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+/*
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+ * Wildcard matching engine for use with SFTP-based file transfer
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+ * programs (PSFTP, new-look PSCP): since SFTP has no notion of
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+ * getting the remote side to do globbing (and rightly so) we have
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+ * to do it locally, by retrieving all the filenames in a directory
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+ * and checking each against the wildcard pattern.
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+ */
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+
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+#include <assert.h>
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+#include <stdlib.h>
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+#include <string.h>
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+
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+#include "wildcard.h"
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+
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+/*
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+ * Definition of wildcard syntax:
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+ *
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+ * - * matches any sequence of characters, including zero.
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+ * - ? matches exactly one character which can be anything.
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+ * - [abc] matches exactly one character which is a, b or c.
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+ * - [a-f] matches anything from a through f.
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+ * - [^a-f] matches anything _except_ a through f.
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+ * - [-_] matches - or _; [^-_] matches anything else. (The - is
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+ * non-special if it occurs immediately after the opening
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+ * bracket or ^.)
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+ * - [a^] matches an a or a ^. (The ^ is non-special if it does
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+ * _not_ occur immediately after the opening bracket.)
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+ * - \*, \?, \[, \], \\ match the single characters *, ?, [, ], \.
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+ * - All other characters are non-special and match themselves.
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+ */
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+
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+/*
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+ * Some notes on differences from POSIX globs (IEEE Std 1003.1, 2003 ed.):
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+ * - backslashes act as escapes even within [] bracket expressions
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+ * - does not support [!...] for non-matching list (POSIX are weird);
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+ * NB POSIX allows [^...] as well via "A bracket expression starting
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+ * with an unquoted circumflex character produces unspecified
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+ * results". If we wanted to allow [!...] we might want to define
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+ * [^!] as having its literal meaning (match '^' or '!').
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+ * - none of the scary [[:class:]] stuff, etc
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+ */
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+
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+/*
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+ * The wildcard matching technique we use is very simple and
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+ * potentially O(N^2) in running time, but I don't anticipate it
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+ * being that bad in reality (particularly since N will be the size
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+ * of a filename, which isn't all that much). Perhaps one day, once
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+ * PuTTY has grown a regexp matcher for some other reason, I might
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+ * come back and reimplement wildcards by translating them into
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+ * regexps or directly into NFAs; but for the moment, in the
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+ * absence of any other need for the NFA->DFA translation engine,
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+ * anything more than the simplest possible wildcard matcher is
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+ * vast code-size overkill.
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+ *
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+ * Essentially, these wildcards are much simpler than regexps in
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+ * that they consist of a sequence of rigid fragments (? and [...]
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+ * can never match more or less than one character) separated by
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+ * asterisks. It is therefore extremely simple to look at a rigid
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+ * fragment and determine whether or not it begins at a particular
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+ * point in the test string; so we can search along the string
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+ * until we find each fragment, then search for the next. As long
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+ * as we find each fragment in the _first_ place it occurs, there
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+ * will never be a danger of having to backpedal and try to find it
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+ * again somewhere else.
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+ */
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+
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+enum {
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+ WC_TRAILINGBACKSLASH = 1,
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+ WC_UNCLOSEDCLASS,
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+ WC_INVALIDRANGE
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+};
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+
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+/*
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+ * Error reporting is done by returning various negative values
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+ * from the wildcard routines. Passing any such value to wc_error
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+ * will give a human-readable message.
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+ */
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+const char *wc_error(int value)
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+{
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+ value = abs(value);
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+ switch (value) {
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+ case WC_TRAILINGBACKSLASH:
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+ return "'\' occurred at end of string (expected another character)";
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+ case WC_UNCLOSEDCLASS:
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+ return "expected ']' to close character class";
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+ case WC_INVALIDRANGE:
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+ return "character range was not terminated (']' just after '-')";
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+ }
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+ return "INTERNAL ERROR: unrecognised wildcard error number";
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+}
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+
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+/*
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+ * This is the routine that tests a target string to see if an
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+ * initial substring of it matches a fragment. If successful, it
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+ * returns 1, and advances both `fragment' and `target' past the
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+ * fragment and matching substring respectively. If unsuccessful it
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+ * returns zero. If the wildcard fragment suffers a syntax error,
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+ * it returns <0 and the precise value indexes into wc_error.
