--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/druntime/src/compiler/ldc/aApplyR.d	Tue Jun 02 17:43:06 2009 +0100
@@ -0,0 +1,957 @@
+/**
+ * This code handles decoding UTF strings for foreach_reverse loops.  There are
+ * 6 combinations of conversions between char, wchar, and dchar, and 2 of each
+ * of those.
+ *
+ * Copyright: Copyright Digital Mars 2004 - 2009.
+ * License:   <a href="http://www.boost.org/LICENSE_1_0.txt>Boost License 1.0</a>.
+ * Authors:   Walter Bright, Sean Kelly
+ *
+ *          Copyright Digital Mars 2004 - 2009.
+ * Distributed under the Boost Software License, Version 1.0.
+ *    (See accompanying file LICENSE_1_0.txt or copy at
+ *          http://www.boost.org/LICENSE_1_0.txt)
+ */
+module rt.aApplyR;
+
+/* This code handles decoding UTF strings for foreach_reverse loops.
+ * There are 6 combinations of conversions between char, wchar,
+ * and dchar, and 2 of each of those.
+ */
+
+private import rt.util.utf;
+
+/**********************************************/
+/* 1 argument versions */
+
+// dg is D, but _aApplyRcd() is C
+extern (D) typedef int delegate(void *) dg_t;
+
+extern (C) int _aApplyRcd1(in char[] aa, dg_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRcd1(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0; )
+    {   dchar d;
+
+        i--;
+        d = aa[i];
+        if (d & 0x80)
+        {   char c = cast(char)d;
+            uint j;
+            uint m = 0x3F;
+            d = 0;
+            while ((c & 0xC0) != 0xC0)
+            {   if (i == 0)
+                    onUnicodeError("Invalid UTF-8 sequence", 0);
+                i--;
+                d |= (c & 0x3F) << j;
+                j += 6;
+                m >>= 1;
+                c = aa[i];
+            }
+            d |= (c & m) << j;
+        }
+        result = dg(cast(void *)&d);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRcd1.unittest\n");
+
+    auto s = "hello"c[];
+    int i;
+
+    foreach_reverse(dchar d; s)
+    {
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(dchar d; s)
+    {
+        //printf("i = %d, d = %x\n", i, d);
+        switch (i)
+        {
+            case 0:     assert(d == 'b'); break;
+            case 1:     assert(d == '\U00100456'); break;
+            case 2:     assert(d == '\u1234'); break;
+            case 3:     assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 4);
+}
+
+/*****************************/
+
+extern (C) int _aApplyRwd1(in wchar[] aa, dg_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRwd1(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0; )
+    {   dchar d;
+
+        i--;
+        d = aa[i];
+        if (d >= 0xDC00 && d <= 0xDFFF)
+        {   if (i == 0)
+                onUnicodeError("Invalid UTF-16 sequence", 0);
+            i--;
+            d = ((aa[i] - 0xD7C0) << 10) + (d - 0xDC00);
+        }
+        result = dg(cast(void *)&d);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRwd1.unittest\n");
+
+    auto s = "hello"w[];
+    int i;
+
+    foreach_reverse(dchar d; s)
+    {
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(dchar d; s)
+    {
+        //printf("i = %d, d = %x\n", i, d);
+        switch (i)
+        {
+            case 0:     assert(d == 'b'); break;
+            case 1:     assert(d == '\U00100456'); break;
+            case 2:     assert(d == '\u1234'); break;
+            case 3:     assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 4);
+}
+
+/*****************************/
+
+extern (C) int _aApplyRcw1(in char[] aa, dg_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRcw1(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0; )
+    {   dchar d;
+        wchar w;
+
+        i--;
+        w = aa[i];
+        if (w & 0x80)
+        {   char c = cast(char)w;
+            uint j;
+            uint m = 0x3F;
+            d = 0;
+            while ((c & 0xC0) != 0xC0)
+            {   if (i == 0)
+                    onUnicodeError("Invalid UTF-8 sequence", 0);
+                i--;
+                d |= (c & 0x3F) << j;
+                j += 6;
+                m >>= 1;
+                c = aa[i];
+            }
+            d |= (c & m) << j;
+
+            if (d <= 0xFFFF)
+                w = cast(wchar) d;
+            else
+            {
