+  fclose(file);
+  if (data) {
+    free(data);
+  }
+  return 0;
+}
+
+bool make_relative_path(
+    size_t max_path_length, const char* filepath, const char* path,
+    char* relative) {
+  assert(filepath);
+  assert(path);
+  assert(relative);
+
+  // Handle empty filepath.
+  const size_t filepath_len = strlen(filepath);
+  if (filepath_len == 0) {
+    memcpy(relative, path, max_path_length);
+    return true;
+  }
+
+  memcpy(relative, filepath, max_path_length);
+  // Search for the last / in the tile map file path to get its parent
+  // directory.
+  assert(filepath_len > 0);
+  size_t tm_dir_len = 0;
+  for (tm_dir_len = strlen(filepath) - 1; tm_dir_len > 0; --tm_dir_len) {
+    if (filepath[tm_dir_len] == '/') {
+      break;
+    }
+  }
+  tm_dir_len++; // Preserve the backslash.
+
+  // Copy the tile set file path where the parent dir ends.
+  // Make sure there is enough space in the output.
+  const size_t path_len = strlen(path);
+  if ((tm_dir_len + path_len + 1) >= max_path_length) {
+    return false;
+  }
+  memcpy(&relative[tm_dir_len], path, path_len);
+  return true;
+}