Toward first png.

src/compression/CyclicRedundancyChecker.cpp

@@ -0,0 +1,42 @@
+#include "CyclicRedundancyChecker.h"
+
+void CyclicRedundancyChecker::createTable()
+{
+    unsigned long c{0};
+    for (int n = 0; n < 256; n++)
+    {
+        c = (unsigned long) n;
+        for (int k = 0; k < 8; k++)
+        {
+            if (c & 1)
+            {
+                c = 0xedb88320L ^ (c >> 1);
+            }
+            else
+            {
+                c = c >> 1;
+            }
+        }
+        mTable[n] = c;
+    }
+    mTableComputed = true;
+}
+
+void CyclicRedundancyChecker::addValue(unsigned char val)
+{
+    if (!mTableComputed)
+    {
+        createTable();
+    }
+    mLastValue = mTable[(mLastValue ^ val) & 0xff] ^ (mLastValue >> 8);
+}
+
+uint32_t CyclicRedundancyChecker::getChecksum() const
+{
+    return mLastValue ^ 0xffffffffL;
+}
+
+void CyclicRedundancyChecker::reset()
+{
+    mLastValue = 0xffffffffL;
+}