+                w = cast(wchar) ((((d - 0x10000) >> 10) & 0x3FF) + 0xD800);
+                result = dg(cast(void *)&w);
+                if (result)
+                    break;
+                w = cast(wchar) (((d - 0x10000) & 0x3FF) + 0xDC00);
+            }
+        }
+        result = dg(cast(void *)&w);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRcw1.unittest\n");
+
+    auto s = "hello"c[];
+    int i;
+
+    foreach_reverse(wchar d; s)
+    {
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(wchar d; s)
+    {
+        //printf("i = %d, d = %x\n", i, d);
+        switch (i)
+        {
+            case 0:     assert(d == 'b'); break;
+            case 1:     assert(d == 0xDBC1); break;
+            case 2:     assert(d == 0xDC56); break;
+            case 3:     assert(d == 0x1234); break;
+            case 4:     assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+}
+
+/*****************************/
+
+extern (C) int _aApplyRwc1(in wchar[] aa, dg_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRwc1(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0; )
+    {   dchar d;
+        char c;
+
+        i--;
+        d = aa[i];
+        if (d >= 0xDC00 && d <= 0xDFFF)
+        {   if (i == 0)
+                onUnicodeError("Invalid UTF-16 sequence", 0);
+            i--;
+            d = ((aa[i] - 0xD7C0) << 10) + (d - 0xDC00);
+        }
+
+        if (d & ~0x7F)
+        {
+            char[4] buf;
+
+            auto b = toUTF8(buf, d);
+            foreach (char c2; b)
+            {
+                result = dg(cast(void *)&c2);
+                if (result)
+                    return result;
+            }
+            continue;
+        }
+        c = cast(char)d;
+        result = dg(cast(void *)&c);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRwc1.unittest\n");
+
+    auto s = "hello"w[];
+    int i;
+
+    foreach_reverse(char d; s)
+    {
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(char d; s)
+    {
+        //printf("i = %d, d = %x\n", i, d);
+        switch (i)
+        {
+            case 0:     assert(d == 'b'); break;
+            case 1:     assert(d == 0xF4); break;
+            case 2:     assert(d == 0x80); break;
+            case 3:     assert(d == 0x91); break;
+            case 4:     assert(d == 0x96); break;
+            case 5:     assert(d == 0xE1); break;
+            case 6:     assert(d == 0x88); break;
+            case 7:     assert(d == 0xB4); break;
+            case 8:     assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 9);
+}
+
+/*****************************/
+
+extern (C) int _aApplyRdc1(in dchar[] aa, dg_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRdc1(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0;)
+    {   dchar d = aa[--i];
+        char c;
+
+        if (d & ~0x7F)
+        {
+            char[4] buf;
+
+            auto b = toUTF8(buf, d);
+            foreach (char c2; b)
+            {
+                result = dg(cast(void *)&c2);
+                if (result)
+                    return result;
+            }
+            continue;
+        }
+        else
+        {
+            c = cast(char)d;
+        }
+        result = dg(cast(void *)&c);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRdc1.unittest\n");
+
+    auto s = "hello"d[];
+    int i;
+
+    foreach_reverse(char d; s)
+    {
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(char d; s)
+    {
+        //printf("i = %d, d = %x\n", i, d);
+        switch (i)
+        {
+            case 0:     assert(d == 'b'); break;
+            case 1:     assert(d == 0xF4); break;
+            case 2:     assert(d == 0x80); break;
+            case 3:     assert(d == 0x91); break;
+            case 4:     assert(d == 0x96); break;
+            case 5:     assert(d == 0xE1); break;
+            case 6:     assert(d == 0x88); break;
+            case 7:     assert(d == 0xB4); break;
+            case 8:     assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 9);
+}
+
+/*****************************/
+
+extern (C) int _aApplyRdw1(in dchar[] aa, dg_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRdw1(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0; )
+    {   dchar d = aa[--i];
+        wchar w;
+
+        if (d <= 0xFFFF)
+            w = cast(wchar) d;
