From 2d17b6fe4fc3ad986b4e8b8622cc9f128c9767de Mon Sep 17 00:00:00 2001
From: Joshua Leahy <jleahy@xtxmarkets.com>
Date: Fri, 1 Jul 2022 11:54:33 +0100
Subject: [PATCH] CRC32C function

---
 pyeggsfs/crc32c.py | 87 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100755 pyeggsfs/crc32c.py

diff --git a/pyeggsfs/crc32c.py b/pyeggsfs/crc32c.py
new file mode 100755
index 00000000..a7af8df8
--- /dev/null
+++ b/pyeggsfs/crc32c.py
@@ -0,0 +1,87 @@
+#!/usr/bin/env python
+
+CRC_TABLE = [
+    0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4,
+    0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb,
+    0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b,
+    0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24,
+    0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b,
+    0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
+    0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54,
+    0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b,
+    0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a,
+    0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35,
+    0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5,
+    0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
+    0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45,
+    0xf779deae, 0x05125dad, 0x1642ae59, 0xe4292d5a,
+    0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a,
+    0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595,
+    0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48,
+    0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
+    0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687,
+    0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198,
+    0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927,
+    0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38,
+    0xdbfc821c, 0x2997011f, 0x3ac7f2eb, 0xc8ac71e8,
+    0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7,
+    0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096,
+    0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789,
+    0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859,
+    0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46,
+    0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9,
+    0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6,
+    0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36,
+    0x3cdb9bdd, 0xceb018de, 0xdde0eb2a, 0x2f8b6829,
+    0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c,
+    0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93,
+    0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043,
+    0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c,
+    0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3,
+    0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc,
+    0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c,
+    0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033,
+    0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652,
+    0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d,
+    0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d,
+    0xef087a76, 0x1d63f975, 0x0e330a81, 0xfc588982,
+    0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d,
+    0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622,
+    0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2,
+    0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed,
+    0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530,
+    0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f,
+    0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff,
+    0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0,
+    0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f,
+    0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540,
+    0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90,
+    0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f,
+    0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee,
+    0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1,
+    0x69e9f0d5, 0x9b8273d6, 0x88d28022, 0x7ab90321,
+    0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e,
+    0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81,
+    0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e,
+    0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e,
+    0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351,
+]
+
+def crc32c(buf : bytes):
+    crc = 0xffffffff
+    for b in buf:
+        idx = (crc & 0xff) ^ b
+        crc = CRC_TABLE[idx] ^ (crc >> 8)
+    crc ^= 0xffffffff
+    crc = crc.to_bytes(4, 'little')
+    return crc
+
+if __name__ == '__main__':
+    # from rfc3720 (iscsi)
+    assert crc32c(b'\x00'*32) == b'\xaa\x36\x91\x8a'
+    assert crc32c(b'\xff'*32) == b'\x43\xab\xa8\x62'
+    assert crc32c(bytes(range(32))) == b'\x4e\x79\xdd\x46'
+    assert crc32c(bytes(reversed(range(32)))) == b'\x5c\xdb\x3f\x11'
+    iscsi_read_pdu = b'\x01\xc0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x14\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x14\x00\x00\x00\x18\x28\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00'
+    assert crc32c(iscsi_read_pdu) == b'\x56\x3a\x96\xd9'
+