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[CMD] Fix delayed expansion of variables.

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CORE-13682

- Split SubstituteVars() into its main loop and a helper SubstituteVar()
  that just substitutes only one variable.

- Use this new helper as the basis of the proper implementation of the
  delayed expansion of variables.

- Fix a bug introduced in commit 495c82cc, when GetBatchVar() fails.
This commit is contained in:
Hermès Bélusca-Maïto 2020-06-04 02:56:18 +02:00
parent cb2a9c31a6
commit cdc8e45b48
No known key found for this signature in database
GPG Key ID: 3B2539C65E7B93D0
2 changed files with 220 additions and 56 deletions
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255
base/shell/cmd/cmd.c
View File

@ -1318,32 +1318,52 @@ GetBatchVar(
}
BOOL
SubstituteVars(TCHAR *Src, TCHAR *Dest, TCHAR Delim)
SubstituteVar(
IN PCTSTR Src,
OUT size_t* SrcIncLen, // VarNameLen
OUT PTCHAR Dest,
IN PTCHAR DestEnd,
OUT size_t* DestIncLen,
IN TCHAR Delim)
{
#define APPEND(From, Length) { \
#define APPEND(From, Length) \
do { \
if (Dest + (Length) > DestEnd) \
goto too_long; \
memcpy(Dest, From, (Length) * sizeof(TCHAR)); \
Dest += Length; }
#define APPEND1(Char) { \
memcpy(Dest, (From), (Length) * sizeof(TCHAR)); \
Dest += (Length); \
} while (0)
#define APPEND1(Char) \
do { \
if (Dest >= DestEnd) \
goto too_long; \
*Dest++ = Char; }
*Dest++ = (Char); \
} while (0)
TCHAR *DestEnd = Dest + CMDLINE_LENGTH - 1;
const TCHAR *Var;
int VarLength;
TCHAR *SubstStart;
PCTSTR Var;
PCTSTR Start, End, SubstStart;
TCHAR EndChr;
while (*Src)
{
if (*Src != Delim)
{
APPEND1(*Src++)
continue;
}
size_t VarLength;
Src++;
Start = Src;
End = Dest;
*SrcIncLen = 0;
*DestIncLen = 0;
if (!Delim)
return FALSE;
if (*Src != Delim)
return FALSE;
++Src;
/* If we are already at the end of the string, fail the substitution */
SubstStart = Src;
if (!*Src || *Src == _T('\r') || *Src == _T('\n'))
goto bad_subst;
{
if (bc && Delim == _T('%'))
{
UINT NameLen;
@ -1353,15 +1373,15 @@ SubstituteVars(TCHAR *Src, TCHAR *Dest, TCHAR Delim)
/* Return the partially-parsed command to be
* echoed for error diagnostics purposes. */
APPEND1(Delim);
APPEND(Src, DestEnd-Dest);
APPEND(Src, _tcslen(Src) + 1);
return FALSE;
}
if (Var != NULL)
{
VarLength = _tcslen(Var);
APPEND(Var, VarLength)
APPEND(Var, VarLength);
Src += NameLen;
continue;
goto success;
}
}
@ -1369,22 +1389,25 @@ SubstituteVars(TCHAR *Src, TCHAR *Dest, TCHAR Delim)
* end the name and begin the optional modifier, but not if it
* is immediately followed by the delimiter (%VAR:%). */
SubstStart = Src;
while (*Src != Delim && !(*Src == _T(':') && Src[1] != Delim))
while (*Src && *Src != Delim && !(*Src == _T(':') && Src[1] != Delim))
{
if (!*Src)
goto bad_subst;
Src++;
++Src;
}
/* If we are either at the end of the string, or the delimiter
* has been repeated more than once, fail the substitution. */
if (!*Src || Src == SubstStart)
goto bad_subst;
EndChr = *Src;
*Src = _T('\0');
