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(svn r11559) -Fix [FS#1505]: overflow when drawing graphics with high company values.

This commit is contained in:
rubidium
2007-12-02 19:21:56 +00:00
parent b5a902703e
commit faf096f506
3 changed files with 53 additions and 7 deletions

View File

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