erl_bits.c

OTP是开放电信平台的简称

	byte* ptr = LSB; 
	byte c = 1;

	/* sign extend MSB */
	*MSB |= ~MAKE_MASK(bits);

	/* two's complement */
	while (ptr <= MSB) {
	    byte pd = ~(*ptr);
	    byte d = pd + c;
	    c = (d < pd);
	    *ptr++ = d;
	}
	sgn = 1;
    }

    /* normalize */
    while ((*MSB == 0) && (MSB > LSB)) {
	MSB--;
	bytes--;
    }

    /* check for guaranteed small num */
    switch (bytes) {
    case 1:
	v32 = LSB[0];
	goto big_small;
    case 2:
	v32 = LSB[0] + (LSB[1]<<8); 
	goto big_small; 
    case 3: 
	v32 = LSB[0] + (LSB[1]<<8) + (LSB[2]<<16); 
	goto big_small;
#if !defined(ARCH_64)
    case 4:
	v32 = (LSB[0] + (LSB[1]<<8) + (LSB[2]<<16) + (LSB[3]<<24));
	if (!IS_USMALL(sgn, v32)) {
	  goto make_big;
	}
#else
    case 4:
      ReadToVariable(v32, LSB, 4);					
      goto big_small;
    case 5:	
      ReadToVariable(v32, LSB, 5);					
      goto big_small;
    case 6:	
      ReadToVariable(v32, LSB, 6);
      goto big_small; 
    case 7:
      ReadToVariable(v32, LSB, 7);
      goto big_small; 
    case 8:
      ReadToVariable(v32, LSB, 8);
      if (!IS_USMALL(sgn, v32)) {
	goto make_big;   
	}
#endif   
    big_small:			/* v32 loaded with value which fits in fixnum */
	if (sgn) {
	    res = make_small(-((Sint)v32));
	} else {
	    res = make_small(v32);
	}
	break;
    make_big:
	hp = HeapOnlyAlloc(p, BIG_UINT_HEAP_SIZE);
	if (sgn) {
	  hp[0] = make_neg_bignum_header(1);
	} else {
	  hp[0] = make_pos_bignum_header(1);
	}
	BIG_DIGIT(hp,0) = DLOW(v32);
	BIG_DIGIT(hp,1) = DHIGH(v32);
	res = make_big(hp);
	break;
    default:
	words_needed = 1+WSIZE(bytes);
	hp = HeapOnlyAlloc(p, words_needed);
	hp_end = hp + words_needed;
	res = bytes_to_big(LSB, bytes, sgn, hp); 
	if (is_small(res)) {
	    p->htop = hp;
	} else if ((actual = bignum_header_arity(*hp)+1) < words_needed) {
	    p->htop = hp + actual;
	}
	break;
    }

    if (LSB != bigbuf) {
	erts_free(ERTS_ALC_T_TMP, (void *) LSB);
    }
    return res;
}

Eterm
erts_bs_get_binary_2(Process *p, Uint num_bits, unsigned flags, ErlBinMatchBuffer* mb)
{
    ErlSubBin* sb;
    size_t num_bytes;		/* Number of bytes in binary. */

    if (num_bits == 0) {		/* Empty binary. */
	return new_binary(p, NULL, 0);
    }
    if (mb->size - mb->offset < num_bits) {	/* Asked for too many bits.  */
	return THE_NON_VALUE;
    }
    

    /*
     * From now on, we can't fail.
     */

    num_bytes = NBYTES(num_bits);
    sb = (ErlSubBin *) HeapOnlyAlloc(p, ERL_SUB_BIN_SIZE);
    
    sb->thing_word = HEADER_SUB_BIN;
    sb->orig = mb->orig;
    sb->size = BYTE_OFFSET(num_bits);
    sb->bitsize = BIT_OFFSET(num_bits);
    sb->offs = BYTE_OFFSET(mb->offset);
    sb->bitoffs = BIT_OFFSET(mb->offset);
    mb->offset += num_bits;
    
    return make_binary(sb);
}

Eterm
erts_bs_get_float_2(Process *p, Uint num_bits, unsigned flags, ErlBinMatchBuffer* mb)
{
    Eterm* hp;
    float f32;
    double f64;
    byte* fptr;
    FloatDef f;

