86 lines
2.3 KiB
C++
86 lines
2.3 KiB
C++
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// HEXTOSTR.CPP
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//
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// Utility functions to convert hexadecimal numbers into equivalent string
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// representations.
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//
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// Note: These functions are in their own file, rather than in STRUTIL.CPP,
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// because they use a const array. The current implementation of the linker
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// pulls this array into binaries if they use any function in the source file,
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// not just the functions which reference this array.
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#include "precomp.h"
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#include <strutil.h>
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const CHAR rgchHexNumMap[] =
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{
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'0', '1', '2', '3', '4', '5', '6', '7',
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'8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
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};
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//
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// QWordToHexString()
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//
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// Converts a ULARGE_INTEGER to an ANSI string (not prefixed with 0x or 0X)
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//
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// NOTE: pszString must point to a buffer of at least CCHMAX_ULARGE_INTEGER chars
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//
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// Returns the number of characters written (not including the NULL terminator)
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int NMINTERNAL QWordToHexStringA(ULARGE_INTEGER qw, LPSTR pszString)
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{
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ASSERT(!IsBadWritePtr(pszString, sizeof(*pszString)*CCHMAX_HEX_ULARGE_INTEGER));
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LPSTR pszCurrent = pszString;
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DWORD dwQwParts[] = {qw.HighPart, qw.LowPart};
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int i;
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// Walk the QWORD four bits at a time, mapping them to the appropriate
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// char and storing them in the caller-supplied buffer.
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// We loop through the QWORD twice, working on each DWORD separately
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for (i = 0; i < ARRAY_ELEMENTS(dwQwParts); i++)
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{
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DWORD dwQwPart = dwQwParts[i];
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// Optimization: We only need to look at this DWORD part if it's
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// non-zero or we've already put chars in our buffer.
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if (dwQwPart || pszCurrent != pszString)
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{
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// <j> is the zero-based index of the low bit of the four-bit
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// range on which we're operating.
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int j;
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DWORD dwMask;
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for (j = BITS_PER_HEX_CHAR * (CCH_HEX_DWORD - 1),
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dwMask = 0xFL << j;
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j >= 0;
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j -= BITS_PER_HEX_CHAR,
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dwMask >>= BITS_PER_HEX_CHAR)
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{
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DWORD iDigit = (dwQwPart & dwMask) >> j;
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ASSERT(0xF >= iDigit);
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// We use this test to skip leading zeros
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if (pszCurrent != pszString || iDigit)
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{
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*pszCurrent++ = rgchHexNumMap[iDigit];
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}
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}
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}
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}
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// If the number was zero, we need to set it explicitly
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if (pszCurrent == pszString)
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{
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*pszCurrent++ = '0';
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}
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// Null terminate the string
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*pszCurrent = '\0';
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// Return the number of chars, not counting the null terminator
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return (int)(pszCurrent - pszString);
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}
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