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/*

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  This file is part of Beremiz, a Integrated Development Environment for

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  programming IEC 61131-3 automates supporting plcopen standard and CanFestival.

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  See COPYING.runtime

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  Copyright (C) 2018: Sergey Surkov <surkov.sv@summatechnology.ru>

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  Copyright (C) 2018: Andrey Skvortsov <andrej.skvortzov@gmail.com>

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*/

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#ifndef HAVE_RETAIN

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#include <stdio.h>

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#include <stdint.h>

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#include <unistd.h>

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#include "iec_types.h"

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int GetRetainSize(void);

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/* Retain buffer.  */

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FILE *retain_buffer;

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const char rb_file[]      = "retain_buffer_file";

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const char rb_file_bckp[] = "retain_buffer_file.bak";

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/* Retain header struct.  */

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struct retain_info_t {

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	uint32_t retain_size;

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	uint32_t hash_size;

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	uint8_t* hash;

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	uint32_t header_offset;

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	uint32_t header_crc;

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};

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/* Init retain info structure.  */

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struct retain_info_t retain_info;

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/* CRC lookup table and initial state.  */

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uint32_t crc32_table[256];

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uint32_t retain_crc;

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/* Generate CRC32 lookup table.  */

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void GenerateCRC32Table(void)

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{

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	unsigned int i, j;

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	/* Use CRC-32-IEEE 802.3 polynomial 0x04C11DB7 (bit reflected).  */

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	uint32_t poly = 0xEDB88320;

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	for (i = 0; i <= 0xFF; i++)

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	{

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		uint32_t c = i;

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		for (j = 0 ; j < 8 ; j++)

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			c = (c & 1) ? (c >> 1 ) ^ poly : (c >> 1);

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		crc32_table[i] = c;

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	}

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}

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/* Calculate CRC32 for len bytes from pointer buf with init starting value.  */

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uint32_t GenerateCRC32Sum(const void* buf, unsigned int len, uint32_t init)

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{

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	uint32_t crc = ~init;

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	unsigned char* current = (unsigned char*) buf;

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	while (len--)

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		crc = crc32_table[(crc ^ *current++) & 0xFF] ^ (crc >> 8);

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	return ~crc;

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}

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/* Calc CRC32 for retain file byte by byte.  */

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int CheckFileCRC(FILE* file_buffer)

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{

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	/* Set the magic constant for one-pass CRC calc according to ZIP CRC32.  */

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	const uint32_t magic_number = 0x2144df1c;

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	/* CRC initial state.  */

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	uint32_t calc_crc32 = 0;

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	char data_block = 0;

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	while(!feof(file_buffer)){

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		if (fread(&data_block, sizeof(data_block), 1, file_buffer))

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			calc_crc32 = GenerateCRC32Sum(&data_block, sizeof(data_block), calc_crc32);

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	}

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	/* Compare crc result with a magic number.  */

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	return (calc_crc32 == magic_number) ? 1 : 0;

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}

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/* Compare current hash with hash from file byte by byte.  */

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int CheckFilehash(void)

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{

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	unsigned int k;

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	int offset = sizeof(retain_info.retain_size);

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	rewind(retain_buffer);

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	fseek(retain_buffer, offset , SEEK_SET);

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	uint32_t size;

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	fread(&size, sizeof(size), 1, retain_buffer);

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	if (size != retain_info.hash_size)

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		return 0;

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	for(k = 0; k < retain_info.hash_size; k++){

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		uint8_t file_digit;

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		fread(&file_digit, sizeof(file_digit), 1, retain_buffer);

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		if (file_digit != *(retain_info.hash+k))

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			return 0;

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	}

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	return 1;

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}

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void InitRetain(void)

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{

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	unsigned int i;

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	/* Generate CRC32 lookup table.  */

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	GenerateCRC32Table();

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	/* Get retain size in bytes */

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	retain_info.retain_size = GetRetainSize();

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	/* Hash stored in retain file as array of char in hex digits

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	   (that's why we divide strlen in two).  */

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	retain_info.hash_size = PLC_ID ? strlen(PLC_ID)/2 : 0;

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	//retain_info.hash_size = 0;

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	retain_info.hash = malloc(retain_info.hash_size);

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	/* Transform hash string into byte sequence.  */

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	for (i = 0; i < retain_info.hash_size; i++) {

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		int byte = 0;

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		sscanf((PLC_ID + i*2), "%02X", &byte);

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		retain_info.hash[i] = byte;

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	}

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	/* Calc header offset.  */

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	retain_info.header_offset = sizeof(retain_info.retain_size) + \

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		sizeof(retain_info.hash_size) + \

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		retain_info.hash_size;

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	/*  Set header CRC initial state.  */

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	retain_info.header_crc = 0;

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	/* Calc crc for header.  */

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	retain_info.header_crc = GenerateCRC32Sum(

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		&retain_info.retain_size,

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		sizeof(retain_info.retain_size),

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		retain_info.header_crc);

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	retain_info.header_crc = GenerateCRC32Sum(

