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(svn r11559) -Fix [FS#1505]: overflow when drawing graphics with high company values.
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@@ -65,7 +65,7 @@ struct GraphDrawer {
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uint height; ///< The height of the graph in pixels.
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StringID format_str_y_axis;
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byte colors[GRAPH_MAX_DATASETS];
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Money cost[GRAPH_MAX_DATASETS][24]; ///< last 2 years
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OverflowSafeInt64 cost[GRAPH_MAX_DATASETS][24]; ///< last 2 years
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};
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static void DrawGraph(const GraphDrawer *gw)
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@@ -133,7 +133,7 @@ static void DrawGraph(const GraphDrawer *gw)
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for (int i = 0; i < gw->num_dataset; i++) {
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if (!HasBit(gw->excluded_data, i)) {
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for (int j = 0; j < gw->num_on_x_axis; j++) {
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Money datapoint = gw->cost[i][j];
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OverflowSafeInt64 datapoint = gw->cost[i][j];
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if (datapoint != INVALID_DATAPOINT) {
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/* For now, if the graph has negative values the scaling is
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@@ -215,12 +215,31 @@ static void DrawGraph(const GraphDrawer *gw)
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uint prev_y = INVALID_DATAPOINT_POS;
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for (int j = 0; j < gw->num_on_x_axis; j++) {
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Money datapoint = gw->cost[i][j];
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OverflowSafeInt64 datapoint = gw->cost[i][j];
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if (datapoint != INVALID_DATAPOINT) {
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/* XXX: This can overflow if x_axis_offset * datapoint is
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* too big to fit in an int64. */
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y = gw->top + x_axis_offset - (x_axis_offset * datapoint) / highest_value;
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/*
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* Check whether we need to reduce the 'accuracy' of the
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* datapoint value and the highest value to splut overflows.
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* And when 'drawing' 'one million' or 'one million and one'
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* there is no significant difference, so the least
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* significant bits can just be removed.
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*
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* If there are more bits needed than would fit in a 32 bits
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* integer, so at about 31 bits because of the sign bit, the
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* least significant bits are removed.
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*/
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int mult_range = FindLastBit(x_axis_offset) + FindLastBit(abs(datapoint));
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int reduce_range = max(mult_range - 31, 0);
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/* Handle negative values differently (don't shift sign) */
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if (datapoint < 0) {
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datapoint = -(abs(datapoint) >> reduce_range);
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} else {
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datapoint >>= reduce_range;
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}
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y = gw->top + x_axis_offset - (x_axis_offset * datapoint) / (highest_value >> reduce_range);
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/* Draw the point. */
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GfxFillRect(x - 1, y - 1, x + 1, y + 1, color);
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