[vulkan] Improve pipe performance on Fuchsia.

This makes use of the new Call method to write and
readback using a single IPC call. The IOStream
interface has been updated to allow for this optimization.

It also implements buffered reads. Each time we readback
data on Fuchsia we attempt to read a larger fixed size,
which we consume until another read is needed.

Change-Id: Ia7aabb5849c651f6d777da996e9d6d271722d0c8

1 files changed, 7 insertions, 1 deletions

diff --git a/host/include/libOpenglRender/IOStream.h b/host/include/libOpenglRender/IOStream.h
index d06440e6..ad820724 100644
--- a/host/include/libOpenglRender/IOStream.h
+++ b/host/include/libOpenglRender/IOStream.h
@@ -33,6 +33,7 @@ public:
     virtual void *allocBuffer(size_t minSize) = 0;
     virtual int commitBuffer(size_t size) = 0;
     virtual const unsigned char *readFully( void *buf, size_t len) = 0;
+    virtual const unsigned char *commitBufferAndReadFully(size_t size, void *buf, size_t len) = 0;
     virtual const unsigned char *read( void *buf, size_t *inout_len) = 0;
     virtual int writeFully(const void* buf, size_t len) = 0;
 
@@ -79,7 +80,12 @@ public:
     }
 
     const unsigned char *readback(void *buf, size_t len) {
-        flush();
+        if (m_buf && m_free != m_bufsize) {
+            size_t size = m_bufsize - m_free;
+            m_buf = NULL;
+            m_free = 0;
+            return commitBufferAndReadFully(size, buf, len);
+        }
         return readFully(buf, len);
     }