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Hellfire/Storm/SOURCE/SSTR.CPP
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Justin Marshall 101266ab72 Initial commit.
2026-04-27 10:35:40 -07:00

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/****************************************************************************
*
* SSTR.CPP
* String manipulation functions
*
* By Michael O'Brien (5/29/97)
*
***/
#include "pch.h"
#pragma hdrstop
#define QUOTECHAR '\"'
typedef union _PACKED {
DWORD dword;
BYTE byte[4];
} PACKED, *PACKEDPTR;
static const DWORD s_hashtable[16] = {0x486e26ee,0xdcaa16b3,0xe1918eef,0x202dafdb,
0x341c7dc7,0x1c365303,0x40ef2d37,0x65fd5e49,
0xd6057177,0x904ece93,0x1c38024f,0x98fd323b,
0xe3061ae7,0xa39b0fa1,0x9797f25f,0xe4444563};
/****************************************************************************
*
* MACROS
*
* These macros implement routines to copy strings either a byte or dword at
* at time, and to search for null terminators either a byte or dword at a
* time.
*
* To check a dword for a null terminator, the macros add the 32-bit
* constant 0x7EFEFEFF to the dword value. This causes an overflow in each
* byte in the dword unless that byte is zero. The macros then xor the
* result with the original to see which bits have changed, in order to
* determine whether there were any bytes that didn't overflow. This test is
* fast (it executes in three clock cycles on an Intel system) and 100%
* accurate in identifying null terminators where they exist. There is one
* case (0x80010101) where it falsely identifies a null terminator where none
* exists, so the code in the macros that is executed in response to a
* positive result has to test all four bytes for a null terminator, not just
* three.
*
* These macros are designed to give good performance on all systems, but are
* especially tweaked for MSVC on Intel systems, where they generate code
* that is the same as the most efficient possible assembly language
* implementation of the algorithm. This tweaking adds some complexity to
* the code, as follows:
*
* - The code to handle a dword with a null terminator in it is placed
* in a separate loop from the code that handles non-terminating dwords,
* rather than a separate "if" statement in the same loop, because
* Microsoft's compiler always generates an unconditional jump rather
* than a conditional one to a target address that can be reached from
* two or more jump statements.
*
* - The code that tests for overflows in the byte components of a dword
* tricks the compiler into thinking that the result of the test is used
* for more than just the conditional jump, so that the compiler will
* generate an "and" rather than a "test" instruction, because "and" is
* fully pairable on a Pentium processor while "test" with an immediate
* is not.
*
* - The code that checks for null bytes in a dword also emulates a "not"
* instruction by subtracting the value from 0xFFFFFFFF. Subtracting a
* value from a register and then restoring the contents of that register
* requires a total of one clock cycle on a Pentium, which is the same as
* a "not" instruction; however, it increases the opportunities for the
* compiler to reshuffle code in order to avoid delays caused by data
* dependence, and that makes a critical speed difference in this case.
*
* - The same code also tricks the compiler into thinking that the constant
* 0xFFFFFFFF might be changed at some point, so that it will store it
* in a register rather than using it as an immediate value, because
* otherwise MSVC generates code to load the immediate value into a
* register once for each iteration of the loop.
*
* Most of these tweaks are separated out in an Intel-specific macro, so that
* a more straightforward implementation of the algorithm gets used on non-
* Intel systems.
