Feature optimize merge function

fastexcel-writer/src/main/java/org/dhatim/fastexcel/Worksheet.java

@@ -688,18 +688,6 @@ public Range range(int top, int left, int bottom, int right) {
         return new Range(this, top, left, bottom, right);
     }
 
-    /**
-     * Check if the given cell is within merged ranges.
-     *
-     * @param r Zero-based row number.
-     * @param c Zero-based column number.
-     * @return {@code true} if the cell is within merged ranges, {@code false}
-     * otherwise.
-     */
-    private boolean isCellInMergedRanges(int r, int c) {
-        return mergedRanges.stream().anyMatch(range -> range.contains(r, c));
-    }
-
     /**
      * Write column definitions of this worksheet as an XML element.
      *
@@ -708,6 +696,29 @@ private boolean isCellInMergedRanges(int r, int c) {
      * @throws IOException If an I/O error occurs.
      */
     private void writeCols(Writer w, int nbCols) throws IOException {
+        // Get merged range bitMatrix
+        int maxRows = (mergedRanges.stream().filter(Objects::nonNull).map(Range::getBottom).reduce(0, Math::max)) + 1;
+        int maxCols = (mergedRanges.stream().filter(Objects::nonNull).map(Range::getRight).reduce(0, Math::max)) + 1;
+        if (rows.size() > maxRows) {
+            maxRows = rows.size();
+        }
+        if (nbCols > maxCols) {
+            maxCols = nbCols;
+        }
+        int rowSize = (maxCols + 31) / 32;
+        int[] bits = new int[rowSize * maxRows];
+        mergedRanges.forEach(r -> {
+            int top = r.getTop();
+            int left = r.getLeft();
+            int right = r.getRight();
+            int bottom = r.getBottom();
+            for (int y = top; y < bottom; y++) {
+                int offset = y * rowSize;
+                for (int x = left; x < right; x++) {
+                    bits[offset + (x / 32)] |= 1 << (x & 0x1f);
+                }
+            }
+        });
         // Adjust column widths
         boolean started = false;
         for (int c = 0; c < nbCols; ++c) {
@@ -718,8 +729,10 @@ private void writeCols(Writer w, int nbCols) throws IOException {
                 maxWidth = colWidths.get(c);
             } else {
                 for (int r = 0; r < rows.size(); ++r) {
+                    int offset = r * rowSize + (c / 32);
+                    boolean isCellInMergedRanges = ((bits[offset] >>> (c & 0x1f)) & 1) != 0;
                     // Exclude merged cells from computation && hidden rows
-                    Object o = hiddenRows.contains(r) || isCellInMergedRanges(r, c) ? null : value(r, c);
+                    Object o = hiddenRows.contains(r) || isCellInMergedRanges ? null : value(r, c);
                     if (o != null && !(o instanceof Formula)) {
                         int length = o.toString().length();
                         maxWidth = Math.max(maxWidth, (int) ((length * 7 + 10) / 7.0 * 256) / 256.0);
@@ -739,6 +752,7 @@ private void writeCols(Writer w, int nbCols) throws IOException {
         }
     }
 
+
     /**
      * Write a column as an XML element.
      *
@@ -1265,10 +1279,10 @@ public void header(String text, Position position) {
      * list of named ranges under the provided name.
      * It will be visible when this sheet is open in the
      * cell range dropdown menu under the specified name.
-     * 
+     *
      * @param range Range of cells that needs to be named.
      * @param name String representing the given cell range's name.
-     * 
+     *
      */
     public void addNamedRange(Range range, String name) {
         this.namedRanges.put(name, range);

fastexcel-writer/src/test/java/org/dhatim/fastexcel/CorrectnessTest.java

@@ -25,7 +25,6 @@
 import java.time.ZonedDateTime;
 import java.util.Date;
 import java.util.function.Consumer;
-import java.util.stream.IntStream;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -196,6 +195,25 @@ void mergedRanges() throws Exception {
         });
     }
 
+    @Test
+    void testForGithubIssue185() throws Exception {
+        long start = System.currentTimeMillis();
+        writeWorkbook(wb -> {
+            Worksheet ws = wb.newWorksheet("Worksheet 1");
+            for (int i = 0; i < 10000; i++) {
+                if ((i + 1) % 100 == 0) {
+                    ws.range(i, 0, i, 19).merge();
+                    continue;
+                }
+                for (int j = 0; j < 20; j++) {
+                    ws.value(i, j, "*****");
+                }
+            }
+        });
+        long end = System.currentTimeMillis();
+        System.out.println("cost:" + (end - start) + "ms");
+    }
+
     @Test
     void shouldBeAbleToNullifyCell() throws IOException {
         writeWorkbook(wb ->{