+        else
+        {
+            w = cast(wchar) ((((d - 0x10000) >> 10) & 0x3FF) + 0xD800);
+            result = dg(cast(void *)&w);
+            if (result)
+                break;
+            w = cast(wchar) (((d - 0x10000) & 0x3FF) + 0xDC00);
+        }
+        result = dg(cast(void *)&w);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRdw1.unittest\n");
+
+    auto s = "hello"d[];
+    int i;
+
+    foreach_reverse(wchar d; s)
+    {
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(wchar d; s)
+    {
+        //printf("i = %d, d = %x\n", i, d);
+        switch (i)
+        {
+            case 0:     assert(d == 'b'); break;
+            case 1:     assert(d == 0xDBC1); break;
+            case 2:     assert(d == 0xDC56); break;
+            case 3:     assert(d == 0x1234); break;
+            case 4:     assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+}
+
+
+/****************************************************************************/
+/* 2 argument versions */
+
+// dg is D, but _aApplyRcd2() is C
+extern (D) typedef int delegate(void *, void *) dg2_t;
+
+extern (C) int _aApplyRcd2(in char[] aa, dg2_t dg)
+{   int result;
+    size_t i;
+    size_t len = aa.length;
+
+    debug(apply) printf("_aApplyRcd2(), len = %d\n", len);
+    for (i = len; i != 0; )
+    {   dchar d;
+
+        i--;
+        d = aa[i];
+        if (d & 0x80)
+        {   char c = cast(char)d;
+            uint j;
+            uint m = 0x3F;
+            d = 0;
+            while ((c & 0xC0) != 0xC0)
+            {   if (i == 0)
+                    onUnicodeError("Invalid UTF-8 sequence", 0);
+                i--;
+                d |= (c & 0x3F) << j;
+                j += 6;
+                m >>= 1;
+                c = aa[i];
+            }
+            d |= (c & m) << j;
+        }
+        result = dg(&i, cast(void *)&d);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRcd2.unittest\n");
+
+    auto s = "hello"c[];
+    int i;
+
+    foreach_reverse(k, dchar d; s)
+    {
+        assert(k == 4 - i);
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(k, dchar d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        switch (i)
+        {
+            case 0:     assert(d == 'b'); assert(k == 8); break;
+            case 1:     assert(d == '\U00100456'); assert(k == 4); break;
+            case 2:     assert(d == '\u1234'); assert(k == 1); break;
+            case 3:     assert(d == 'a'); assert(k == 0); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 4);
+}
+
+/*****************************/
+
+extern (C) int _aApplyRwd2(in wchar[] aa, dg2_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRwd2(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0; )
+    {   dchar d;
+
+        i--;
+        d = aa[i];
+        if (d >= 0xDC00 && d <= 0xDFFF)
+        {   if (i == 0)
+                onUnicodeError("Invalid UTF-16 sequence", 0);
+            i--;
+            d = ((aa[i] - 0xD7C0) << 10) + (d - 0xDC00);
+        }
+        result = dg(&i, cast(void *)&d);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRwd2.unittest\n");
+
+    auto s = "hello"w[];
+    int i;
+
+    foreach_reverse(k, dchar d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        assert(k == 4 - i);
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(k, dchar d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        switch (i)
+        {
+            case 0:     assert(k == 4); assert(d == 'b'); break;
+            case 1:     assert(k == 2); assert(d == '\U00100456'); break;
+            case 2:     assert(k == 1); assert(d == '\u1234'); break;
+            case 3:     assert(k == 0); assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 4);
+}
+
+/*****************************/
+
+extern (C) int _aApplyRcw2(in char[] aa, dg2_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRcw2(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0; )
+    {   dchar d;
+        wchar w;
+
+        i--;
+        w = aa[i];
+        if (w & 0x80)
+        {   char c = cast(char)w;
+            uint j;
+            uint m = 0x3F;
+            d = 0;
+            while ((c & 0xC0) != 0xC0)
+            {   if (i == 0)
+                    onUnicodeError("Invalid UTF-8 sequence", 0);
+                i--;
