/**
  * SHA1 - Secure Hash Algorithm 
  * This code is a direct implementation of the algorithm presented in rfc3174.
  * No optimizations has been used, although I tried to keep it small in flashsize
  * It is written in assumption that the target architecture is little endian.
  */
#include "sha1.h"

#define H1 0x67452301
#define H2 0xEFCDAB89
#define H3 0x98BADCFE
#define H4 0x10325476
#define H5 0xC3D2E1F0

#define K1 0x5A827999
#define K2 0x6ED9EBA1
#define K3 0x8F1BBCDC
#define K4 0xCA62C1D6

#define _LROT32(x,n) (( (uint32_t)(x) << n ) | ( (uint32_t)(x) >>(32-n) ))  

/*putting this here saves a lot of code space*/
static uint32_t _sha1_chunk[80] __attribute__ ((section (".noinit"))); 
static uint8_t chunk_cnt __attribute__ ((section (".noinit"))); 

void sha1_addbyte(uint8_t c){
	uint8_t* p=(uint8_t*)_sha1_chunk;
	uint8_t i=(chunk_cnt & 0x03);

    /* chunk_cnt-i)+3-i deals with the endianess */
	p[(chunk_cnt-i)+3-i]=c;
	chunk_cnt++;
	if(chunk_cnt==64){
		/*chunk extension*/
		uint32_t a,b,c,d,e;
		for(i=16; i<80; ++i){    
            _sha1_chunk[i]= _LROT32( _sha1_chunk[i- 3] ^ 
                                     _sha1_chunk[i- 8] ^ 
                                     _sha1_chunk[i-14] ^ 
                                     _sha1_chunk[i-16], 1 );  
		}
		a=sha1_digest[4];
		b=sha1_digest[3];
		c=sha1_digest[2];
		d=sha1_digest[1];
		e=sha1_digest[0];
	
		/*main loop*/
		for(i=0;i<80;i++){
         	uint32_t f,k,temp;
		
			if(i<20){
				k=K1;
				f=(b & c) | ((~b) & d);
			}else if(i<40){
				k=K2;
				f=b ^ c ^ d;
			}else if(i<60){
				k=K3;	
				f=(b & c) | (b & d) | (c & d);
			}else{
				k=K4;
				f=b ^ c ^ d;
			}
			temp = e + k + f+_LROT32(a,5)+_sha1_chunk[i];
			e = d;
			d = c;
			c = _LROT32(b,30);
			b = a;
			a = temp;
		}

		sha1_digest[4]+=a;
		sha1_digest[3]+=b;
		sha1_digest[2]+=c;
		sha1_digest[1]+=d;
		sha1_digest[0]+=e;

		chunk_cnt=0;
	}
}

void sha1_fill(int32_t len){
	/*"append a 1-bit to the message"*/
	/*"append 0-bits to the message to obtain a length of len%512=448"*/
	/*"append length of message in bits as 64-bit integer"*/
    uint8_t j;
    uint8_t end=(uint8_t)((120-(len-(len/64)*64+1))%64);
    sha1_addbyte(0x80);
	for(j=0;j<end;j++){
		sha1_addbyte(0x00);
	}
	{
		uint64_t l=len*8;
		//pay attention to the endiness here
		sha1_addbyte( ((char*)(&l))[7]);
		sha1_addbyte( ((char*)(&l))[6]);
		sha1_addbyte( ((char*)(&l))[5]);
		sha1_addbyte( ((char*)(&l))[4]);
		sha1_addbyte( ((char*)(&l))[3]);
		sha1_addbyte( ((char*)(&l))[2]);
		sha1_addbyte( ((char*)(&l))[1]);
		sha1_addbyte( ((char*)(&l))[0]);
	}
}

void sha1(char* msg, int32_t len){
	int32_t i;
	uint8_t j;
	sha1_init();

	for(i=0; i<=len; i+=64){
		if(i+64>=len){
			for(j=0;j<len-i;j++){
				sha1_addbyte(msg[i+j]);
			}
			sha1_fill(len);
			continue;
		}
		for(j=0;j<64;j++){
			sha1_addbyte(msg[i+j]);
		}
	}
}

void sha1_init(void){
    chunk_cnt=0;
	sha1_digest[4]=H1;
	sha1_digest[3]=H2;
	sha1_digest[2]=H3;
	sha1_digest[1]=H4;
	sha1_digest[0]=H5;
}