util: Added util_format_is_array.

This function checks whether a format description is in a simple array format.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>

src/gallium/auxiliary/util/u_format.c

@@ -158,6 +158,38 @@ util_format_is_pure_uint(enum pipe_format format)
    return (desc->channel[i].type == UTIL_FORMAT_TYPE_UNSIGNED && desc->channel[i].pure_integer) ? TRUE : FALSE;
 }
 
+boolean
+util_format_is_array(const struct util_format_description *desc)
+{
+   unsigned chan;
+
+   if (desc->layout != UTIL_FORMAT_LAYOUT_PLAIN ||
+       desc->colorspace != UTIL_FORMAT_COLORSPACE_RGB ||
+       desc->block.width != 1 ||
+       desc->block.height != 1) {
+      return FALSE;
+   }
+
+   for (chan = 0; chan < desc->nr_channels; ++chan) {
+      if (desc->swizzle[chan] != chan)
+         return FALSE;
+
+      if (desc->channel[chan].type != desc->channel[0].type)
+         return FALSE;
+
+      if (desc->channel[chan].normalized != desc->channel[0].normalized)
+         return FALSE;
+
+      if (desc->channel[chan].pure_integer != desc->channel[0].pure_integer)
+         return FALSE;
+
+      if (desc->channel[chan].size != desc->channel[0].size)
+         return FALSE;
+   }
+
+   return TRUE;
+}
+
 boolean
 util_format_is_luminance_alpha(enum pipe_format format)
 {

src/gallium/auxiliary/util/u_format.h

@@ -590,6 +590,13 @@ util_format_is_pure_sint(enum pipe_format format);
 boolean
 util_format_is_pure_uint(enum pipe_format format);
 
+/**
+ * Whether the format is a simple array format where all channels
+ * are of the same type and can be loaded from memory as a vector
+ */
+boolean
+util_format_is_array(const struct util_format_description *desc);
+
 /**
  * Check if the src format can be blitted to the destination format with
  * a simple memcpy.  For example, blitting from RGBA to RGBx is OK, but not