1 files changed, 47 insertions, 0 deletions
diff --git a/libmkv/nut-crc32.c b/libmkv/nut-crc32.c
new file mode 100644
index 0000000..e81c5d7
--- /dev/null
+++ b/libmkv/nut-crc32.c
@@ -0,0 +1,47 @@
+#define _GNU_SOURCE /* for error() */
+#include <errno.h>  /* for errno */
+#include <error.h>  /* for error() */
+#include <stdint.h> /* for uint{n}_t */
+#include <stdio.h>  /* for printf() */
+#include <unistd.h> /* for read() */
+
+void nut_crc32_init(uint32_t *crc) {
+	/* "Starting value is zero."  */
+	*crc = 0;
+}
+
+void nut_crc32_write(uint32_t *crc, uint8_t *dat, size_t len) {
+	/* "Generator polynomial is 0x104C11DB7."  */
+	static const uint32_t table[16] = {
+		0x00000000, 0x04C11DB7, 0x09823B6E, 0x0D4326D9,
+		0x130476DC, 0x17C56B6B, 0x1A864DB2, 0x1E475005,
+		0x2608EDB8, 0x22C9F00F, 0x2F8AD6D6, 0x2B4BCB61,
+		0x350C9B64, 0x31CD86D3, 0x3C8EA00A, 0x384FBDBD,
+	};
+
+	while (len--) {
+		*crc ^= *dat++ << 24;
+		*crc = (*crc<<4) ^ table[*crc>>28];
+		*crc = (*crc<<4) ^ table[*crc>>28];
+	}
+}
+
+int main() {
+	uint32_t crc;
+	uint8_t  buf[128];
+
+	nut_crc32_init(&crc);
+
+	size_t tot = 0;
+	for (;;) {
+		ssize_t n = read(0, buf, sizeof(buf));
+		if (n <= 0)
+			break;
+		nut_crc32_write(&crc, buf, n);
+		tot += n;
+	}
+	printf("crc32 = 0x%08x ; size = %zu\n", crc, tot);
+	if (errno)
+		error(1, errno, "read");
+	return 0;
+}