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		&retain_info.hash_size,

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		sizeof(retain_info.hash_size),

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		retain_info.header_crc);

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	retain_info.header_crc = GenerateCRC32Sum(

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		retain_info.hash,

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		retain_info.hash_size,

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		retain_info.header_crc);

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}

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void CleanupRetain(void)

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{

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	/* Free hash memory.  */

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	free(retain_info.hash);

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}

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int CheckRetainFile(const char * file)

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{

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	retain_buffer = fopen(file, "rb");

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	if (retain_buffer) {

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		/* Check CRC32 and hash.  */

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		if (CheckFileCRC(retain_buffer))

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			if (CheckFilehash())

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				return 1;

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		fclose(retain_buffer);

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		retain_buffer = NULL;

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	}

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	return 0;

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}

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int CheckRetainBuffer(void)

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{

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	retain_buffer = NULL;

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	if (!retain_info.retain_size)

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		return 1;

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	/* Check latest retain file.  */

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	if (CheckRetainFile(rb_file))

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		return 1;

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	/* Check if we have backup.  */

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	if (CheckRetainFile(rb_file_bckp))

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		return 1;

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	/* We don't have any valid retain buffer - nothing to remind.  */

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	return 0;

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}

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#ifndef FILE_RETAIN_SAVE_PERIOD_S

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#define FILE_RETAIN_SAVE_PERIOD_S 1.0

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#endif

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static double CalcDiffSeconds(IEC_TIME* t1, IEC_TIME *t2)

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{

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	IEC_TIME dt ={

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		t1->tv_sec  - t2->tv_sec,

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		t1->tv_nsec - t2->tv_nsec

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	};

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	if ((dt.tv_nsec < -1000000000) || ((dt.tv_sec > 0) && (dt.tv_nsec < 0))){

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		dt.tv_sec--;

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		dt.tv_nsec += 1000000000;

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	}

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	if ((dt.tv_nsec > +1000000000) || ((dt.tv_sec < 0) && (dt.tv_nsec > 0))){

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		dt.tv_sec++;

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		dt.tv_nsec -= 1000000000;

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	}

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	return dt.tv_sec + 1e-9*dt.tv_nsec;

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}

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int RetainSaveNeeded(void)

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{

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	int ret = 0;

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	static IEC_TIME last_save;

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	IEC_TIME now;

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	double diff_s;

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	/* no retain */

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	if (!retain_info.retain_size)

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		return 0;

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	/* periodic retain flush to avoid high I/O load */

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	PLC_GetTime(&now);

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	diff_s = CalcDiffSeconds(&now, &last_save);

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	if ((diff_s > FILE_RETAIN_SAVE_PERIOD_S) || ForceSaveRetainReq()) {

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		ret = 1;

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		last_save = now;

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	}

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	return ret;

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}

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void ValidateRetainBuffer(void)

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{

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	if (!retain_buffer)

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		return;

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	/* Add retain data CRC to the end of buffer file.  */

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	fseek(retain_buffer, 0, SEEK_END);

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	fwrite(&retain_crc, sizeof(retain_crc), 1, retain_buffer);

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	/* Sync file buffer and close file.  */

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#ifdef __WIN32

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	fflush(retain_buffer);

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#else

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	fsync(fileno(retain_buffer));

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#endif

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	fclose(retain_buffer);

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	retain_buffer = NULL;

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}

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void InValidateRetainBuffer(void)

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{

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	if (!RetainSaveNeeded())

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		return;

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	/* Rename old retain file into *.bak if it exists.  */

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	rename(rb_file, rb_file_bckp);

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	/* Set file CRC initial value.  */

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	retain_crc = retain_info.header_crc;

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	/* Create new retain file.  */

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	retain_buffer = fopen(rb_file, "wb+");

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	if (!retain_buffer) {

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		fprintf(stderr, "Failed to create retain file : %s\n", rb_file);

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		return;

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	}

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	/* Write header to the new file.  */

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	fwrite(&retain_info.retain_size,

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		sizeof(retain_info.retain_size), 1, retain_buffer);

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	fwrite(&retain_info.hash_size,

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		sizeof(retain_info.hash_size),   1, retain_buffer);

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	fwrite(retain_info.hash ,

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		sizeof(char), retain_info.hash_size, retain_buffer);

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}

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void Retain(unsigned int offset, unsigned int count, void *p)

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{

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	if (!retain_buffer)

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		return;

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	/* Generate CRC 32 for each data block.  */

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	retain_crc = GenerateCRC32Sum(p, count, retain_crc);

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	/* Save current var in file.  */

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	fseek(retain_buffer, retain_info.header_offset+offset, SEEK_SET);

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	fwrite(p, count, 1, retain_buffer);

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}

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void Remind(unsigned int offset, unsigned int count, void *p)

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{

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	/* Remind variable from file.  */

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	fseek(retain_buffer, retain_info.header_offset+offset, SEEK_SET);

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	fread((void *)p, count, 1, retain_buffer);

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}

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#endif // !HAVE_RETAIN