/* Copyright (C) Teemu Suutari */

#include <cstdint>

#include "Buffer.hpp"
#include "OverflowCheck.hpp"


namespace ancient::internal
{

static const uint32_t CRC32Table[256]={
	0x00000000U,0x77073096U,0xee0e612cU,0x990951baU,0x076dc419U,0x706af48fU,0xe963a535U,0x9e6495a3U,
	0x0edb8832U,0x79dcb8a4U,0xe0d5e91eU,0x97d2d988U,0x09b64c2bU,0x7eb17cbdU,0xe7b82d07U,0x90bf1d91U,
	0x1db71064U,0x6ab020f2U,0xf3b97148U,0x84be41deU,0x1adad47dU,0x6ddde4ebU,0xf4d4b551U,0x83d385c7U,
	0x136c9856U,0x646ba8c0U,0xfd62f97aU,0x8a65c9ecU,0x14015c4fU,0x63066cd9U,0xfa0f3d63U,0x8d080df5U,
	0x3b6e20c8U,0x4c69105eU,0xd56041e4U,0xa2677172U,0x3c03e4d1U,0x4b04d447U,0xd20d85fdU,0xa50ab56bU,
	0x35b5a8faU,0x42b2986cU,0xdbbbc9d6U,0xacbcf940U,0x32d86ce3U,0x45df5c75U,0xdcd60dcfU,0xabd13d59U,
	0x26d930acU,0x51de003aU,0xc8d75180U,0xbfd06116U,0x21b4f4b5U,0x56b3c423U,0xcfba9599U,0xb8bda50fU,
	0x2802b89eU,0x5f058808U,0xc60cd9b2U,0xb10be924U,0x2f6f7c87U,0x58684c11U,0xc1611dabU,0xb6662d3dU,
	0x76dc4190U,0x01db7106U,0x98d220bcU,0xefd5102aU,0x71b18589U,0x06b6b51fU,0x9fbfe4a5U,0xe8b8d433U,
	0x7807c9a2U,0x0f00f934U,0x9609a88eU,0xe10e9818U,0x7f6a0dbbU,0x086d3d2dU,0x91646c97U,0xe6635c01U,
	0x6b6b51f4U,0x1c6c6162U,0x856530d8U,0xf262004eU,0x6c0695edU,0x1b01a57bU,0x8208f4c1U,0xf50fc457U,
	0x65b0d9c6U,0x12b7e950U,0x8bbeb8eaU,0xfcb9887cU,0x62dd1ddfU,0x15da2d49U,0x8cd37cf3U,0xfbd44c65U,
	0x4db26158U,0x3ab551ceU,0xa3bc0074U,0xd4bb30e2U,0x4adfa541U,0x3dd895d7U,0xa4d1c46dU,0xd3d6f4fbU,
	0x4369e96aU,0x346ed9fcU,0xad678846U,0xda60b8d0U,0x44042d73U,0x33031de5U,0xaa0a4c5fU,0xdd0d7cc9U,
	0x5005713cU,0x270241aaU,0xbe0b1010U,0xc90c2086U,0x5768b525U,0x206f85b3U,0xb966d409U,0xce61e49fU,
	0x5edef90eU,0x29d9c998U,0xb0d09822U,0xc7d7a8b4U,0x59b33d17U,0x2eb40d81U,0xb7bd5c3bU,0xc0ba6cadU,
	0xedb88320U,0x9abfb3b6U,0x03b6e20cU,0x74b1d29aU,0xead54739U,0x9dd277afU,0x04db2615U,0x73dc1683U,
	0xe3630b12U,0x94643b84U,0x0d6d6a3eU,0x7a6a5aa8U,0xe40ecf0bU,0x9309ff9dU,0x0a00ae27U,0x7d079eb1U,
	0xf00f9344U,0x8708a3d2U,0x1e01f268U,0x6906c2feU,0xf762575dU,0x806567cbU,0x196c3671U,0x6e6b06e7U,
	0xfed41b76U,0x89d32be0U,0x10da7a5aU,0x67dd4accU,0xf9b9df6fU,0x8ebeeff9U,0x17b7be43U,0x60b08ed5U,
	0xd6d6a3e8U,0xa1d1937eU,0x38d8c2c4U,0x4fdff252U,0xd1bb67f1U,0xa6bc5767U,0x3fb506ddU,0x48b2364bU,
	0xd80d2bdaU,0xaf0a1b4cU,0x36034af6U,0x41047a60U,0xdf60efc3U,0xa867df55U,0x316e8eefU,0x4669be79U,
	0xcb61b38cU,0xbc66831aU,0x256fd2a0U,0x5268e236U,0xcc0c7795U,0xbb0b4703U,0x220216b9U,0x5505262fU,
	0xc5ba3bbeU,0xb2bd0b28U,0x2bb45a92U,0x5cb36a04U,0xc2d7ffa7U,0xb5d0cf31U,0x2cd99e8bU,0x5bdeae1dU,
	0x9b64c2b0U,0xec63f226U,0x756aa39cU,0x026d930aU,0x9c0906a9U,0xeb0e363fU,0x72076785U,0x05005713U,
	0x95bf4a82U,0xe2b87a14U,0x7bb12baeU,0x0cb61b38U,0x92d28e9bU,0xe5d5be0dU,0x7cdcefb7U,0x0bdbdf21U,
	0x86d3d2d4U,0xf1d4e242U,0x68ddb3f8U,0x1fda836eU,0x81be16cdU,0xf6b9265bU,0x6fb077e1U,0x18b74777U,
	0x88085ae6U,0xff0f6a70U,0x66063bcaU,0x11010b5cU,0x8f659effU,0xf862ae69U,0x616bffd3U,0x166ccf45U,
	0xa00ae278U,0xd70dd2eeU,0x4e048354U,0x3903b3c2U,0xa7672661U,0xd06016f7U,0x4969474dU,0x3e6e77dbU,
	0xaed16a4aU,0xd9d65adcU,0x40df0b66U,0x37d83bf0U,0xa9bcae53U,0xdebb9ec5U,0x47b2cf7fU,0x30b5ffe9U,
	0xbdbdf21cU,0xcabac28aU,0x53b39330U,0x24b4a3a6U,0xbad03605U,0xcdd70693U,0x54de5729U,0x23d967bfU,
	0xb3667a2eU,0xc4614ab8U,0x5d681b02U,0x2a6f2b94U,0xb40bbe37U,0xc30c8ea1U,0x5a05df1bU,0x2d02ef8dU};