    if (num_bits == 0) {
	f.fd = 0.0;
	hp = HeapOnlyAlloc(p, FLOAT_SIZE_OBJECT);
	PUT_DOUBLE(f, hp);
	return make_float(hp);
    }
    if (mb->size - mb->offset < num_bits) {	/* Asked for too many bits.  */
	return THE_NON_VALUE;
    }
    if (num_bits == 32) {
	fptr = (byte *) &f32;
    } else if (num_bits == 64) {
	fptr = (byte *) &f64;
    } else {
	return THE_NON_VALUE;
    }

    if (BIT_IS_MACHINE_ENDIAN(flags)) {
	erts_copy_bits(mb->base, mb->offset, 1,
		  fptr, 0, 1,
		  num_bits);
    } else {
	erts_copy_bits(mb->base, mb->offset, 1,
		  fptr + NBYTES(num_bits) - 1, 0, -1,
		  num_bits);
    }
    ERTS_FP_CHECK_INIT(p);
    if (num_bits == 32) {
	ERTS_FP_ERROR_THOROUGH(p, f32, return THE_NON_VALUE);
	f.fd = f32;
    } else {
	ERTS_FP_ERROR_THOROUGH(p, f64, return THE_NON_VALUE);
	f.fd = f64;
    }
    mb->offset += num_bits;
    hp = HeapOnlyAlloc(p, FLOAT_SIZE_OBJECT);
    PUT_DOUBLE(f, hp);
    return make_float(hp);
}

Eterm
erts_bs_get_binary_all_2(Process *p, ErlBinMatchBuffer* mb)
{
  ErlSubBin* sb;
  Uint size;
  size =  mb->size-mb->offset;
  sb = (ErlSubBin *) HeapOnlyAlloc(p, ERL_SUB_BIN_SIZE);
  sb->thing_word = HEADER_SUB_BIN;
  sb->size = BYTE_OFFSET(size);
  sb->bitsize = BIT_OFFSET(size);
  sb->offs = BYTE_OFFSET(mb->offset);
  sb->bitoffs = BIT_OFFSET(mb->offset);
  sb->orig = mb->orig;
  mb->offset = mb->size;  
  return make_binary(sb);
}

void
erts_bs_save_2(int index, ErlBinMatchState* ms)
{
  ms->save_offset[index] = (ms->mb).offset;
}

void
  erts_bs_restore_2(int index, ErlBinMatchState* ms)
{
  (ms->mb).offset = ms->save_offset[index];
}


/****************************************************************
 ***
 *** Building binaries
 ***
 ****************************************************************/


/* COPY_VAL:
 * copy sz byte from val to dst buffer, 
 * dst, val are updated!!!
 */

#define COPY_VAL(dst,ddir,val,sz) do { \
   Uint __sz = (sz); \
   while(__sz) { \
     switch(__sz) { \
     default: \
     case 4: *dst = (val&0xff); dst += ddir; val >>= 8; __sz--; \
     case 3: *dst = (val&0xff); dst += ddir; val >>= 8; __sz--; \
     case 2: *dst = (val&0xff); dst += ddir; val >>= 8; __sz--; \
     case 1: *dst = (val&0xff); dst += ddir; val >>= 8; __sz--; \
     } \
   } \
 } while(0)

/* calculate a - *cp (carry)  (store result in b), *cp is updated! */
#define SUBc(a, cp, b) do { \
   byte __x = (a); \
   byte __y = (__x - (*(cp))); \
   (*cp) = (__y > __x); \
   *(b) = ~__y; \
 } while(0)
  
static int
fmt_int(byte *buf, Uint sz, Eterm val, Uint size, Uint flags)
{
    unsigned long offs;

    if (size == 0) {
	return 0;
    }

    offs = BIT_OFFSET(size);

    if (is_small(val)) {
	Sint v = signed_val(val);
	if (flags & BSF_LITTLE) { /* Little endian */
	    sz--;
	    COPY_VAL(buf,1,v,sz);
	    *buf = offs ? ((v << (8-offs)) & 0xff) : (v & 0xff);
	} else {		/* Big endian */
	    buf += (sz - 1);
	    if (offs) {
		*buf-- = (v << (8-offs)) & 0xff;
		sz--;
		v >>= offs;
	    }
	    COPY_VAL(buf,-1,v,sz);
	}
    } else if (is_big(val)) {
	int sign   = big_sign(val);
	Uint ds  = big_size(val)*sizeof(digit_t);  /* number of digits bytes */
	digit_t* dp = big_v(val);
	int n = MIN(sz,ds);

