55 lines
1.8 KiB
C
55 lines
1.8 KiB
C
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/*
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*
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* signatr.h
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*
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* This file defines the signatures of various T.120 objects. These
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* signatures are used mainly for debugging debug and retail versions
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* of T.120.
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*
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* T.120 used to have many many dictionaries where pointers to objects were put using
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* 16-bit values as keys to search the dictionary and get the pointer to
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* the appropriate object. These lookups were inefficient for three
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* reasons:
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*
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* 1. The lookup takes time
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* 2. The dictionaries take space
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* 3. A 16-bit value passed around requires masking to extract in a
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* 32-bit machine, that is, extra instructions.
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*
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* To eliminate these efficiency problems, the pointers to the objects are
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* used as handles to them (unique values identifying the objects).
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* But, to catch bugs caused by modifications of these handles as they are
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* passed around, we need to put a signature in each object that lets us
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* verify whether an object of type X is really an object of type X. The way
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* we do this is by specifying a unique signature for type X and putting this
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* signature into every object of type X.
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*
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* Each signature contains only 8 significant bytes.
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*/
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#ifndef _T120_SIGNATURES
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#define _T120_SIGNATURES
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// Signature length
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#define SIGNATURE_LENGTH 8
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#ifdef _DEBUG
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// The macro to compare signatures
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#define SIGNATURE_MATCH(p, s) (memcmp ((p)->mSignature, (s), SIGNATURE_LENGTH) == 0)
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// The macro to copy signatures
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#define SIGNATURE_COPY(s) (memcpy (mSignature, (s), SIGNATURE_LENGTH))
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#else // _DEBUG
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#define SIGNATURE_MATCH(p, s) (TRUE)
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# ifndef SHIP_BUILD
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# define SIGNATURE_COPY(s) (memcpy (mSignature, (s), SIGNATURE_LENGTH))
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# else // SHIP_BUILD
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# define SIGNATURE_COPY(s)
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# endif // SHIP_BUILD
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#endif // _DEBUG
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extern const char *MemorySignature;
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#endif // _T120_SIGNATURES
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