Jack wrote:

Hi

I am having a little trouble trying to read a binary file, I would like

to write an ascii to Metastock converter in python but am not having a

lot of success.

The file formats are

http://sf.gds.tuwien.ac.at/00-pdf/m/.../MetaStock.pdf

If any one can point me in the right direction it would be much

appreciated.

So far I have tried opening file "rb" then trying to use struct and

then binascii but I am not too sure what I should be doing and fuction

I should be using in binascii ?

TIA

Jack,

What you may not realize is that Metastock is using an oddball floating

point format.

I have not looked at this for many years now but remember using a small

VB-callable dll with functions BasicToIEEE and IEEEToBasic. This may

help you in recoding conversions into Python.

float BasicToIEEE (unsigned char *value)

{ float result;

unsigned char *msbin = (unsigned char *) value;

unsigned char *ieee = (unsigned char *) &result;

unsigned char sign = 0x00;

unsigned char ieee_exp = 0x00;

int i;

/* MS Binary Format */

/* byte order => m3 | m2 | m1 | exponent */

/* m1 is most significant byte => sbbb|bbbb */

/* m3 is the least significant byte */

/* m = mantissa byte */

/* s = sign bit */

/* b = bit */

sign = msbin[2] & 0x80; /* 1000|0000b */

/* IEEE Single Precision Float Format */

/* m3 m2 m1 exponent */

/* mmmm|mmmm mmmm|mmmm emmm|mmmm seee|eeee */

/* s = sign bit */

/* e = exponent bit */

/* m = mantissa bit */

for (i=0; i<4; i++) ieee[i] = 0;

/* any msbin w/ exponent of zero = zero */

if (msbin[3] == 0) return 0;

ieee[3] |= sign;

/* MBF is bias 128 and IEEE is bias 127. ALSO, MBF places */

/* the decimal point before the assumed bit, while */

/* IEEE places the decimal point after the assumed bit. */

ieee_exp = msbin[3] - 2; /* actually, msbin[3]-1-128+127 */

/* the first 7 bits of the exponent in ieee[3] */

ieee[3] |= ieee_exp >> 1;

/* the one remaining bit in first bin of ieee[2] */

ieee[2] |= ieee_exp << 7;

/* 0111|1111b : mask out the msbin sign bit */

ieee[2] |= msbin[2] & 0x7f;

ieee[1] = msbin[1];

ieee[0] = msbin[0];

return (result);

}

bool IEEEToBasic (float *value, unsigned char *result)

{ unsigned char *ieee = (unsigned char *) value;

unsigned char *msbin = (unsigned char *) result;

unsigned char sign = 0x00;

unsigned char msbin_exp = 0x00;

int i;

/* See _fmsbintoieee() for details of formats */

sign = ieee[3] & 0x80;

msbin_exp |= ieee[3] << 1;

msbin_exp |= ieee[2] >> 7;

/* An ieee exponent of 0xfe overflows in MBF */

if (msbin_exp == 0xfe) return (FALSE);

msbin_exp += 2; /* actually, -127 + 128 + 1 */

for (i=0; i<4; i++) msbin[i] = 0;

msbin[3] = msbin_exp;

msbin[2] |= sign;

msbin[2] |= ieee[2] & 0x7f;

msbin[1] = ieee[1];

msbin[0] = ieee[0];

return (TRUE);

}

Good luck,

malv