From 7cf09140925e75fd03437696eb93e252640e290d Mon Sep 17 00:00:00 2001
From: Tau <tau@nowhere>
Date: Thu, 8 Nov 2018 10:20:21 -0500
Subject: [PATCH] util/crc.c: Add simple CRC-32 implementation

---
 util/crc.c       | 28 ++++++++++++++++++++++++++++
 util/crc.h       |  6 ++++++
 util/meson.build |  2 ++
 3 files changed, 36 insertions(+)
 create mode 100644 util/crc.c
 create mode 100644 util/crc.h

diff --git a/util/crc.c b/util/crc.c
new file mode 100644
index 0000000..5e4defb
--- /dev/null
+++ b/util/crc.c
@@ -0,0 +1,28 @@
+#include <stddef.h>
+#include <stdint.h>
+
+#include "util/crc.h"
+
+uint32_t crc32(const void *src, size_t nbytes, uint32_t in)
+{
+    const uint8_t *bytes;
+    uint32_t crc;
+    size_t i;
+
+    bytes = src;
+    crc = ~in;
+
+    for (i = 0 ; i < nbytes * 8 ; i++) {
+        if (i % 8 == 0) {
+            crc ^= *bytes++;
+        }
+
+        if (crc & 1) {
+            crc = (crc >> 1) ^ 0xEDB88320;
+        } else {
+            crc = (crc >> 1);
+        }
+    }
+
+    return ~crc;
+}
diff --git a/util/crc.h b/util/crc.h
new file mode 100644
index 0000000..16ca927
--- /dev/null
+++ b/util/crc.h
@@ -0,0 +1,6 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+uint32_t crc32(const void *src, size_t nbytes, uint32_t in);
diff --git a/util/meson.build b/util/meson.build
index 9eab6d3..c9f447f 100644
--- a/util/meson.build
+++ b/util/meson.build
@@ -7,6 +7,8 @@ util_lib = static_library(
         capnhook.get_variable('hook_dep'),
     ],
     sources : [
+        'crc.c',
+        'crc.h',
         'dprintf.c',
         'dprintf.h',
         'setupapi.c',