+
−/*
+
− * This Source Code Form is subject to the terms of the Mozilla Public
+
− * License, v. 2.0.  If a copy of the MPL was not distributed with this
+
− * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
− *
+
− * Copyright 2013-2022 MonetDB B.V.
+
− */
+
−
+
−/* monetdb_config.h must be included as the first include file */
+
−#include <monetdb_config.h>
+
−
+
−/* mal_exception.h actually contains everything we need */
+
−#include <mal_exception.h>
+
−
+
−/* system include files */
+
−#include <string.h>
+
−
+
−/* dst is a buffer of length larger than len (i.e. dst[len] exists),
+
− * src is a UTF-8-encoded string of length exactly len bytes */
+
−static void
+
−do_reverse(char *dst, const char *src, size_t len)
+
−{
+
−	dst[len] = 0;
+
−	if (strNil(src)) {
+
−		/* special case for nil:str */
+
−		assert(len == strlen(str_nil));
+
−		strcpy(dst, str_nil);
+
−		return;
+
−	}
+
−	/* all strings in MonetDB are encoded using UTF-8; we must
+
−	 * make sure that the reversed string is also encoded in valid
+
−	 * UTF-8, so we treat multibyte characters as single units */
+
−	while (*src) {
+
−		if ((*src & 0xF8) == 0xF0) {
+
−			/* 4 byte UTF-8 sequence */
+
−			assert(len >= 4);
+
−			dst[len - 4] = *src++;
+
−			assert((*src & 0xC0) == 0x80);
+
−			dst[len - 3] = *src++;
+
−			assert((*src & 0xC0) == 0x80);
+
−			dst[len - 2] = *src++;
+
−			assert((*src & 0xC0) == 0x80);
+
−			dst[len - 1] = *src++;
+
−			len -= 4;
+
−		} else if ((*src & 0xF0) == 0xE0) {
+
−			/* 3 byte UTF-8 sequence */
+
−			assert(len >= 3);
+
−			dst[len - 3] = *src++;
+
−			assert((*src & 0xC0) == 0x80);
+
−			dst[len - 2] = *src++;
+
−			assert((*src & 0xC0) == 0x80);
+
−			dst[len - 1] = *src++;
+
−			len -= 3;
+
−		} else if ((*src & 0xE0) == 0xC0) {
+
−			/* 2 byte UTF-8 sequence */
+
−			assert(len >= 2);
+
−			dst[len - 2] = *src++;
+
−			assert((*src & 0xC0) == 0x80);
+
−			dst[len - 1] = *src++;
+
−			len -= 2;
+
−		} else {
+
−			/* 1 byte UTF-8 "sequence" */
+
−			assert(len >= 1);
+
−			assert((*src & 0x80) == 0);
+
−			dst[--len] = *src++;
+
−		}
+
−	}
+
−	assert(len == 0);
+
−}
+
−
+
−static char *
+
−UDFreverse(char **retval, const char **arg)
+
−{
+
−	size_t len;
+
−
+
−	len = strlen(*arg);
+
−	*retval = GDKmalloc(len + 1);
+
−	if (*retval == NULL)
+
−		throw(MAL, "revstr.revstr", MAL_MALLOC_FAIL);
+
−
+
−	do_reverse(*retval, *arg, len);
+
−
+
−	return MAL_SUCCEED;
+
−
+
−}
+
−
+
−static char *
+
−UDFBATreverse(bat *retval, const bat *arg)
+
−{
+
−	BAT *b, *bn;
+
−	BATiter bi;
+
−	BUN p, q;
+
−	const char *src;
+
−	size_t len;
+
−	char *dst;
+
−	size_t dstlen;
+
−
+
−	/* allocate temporary space for reversed strings; we grow this
+
−	 * if we need more */
+
−	dstlen = 1024;
+
−	dst = GDKmalloc(dstlen);
+
−	if (dst == NULL)
+
−		throw(MAL, "batrevstr.revstr", MAL_MALLOC_FAIL);
+
−
+
−	b = BATdescriptor(*arg);
+
−	if (b == NULL) {
+
−		GDKfree(dst);
+
−		throw(MAL, "batrevstr.revstr", RUNTIME_OBJECT_MISSING);
+
−	}
+
−
+
−	/* we should only get called for string BATs */
+
−	assert(b->ttype == TYPE_str);
+
−
+
−	/* allocate result BAT */
+
−	bn = COLnew(b->hseqbase, TYPE_str, BATcount(b), TRANSIENT);
+
−	if (bn == NULL) {
+
−		BBPunfix(b->batCacheid);
+
−		GDKfree(dst);
+
−		throw(MAL, "batrevstr.revstr", MAL_MALLOC_FAIL);
+
−	}
+
−
+
−	/* loop through BAT b; p is index of the entry we're working
+
−	 * on, q is used internally by BATloop to do the iterating */
+
−	bi = bat_iterator(b);
+
−	BATloop(b, p, q) {
+
−		src = (const char *) BUNtail(bi, p);
+
−		len = strlen(src);
+
−		/* make sure dst is large enough */
+
−		if (len >= dstlen) {
+
−			char *ndst;
+
−
+
−			dstlen = len + 1024;
+
−			ndst = GDKrealloc(dst, dstlen);
+
−			if (ndst == NULL) {
+
−				/* if GDKrealloc fails, dst is still
+
−				 * allocated */
+
−				goto bailout;
+
−			}
+
−			dst = ndst;
+
−		}
+
−		do_reverse(dst, src, len);
+
−		if (BUNappend(bn, dst, false) != GDK_SUCCEED) {
+
−			/* BUNappend can fail since it may have to
+
−			 * grow memory areas--especially true for
+
−			 * string BATs */
+
−			goto bailout;
+
−		}
+
−	}
+
−	bat_iterator_end(&bi);
+
−	GDKfree(dst);
+
−
+
−	BBPunfix(b->batCacheid);
+
−
+
−	*retval = bn->batCacheid;
+
−	BBPkeepref(bn);
+
−
+
−	return MAL_SUCCEED;
+
−
+
−  bailout:
+
−	/* we only get here in the case of an allocation error; clean
+
−	 * up the mess we've created and throw an exception */
+
−	bat_iterator_end(&bi);
+
−	GDKfree(dst);
+
−	BBPunfix(b->batCacheid);
+
−	BBPunfix(bn->batCacheid);
+
−	throw(MAL, "batrevstr.revstr", MAL_MALLOC_FAIL);
+
−}
+
−
+
−#include "mel.h"
+
−
+
−static char reverse_sql[] = "CREATE FUNCTION revstr(src STRING)"
+
−	" RETURNS STRING EXTERNAL NAME revstr.revstr;";
+
−
+
−static mel_func reverse_init_funcs[] = {
+
−	command("revstr", "revstr", UDFreverse, false,
+
−		"Reverse a string",
+
−		args(1,2, arg("",str),arg("ra1",str))),
+
−	command("batrevstr", "revstr", UDFBATreverse, false,
+
−		"Reverse a BAT of strings",
+
−		args(1,2, batarg("",str),batarg("b",str))),
+
−	{ .imp=NULL }		/* sentinel */
+
−};
+
−
+
−#include "mal_import.h"
+
−#include "sql_import.h"
+
−#ifdef _MSC_VER
+
−#undef read
+
−#pragma section(".CRT$XCU",read)
+
−#endif
+
−LIB_STARTUP_FUNC(init_reverse)
+
−{
+
−	mal_module("revstr", NULL, reverse_init_funcs);
+
−	sql_register("revstr", reverse_sql);
+
−}