	if (flags & BSF_LITTLE) {
	    sz -= n;                       /* pad with this amount */
	    if (sign) {
		int c = 1;
		while(n >= sizeof(digit_t)) {
		    digit_t d = *dp++;
		    int i;
		    for(i = 0; i < sizeof(digit_t); ++i) {
			SUBc((d&0xff), &c, buf);
			buf++;
			d >>= 8;
		    }
		    n -= sizeof(digit_t);
		}
		if (n) {
		    digit_t d = *dp;
		    do {
			SUBc((d&0xff), &c, buf);
			buf++;
			d >>= 8;
		    } while (--n > 0);
		}
		/* pad */
		while(sz--) {
		    SUBc(0, &c, buf);
		    buf++;
		}
	    }
	    else {
		while(n >= sizeof(digit_t)) {
		    digit_t d = *dp++;
		    int i;
		    for(i = 0; i < sizeof(digit_t); ++i) {
			*buf++ = (d & 0xff);
			d >>= 8;
		    }
		    n -= sizeof(digit_t);
		}
		if (n) {
		    digit_t d = *dp;
		    do {
			*buf++ = (d & 0xff);
			d >>= 8;
		    } while (--n > 0);
		}
		/* pad */
		while(sz) {
		    *buf++ = 0;
		    sz--;
		}
	    }
	    /* adjust MSB!!! */
	    if (offs) {
		buf--;
		*buf <<= (8 - offs);
	    }
	}
	else {   /* BIG ENDIAN */
	    Uint acc = 0;	/* acc must be large enough to fit two digits */

	    buf += (sz - 1);              /* end of buffer */
	    sz -= n;                      /* pad with this amount */
	    offs = offs ? (8-offs) : 0;   /* shift offset */

	    if (sign) { /* SIGNED */
		int c = 1;

		while(n >= sizeof(digit_t)) {
		    int i;
		    acc |= (*dp++ << offs);
		    for(i = 0; i < sizeof(digit_t); ++i) {
			SUBc((acc&0xff), &c, buf);
			buf--;
			acc >>= 8;
		    }
		    n -= sizeof(digit_t);
		}
		if (n) {
		    acc |= (*dp << offs);
		    do {
			SUBc((acc & 0xff), &c, buf);
			buf--;
			acc >>= 8;
		    } while (--n > 0);
		}
		/* pad */
		while(sz--) {
		    SUBc((acc & 0xff), &c, buf);
		    buf--;
		    acc >>= 8;
		}
	    }
	    else { /* UNSIGNED */
		while(n >= sizeof(digit_t)) {
		    int i;
		    acc |= (*dp++ << offs);
		    for(i = 0; i < sizeof(digit_t); ++i) {
			*buf-- = (acc & 0xff);
			acc >>= 8;
		    }
		    n -= sizeof(digit_t);
		}
		if (n) {
		    acc |= (*dp << offs);
		    do {
			*buf-- = acc & 0xff;
			acc >>= 8;
		    } while (--n > 0);
		}
		while(sz--) {
		    *buf-- = acc & 0xff;
		    acc >>= 8;
		}
	    }
	}
    } else {			/* Neither small nor big */
	return -1;
    }
    return 0;
}

static void
ERTS_INLINE need_byte_buf(ERL_BITS_PROTO_1(int need))
{
    if (byte_buf_len < need) {
#ifdef ERTS_SMP
	erts_smp_atomic_add(&bits_bufs_size, need - byte_buf_len);
#endif
	byte_buf_len = need;
	byte_buf = erts_realloc(ERTS_ALC_T_BITS_BUF, byte_buf, byte_buf_len);
    }
}

int
erts_new_bs_put_integer(ERL_BITS_PROTO_3(Eterm arg, Uint num_bits, unsigned flags))
{
    unsigned bin_offset = erts_bin_offset;

    if (BIT_OFFSET(bin_offset) == 0) {
	if (fmt_int(erts_current_bin+BYTE_OFFSET(bin_offset),
		    NBYTES(num_bits), arg, num_bits, flags) < 0) {
	    return 0;
	}
    } else {
	byte *iptr;
	
