/*
 * Copyright 2008, Ingo Weinhold, ingo_weinhold@gmx.de.
 * Distributed under the terms of the MIT License.
 */


#include "SHA256.h"

#include <stdio.h>
#include <string.h>

#include <ByteOrder.h>


namespace BPrivate {


static const uint32 kChunkSize = 64;    // 64 bytes == 512 bits

static const uint32 kRounds[64] = {
   0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
   0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
   0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
   0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
   0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
   0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
   0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
   0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
};
static const uint32 kHash[8] = {
        0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
        0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
};


static inline uint32
rotate_right(uint32 value, int bits)
{
        return (value >> bits) | (value << (32 - bits));
}


//      #pragma mark -


SHA256::SHA256()
{
        Init();
}


SHA256::~SHA256()
{
}


void
SHA256::Init()
{
        memcpy(fHash, kHash, sizeof(kHash));

        fBytesInBuffer = 0;
        fMessageSize = 0;
        fDigested = false;
}


void
SHA256::Update(const void* _buffer, size_t size)
{
        const uint8* buffer = (const uint8*)_buffer;
        fMessageSize += size;

        while (fBytesInBuffer + size >= kChunkSize) {
                size_t toCopy = kChunkSize - fBytesInBuffer;
                memcpy((uint8*)fBuffer + fBytesInBuffer, buffer, toCopy);
                buffer += toCopy;
                size -= toCopy;

                _ProcessChunk();
                fBytesInBuffer = 0;
        }

        if (size > 0) {
                memcpy((uint8*)fBuffer + fBytesInBuffer, buffer, size);
                fBytesInBuffer += size;
        }
}


const uint8*
SHA256::Digest()
{
        if (!fDigested) {
                // We need to append a 1 bit, append padding with 0 bits, and append
                // the message size in bits (64 bit big-endian int), so that the whole
                // is chunk-aligned. So we either have to process one last chunk or two
                // chunks.

                // append the 1 bit
                ((uint8*)fBuffer)[fBytesInBuffer] = 0x80;
                fBytesInBuffer++;

                // if the message size doesn't fit anymore, we pad the chunk and
                // process it
                if (fBytesInBuffer > kChunkSize - 8) {
                        memset((uint8*)fBuffer + fBytesInBuffer, 0,
                                kChunkSize - fBytesInBuffer);
                        _ProcessChunk();
                        fBytesInBuffer = 0;
                }

                // pad the buffer
                if (fBytesInBuffer < kChunkSize - 8) {
                        memset((uint8*)fBuffer + fBytesInBuffer, 0,
                                kChunkSize - 8 - fBytesInBuffer);
                }

                // write the (big-endian) message size in bits
                uint64* target = (uint64*)((uint8*)fBuffer + kChunkSize - 8);
                *target = B_HOST_TO_BENDIAN_INT64((uint64)fMessageSize * 8);

                _ProcessChunk();

                // set digest
                for (int i = 0; i < 8; i++)
                        fDigest[i] = B_HOST_TO_BENDIAN_INT32(fHash[i]);

                fDigested = true;
        }

        return (uint8*)fDigest;
}


void
SHA256::_ProcessChunk()
{
        // convert endianess -- the data are supposed to be a stream of
        // 32 bit big-endian integers
        #if B_HOST_IS_LENDIAN
                for (int i = 0; i < (int)kChunkSize / 4; i++)
                        fBuffer[i] = B_SWAP_INT32(fBuffer[i]);
        #endif

        // pre-process buffer (extend to 64 elements)
        for (int i = 16; i < 64; i++) {
                uint32 v0 = fBuffer[i - 15];
                uint32 v1 = fBuffer[i - 2];
                uint32 s0 = rotate_right(v0, 7) ^ rotate_right(v0, 18) ^ (v0 >> 3);
                uint32 s1 = rotate_right(v1, 17) ^ rotate_right(v1, 19) ^ (v1 >> 10);
                fBuffer[i] = fBuffer[i - 16] + s0 + fBuffer[i - 7] + s1;
        }

        uint32 a = fHash[0];
        uint32 b = fHash[1];
        uint32 c = fHash[2];
        uint32 d = fHash[3];
        uint32 e = fHash[4];
        uint32 f = fHash[5];
        uint32 g = fHash[6];
        uint32 h = fHash[7];

        // process the buffer
        for (int i = 0; i < 64; i++) {
                uint32 s0 = rotate_right(a, 2) ^ rotate_right(a, 13)
                        ^ rotate_right(a, 22);
                uint32 maj = (a & b) ^ (a & c) ^ (b & c);
                uint32 t2 = s0 + maj;
                uint32 s1 = rotate_right(e, 6) ^ rotate_right(e, 11)
                        ^ rotate_right(e, 25);
                uint32 ch = (e & f) ^ (~e & g);
                uint32 t1 = h + s1 + ch + kRounds[i] + fBuffer[i];

                h = g;
                g = f;
                f = e;
                e = d + t1;
                d = c;
                c = b;
                b = a;
                a = t1 + t2;
        }

        fHash[0] += a;
        fHash[1] += b;
        fHash[2] += c;
        fHash[3] += d;
        fHash[4] += e;
        fHash[5] += f;
        fHash[6] += g;
        fHash[7] += h;
}


} // namespace BPrivate