From 6ffb06af70faa5657f2c6091fe23500007e2bd44 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Wed, 17 Aug 2022 21:26:29 +0200
Subject: user/ethdump: file per protocol, ethernet frame functions

---
 src/user/app/ethdump/util.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 src/user/app/ethdump/util.c

(limited to 'src/user/app/ethdump/util.c')

diff --git a/src/user/app/ethdump/util.c b/src/user/app/ethdump/util.c
new file mode 100644
index 0000000..b0d8785
--- /dev/null
+++ b/src/user/app/ethdump/util.c
@@ -0,0 +1,33 @@
+#include "util.h"
+
+void hexdump(const void *vbuf, size_t len) {
+	const uint8_t *buf = vbuf;
+	for (size_t i = 0; i < len; i += 16) {
+		printf("%08x  ", i);
+
+		for (size_t j = i; j < i + 8 && j < len; j++)
+			printf("%02x ", buf[j]);
+		printf(" ");
+		for (size_t j = i + 8; j < i + 16 && j < len; j++)
+			printf("%02x ", buf[j]);
+		printf("\n");
+	}
+}
+
+/* https://www.w3.org/TR/PNG/#D-CRCAppendix */
+static uint32_t crc_table[256];
+uint32_t crc32(const uint8_t *buf, size_t len) {
+	if (!crc_table[1]) {
+		for (int i = 0; i < 256; i++) {
+			uint32_t c = i;
+			for (int j = 0; j < 8; j++)
+				c = ((c&1) ? 0xedb88320 : 0) ^ (c >> 1);
+			crc_table[i] = c;
+		}
+	}
+
+	uint32_t c = 0xFFFFFFFF;
+	for (size_t i = 0; i < len; i++)
+		c = crc_table[(c ^ buf[i]) & 0xff] ^ (c >> 8);
+	return ~c;
+}
-- 
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