uint32_t CRC32(const Buffer &buffer,size_t offset,size_t len,uint32_t accumulator)
{

	if (!len || OverflowCheck::sum(offset,len)>buffer.size()) throw Buffer::OutOfBoundsError();
	const uint8_t *ptr=buffer.data()+offset;
	accumulator=~accumulator;
	for (size_t i=0;i<len;i++)
		accumulator=(accumulator>>8)^CRC32Table[(accumulator&0xff)^ptr[i]];
	return ~accumulator;
}

uint32_t CRC32Byte(uint8_t ch,uint32_t accumulator) noexcept
{
	return ~((~accumulator>>8)^CRC32Table[(~accumulator&0xff)^ch]);
}

// instead of bit-twiddling lets have a separate implementation for reverse

// same table as the previous one, but reflected
static const uint32_t CRC32RevTable[256]={
	0x00000000U,0x04c11db7U,0x09823b6eU,0x0d4326d9U,0x130476dcU,0x17c56b6bU,0x1a864db2U,0x1e475005U,
	0x2608edb8U,0x22c9f00fU,0x2f8ad6d6U,0x2b4bcb61U,0x350c9b64U,0x31cd86d3U,0x3c8ea00aU,0x384fbdbdU,
	0x4c11db70U,0x48d0c6c7U,0x4593e01eU,0x4152fda9U,0x5f15adacU,0x5bd4b01bU,0x569796c2U,0x52568b75U,
	0x6a1936c8U,0x6ed82b7fU,0x639b0da6U,0x675a1011U,0x791d4014U,0x7ddc5da3U,0x709f7b7aU,0x745e66cdU,
	0x9823b6e0U,0x9ce2ab57U,0x91a18d8eU,0x95609039U,0x8b27c03cU,0x8fe6dd8bU,0x82a5fb52U,0x8664e6e5U,
	0xbe2b5b58U,0xbaea46efU,0xb7a96036U,0xb3687d81U,0xad2f2d84U,0xa9ee3033U,0xa4ad16eaU,0xa06c0b5dU,
	0xd4326d90U,0xd0f37027U,0xddb056feU,0xd9714b49U,0xc7361b4cU,0xc3f706fbU,0xceb42022U,0xca753d95U,
	0xf23a8028U,0xf6fb9d9fU,0xfbb8bb46U,0xff79a6f1U,0xe13ef6f4U,0xe5ffeb43U,0xe8bccd9aU,0xec7dd02dU,
	0x34867077U,0x30476dc0U,0x3d044b19U,0x39c556aeU,0x278206abU,0x23431b1cU,0x2e003dc5U,0x2ac12072U,
	0x128e9dcfU,0x164f8078U,0x1b0ca6a1U,0x1fcdbb16U,0x018aeb13U,0x054bf6a4U,0x0808d07dU,0x0cc9cdcaU,
	0x7897ab07U,0x7c56b6b0U,0x71159069U,0x75d48ddeU,0x6b93dddbU,0x6f52c06cU,0x6211e6b5U,0x66d0fb02U,
	0x5e9f46bfU,0x5a5e5b08U,0x571d7dd1U,0x53dc6066U,0x4d9b3063U,0x495a2dd4U,0x44190b0dU,0x40d816baU,
	0xaca5c697U,0xa864db20U,0xa527fdf9U,0xa1e6e04eU,0xbfa1b04bU,0xbb60adfcU,0xb6238b25U,0xb2e29692U,
	0x8aad2b2fU,0x8e6c3698U,0x832f1041U,0x87ee0df6U,0x99a95df3U,0x9d684044U,0x902b669dU,0x94ea7b2aU,
	0xe0b41de7U,0xe4750050U,0xe9362689U,0xedf73b3eU,0xf3b06b3bU,0xf771768cU,0xfa325055U,0xfef34de2U,
