base: Redesign internal frame buffer handling

Currently, frame buffer handling in gem5 is quite ad hoc. In practice,
we pass around naked pointers to raw pixel data and expect consumers
to convert frame buffers using the (broken) VideoConverter.

This changeset completely redesigns the way we handle frame buffers
internally. In summary, it fixes several color conversion bugs, adds
support for more color formats (e.g., big endian), and makes the code
base easier to follow.

In the new world, gem5 always represents pixel data using the Pixel
struct when pixels need to be passed between different classes (e.g.,
a display controller and the VNC server). Producers of entire frames
(e.g., display controllers) should use the FrameBuffer class to
represent a frame.

Frame producers are expected to create one instance of the FrameBuffer
class in their constructors and register it with its consumers
once. Consumers are expected to check the dimensions of the frame
buffer when they consume it.

Conversion between the external representation and the internal
representation is supported for all common "true color" RGB formats of
up to 32-bit color depth. The external pixel representation is
expected to be between 1 and 4 bytes in either big endian or little
endian. Color channels are assumed to be contiguous ranges of bits
within each pixel word. The external pixel value is scaled to an 8-bit
internal representation using a floating multiplication to map it to
the entire 8-bit range.

1 files changed, 173 insertions, 0 deletions

diff --git a/src/base/framebuffer.cc b/src/base/framebuffer.cc
new file mode 100644
index 000000000..dc4c2e1c2
--- /dev/null
+++ b/src/base/framebuffer.cc
@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) 2015 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Andreas Sandberg
+ */
+
+#include "base/framebuffer.hh"
+
+#include <zlib.h>
+
+#include <cassert>
+
+#include "base/bitfield.hh"
+
+const PixelConverter PixelConverter::rgba8888_le(4, 0, 8, 16, 8, 8, 8);
+const PixelConverter PixelConverter::rgba8888_be(4, 0, 8, 16, 8, 8, 8,
+                                                 BigEndianByteOrder);
+const PixelConverter PixelConverter::rgb565_le(2,  0, 5, 11, 5, 6, 5);
+const PixelConverter PixelConverter::rgb565_be(2,  0, 5, 11, 5, 6, 5,
+                                               BigEndianByteOrder);
+
+const FrameBuffer FrameBuffer::dummy(320, 240);
+
+PixelConverter::PixelConverter(unsigned _length,
+                               unsigned ro, unsigned go, unsigned bo,
+                               unsigned rw, unsigned gw, unsigned bw,
+                               ByteOrder _byte_order)
+    : length(_length),
+      depth(rw + gw + bw),
+      byte_order(_byte_order),
+      ch_r(ro, rw),
+      ch_g(go, gw),
+      ch_b(bo, bw)
+{
+    assert(length > 1);
+}
+
+PixelConverter::Channel::Channel(unsigned _offset, unsigned width)
+    : offset(_offset),
+      mask(::mask(width)),
+      factor(255.0 / mask)
+{
+}
+
+uint32_t
+PixelConverter::readWord(const uint8_t *p) const
+{
+    uint32_t word(0);
+
+    if (byte_order == LittleEndianByteOrder) {
+        for (int i = 0; i < length; ++i)
+            word |= p[i] << (8 * i);
+    } else {
+        for (int i = 0; i < length; ++i)
+            word |= p[i] << (8 * (length - i - 1));
+    }
+
+    return word;
+}
+
+void
+PixelConverter::writeWord(uint8_t *p, uint32_t word) const
+{
+    if (byte_order == LittleEndianByteOrder) {
+        for (int i = 0; i < length; ++i)
+            p[i] = (word >> (8 * i)) & 0xFF;
+    } else {
+        for (int i = 0; i < length; ++i)
+            p[i] = (word >> (8 * (length - i - 1))) & 0xFF;
+    }
+}
+
+
+
+
+FrameBuffer::FrameBuffer(unsigned width, unsigned height)
+    : pixels(width * height),
+      _width(width), _height(height)
+{
+    clear();
+}
+
+FrameBuffer::FrameBuffer()
+    : _width(0), _height(0)
+{
+}
+
+FrameBuffer::~FrameBuffer()
+{
+}
+
+void
+FrameBuffer::resize(unsigned width, unsigned height)
+{
+    _width = width;
+    _height = height;
+
+    pixels.resize(width * height);
+}
+
+void
+FrameBuffer::fill(const Pixel &pixel)
+{
+    for (auto &p : pixels)
+        p = pixel;
+}
+
+void
+FrameBuffer::clear()
+{
+    static const Pixel black(0, 0, 0);
+
+    fill(black);
+}
+
+void
+FrameBuffer::copyIn(const uint8_t *fb, const PixelConverter &conv)
+{
+    for (auto &p : pixels) {
+        p = conv.toPixel(fb);
+        fb += conv.length;
+    }
+}
+
+void
+FrameBuffer::copyOut(uint8_t *fb, const PixelConverter &conv) const
+{
+    for (auto &p : pixels) {
+        conv.fromPixel(fb, p);
+        fb += conv.length;
+    }
+}
+
+uint64_t
+FrameBuffer::getHash() const
+{
+    return adler32(0UL,
+                   reinterpret_cast<const Bytef *>(pixels.data()),
+                   area() * sizeof(Pixel));
+}