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+ */
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+static int wc_match_fragment(const char **fragment, const char **target,
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+ const char *target_end)
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+{
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+ const char *f, *t;
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+
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+ f = *fragment;
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+ t = *target;
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+ /*
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+ * The fragment terminates at either the end of the string, or
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+ * the first (unescaped) *.
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+ */
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+ while (*f && *f != '*' && t < target_end) {
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+ /*
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+ * Extract one character from t, and one character's worth
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+ * of pattern from f, and step along both. Return 0 if they
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+ * fail to match.
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+ */
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+ if (*f == '\\') {
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+ /*
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+ * Backslash, which means f[1] is to be treated as a
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+ * literal character no matter what it is. It may not
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+ * be the end of the string.
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+ */
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+ if (!f[1])
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+ return -WC_TRAILINGBACKSLASH; /* error */
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+ if (f[1] != *t)
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+ return 0; /* failed to match */
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+ f += 2;
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+ } else if (*f == '?') {
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+ /*
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+ * Question mark matches anything.
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+ */
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+ f++;
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+ } else if (*f == '[') {
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+ bool invert = false;
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+ bool matched = false;
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+ /*
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+ * Open bracket introduces a character class.
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+ */
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+ f++;
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+ if (*f == '^') {
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+ invert = true;
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+ f++;
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+ }
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+ while (*f != ']') {
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+ if (*f == '\\')
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+ f++; /* backslashes still work */
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+ if (!*f)
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+ return -WC_UNCLOSEDCLASS; /* error again */
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+ if (f[1] == '-') {
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+ int lower, upper, ourchr;
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+ lower = (unsigned char) *f++;
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+ f++; /* eat the minus */
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+ if (*f == ']')
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+ return -WC_INVALIDRANGE; /* different error! */
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+ if (*f == '\\')
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+ f++; /* backslashes _still_ work */
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+ if (!*f)
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+ return -WC_UNCLOSEDCLASS; /* error again */
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+ upper = (unsigned char) *f++;
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+ ourchr = (unsigned char) *t;
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+ if (lower > upper) {
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+ int t = lower; lower = upper; upper = t;
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+ }
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+ if (ourchr >= lower && ourchr <= upper)
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+ matched = true;
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+ } else {
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+ matched |= (*t == *f++);
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+ }
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+ }
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+ if (invert == matched)
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+ return 0; /* failed to match character class */
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+ f++; /* eat the ] */
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+ } else {
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+ /*
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+ * Non-special character matches itself.
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+ */
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+ if (*f != *t)
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+ return 0;
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+ f++;
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+ }
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+ /*
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+ * Now we've done that, increment t past the character we
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+ * matched.
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+ */
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+ t++;
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+ }
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+ if (!*f || *f == '*') {
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+ /*
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+ * We have reached the end of f without finding a mismatch;
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+ * so we're done. Update the caller pointers and return 1.
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+ */
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+ *fragment = f;
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+ *target = t;
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+ return 1;
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+ }
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+ /*
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+ * Otherwise, we must have reached the end of t before we
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+ * reached the end of f; so we've failed. Return 0.
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+ */
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+ return 0;
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+}
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+
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+/*
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+ * This is the real wildcard matching routine. It returns 1 for a
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+ * successful match, 0 for an unsuccessful match, and <0 for a
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+ * syntax error in the wildcard.
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+ */
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+static int wc_match_inner(
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+ const char *wildcard, const char *target, size_t target_len)
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+{
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+ const char *target_end = target + target_len;
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+ int ret;
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+
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+ /*
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+ * Every time we see a '*' _followed_ by a fragment, we just
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+ * search along the string for a location at which the fragment
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+ * matches. The only special case is when we see a fragment
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+ * right at the start, in which case we just call the matching
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+ * routine once and give up if it fails.
