/*
* Split a complete command line into argc/argv, attempting to do it
* exactly the same way the Visual Studio C library would do it (so
* that our console utilities, which receive argc and argv already
* broken apart by the C library, will have their command lines
* processed in the same way as the GUI utilities which get a whole
* command line and must call this function).
*
* Does not modify the input command line.
*
* The final parameter (argstart) is used to return a second array
* of char * pointers, the same length as argv, each one pointing
* at the start of the corresponding element of argv in the
* original command line. So if you get half way through processing
* your command line in argc/argv form and then decide you want to
* treat the rest as a raw string, you can. If you don't want to,
* `argstart' can be safely left NULL.
*/
#include "putty.h"
/*
* The precise argument-breaking rules vary with compiler version, or
* rather, with the crt0-type startup code that comes with each
* compiler's C library. We do our best to match the compiler version,
* so that we faithfully imitate in our GUI utilities what the
* corresponding set of CLI utilities can't be prevented from doing.
*
* The basic rules are:
*
* - Single quotes are not special characters.
*
* - Double quotes are removed, but within them spaces cease to be
* special.
*
* - Backslashes are _only_ special when a sequence of them appear
* just before a double quote. In this situation, they are treated
* like C backslashes: so \" just gives a literal quote, \\" gives
* a literal backslash and then opens or closes a double-quoted
* segment, \\\" gives a literal backslash and then a literal
* quote, \\\\" gives two literal backslashes and then opens/closes
* a double-quoted segment, and so forth. Note that this behaviour
* is identical inside and outside double quotes.
*
* - Two successive double quotes become one literal double quote,
* but only _inside_ a double-quoted segment. Outside, they just
* form an empty double-quoted segment (which may cause an empty
* argument word).
*
* That only leaves the interesting question of what happens when one
* or more backslashes precedes two or more double quotes, starting
* inside a double-quoted string.
*
* Modern Visual Studio (as of 2021)
* ---------------------------------
*
* I investigated this in an ordinary CLI program, using the
* toolchain's crt0 to split a command line of the form
*
* "a\\\"""b c" d
*
* Here I tabulate number of backslashes (across the top) against
* number of quotes (down the left), and indicate how many backslashes
* are output, how many quotes are output, and whether a quoted
* segment is open at the end of the sequence:
*
* backslashes
*
* 0 1 2 3 4
*
* 0 0,0,y | 1,0,y 2,0,y 3,0,y 4,0,y
* --------+-----------------------------
* 1 0,0,n | 0,1,y 1,0,n 1,1,y 2,0,n
* q 2 0,1,y | 0,1,n 1,1,y 1,1,n 2,1,y
* u 3 0,1,n | 0,2,y 1,1,n 1,2,y 2,1,n
* o 4 0,2,y | 0,2,n 1,2,y 1,2,n 2,2,y
* t 5 0,2,n | 0,3,y 1,2,n 1,3,y 2,2,n
* e 6 0,3,y | 0,3,n 1,3,y 1,3,n 2,3,y
* s 7 0,3,n | 0,4,y 1,3,n 1,4,y 2,3,n
* 8 0,4,y | 0,4,n 1,4,y 1,4,n 2,4,y
*
* The row at the top of this table, with quotes=0, demonstrates what
* I claimed above, that when a sequence of backslashes are not
* followed by a double quote, they don't act specially at all. The
* rest of the table shows that the backslashes escape each other in
* pairs (so that with 2n or 2n+1 input backslashes you get n output
* ones); if there's an odd number of input backslashes then the last
* one escapes the first double quote (so you get a literal quote and
* enter a quoted string); thereafter, each input quote character
* either opens or closes a quoted string, and if it closes one, it
* generates a literal " as a side effect.
*
* Older Visual Studio
* -------------------
*
* But here's the corresponding table from the older Visual Studio 7:
*
* backslashes
*
* 0 1 2 3 4
*
* 0 0,0,y | 1,0,y 2,0,y 3,0,y 4,0,y
* --------+-----------------------------
* 1 0,0,n | 0,1,y 1,0,n 1,1,y 2,0,n
* q 2 0,1,n | 0,1,n 1,1,n 1,1,n 2,1,n
* u 3 0,1,y | 0,2,n 1,1,y 1,2,n 2,1,y
* o 4 0,1,n | 0,2,y 1,1,n 1,2,y 2,1,n
* t 5 0,2,n | 0,2,n 1,2,n 1,2,n 2,2,n
* e 6 0,2,y | 0,3,n 1,2,y 1,3,n 2,2,y
* s 7 0,2,n | 0,3,y 1,2,n 1,3,y 2,2,n
* 8 0,3,n | 0,3,n 1,3,n 1,3,n 2,3,n
* 9 0,3,y | 0,4,n 1,3,y 1,4,n 2,3,y
* 10 0,3,n | 0,4,y 1,3,n 1,4,y 2,3,n
* 11 0,4,n | 0,4,n 1,4,n 1,4,n 2,4,n
*
* There is very weird mod-3 behaviour going on here in the number of
* quotes, and it even applies when there aren't any backslashes! How
* ghastly.
*
* With a bit of thought, this extremely odd diagram suddenly
* coalesced itself into a coherent, if still ghastly, model of how
* things work:
*
* - As before, backslashes are only special when one or more of them
* appear contiguously before at least one double quote. In this
* situation the backslashes do exactly what you'd expect: each one
* quotes the next thing in front of it, so you end up with n/2
* literal backslashes (if n is even) or (n-1)/2 literal
* backslashes and a literal quote (if n is odd). In the latter
* case the double quote character right after the backslashes is
* used up.
*
* - After that, any remaining double quotes are processed. A string
* of contiguous unescaped double quotes has a mod-3 behaviour:
*
* * inside a quoted segment, a quote ends the segment.