*
***/
//===========================================================================
#ifdef _X86_
static DWORD s_check_markresultused;
#define INITDWORDOPERATIONS \
DWORD check_modnum; \
DWORD check_notnum = 0xFFFFFFFF
#define CHECKFORNULLBYTES(num) \
(check_modnum = (num)+0x7EFEFEFF, \
check_notnum -= (num), \
check_modnum ^= check_notnum, \
check_notnum |= (num), \
check_modnum &= 0x81010101)
#define CHECK_ENDLOOP \
s_check_markresultused = check_modnum
#else
#define INITDWORDOPERATIONS
#define CHECKFORNULLBYTES(num) \
(((((num)+0x7EFEFEFF) ^ (num)) & 0x81010100) != 0x81010100)
#define CHECK_ENDLOOP
#endif
//===========================================================================
#ifdef _X86_
#define CHECKFORNULLBYTE0(packed) (!packed.byte[0])
#define CHECKFORNULLBYTE1(packed) (!packed.byte[1])
#define CHECKFORNULLBYTE2(packed) (!(packed.dword & 0x00FF0000))
#define CHECKFORNULLBYTE3(packed) (!(packed.dword & 0xFF000000))
#else
#define CHECKFORNULLBYTE0(packed) (!packed.byte[0])
#define CHECKFORNULLBYTE1(packed) (!packed.byte[1])
#define CHECKFORNULLBYTE2(packed) (!packed.byte[2])
#define CHECKFORNULLBYTE3(packed) (!packed.byte[3])
#endif
//===========================================================================
#define BEGINSKIP
//===========================================================================
#define SKIPLEADINGBYTES \
for (; \
(DWORD)currdest & 3; \
++currdest) \
if (!*currdest) \
goto endskip
//===========================================================================
#define SKIPALIGNEDDWORDS \
do { \
PACKED packed = *(PACKEDPTR)currdest; \
currdest += sizeof(PACKED); \
if (!CHECKFORNULLBYTES(packed.dword)) \
continue; \
if (CHECKFORNULLBYTE0(packed)) { \
currdest -= 4; \
goto endskip; \
} \
if (CHECKFORNULLBYTE1(packed)) { \
currdest -= 3; \
goto endskip; \
} \
if (CHECKFORNULLBYTE2(packed)) { \
currdest -= 2; \
goto endskip; \
} \
if (CHECKFORNULLBYTE3(packed)) { \
currdest -= 1; \
goto endskip; \
} \
CHECK_ENDLOOP; \
} while (1)
//===========================================================================
#define ENDSKIP \
endskip:
//===========================================================================
#define BEGINCOPY \
DWORD negoffset = (DWORD)-(int)(destsize-(currdest-dest))
//===========================================================================
#define COPYLEADINGBYTES \
while (((DWORD)source & 3) && negoffset) \
if (!(*(enddest+negoffset++) = *source++)) \
goto endcopy;
//===========================================================================
#define COPYALIGNEDDWORDS \
if ((int)(negoffset += 3) < 0) { \
enddest -= 3; \
\
PACKED packed = *(PACKEDPTR)source; \
source += sizeof(PACKED); \
while (!CHECKFORNULLBYTES(packed.dword)) { \
*(PACKEDPTR)(enddest+negoffset) = packed; \
if ((int)(negoffset += 4) >= 0) \
goto donealigned; \
packed = *(PACKEDPTR)source; \
source += sizeof(PACKED); \
} \
for (;;) { \
if (CHECKFORNULLBYTE0(packed)) { \
*(enddest+negoffset) = packed.byte[0]; \
negoffset += 1; \
goto endcopy; \
} \
if (CHECKFORNULLBYTE1(packed)) { \
*(LPWORD)(enddest+negoffset) = (WORD)(packed.dword); \
negoffset += 2; \
goto endcopy; \
} \
if (CHECKFORNULLBYTE2(packed)) { \
*(LPWORD)(enddest+negoffset) = (WORD)(packed.dword); \
*(enddest+negoffset+2) = 0; \
negoffset += 3; \
goto endcopy; \
} \
*(PACKEDPTR)(enddest+negoffset) = packed; \
negoffset += sizeof(PACKED); \
if (CHECKFORNULLBYTE3(packed)) \
goto endcopy; \
CHECK_ENDLOOP; \
if ((int)negoffset >= 0) \
goto donealigned; \
packed = *(PACKEDPTR)source; \
source += sizeof(PACKED); \
} \
\
donealigned: \
enddest += 3; \
} \
negoffset -= 3
//===========================================================================
#define COPYTRAILINGBYTES \
while (negoffset) \
