imported Henry Spencer's regex implementation from Tcl

Source: github.com/garyhouston/hsrex

* This version should be a Thompson NFA, using backtracking only
  for backreferences, so it should be much safer than PCRE (GRegex).
  Search times should be linear and there should be no way to cause
  stack overflows (unless we would generate backreferences).
* Importing the lib makes sure we don't add another compile-time
  dependency. Also, we could implement our own regcomp() which
  translates directly from TECO patterns.
* This is still WIP and currently only works with the ASCII version.
  The widechar version does not define re_comp() and re_exec().
* Apparently we can't have an ASCII and widechar version at the same time,
  so we must build two libtool libraries and somehow mangle the names.
* Ideally the widechar version will also work with UTF-8 strings.
* An alternative might be to import the Gnulib regex module.
  How does it choose the encoding anyway?
* Or we could just use Oniguruma - but this would have to be a new
  external library dependency.

1 files changed, 129 insertions, 0 deletions

diff --git a/contrib/hsrex/regerror.c b/contrib/hsrex/regerror.c
new file mode 100644
index 0000000..49b6f3e
--- /dev/null
+++ b/contrib/hsrex/regerror.c
@@ -0,0 +1,129 @@
+/*
+ * regerror - error-code expansion
+ *
+ * Copyright (c) 1998, 1999 Henry Spencer.  All rights reserved.
+ *
+ * Development of this software was funded, in part, by Cray Research Inc.,
+ * UUNET Communications Services Inc., Sun Microsystems Inc., and Scriptics
+ * Corporation, none of whom are responsible for the results.  The author
+ * thanks all of them.
+ *
+ * Redistribution and use in source and binary forms -- with or without
+ * modification -- are permitted for any purpose, provided that
+ * redistributions in source form retain this entire copyright notice and
+ * indicate the origin and nature of any modifications.
+ *
+ * I'd appreciate being given credit for this package in the documentation of
+ * software which uses it, but that is not a requirement.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
+ * HENRY SPENCER BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "regguts.h"
+
+/*
+ * Unknown-error explanation.
+ */
+
+static char unk[] = "*** unknown regex error code 0x%x ***";
+
+/*
+ * Struct to map among codes, code names, and explanations.
+ */
+
+static struct rerr {
+    int code;
+    const char *name;
+    const char *explain;
+} rerrs[] = {
+    /* The actual table is built from regex.h */
+#include "regerrs.h"
+    { -1, "", "oops" },		/* explanation special-cased in code */
+};
+
+/*
+ - regerror - the interface to error numbers
+ */
+/* ARGSUSED */
+size_t				/* Actual space needed (including NUL) */
+regerror(
+    int code,			/* Error code, or REG_ATOI or REG_ITOA */
+    const regex_t *preg,	/* Associated regex_t (unused at present) */
+    char *errbuf,		/* Result buffer (unless errbuf_size==0) */
+    size_t errbuf_size)		/* Available space in errbuf, can be 0 */
+{
+    struct rerr *r;
+    const char *msg;
+    char convbuf[sizeof(unk)+50]; /* 50 = plenty for int */
+    size_t len;
+    int icode;
+
+    switch (code) {
+    case REG_ATOI:		/* Convert name to number */
+	for (r = rerrs; r->code >= 0; r++) {
+	    if (strcmp(r->name, errbuf) == 0) {
+		break;
+	    }
+	}
+	sprintf(convbuf, "%d", r->code); /* -1 for unknown */
+	msg = convbuf;
+	break;
+    case REG_ITOA:		/* Convert number to name */
+	icode = atoi(errbuf);	/* Not our problem if this fails */
+	for (r = rerrs; r->code >= 0; r++) {
+	    if (r->code == icode) {
+		break;
+	    }
+	}
+	if (r->code >= 0) {
+	    msg = r->name;
+	} else {		/* Unknown; tell him the number */
+	    sprintf(convbuf, "REG_%u", (unsigned)icode);
+	    msg = convbuf;
+	}
+	break;
+    default:			/* A real, normal error code */
+	for (r = rerrs; r->code >= 0; r++) {
+	    if (r->code == code) {
+		break;
+	    }
+	}
+	if (r->code >= 0) {
+	    msg = r->explain;
+	} else {		/* Unknown; say so */
+	    sprintf(convbuf, unk, code);
+	    msg = convbuf;
+	}
+	break;
+    }
+
+    len = strlen(msg) + 1;	/* Space needed, including NUL */
+    if (errbuf_size > 0) {
+	if (errbuf_size > len) {
+	    strcpy(errbuf, msg);
+	} else {		/* Truncate to fit */
+	    strncpy(errbuf, msg, errbuf_size-1);
+	    errbuf[errbuf_size-1] = '\0';
+	}
+    }
+
+    return len;
+}
+
+/*
+ * Local Variables:
+ * mode: c
+ * c-basic-offset: 4
+ * fill-column: 78
+ * End:
+ */