* * _immediately_ after ending a quoted segment, a quote simply
* produces a literal quote.
* * otherwise, outside a quoted segment, a quote begins a quoted
* segment.
*
* So, for example, if we started inside a quoted segment then two
* contiguous quotes would close the segment and produce a literal
* quote; three would close the segment, produce a literal quote,
* and open a new segment. If we started outside a quoted segment,
* then two contiguous quotes would open and then close a segment,
* producing no output (but potentially creating a zero-length
* argument); but three quotes would open and close a segment and
* then produce a literal quote.
*
* I don't know exactly when the bug fix happened, but I know that VS7
* had the odd mod-3 behaviour. So the #if below will ensure that
* modern (2015 onwards) versions of VS use the new more sensible
* behaviour, and VS7 uses the old one. Things in between may be
* wrong; if anyone cares, patches to change the cutoff version in
* this #if are welcome.
*/
#if _MSC_VER < 1400
#define MOD3 1
#else
#define MOD3 0
#endif
#ifdef SPLIT_INTO_ARGV_W
#define FUNCTION split_into_argv_w
#define CHAR wchar_t
#define STRLEN wcslen
#else
#define FUNCTION split_into_argv
#define CHAR char
#define STRLEN strlen
#endif
static inline bool is_word_sep(CHAR c)
{
return c == ' ' || c == '\t';
}
void FUNCTION(CHAR *cmdline, bool includes_program_name,
int *argc, CHAR ***argv, CHAR ***argstart)
{
CHAR *p;
CHAR *outputline, *q;
CHAR **outputargv, **outputargstart;
int outputargc;
/*
* First deal with the simplest of all special cases: if there
* aren't any arguments, return 0,NULL,NULL.
*/
while (*cmdline && is_word_sep(*cmdline)) cmdline++;
if (!*cmdline) {
if (argc) *argc = 0;
if (argv) *argv = NULL;
if (argstart) *argstart = NULL;
return;
}
/*
* This will guaranteeably be big enough; we can realloc it
* down later.
*/
{
size_t len = STRLEN(cmdline);
outputline = snewn(1+len, CHAR);
outputargv = snewn((len+1) / 2, CHAR *);
outputargstart = snewn((len+1) / 2, CHAR *);
}
p = cmdline; q = outputline; outputargc = 0;
while (*p) {
bool quote;
/* Skip whitespace searching for start of argument. */
while (*p && is_word_sep(*p)) p++;
if (!*p) break;
/*
* Check if this argument is the program name. If so,
* different rules apply.
*
* In most arguments, the special characters are the double
* quote and the backslash. An exception is the program name
* at the start of the command line, in which backslashes are
* _not_ special - if one appears before a quote, it does not
* make the quote literal.
*
* The C library must implement this special rule, and we must
* follow suit here, in order to match the way CreateProcess
* scans the command line to determine the program name. It
* will consider that all these commands refer to the same
* file equally validly:
*
* "C:\Program Files\Foo"\bar.exe
* "C:\Program Files\Foo\"bar.exe
* "C:\Program Files\Foo\bar.exe"
*
* Each one contains a quoted section that protects the space
* in "Program Files", and the closing quote takes effect the
* same in all cases - even though, in the middle case, it's
* immediately preceded by one of the path separators in the
* name. For CreateProcess, backslashes aren't special.
*
* So, if our caller told us that the input command line
* includes the program name (which it does if it came from
* GetCommandLine, but not if it was passed in to WinMain),
* then we must treat the 0th output argument specially, by
* not considering backslashes to affect the quoting.
*/
bool backslash_special = !(outputargc == 0 && includes_program_name);
/* We have an argument; start it. */
outputargv[outputargc] = q;
outputargstart[outputargc] = p;
outputargc++;
quote = false;
/* Copy data into the argument until it's finished. */
while (*p) {
if (!quote && is_word_sep(*p))
break; /* argument is finished */
if (*p == '"' || (*p == '\\' && backslash_special)) {
/*
* We have a sequence of zero or more backslashes
* followed by a sequence of zero or more quotes.
* Count up how many of each, and then deal with
* them as appropriate.
*/
int i, slashes = 0, quotes = 0;
while (*p == '\\') slashes++, p++;
while (*p == '"') quotes++, p++;
if (!quotes) {
/*
* Special case: if there are no quotes,
* slashes are not special at all, so just copy
* n slashes to the output string.
*/
while (slashes--) *q++ = '\\';
} else {
/* Slashes annihilate in pairs. */
while (slashes >= 2) slashes -= 2, *q++ = '\\';
/* One remaining slash takes out the first quote. */
if (slashes) quotes--, *q++ = '"';
if (quotes > 0) {
/* Outside a quote segment, a quote starts one. */
if (!quote) quotes--;
#if !MOD3
/* New behaviour: produce n/2 literal quotes... */
for (i = 2; i <= quotes; i += 2) *q++ = '"';
/* ... and end in a quote segment iff 2 divides n. */
quote = (quotes % 2 == 0);
#else
/* Old behaviour: produce (n+1)/3 literal quotes... */
for (i = 3; i <= quotes+1; i += 3) *q++ = '"';
/* ... and end in a quote segment iff 3 divides n. */
quote = (quotes % 3 == 0);
#endif
}
}
} else {
*q++ = *p++;
}
}
/* At the end of an argument, just append a trailing NUL. */
*q++ = '\0';
}
outputargv = sresize(outputargv, outputargc, CHAR *);
outputargstart = sresize(outputargstart, outputargc, CHAR *);
if (argc) *argc = outputargc;
if (argv) *argv = outputargv; else sfree(outputargv);
if (argstart) *argstart = outputargstart; else sfree(outputargstart);
}