if (!(*(enddest+negoffset++) = *source++)) \
goto endcopy; \
*enddest = 0
//===========================================================================
#define ENDCOPY \
endcopy: \
currdest = enddest+(negoffset-1);
/****************************************************************************
*
* EXPORTED FUNCTIONS
*
***/
//===========================================================================
LPTSTR APIENTRY SStrChr (LPCTSTR string,
char ch,
BOOL reverse) {
LPTSTR last = NULL;
if (reverse) {
for (LPCTSTR curr = string; *curr; ++curr)
if (*curr == ch)
last = (LPTSTR)curr;
}
else {
for (LPCTSTR curr = string; *curr; ++curr)
if (*curr == ch)
return (LPTSTR)curr;
}
return last;
}
//===========================================================================
DWORD APIENTRY SStrCopy (LPTSTR dest,
LPCTSTR source,
DWORD destsize) {
if (!destsize--)
return 0;
INITDWORDOPERATIONS;
LPTSTR currdest = dest;
LPTSTR enddest = dest+destsize;
BEGINCOPY;
COPYLEADINGBYTES;
COPYALIGNEDDWORDS;
COPYTRAILINGBYTES;
ENDCOPY;
return currdest-dest;
}
//===========================================================================
DWORD APIENTRY SStrHash (LPCTSTR string,
DWORD flags,
DWORD seed) {
DWORD result = seed ? seed : 0x7FED7FED;
DWORD adjust = 0xEEEEEEEE;
DWORD ch;
if (flags & SSTR_HASH_CASESENSITIVE)
while ((ch = (DWORD)(BYTE)*(string++)) != 0) {
result = (result+adjust) ^ (s_hashtable[ch >> 4] - s_hashtable[ch & 0x0F]);
adjust += ch+result+(adjust << 5)+3;
}
else
while ((ch = (DWORD)(BYTE)*(string++)) != 0) {
if ((ch >= (DWORD)'a') && (ch <= (DWORD)'z'))
ch = ch+(DWORD)'A'-(DWORD)'a';
if (ch == (DWORD)'/')
ch = (DWORD)'\\';
result = (result+adjust) ^ (s_hashtable[ch >> 4] - s_hashtable[ch & 0x0F]);
adjust += ch+result+(adjust << 5)+3;
}
if (!result)
++result;
return result;
}
//===========================================================================
DWORD APIENTRY SStrLen (LPCTSTR string) {
INITDWORDOPERATIONS;
LPCTSTR currdest = string;
BEGINSKIP;
SKIPLEADINGBYTES;
SKIPALIGNEDDWORDS;
ENDSKIP;
return currdest-string;
}
//===========================================================================
void APIENTRY SStrPack (LPTSTR dest,
LPCTSTR source,
DWORD destsize) {
if (!destsize--)
return;
INITDWORDOPERATIONS;
LPTSTR currdest = dest;
LPTSTR enddest = dest+destsize;
// FORCE THE DESTINATION BUFFER TO BE NULL TERMINATED
if (destsize != SSTR_UNBOUNDED)
*enddest = 0;
BEGINSKIP;
SKIPLEADINGBYTES;
SKIPALIGNEDDWORDS;
ENDSKIP;
BEGINCOPY;
COPYLEADINGBYTES;
COPYALIGNEDDWORDS;
COPYTRAILINGBYTES;
ENDCOPY;
}
//===========================================================================
void APIENTRY SStrTokenize (LPCTSTR *string,
LPTSTR buffer,
DWORD bufferchars,
LPCTSTR whitespace,
BOOL *quoted) {
BOOL checkquotes = (SStrChr(whitespace,QUOTECHAR) != NULL);
BOOL inquotes = FALSE;
BOOL usedquotes = FALSE;
LPCTSTR currsource = *string;
// SKIP PAST ALL LEADING WHITESPACE
while ((*currsource) && SStrChr(whitespace,*currsource)) {
if (checkquotes && (*currsource == QUOTECHAR)) {
usedquotes = TRUE;
inquotes = !inquotes;
}
++currsource;
}
// COPY THE TOKEN
DWORD destchars = 0;
char ch;
while ((ch = *currsource) != 0)
if (checkquotes && (ch == QUOTECHAR)) {
if (destchars && !inquotes)
break;
usedquotes = TRUE;
inquotes = !inquotes;
++currsource;
if (!inquotes)
break;
}
else if (inquotes || !SStrChr(whitespace,ch)) {
if (destchars+1 < bufferchars)
buffer[destchars++] = ch;
++currsource;
}
else {
++currsource;
break;
}
// NULL TERMINATE THE BUFFER
if (destchars < bufferchars)
buffer[destchars] = 0;
// RETURN AN UPDATED POINTER INTO THE SOURCE STRING
*string = currsource;
// RETURN TO THE APPLICATION A BOOLEAN TELLING WHETHER THIS TOKEN
// WAS IN QUOTES
if (quoted)
*quoted = usedquotes;
}
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