Meta: Cleanup of header files such that they are partially shared

The /include directory contains definitons that both the kernel and libc
need to be in sync.

1 files changed, 61 insertions, 0 deletions

diff --git a/userland/libc/stdlib/realpath.c b/userland/libc/stdlib/realpath.c
new file mode 100644
index 0000000..438ed8d
--- /dev/null
+++ b/userland/libc/stdlib/realpath.c
@@ -0,0 +1,61 @@
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+// FIXME: This is nowhere near complete
+char *realpath(const char *filename, char *resolvedname) {
+  assert(resolvedname);
+  // FIXME: This really should have bounds checking
+  char cwd[256];
+  getcwd(cwd, 256);
+  strcat(cwd, filename);
+  const char *path = cwd;
+  char *result = resolvedname;
+  // It has to be a absolute path
+  if ('/' != *path)
+    return 0;
+  const char *result_start = result;
+  int start_directory = 0;
+  int should_insert_slash = 0;
+  for (; *path; path++) {
+    if (start_directory) {
+      start_directory = 0;
+      if ('/' == *path) {
+        path++;
+      } else if (0 == memcmp(path, "./", 2) || 0 == memcmp(path, ".\0", 2)) {
+        path++;
+      } else if (0 == memcmp(path, "../", 3) || 0 == memcmp(path, "..\0", 3)) {
+        path += 2;
+        if (result_start + 2 > result) {
+          // The path is probably something like "/.." or
+          // "/../foo". A "/.." should become a "/"
+          // Therefore it skips going back to the parent
+          if (*path == '/') {
+            if (result_start == result)
+              return 0;
+            result--;
+          }
+        } else {
+          if ('/' != *path) {
+            should_insert_slash = 1;
+          }
+          result--;
+          result--;
+          for (; result_start <= result && '/' != *result; result--)
+            ;
+        }
+      }
+    }
+    start_directory = ('/' == *path);
+    if ('\0' == *path)
+      break;
+    *result = *path;
+    result++;
+  }
+  if (should_insert_slash) {
+    *result = '/';
+    result++;
+  }
+  *result = '\0';
+  return 1;
+}