71 lines
1.7 KiB
Groff
71 lines
1.7 KiB
Groff
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.\"
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.\" Copyright 1992 by Jutta Degener and Carsten Bormann, Technische
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.\" Universitaet Berlin. See the accompanying file "COPYRIGHT" for
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.\" details. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
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.\"
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.PU
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.TH BITTER 1
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.SH NAME
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bitter, sweet \(em code-generators for packing bits
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.SH SYNOPSIS
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bitter < input > output
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.br
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sweet < input > output
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.SH "DESCRIPTION"
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Bitter and sweet are two filters which turn a description of the
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form
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.nf
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name number-of-bits
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name number-of-bits
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...
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.nf
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into code.
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.PP
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Bitter generates code that packs the specified bits from their
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variables into an array of unsigned char referenced by an
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advancing pointer c.
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.PP
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Sweet generates code that unpacks the specified bits from an array
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of unsigned char referenced by a mutable pointer c into the
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named variables.
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.\" .SH OPTIONS
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.\" .SH "RETURN VALUE"
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.\" .SH ERRORS
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.SH EXAMPLES
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.nf
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% cat in
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amaretto 1
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banana 2
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cherry 3
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strawberry 4
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vanilla 15
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walnut 15
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% bitter < in
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*c++ = ((amaretto & 0x1) << 7)
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| ((banana & 0x3) << 5)
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| ((cherry & 0x7) << 2)
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| ((strawberry >> 2) & 0x3);
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*c++ = ((strawberry & 0x3) << 6)
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| ((vanilla >> 9) & 0x3F);
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*c++ = ((vanilla >> 1) & 0xFF);
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*c++ = ((vanilla & 0x1) << 7)
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| ((walnut >> 8) & 0x7F);
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*c++ = walnut & 0xFF;
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% sweet < in
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amaretto = (*c >> 7) & 0x1;
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banana = (*c >> 5) & 0x3;
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cherry = (*c >> 2) & 0x7;
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strawberry = (*c++ & 0x3) << 2;
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strawberry |= (*c >> 6) & 0x3;
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vanilla = (*c++ & 0x3F) << 9;
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vanilla |= (*c++ & 0xFF) << 1;
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vanilla |= (*c >> 7) & 0x1;
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walnut = (*c++ & 0x7F) << 8;
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walnut |= *c++;
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.SH NOTES
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This is a quick hack for the gsm_encode() and gsm_decode() routines.
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.SH BUGS
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Please direct bug reports to jutta@cs.tu-berlin.de and cabo@cs.tu-berlin.de.
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