	0xc6bcf05fU,0xc27dede8U,0xcf3ecb31U,0xcbffd686U,0xd5b88683U,0xd1799b34U,0xdc3abdedU,0xd8fba05aU,
	0x690ce0eeU,0x6dcdfd59U,0x608edb80U,0x644fc637U,0x7a089632U,0x7ec98b85U,0x738aad5cU,0x774bb0ebU,
	0x4f040d56U,0x4bc510e1U,0x46863638U,0x42472b8fU,0x5c007b8aU,0x58c1663dU,0x558240e4U,0x51435d53U,
	0x251d3b9eU,0x21dc2629U,0x2c9f00f0U,0x285e1d47U,0x36194d42U,0x32d850f5U,0x3f9b762cU,0x3b5a6b9bU,
	0x0315d626U,0x07d4cb91U,0x0a97ed48U,0x0e56f0ffU,0x1011a0faU,0x14d0bd4dU,0x19939b94U,0x1d528623U,
	0xf12f560eU,0xf5ee4bb9U,0xf8ad6d60U,0xfc6c70d7U,0xe22b20d2U,0xe6ea3d65U,0xeba91bbcU,0xef68060bU,
	0xd727bbb6U,0xd3e6a601U,0xdea580d8U,0xda649d6fU,0xc423cd6aU,0xc0e2d0ddU,0xcda1f604U,0xc960ebb3U,
	0xbd3e8d7eU,0xb9ff90c9U,0xb4bcb610U,0xb07daba7U,0xae3afba2U,0xaafbe615U,0xa7b8c0ccU,0xa379dd7bU,
	0x9b3660c6U,0x9ff77d71U,0x92b45ba8U,0x9675461fU,0x8832161aU,0x8cf30badU,0x81b02d74U,0x857130c3U,
	0x5d8a9099U,0x594b8d2eU,0x5408abf7U,0x50c9b640U,0x4e8ee645U,0x4a4ffbf2U,0x470cdd2bU,0x43cdc09cU,
	0x7b827d21U,0x7f436096U,0x7200464fU,0x76c15bf8U,0x68860bfdU,0x6c47164aU,0x61043093U,0x65c52d24U,
	0x119b4be9U,0x155a565eU,0x18197087U,0x1cd86d30U,0x029f3d35U,0x065e2082U,0x0b1d065bU,0x0fdc1becU,
	0x3793a651U,0x3352bbe6U,0x3e119d3fU,0x3ad08088U,0x2497d08dU,0x2056cd3aU,0x2d15ebe3U,0x29d4f654U,
	0xc5a92679U,0xc1683bceU,0xcc2b1d17U,0xc8ea00a0U,0xd6ad50a5U,0xd26c4d12U,0xdf2f6bcbU,0xdbee767cU,
	0xe3a1cbc1U,0xe760d676U,0xea23f0afU,0xeee2ed18U,0xf0a5bd1dU,0xf464a0aaU,0xf9278673U,0xfde69bc4U,
	0x89b8fd09U,0x8d79e0beU,0x803ac667U,0x84fbdbd0U,0x9abc8bd5U,0x9e7d9662U,0x933eb0bbU,0x97ffad0cU,
	0xafb010b1U,0xab710d06U,0xa6322bdfU,0xa2f33668U,0xbcb4666dU,0xb8757bdaU,0xb5365d03U,0xb1f740b4U};

uint32_t CRC32Rev(const Buffer &buffer,size_t offset,size_t len,uint32_t accumulator)
{

	if (!len || OverflowCheck::sum(offset,len)>buffer.size()) throw Buffer::OutOfBoundsError();
	const uint8_t *ptr=buffer.data()+offset;
	accumulator=~accumulator;
	for (size_t i=0;i<len;i++)
		accumulator=(accumulator<<8)^CRC32RevTable[(accumulator>>24)^ptr[i]];
	return ~accumulator;
}

uint32_t CRC32RevByte(uint8_t ch,uint32_t &accumulator) noexcept
{
	return ~((~accumulator<<8)^CRC32RevTable[(~accumulator>>24)^ch]);
}

}