Fuck git

external/unarr/common/crc32.c

@@ -0,0 +1,86 @@
+/* Copyright 2022 the unarr project authors (see AUTHORS file).
+   License: LGPLv3 */
+#include "unarr-imp.h"
+
+#if !defined HAVE_ZLIB || !defined USE_ZLIB_CRC
+
+/*
+   crc32 calculation based on Intel slice-by-8 algorithm with lookup-table generation code
+   adapted from https://gnunet.org/svn/gnunet/src/util/crypto_crc.c (public domain)        */
+
+static inline uint32_t uint32le(const uint8_t *data) { return data[0] | data[1] << 8 | data[2] << 16 | (uint32_t)data[3] << 24; }
+
+static bool crc_table_ready = false;
+static uint32_t crc_table[8][256];
+
+uint32_t ar_crc32(uint32_t crc32, const uint8_t * data, size_t data_len)
+{
+    if (!crc_table_ready) {
+
+        static const uint32_t crc_poly = 0xEDB88320;
+
+        uint32_t h = 1;
+        crc_table[0][0] = 0;
+
+        for (unsigned int i = 128; i; i >>= 1) {
+            h = (h >> 1) ^ ((h & 1) ? crc_poly : 0);
+            for (unsigned int j = 0; j < 256; j += 2 * i) {
+                crc_table[0][i+j] = crc_table[0][j] ^ h;
+            }
+        }
+
+        for (unsigned int i = 0; i < 256; i++) {
+            for (unsigned int j = 1; j < 8; j++) {
+                crc_table[j][i] = (crc_table[j-1][i] >> 8) ^ crc_table[0][crc_table[j-1][i] & 0xFF];
+            }
+        }
+
+        crc_table_ready = true;
+    }
+
+    crc32 ^= 0xFFFFFFFF;
+
+    while (data_len >= 8) {
+
+        uint32_t tmp = crc32 ^ uint32le(data);
+
+        crc32 = crc_table[7][ tmp        & 0xFF ] ^
+                crc_table[6][(tmp >>  8) & 0xFF ] ^
+                crc_table[5][(tmp >> 16) & 0xFF ] ^
+                crc_table[4][ tmp >> 24         ];
+
+        tmp = uint32le(data + 4);
+
+        crc32 ^= crc_table[3][tmp        & 0xFF] ^
+                crc_table[2][(tmp >>  8) & 0xFF] ^
+                crc_table[1][(tmp >> 16) & 0xFF] ^
+                crc_table[0][ tmp >> 24        ];
+
+        data += 8;
+        data_len -= 8;
+    }
+
+    while (data_len-- > 0) {
+        crc32 = (crc32 >> 8) ^ crc_table[0][(crc32 ^ *data++) & 0xFF];
+    }
+
+    return crc32 ^ 0xFFFFFFFF;
+}
+
+#else
+
+#include <zlib.h>
+
+uint32_t ar_crc32(uint32_t crc, const unsigned char *data, size_t data_len)
+{
+#if SIZE_MAX > UINT32_MAX
+    while (data_len > UINT32_MAX) {
+        crc = crc32(crc, data, UINT32_MAX);
+        data += UINT32_MAX;
+        data_len -= UINT32_MAX;
+    }
+#endif
+    return crc32(crc, data, (uint32_t)data_len);
+}
+
+#endif