libioutil Implement a file reader

libioutil/filereader.c

@@ -0,0 +1,61 @@
+#include <desc.h>
+#include <filereader.h>
+#include <path_defs.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+#include <system.h>
+
+int filereader_init (struct filereader* fw, const char* volume, const char* path) {
+  memset (fw, 0, sizeof (*fw));
+  strncpy (fw->volume, volume, VOLUME_MAX);
+  strncpy (fw->path, path, PATH_MAX);
+
+  int ret;
+  struct desc desc;
+
+  if ((ret = volume_open (fw->volume)) < 0)
+    return -FR_VOLUME_OPEN_ERROR;
+
+  if ((ret = describe (fw->path, &desc)) < 0) {
+    volume_close ();
+    return -FR_DESC_ERROR;
+  }
+
+  if (desc.type != FS_FILE)
+    return -FR_NOT_FILE;
+
+  fw->file_size = desc.size;
+  fw->flags |= FR_OPEN;
+
+  return FR_OK;
+}
+
+int filereader_fini (struct filereader* fw) {
+  if ((fw->flags & FR_OPEN)) {
+    volume_close ();
+    fw->flags &= ~FR_OPEN;
+  }
+
+  return FR_OK;
+}
+
+int filereader_read (struct filereader* fw, uint8_t* buffer, size_t buffer_size) {
+  if (!(fw->flags & FR_OPEN))
+    return -FR_VOLUME_NOT_OPENED;
+
+  int ret;
+
+  if (buffer_size > 0) {
+    if (!(fw->read_cursor + buffer_size <= fw->file_size))
+      return -FR_CURSOR_OOB;
+
+    if ((ret = read_file (fw->path, fw->read_cursor, buffer, buffer_size)) < 0)
+      return -FR_READ_ERROR;
+
+    fw->read_cursor += buffer_size;
+  }
+
+  return FR_OK;
+}