Add path.

1 files changed, 104 insertions, 0 deletions

diff --git a/filesystem/src/path.c b/filesystem/src/path.c
new file mode 100644
index 0000000..2ce5a04
--- /dev/null
+++ b/filesystem/src/path.c
@@ -0,0 +1,104 @@
+#include <path.h>
+
+#include <cassert.h>
+#include <stdlib.h>
+#include <string.h>
+
+static const path Empty = (path){0, 0};
+
+path path_new(const char* str) {
+  assert(str);
+  const size_t size = strlen(str);
+  if (size > 0) {
+    char* data = calloc(size + 1, sizeof(char)); // +1 for null
+    memcpy(data, str, size);
+    data[size] = 0;
+    return (path){data, size};
+  }
+  return Empty;
+}
+
+void path_del(path* path) {
+  if (path) {
+    free(path->data);
+    path->data = 0;
+    path->size = 0;
+  }
+}
+
+path path_parent_dir(path p) {
+  assert(p.data);
+
+  if (p.size == 0) {
+    return Empty;
+  }
+  size_t i = p.size - 1;
+  // If the path ends with '/', skip the characters.
+  while ((i > 0) && (p.data[i] == '/')) {
+    i--;
+  }
+  // Search backwards for the parent dir.
+  for (; i > 0; --i) {
+    if (p.data[i] == '/') {
+      return (path){p.data, i + 1};
+    }
+  }
+  return Empty; // No parent.
+}
+
+path path_concat(path left, path right) {
+  assert(left.data);
+  assert(right.data);
+
+  // +1 for separator.
+  const size_t out_size = left.size + right.size + 1;
+  // +1 for null.
+  char* out = calloc(out_size + 1, sizeof(char));
+  ASSERT(out);
+
+  memcpy(out, left.data, left.size);
+  out[left.size] = '/';
+  memcpy(out + left.size + 1, right.data, right.size);
+  out[out_size] = 0;
+
+  return (path){out, out_size};
+}
+
+bool path_make_relative(
+    const char* filepath, const char* path, char* relative,
+    size_t relative_length) {
+  assert(filepath);
+  assert(path);
+  assert(relative);
+
+  const size_t filepath_len = strlen(filepath);
+  const size_t path_len     = strlen(path);
+  assert(filepath_len < relative_length);
+  assert(path_len < relative_length);
+
+  // Handle empty filepath.
+  if (filepath_len == 0) {
+    memcpy(relative, path, path_len);
+    return true;
+  }
+
+  // Search for the last / in the 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 file path where the parent dir ends.
+  // Make sure there is enough space in the output.
+  if ((tm_dir_len + path_len + 1) >= relative_length) {
+    return false;
+  }
+  memcpy(relative, filepath, tm_dir_len);
+  memcpy(&relative[tm_dir_len], path, path_len);
+
+  return true;
+}