+/*
+ * 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.
+ */
+void split_into_argv(char *cmdline, int *argc, char ***argv,
+ char ***argstart)
+{
+ char *p;
+ char *outputline, *q;
+ char **outputargv, **outputargstart;
+ int outputargc;
+
+ /*
+ * These argument-breaking rules apply to Visual Studio 7, which
+ * is currently the compiler expected to be used for the Windows
+ * port of my puzzles. Visual Studio 10 has different rules,
+ * lacking the curious mod 3 behaviour of consecutive quotes
+ * described below; I presume they fixed a bug. As and when we
+ * migrate to a newer compiler, we'll have to adjust this to
+ * match; however, for the moment we faithfully imitate in our GUI
+ * utilities what our CLI utilities can't be prevented from doing.
+ *
+ * When I investigated this, at first glance the rules appeared to
+ * be:
+ *
+ * - 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. And the
+ * answer to that appears somewhat bizarre. 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,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
+ *
+ *
+ * [Test fragment was of the form "a\\\"""b c" d.]
+ *
+ * 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.
+ */
+
+ /*
+ * First deal with the simplest of all special cases: if there
+ * aren't any arguments, return 0,NULL,NULL.
+ */
+ while (*cmdline && isspace(*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.
+ */
+ outputline = snewn(1+strlen(cmdline), char);
+ outputargv = snewn(strlen(cmdline)+1 / 2, char *);
+ outputargstart = snewn(strlen(cmdline)+1 / 2, char *);
+
+ p = cmdline; q = outputline; outputargc = 0;
+
+ while (*p) {
+ int quote;
+
+ /* Skip whitespace searching for start of argument. */
+ while (*p && isspace(*p)) p++;
+ if (!*p) break;
+
+ /* We have an argument; start it. */
+ outputargv[outputargc] = q;
+ outputargstart[outputargc] = p;
+ outputargc++;
+ quote = 0;
+
+ /* Copy data into the argument until it's finished. */
+ while (*p) {
+ if (!quote && isspace(*p))
+ break; /* argument is finished */
+
+ if (*p == '"' || *p == '\\') {
+ /*
+ * 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--, quote = 1;
+
+ /* Now we 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);
+ }
+ }
+ } 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);
+}
+