*(PTSTR)Src = _T('\0'); // FIXME: HACK!
Var = GetEnvVarOrSpecial(SubstStart);
*Src++ = EndChr;
*(PTSTR)Src++ = EndChr;
if (Var == NULL)
{
/* In a batch file, %NONEXISTENT% "expands" to an empty string */
/* In a batch context, %NONEXISTENT% "expands" to an
* empty string, otherwise fail the substitution. */
if (bc)
continue;
goto success;
goto bad_subst;
}
VarLength = _tcslen(Var);
@ -1392,21 +1415,22 @@ SubstituteVars(TCHAR *Src, TCHAR *Dest, TCHAR Delim)
if (EndChr == Delim)
{
/* %VAR% - use as-is */
APPEND(Var, VarLength)
APPEND(Var, VarLength);
}
else if (*Src == _T('~'))
{
/* %VAR:~[start][,length]% - substring
* Negative values are offsets from the end */
int Start = _tcstol(Src + 1, &Src, 0);
int End = VarLength;
* Negative values are offsets from the end.
*/
size_t Start = _tcstol(Src + 1, (PTSTR*)&Src, 0);
size_t End = VarLength;
if (Start < 0)
Start += VarLength;
Start = max(Start, 0);
Start = min(Start, VarLength);
if (*Src == _T(','))
{
End = _tcstol(Src + 1, &Src, 0);
End = _tcstol(Src + 1, (PTSTR*)&Src, 0);
End += (End < 0) ? VarLength : Start;
End = max(End, Start);
End = min(End, VarLength);
@ -1417,13 +1441,14 @@ SubstituteVars(TCHAR *Src, TCHAR *Dest, TCHAR Delim)
}
else
{
/* %VAR:old=new% - replace all occurrences of old with new
* %VAR:*old=new% - replace first occurrence only,
* and remove everything before it */
TCHAR *Old, *New;
DWORD OldLength, NewLength;
/* %VAR:old=new% - Replace all occurrences of old with new.
* %VAR:*old=new% - Replace first occurrence only,
* and remove everything before it.
*/
PCTSTR Old, New;
size_t OldLength, NewLength;
BOOL Star = FALSE;
int LastMatch = 0, i = 0;
size_t LastMatch = 0, i = 0;
if (*Src == _T('*'))
{
@ -1431,7 +1456,7 @@ SubstituteVars(TCHAR *Src, TCHAR *Dest, TCHAR Delim)
Src++;
}
/* the string to replace may contain the delimiter */
/* The string to replace may contain the delimiter */
Src = _tcschr(Old = Src, _T('='));
if (Src == NULL)
goto bad_subst;
@ -1449,8 +1474,8 @@ SubstituteVars(TCHAR *Src, TCHAR *Dest, TCHAR Delim)
if (_tcsnicmp(&Var[i], Old, OldLength) == 0)
{
if (!Star)
APPEND(&Var[LastMatch], i - LastMatch)
APPEND(New, NewLength)
APPEND(&Var[LastMatch], i - LastMatch);
APPEND(New, NewLength);
i += OldLength;
LastMatch = i;
if (Star)
@ -1459,21 +1484,87 @@ SubstituteVars(TCHAR *Src, TCHAR *Dest, TCHAR Delim)
}
i++;
}
APPEND(&Var[LastMatch], VarLength - LastMatch)
APPEND(&Var[LastMatch], VarLength - LastMatch);
}
continue;
goto success;
bad_subst:
Src = SubstStart;
/* Only if no batch context active do we echo the delimiter */
if (!bc)
APPEND1(Delim)
APPEND1(Delim);
}
*Dest = _T('\0');
success:
*SrcIncLen = (Src - Start);
*DestIncLen = (Dest - End);
return TRUE;
too_long:
ConOutResPrintf(STRING_ALIAS_ERROR);
nErrorLevel = 9023;
return FALSE;
#undef APPEND
#undef APPEND1
}
BOOL
SubstituteVars(
IN PCTSTR Src,
OUT PTSTR Dest,
IN TCHAR Delim)
{
#define APPEND(From, Length) \
do { \
if (Dest + (Length) > DestEnd) \
goto too_long; \
memcpy(Dest, (From), (Length) * sizeof(TCHAR)); \
Dest += (Length); \
