1 // Copyright 2022 The Abseil Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #ifndef ABSL_CRC_INTERNAL_CRC32C_INLINE_H_
16 #define ABSL_CRC_INTERNAL_CRC32C_INLINE_H_
17
18 #include <cstdint>
19
20 #include "absl/base/config.h"
21 #include "absl/base/internal/endian.h"
22 #include "absl/crc/internal/crc32_x86_arm_combined_simd.h"
23
24 namespace absl {
25 ABSL_NAMESPACE_BEGIN
26 namespace crc_internal {
27
28 // CRC32C implementation optimized for small inputs.
29 // Either computes crc and return true, or if there is
30 // no hardware support does nothing and returns false.
ExtendCrc32cInline(uint32_t * crc,const char * p,size_t n)31 inline bool ExtendCrc32cInline(uint32_t* crc, const char* p, size_t n) {
32 #if defined(ABSL_CRC_INTERNAL_HAVE_ARM_SIMD) || \
33 defined(ABSL_CRC_INTERNAL_HAVE_X86_SIMD)
34 constexpr uint32_t kCrc32Xor = 0xffffffffU;
35 *crc ^= kCrc32Xor;
36 if (n & 1) {
37 *crc = CRC32_u8(*crc, static_cast<uint8_t>(*p));
38 n--;
39 p++;
40 }
41 if (n & 2) {
42 *crc = CRC32_u16(*crc, absl::little_endian::Load16(p));
43 n -= 2;
44 p += 2;
45 }
46 if (n & 4) {
47 *crc = CRC32_u32(*crc, absl::little_endian::Load32(p));
48 n -= 4;
49 p += 4;
50 }
51 while (n) {
52 *crc = CRC32_u64(*crc, absl::little_endian::Load64(p));
53 n -= 8;
54 p += 8;
55 }
56 *crc ^= kCrc32Xor;
57 return true;
58 #else
59 // No hardware support, signal the need to fallback.
60 static_cast<void>(crc);
61 static_cast<void>(p);
62 static_cast<void>(n);
63 return false;
64 #endif // defined(ABSL_CRC_INTERNAL_HAVE_ARM_SIMD) ||
65 // defined(ABSL_CRC_INTERNAL_HAVE_X86_SIMD)
66 }
67
68 } // namespace crc_internal
69 ABSL_NAMESPACE_END
70 } // namespace absl
71
72 #endif // ABSL_CRC_INTERNAL_CRC32C_INLINE_H_
73