	need_byte_buf(ERL_BITS_ARGS_1(NBYTES(num_bits)));
	iptr = byte_buf;
	if (fmt_int(iptr, NBYTES(num_bits), arg, num_bits, flags) < 0) {
	    return 0;
	}
	erts_copy_bits(iptr, 0, 1, erts_current_bin, bin_offset, 1, num_bits);
    }
    erts_bin_offset = bin_offset + num_bits;
    return 1;
}

int
erts_new_bs_put_binary(ERL_BITS_PROTO_2(Eterm arg, Uint num_bits))
{
    byte *bptr;
    Uint bitoffs;
    Uint bitsize; 

    if (!is_binary(arg)) {
	return 0;
    }
    ERTS_GET_BINARY_BYTES(arg, bptr, bitoffs, bitsize);
    if (num_bits > 8*binary_size(arg)+bitsize) {
	return 0;
    }
    copy_binary_to_buffer(erts_current_bin, erts_bin_offset, bptr, bitoffs, num_bits);
    erts_bin_offset += num_bits;
    return 1;
}

int
erts_new_bs_put_binary_all(ERL_BITS_PROTO_1(Eterm arg))
{
   byte *bptr;
   Uint bitoffs;
   Uint bitsize;
   Uint num_bits;

   if (!is_binary(arg)) {
       return 0;
   }
   ERTS_GET_BINARY_BYTES(arg, bptr, bitoffs, bitsize);
   num_bits = 8*binary_size(arg)+bitsize;
   copy_binary_to_buffer(erts_current_bin, erts_bin_offset, bptr, bitoffs, num_bits);
   erts_bin_offset += num_bits;
   return 1;
}

int
erts_new_bs_put_float(Process *c_p, Eterm arg, Uint num_bits, int flags)
{
    ERL_BITS_DEFINE_STATEP(c_p);

    if (BIT_OFFSET(erts_bin_offset) == 0) {
	Uint32 a;
	Uint32 b;
	
	if (num_bits == 64) {
	    union {
		double f64;
		Uint32 i32[2];
	    } u;

	    if (is_float(arg)) {
		FloatDef *fdp = (FloatDef*)(float_val(arg) + 1);
		a = fdp->fw[0];
		b = fdp->fw[1];
	    } else if (is_small(arg)) {
		u.f64 = (double) signed_val(arg);
		a = u.i32[0];
		b = u.i32[1];
	    } else if (is_big(arg)) {
		if (big_to_double(arg, &u.f64) < 0) {
		    return 0;
		}
		a = u.i32[0];
		b = u.i32[1];
	    } else {
		return 0;
	    }
	} else if (num_bits == 32) {
	    union {
		float f32;
		Uint32 i32;
	    } u;

	    b = 0;
	    if (is_float(arg)) {
		FloatDef f;
		GET_DOUBLE(arg, f);
		ERTS_FP_CHECK_INIT(c_p);
		u.f32 = f.fd;
		ERTS_FP_ERROR(c_p,u.f32,;);
		a = u.i32;
	    } else if (is_small(arg)) {
		u.f32 = (float) signed_val(arg);
		a = u.i32;
	    } else if (is_big(arg)) {
		double f64;
		if (big_to_double(arg, &f64) < 0) {
		    return 0;
		}
		ERTS_FP_CHECK_INIT(c_p);
		u.f32 = (float) f64;
		ERTS_FP_ERROR(c_p,u.f32,;);
		a = u.i32;
	    } else {
		return 0;
	    }
	} else {
	    return 0;
	}

	if (BIT_IS_MACHINE_ENDIAN(flags)) {
	    byte* t = erts_current_bin+BYTE_OFFSET(erts_bin_offset);
#ifdef WORDS_BIGENDIAN
	    t[0] = a >> 24;
	    t[1] = a >> 16;
	    t[2] = a >> 8;
	    t[3] = a;
	    if (num_bits == 64) {
		t[4] = b >> 24;
		t[5] = b >> 16;
		t[6] = b >> 8;
		t[7] = b;
	    }
#else
	    t[3] = a >> 24;
	    t[2] = a >> 16;
	    t[1] = a >> 8;
	    t[0] = a;