} while (0)
#define APPEND1(Char) \
do { \
if (Dest >= DestEnd) \
goto too_long; \
*Dest++ = (Char); \
} while (0)
PTCHAR DestEnd = Dest + CMDLINE_LENGTH - 1;
PCTSTR End;
size_t SrcIncLen, DestIncLen;
while (*Src /* && (Dest < DestEnd) */)
{
if (*Src != Delim)
{
End = _tcschr(Src, Delim);
if (End == NULL)
End = Src + _tcslen(Src);
APPEND(Src, End - Src);
Src = End;
continue;
}
if (!SubstituteVar(Src, &SrcIncLen, Dest, DestEnd, &DestIncLen, Delim))
{
return FALSE;
}
else
{
Src += SrcIncLen;
Dest += DestIncLen;
}
}
APPEND1(_T('\0'));
return TRUE;
too_long:
ConOutResPrintf(STRING_ALIAS_ERROR);
nErrorLevel = 9023;
return FALSE;
#undef APPEND
#undef APPEND1
}
@ -1545,11 +1636,15 @@ SubstituteForVars(
return TRUE;
}
LPTSTR
DoDelayedExpansion(LPTSTR Line)
PTSTR
DoDelayedExpansion(
IN PCTSTR Line)
{
TCHAR Buf1[CMDLINE_LENGTH];
TCHAR Buf2[CMDLINE_LENGTH];
PTCHAR Src, Dst;
PTCHAR DestEnd = Buf2 + CMDLINE_LENGTH - 1;
size_t SrcIncLen, DestIncLen;
/* First, substitute FOR variables */
if (!SubstituteForVars(Line, Buf1))
@ -1558,12 +1653,64 @@ DoDelayedExpansion(LPTSTR Line)
if (!bDelayedExpansion || !_tcschr(Buf1, _T('!')))
return cmd_dup(Buf1);
/* FIXME: Delayed substitutions actually aren't quite the same as
* immediate substitutions. In particular, it's possible to escape
* the exclamation point using ^. */
if (!SubstituteVars(Buf1, Buf2, _T('!')))
return NULL;
/*
* Delayed substitutions are not actually completely the same as
* immediate substitutions. In particular, it is possible to escape
* the exclamation point using the escape caret.
*/
/*
* Perform delayed expansion: expand variables around '!',
* and reparse escape carets.
*/
#define APPEND1(Char) \
do { \
if (Dst >= DestEnd) \
goto too_long; \
*Dst++ = (Char); \
} while (0)
Src = Buf1;
Dst = Buf2;
while (*Src && (Src < &Buf1[CMDLINE_LENGTH]))
{
if (*Src == _T('^'))
{
++Src;
if (!*Src || !(Src < &Buf1[CMDLINE_LENGTH]))
break;
APPEND1(*Src++);
}
else if (*Src == _T('!'))
{
if (!SubstituteVar(Src, &SrcIncLen, Dst, DestEnd, &DestIncLen, _T('!')))
{
return NULL; // Got an error during parsing.
}
else
{
Src += SrcIncLen;
Dst += DestIncLen;
}
}
else
{
APPEND1(*Src++);
}
continue;
}
APPEND1(_T('\0'));
return cmd_dup(Buf2);
too_long:
ConOutResPrintf(STRING_ALIAS_ERROR);
nErrorLevel = 9023;
return NULL;
#undef APPEND1
}

21
base/shell/cmd/cmd.h
View File

@ -95,14 +95,31 @@ ExecuteCommandWithEcho(
LPCTSTR GetEnvVarOrSpecial ( LPCTSTR varName );
VOID AddBreakHandler (VOID);
VOID RemoveBreakHandler (VOID);
BOOL SubstituteVars(TCHAR *Src, TCHAR *Dest, TCHAR Delim);
BOOL
SubstituteVar(
IN PCTSTR Src,
OUT size_t* SrcIncLen, // VarNameLen
OUT PTCHAR Dest,
IN PTCHAR DestEnd,
OUT size_t* DestIncLen,
IN TCHAR Delim);
BOOL
SubstituteVars(
IN PCTSTR Src,
OUT PTSTR Dest,
IN TCHAR Delim);
BOOL
SubstituteForVars(
IN PCTSTR Src,
OUT PTSTR Dest);
LPTSTR DoDelayedExpansion(LPTSTR Line);
PTSTR
DoDelayedExpansion(
IN PCTSTR Line);
INT DoCommand(LPTSTR first, LPTSTR rest, struct _PARSED_COMMAND *Cmd);
BOOL ReadLine(TCHAR *commandline, BOOL bMore);