1 files changed, 158 insertions, 0 deletions
diff --git a/plugins/python/cglimpse/entropy.py b/plugins/python/cglimpse/entropy.py
new file mode 100644
index 0000000..f090624
--- /dev/null
+++ b/plugins/python/cglimpse/entropy.py
@@ -0,0 +1,158 @@
+
+import math
+
+from .method import GlimpseMethod
+
+
+class ShannonEntropy(GlimpseMethod):
+
+    def __init__(self, builder):
+        """Prepare a Shannon entropy display."""
+
+        super(ShannonEntropy, self).__init__(builder)
+
+        button = builder.get_object('shannon_color')
+        button.connect('color-set', self._on_color_set)
+
+        self._on_color_set(button)
+
+        self._step = 0x80
+
+        self._v_legend = 'Entropy'
+        self._h_legend = 'Byte offsets'
+
+        self._x_range = [ 0, 1024, 10240 ]
+        self._y_range = [ 0.0, 0.25, 1.0 ]
+
+        self._size = None
+        self._values = []
+
+
+    def _on_color_set(self, button):
+        """React on color chosen for the rendering."""
+
+        color = button.get_rgba()
+        self._color = [ color.red, color.green, color.blue, color.alpha ]
+        self._shadow_color = [ color.red * 0.5, color.green * 0.5, color.blue * 0.5, color.alpha ]
+
+
+    def format_legend(self, value, vert):
+        """Build the label used for a rule."""
+
+        if vert:
+            text = str(value)
+
+        else:
+
+            scale = [ ' kb', ' Mb', ' Gb', ' Tb' ]
+            suffix = ''
+
+            for i in range(len(scale)):
+
+                if value < 1024:
+                    break
+
+                value /= 1024
+                suffix = scale[i]
+
+            text = '%u%s' % (value, suffix)
+
+        return text
+
+
+    def update(self, data):
+        """Provide a description for the method."""
+
+        self._size = len(data)
+
+        step = 2 ** math.ceil(math.log(self._size / 10, 2))
+
+        self._x_range = [ 0, step, 10 * step ]
+
+        self._values = []
+
+        for i in range(0, self._size, self._step):
+
+            counter = [ 0 for i in range(256) ]
+
+            start = i
+            end = i + self._step
+
+            if end > self._size:
+                end = self._size
+
+            for b in data[start : end]:
+                counter[b] += 1
+
+            ent = 0.0
+
+            for c in counter:
+                if c > 0:
+                    freq = c / (end - start)
+                    ent += freq * math.log(freq, 256)
+
+            self._values.append(-ent)
+
+
+    def render(self, cr, area):
+        """Draw the bytes distribution for the current binary, if any."""
+
+        step = 2 ** math.ceil(math.log(self._size / 10, 2))
+
+        if self._size % step == 0:
+            full_size = self._size
+        else:
+            full_size = (self._size + step - 1) & ~(step - 1)
+
+        start = 0
+        last_x = area[0]
+
+        last_y = area[1] + area[3] - (area[3] * self._values[0])
+        cr.move_to(last_x, last_y + 2)
+
+        for i in range(0, self._size, self._step):
+
+            end = i + self._step
+
+            if end > self._size:
+                end = self._size
+
+            x = area[0] + ((end - start) * area[2]) / full_size
+            y = area[1] + area[3] - (area[3] * self._values[int(i / self._step)])
+
+            if last_y != y:
+                cr.line_to(last_x, y + 2)
+
+            cr.line_to(x, y + 2)
+
+            last_x = x
+
+        cr.set_source_rgba(*self._shadow_color)
+        cr.set_line_width(4)
+        cr.stroke()
+
+        last_x = area[0]
+
+        last_y = area[1] + area[3] - (area[3] * self._values[0])
+        cr.move_to(last_x, last_y)
+
+        for i in range(0, self._size, self._step):
+
+            end = i + self._step
+
+            if end > self._size:
+                end = self._size
+
+            x = area[0] + ((end - start) * area[2]) / full_size
+            y = area[1] + area[3] - (area[3] * self._values[int(i / self._step)])
+
+            if last_y != y:
+                cr.line_to(last_x, y)
+
+            cr.line_to(x, y)
+
+            last_x = x
+
+        cr.set_source_rgba(*self._color)
+        cr.set_line_width(2)
+        cr.stroke()