1 files changed, 82 insertions, 0 deletions
diff --git a/src/user/knob/file.c b/src/user/knob/file.c
new file mode 100644
index 0000000..8ab7acd
--- /dev/null
+++ b/src/user/knob/file.c
@@ -0,0 +1,82 @@
+#include <pland/syscall.h>
+#include <knob/format.h>
+#include <knob/heap.h>
+#include <knob/env.h>
+
+struct file {
+  _file_handle_t handle;
+  uint32_t position;
+  uint32_t length;
+};
+
+static const char *try_remove_prefix(const char *path, uint8_t *dn_out) {
+  if ((path[0] != 's') || (path[1] != 'd'))
+    return 0;
+
+  const char *num_part = path + 2;
+  for (uint32_t i = 0; num_part[i]; ++i)
+    if (num_part[i] == ':') {
+
+      uint32_t dn_large;
+      if (!try_sntoi(num_part, i, &dn_large) || dn_large > 255)
+        return 0;
+
+      *dn_out = (uint8_t)dn_large;
+      return num_part + i + 1;
+    }
+
+  return 0;
+}
+
+struct file *open_file(const char *path) {
+  uint8_t dn;
+  const char *path_part = try_remove_prefix(path, &dn);
+  if (path_part)
+    path = path_part;
+  else
+    dn = current_drive;
+
+  _file_handle_t h = _open_file(dn, path);
+  if (!h)
+    return 0;
+
+  struct file *f = get_block(sizeof(struct file));
+  f->handle = h;
+  f->position = 0;
+  f->length = _file_size(h);
+
+  return f;
+}
+
+void close_file(struct file *f) {
+  _close_file(f->handle);
+  free_block(f);
+}
+
+uint32_t read_from_file(struct file *f, uint32_t max, void *buf) {
+  if (f->position + max > f->length)
+    max = f->length - f->position;
+
+  uint32_t read = _file_read(f->handle, f->position, max, buf);
+
+  f->position += read;
+  return read;
+}
+
+uint32_t seek_file_to(struct file *f, uint32_t to) {
+  if (to > f->length)
+    to = f->length;
+  return f->position = to;
+}
+
+int32_t seek_file_by(struct file *f, int32_t by) {
+  uint32_t old = f->position;
+  uint32_t to = old + by > f->length ? f->length : old + by;
+  f->position = to;
+  return to - old;
+}
+
+__attribute__ ((pure))
+uint32_t file_size(struct file *f) {
+  return f->length;
+}
+\ No newline at end of file