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58 lines
1.3 KiB
Markdown
58 lines
1.3 KiB
Markdown
### CRC32c function
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- Same code from : https://stackoverflow.com/a/17646775
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- Fixed some alignment issues, replaced asm code with compiler intrinsics
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- This is Crc32<b>c</b> algorithm, not Crc32
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- Compile time switch to hardware version if supported
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(crc32c instruction on x64), fallback to software version if not available
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- You should compile with "-msse4.2" flag and define HAVE_CRC32C to use hardware
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version
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- Stackoverflow answer has runtime dispatch between hardware and software
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versions if you'd like that.
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```cmake
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## Cmake
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# Needs HAVE_CRC32C definition to enable CPU instruction usage.
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## Only use hardware version in 64 bit architectures.
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include(CheckCCompilerFlag)
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if("${CMAKE_SIZEOF_VOID_P}" EQUAL "8")
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check_c_compiler_flag(-msse4.2 HAVE_CRC32_HARDWARE)
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if (${HAVE_CRC32_HARDWARE})
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set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -msse4.2 -DHAVE_CRC32C")
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endif ()
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endif()
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```
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```c
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#include "sc_crc32.h"
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#include <stdio.h>
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int main(int argc, char *argv[])
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{
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uint32_t crc;
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const uint8_t buf[100] = {0};
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sc_crc32_init();
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// Partial calculation example
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crc = sc_crc32(0, buf, 10);
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crc = sc_crc32(crc, buf + 10, sizeof(buf) - 10);
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printf("crc : %u \n", crc);
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// Calculate at once
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crc = sc_crc32(0, buf, sizeof(buf));
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printf("crc : %u \n", crc);
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return 0;
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}
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``` |