1 files changed, 54 insertions, 0 deletions
diff --git a/neozip/crc32_p.h b/neozip/crc32_p.h
new file mode 100644
index 0000000000..397464a446
--- /dev/null
+++ b/neozip/crc32_p.h
@@ -0,0 +1,54 @@
+/* crc32_p.h -- Private inline functions and macros shared with
+ *              different computation of the CRC-32 checksum
+ *              of a data stream.
+ * Copyright (C) 2026 Nathan Moinvaziri
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ */
+
+#ifndef CRC32_P_H
+#define CRC32_P_H
+
+#define CRC_DO1(c, buf, i) c = crc_table[(c ^ buf[i]) & 0xff] ^ (c >> 8)
+#define CRC_DO2(c, buf, i) {CRC_DO1(c, buf, i); CRC_DO1(c, buf, i+1);}
+#define CRC_DO4(c, buf, i) {CRC_DO2(c, buf, i); CRC_DO2(c, buf, i+2);}
+#define CRC_DO8(c, buf, i) {CRC_DO4(c, buf, i); CRC_DO4(c, buf, i+4);}
+
+Z_FORCEINLINE static uint32_t crc32_copy_small(uint32_t crc, uint8_t *dst, const uint8_t *buf, size_t len,
+                                               const int MAX_LEN, const int COPY) {
+    if (MAX_LEN >= 8) {
+        while (len >= 8) {
+            if (COPY) {
+                memcpy(dst, buf, 8);
+                dst += 8;
+            }
+            CRC_DO8(crc, buf, 0);
+            buf += 8;
+            len -= 8;
+        }
+    }
+    if (len & 4) {
+        if (COPY) {
+            memcpy(dst, buf, 4);
+            dst += 4;
+        }
+        CRC_DO4(crc, buf, 0);
+        buf += 4;
+    }
+    if (len & 2) {
+        if (COPY) {
+            memcpy(dst, buf, 2);
+            dst += 2;
+        }
+        CRC_DO2(crc, buf, 0);
+        buf += 2;
+    }
+    if (len & 1) {
+        if (COPY)
+            *dst = *buf;
+        CRC_DO1(crc, buf, 0);
+    }
+
+    return crc;
+}
+
+#endif /* CRC32_P_H */