legatt
32f4597c4d
- Naming style migrated to camel-case - P7lib logger sources added - Vcpkg manifest, CMake presets and build moved to root - SDL2, Vulkan and RmlUi dependencies added - Logger LOG macro added - Logger configuration - SDL2 window configuration - Vulkan configuration - RmlUi configuration - SDL event loop
86 lines
3.8 KiB
C
86 lines
3.8 KiB
C
////////////////////////////////////////////////////////////////////////////////
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// /
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// 2012-2020 (c) Baical /
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// /
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// This library is free software; you can redistribute it and/or /
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// modify it under the terms of the GNU Lesser General Public /
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// License as published by the Free Software Foundation; either /
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// version 3.0 of the License, or (at your option) any later version. /
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// /
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// This library is distributed in the hope that it will be useful, /
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// but WITHOUT ANY WARRANTY; without even the implied warranty of /
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU /
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// Lesser General Public License for more details. /
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// /
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// You should have received a copy of the GNU Lesser General Public /
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// License along with this library. /
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// /
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////////////////////////////////////////////////////////////////////////////////
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#ifndef PCRC32_H
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#define PCRC32_H
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////////////////////////////////////////////////////////////////////////////////
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//Get_CRC32
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//This function implement 2 calculation kinds:
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// * AT&T assembler for X86 architecture for GNU C compiler
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// * standard C function for all other cases like X64 or ARM
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//Assembler code if faster than generated by GCC (o2) up to 1% it is not a lot
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//but for big amount of data and often calculation is enough to use it.
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static UNUSED_FUNC tUINT32 Get_CRC32(tUINT8 *i_pData, size_t i_szCount)
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{
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tUINT32 l_dwResult = 0xFFFFFFFF;
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if ( (NULL == i_pData)
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|| (0 >= i_szCount)
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)
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{
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return l_dwResult;
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}
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#if defined(__i386__) && defined(__GNUC__) && !defined(__PIC__)
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// Register use:
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// eax - CRC32 value
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// ebx - a lot of things
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// ecx - CRC32 value
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// edx - address of end of buffer
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// esi - address of start of buffer
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// edi - CRC32 table
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__asm__("push %%esi;" // Save the esi and edi registers
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"push %%edi;"
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//"movl l_dwResult, %%ecx;" do it already by constraints
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//"movl g_ppCRC32_Table, %%edi;"
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"leal (%%esi,%%ebx),%%edx;" // Calculate the end of the buffer
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"crc32loop:;"
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"xorl %%eax, %%eax;" // Clear the eax register"
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"movb (%%esi), %%bl;"
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"movb %%cl, %%al;" // Copy crc value into eax
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"incl %%esi;" // Advance the source pointer
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"xorb %%bl, %%al;" // Create the index into the CRC32 table
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"shr $8, %%ecx;"
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"movl (%%edi, %%eax, 4), %%ebx;" // Get the value out of the table
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"xorl %%ebx, %%ecx;" // xor with the current byte
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"cmpl %%edx, %%esi;" // Have we reached the end of the buffer?
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"jne crc32loop;"
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"pop %%edi;"
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"pop %%esi;"
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//output
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:"=c"(l_dwResult)
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//input
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:"D"(g_ppCRC32_Table), "c"(l_dwResult), "S"(i_pData), "b"(i_szCount)
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);
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#else
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for (size_t l_szI = 0; l_szI < i_szCount; l_szI ++)
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{
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l_dwResult = g_ppCRC32_Table[(l_dwResult ^ i_pData[l_szI]) & 0xFF ] ^ (l_dwResult >> 8);
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}
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/* Suppress warning that this is not used */
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(void)g_ppCRC32_Table;
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#endif
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return l_dwResult;
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}
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#endif //PCRC32_H
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