// Copyright 2008 Google Inc. All Rights Reserved.
// Author: mschilder@google.com (Marius Schilder)
//
// Optimized for minimal code size.

#include "sha.h"

#define rol(bits, value) (((value) << (bits)) | ((value) >> (32 - (bits))))

static void SHA1_Transform(SHA_CTX* ctx) {
  uint32_t W[80];
  uint32_t A, B, C, D, E;
  uint8_t* p = ctx->buf.b;
  int t;

  for(t = 0; t < 16; ++t) {
    uint32_t tmp =  *p++ << 24;
    tmp |= *p++ << 16;
    tmp |= *p++ << 8;
    tmp |= *p++;
    W[t] = tmp;
  }

  for(; t < 80; t++) {
    W[t] = rol(1,W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);
  }

  A = ctx->state[0];
  B = ctx->state[1];
  C = ctx->state[2];
  D = ctx->state[3];
  E = ctx->state[4];

  for(t = 0; t < 80; t++) {
    uint32_t tmp = rol(5,A) + E + W[t];

    if (t < 20)
      tmp += (D^(B&(C^D))) + 0x5A827999;
    else if ( t < 40)
      tmp += (B^C^D) + 0x6ED9EBA1;
    else if ( t < 60)
      tmp += ((B&C)|(D&(B|C))) + 0x8F1BBCDC;
    else
      tmp += (B^C^D) + 0xCA62C1D6;

    E = D;
    D = C;
    C = rol(30,B);
    B = A;
    A = tmp;
  }

  ctx->state[0] += A;
  ctx->state[1] += B;
  ctx->state[2] += C;
  ctx->state[3] += D;
  ctx->state[4] += E;
}

void SHA_init(SHA_CTX* ctx) {
  ctx->state[0] = 0x67452301;
  ctx->state[1] = 0xEFCDAB89;
  ctx->state[2] = 0x98BADCFE;
  ctx->state[3] = 0x10325476;
  ctx->state[4] = 0xC3D2E1F0;
  ctx->count = 0;
}


void SHA_update(SHA_CTX* ctx, const void* data, int len) {
  int i = ctx->count % sizeof(ctx->buf);
  const uint8_t* p = (const uint8_t*)data;

  ctx->count += len;

  while (len--) {
    ctx->buf.b[i++] = *p++;
    if (i == sizeof(ctx->buf)) {
      SHA1_Transform(ctx);
      i = 0;
    }
  }
}


const uint8_t* SHA_final(SHA_CTX* ctx) {
  uint8_t *p = ctx->buf.b;
  uint64_t cnt = ctx->count * 8;
  int i;

  SHA_update(ctx, (uint8_t*)"\x80", 1);
  while ((ctx->count % sizeof(ctx->buf)) != (sizeof(ctx->buf) - 8)) {
    SHA_update(ctx, (uint8_t*)"\0", 1);
  }
  for (i = 0; i < 8; ++i) {
    uint8_t tmp = cnt >> ((7 - i) * 8);
    SHA_update(ctx, &tmp, 1);
  }

  for (i = 0; i < 5; i++) {
    uint32_t tmp = ctx->state[i];
    *p++ = tmp >> 24;
    *p++ = tmp >> 16;
    *p++ = tmp >> 8;
    *p++ = tmp >> 0;
  }

  return ctx->buf.b;
}

/* Convenience function */
const uint8_t* SHA(const void* data, int len, uint8_t* digest) {
  const uint8_t* p;
  int i;
  SHA_CTX ctx;
  SHA_init(&ctx);
  SHA_update(&ctx, data, len);
  p = SHA_final(&ctx);
  for (i = 0; i < SHA_DIGEST_SIZE; ++i) {
    digest[i] = *p++;
  }
  return digest;
}