feat: extend bmp with wordCountFor and bmpInit

src/bmp.c

@@ -0,0 +1,90 @@
+#include "bmp.h"
+
+#define bmpBitsPerWord 64
+
+static usize wordCountFor(usize bitCount)
+{
+    return (bitCount + bmpBitsPerWord - 1) / bmpBitsPerWord;
+}
+
+void bmpInit(Bitmap* b, uint64* backingWords, usize bitCount)
+{
+    b->words = backingWords;
+    b->bitCount = bitCount;
+    bmpClearAll(b);
+}
+
+void bmpSet(Bitmap* b, usize index)
+{
+    if (index >= b->bitCount)
+        return;
+    b->words[index / bmpBitsPerWord] |= (1UL << (index % bmpBitsPerWord));
+}
+
+void bmpClear(Bitmap* b, usize index)
+{
+    if (index >= b->bitCount)
+        return;
+    b->words[index / bmpBitsPerWord] &= ~(1UL << (index % bmpBitsPerWord));
+}
+
+bool bmpTest(const Bitmap* b, usize index)
+{
+    if (index >= b->bitCount)
+        return false;
+    return (b->words[index / bmpBitsPerWord] & (1UL << (index % bmpBitsPerWord))) != 0;
+}
+
+void bmpSetRange(Bitmap* b, usize start, usize count)
+{
+    for (usize i = start; i < start + count && i < b->bitCount; i++)
+        bmpSet(b, i);
+}
+
+void bmpClearRange(Bitmap* b, usize start, usize count)
+{
+    for (usize i = start; i < start + count && i < b->bitCount; i++)
+        bmpClear(b, i);
+}
+
+void bmpSetAll(Bitmap* b)
+{
+    usize words = wordCountFor(b->bitCount);
+    for (usize i = 0; i < words; i++)
+        b->words[i] = ~0UL;
+}
+
+void bmpClearAll(Bitmap* b)
+{
+    usize words = wordCountFor(b->bitCount);
+    for (usize i = 0; i < words; i++)
+        b->words[i] = 0;
+}
+
+usize bmpCountSet(const Bitmap* b)
+{
+    usize total = 0;
+    for (usize i = 0; i < b->bitCount; i++) {
+        if (bmpTest(b, i))
+            total++;
+    }
+    return total;
+}
+
+isize bmpFindFirstClear(const Bitmap* b)
+{
+    for (usize i = 0; i < b->bitCount; i++) {
+        if (!bmpTest(b, i))
+            return (isize)i;
+    }
+    return -1;
+}
+
+isize bmpFindFirstSet(const Bitmap* b)
+{
+    for (usize i = 0; i < b->bitCount; i++) {
+        if (bmpTest(b, i))
+            return (isize)i;
+    }
+    return -1;
+}