vtest: add functions to read from buffer

Signed-off-by: David Riley <davidriley@chromium.org>
Reviewed-By: Gert Wollny <gert.wollny@collabora.com>

vtest/vtest.h

@@ -27,9 +27,15 @@
 
 #include <errno.h>
 
+struct vtest_buffer {
+   const void *buffer;
+   int size;
+};
+
 struct vtest_input {
    union {
       int fd;
+      struct vtest_buffer *buffer;
    } data;
    int (*read)(struct vtest_input *input, void *buf, int size);
 };
@@ -50,6 +56,7 @@ int vtest_transfer_put(uint32_t length_dw);
 int vtest_transfer_put2(uint32_t length_dw);
 
 int vtest_block_read(struct vtest_input *input, void *buf, int size);
+int vtest_buf_read(struct vtest_input *input, void *buf, int size);
 
 int vtest_resource_busy_wait(uint32_t length_dw);
 int vtest_renderer_create_fence(void);

vtest/vtest_renderer.c

@@ -187,6 +187,20 @@ static int vtest_send_fd(int socket_fd, int fd)
     return 0;
 }
 
+int vtest_buf_read(struct vtest_input *input, void *buf, int size)
+{
+   struct vtest_buffer *inbuf = input->data.buffer;
+   if (size > inbuf->size) {
+      return 0;
+   }
+
+   memcpy(buf, inbuf->buffer, size);
+   inbuf->buffer += size;
+   inbuf->size -= size;
+
+   return size;
+}
+
 int vtest_create_renderer(struct vtest_input *input, int out_fd, uint32_t length,
                           int ctx_flags)
 {