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+ */
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+ if (*wildcard != '*') {
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+ ret = wc_match_fragment(&wildcard, &target, target_end);
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+ if (ret <= 0)
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+ return ret; /* pass back failure or error alike */
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+ }
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+
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+ while (*wildcard) {
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+ assert(*wildcard == '*');
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+ while (*wildcard == '*')
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+ wildcard++;
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+
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+ /*
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+ * It's possible we've just hit the end of the wildcard
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+ * after seeing a *, in which case there's no need to
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+ * bother searching any more because we've won.
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+ */
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+ if (!*wildcard)
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+ return 1;
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+
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+ /*
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+ * Now `wildcard' points at the next fragment. So we
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+ * attempt to match it against `target', and if that fails
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+ * we increment `target' and try again, and so on. When we
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+ * find we're about to try matching against the empty
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+ * string, we give up and return 0.
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+ */
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+ ret = 0;
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+ while (*target) {
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+ const char *save_w = wildcard, *save_t = target;
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+
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+ ret = wc_match_fragment(&wildcard, &target, target_end);
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+
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+ if (ret < 0)
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+ return ret; /* syntax error */
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+
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+ if (ret > 0 && !*wildcard && target != target_end) {
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+ /*
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+ * Final special case - literally.
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+ *
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+ * This situation arises when we are matching a
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+ * _terminal_ fragment of the wildcard (that is,
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+ * there is nothing after it, e.g. "*a"), and it
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+ * has matched _too early_. For example, matching
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+ * "*a" against "parka" will match the "a" fragment
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+ * against the _first_ a, and then (if it weren't
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+ * for this special case) matching would fail
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+ * because we're at the end of the wildcard but not
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+ * at the end of the target string.
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+ *
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+ * In this case what we must do is measure the
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+ * length of the fragment in the target (which is
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+ * why we saved `target'), jump straight to that
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+ * distance from the end of the string using
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+ * strlen, and match the same fragment again there
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+ * (which is why we saved `wildcard'). Then we
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+ * return whatever that operation returns.
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+ */
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+ target = target_end - (target - save_t);
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+ wildcard = save_w;
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+ return wc_match_fragment(&wildcard, &target, target_end);
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+ }
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+
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+ if (ret > 0)
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+ break;
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+ target++;
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+ }
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+ if (ret > 0)
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+ continue;
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+ return 0;
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+ }
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+
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+ /*
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+ * If we reach here, it must be because we successfully matched
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+ * a fragment and then found ourselves right at the end of the
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+ * wildcard. Hence, we return 1 if and only if we are also
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+ * right at the end of the target.
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+ */
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+ return target == target_end;
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+}
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+
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+int wc_match(const char *wildcard, const char *target)
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+{
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+ return wc_match_inner(wildcard, target, strlen(target));
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+}
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+
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+/*
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+ * Another utility routine that translates a non-wildcard string
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+ * into its raw equivalent by removing any escaping backslashes.
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+ * Expects a target string buffer of anything up to the length of
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+ * the original wildcard. You can also pass NULL as the output
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+ * buffer if you're only interested in the return value.
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+ *
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+ * Returns true on success, or false if a wildcard character was
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+ * encountered. In the latter case the output string MAY not be
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+ * zero-terminated and you should not use it for anything!
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+ */
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+bool wc_unescape(char *output, const char *wildcard)
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+{
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+ while (*wildcard) {
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+ if (*wildcard == '\\') {
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+ wildcard++;
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+ /* We are lenient about trailing backslashes in non-wildcards. */
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+ if (*wildcard) {
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+ if (output)
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+ *output++ = *wildcard;
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+ wildcard++;
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+ }
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+ } else if (*wildcard == '*' || *wildcard == '?' ||
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+ *wildcard == '[' || *wildcard == ']') {
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+ return false; /* it's a wildcard! */
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+ } else {
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+ if (output)
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+ *output++ = *wildcard;
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+ wildcard++;
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+ }
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+ }
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+ if (output)
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+ *output = '\0';
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+ return true; /* it's clean */
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+}
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Brian Fiete