+                d |= (c & 0x3F) << j;
+                j += 6;
+                m >>= 1;
+                c = aa[i];
+            }
+            d |= (c & m) << j;
+
+            if (d <= 0xFFFF)
+                w = cast(wchar) d;
+            else
+            {
+                w = cast(wchar) ((((d - 0x10000) >> 10) & 0x3FF) + 0xD800);
+                result = dg(&i, cast(void *)&w);
+                if (result)
+                    break;
+                w = cast(wchar) (((d - 0x10000) & 0x3FF) + 0xDC00);
+            }
+        }
+        result = dg(&i, cast(void *)&w);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRcw2.unittest\n");
+
+    auto s = "hello"c[];
+    int i;
+
+    foreach_reverse(k, wchar d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        assert(k == 4 - i);
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(k, wchar d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        switch (i)
+        {
+            case 0:     assert(k == 8); assert(d == 'b'); break;
+            case 1:     assert(k == 4); assert(d == 0xDBC1); break;
+            case 2:     assert(k == 4); assert(d == 0xDC56); break;
+            case 3:     assert(k == 1); assert(d == 0x1234); break;
+            case 4:     assert(k == 0); assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+}
+
+/*****************************/
+
+extern (C) int _aApplyRwc2(in wchar[] aa, dg2_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRwc2(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0; )
+    {   dchar d;
+        char c;
+
+        i--;
+        d = aa[i];
+        if (d >= 0xDC00 && d <= 0xDFFF)
+        {   if (i == 0)
+                onUnicodeError("Invalid UTF-16 sequence", 0);
+            i--;
+            d = ((aa[i] - 0xD7C0) << 10) + (d - 0xDC00);
+        }
+
+        if (d & ~0x7F)
+        {
+            char[4] buf;
+
+            auto b = toUTF8(buf, d);
+            foreach (char c2; b)
+            {
+                result = dg(&i, cast(void *)&c2);
+                if (result)
+                    return result;
+            }
+            continue;
+        }
+        c = cast(char)d;
+        result = dg(&i, cast(void *)&c);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRwc2.unittest\n");
+
+    auto s = "hello"w[];
+    int i;
+
+    foreach_reverse(k, char d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        assert(k == 4 - i);
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(k, char d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        switch (i)
+        {
+            case 0:     assert(k == 4); assert(d == 'b'); break;
+            case 1:     assert(k == 2); assert(d == 0xF4); break;
+            case 2:     assert(k == 2); assert(d == 0x80); break;
+            case 3:     assert(k == 2); assert(d == 0x91); break;
+            case 4:     assert(k == 2); assert(d == 0x96); break;
+            case 5:     assert(k == 1); assert(d == 0xE1); break;
+            case 6:     assert(k == 1); assert(d == 0x88); break;
+            case 7:     assert(k == 1); assert(d == 0xB4); break;
+            case 8:     assert(k == 0); assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 9);
+}
+
+/*****************************/
+
+extern (C) int _aApplyRdc2(in dchar[] aa, dg2_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRdc2(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0; )
+    {   dchar d = aa[--i];
+        char c;
+
+        if (d & ~0x7F)
+        {
+            char[4] buf;
+
+            auto b = toUTF8(buf, d);
+            foreach (char c2; b)
+            {
+                result = dg(&i, cast(void *)&c2);
+                if (result)
+                    return result;
+            }
+            continue;
+        }
+        else
+        {   c = cast(char)d;
+        }
+        result = dg(&i, cast(void *)&c);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRdc2.unittest\n");
+
+    auto s = "hello"d[];
+    int i;
+
+    foreach_reverse(k, char d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        assert(k == 4 - i);
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(k, char d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        switch (i)
+        {
+            case 0:     assert(k == 3); assert(d == 'b'); break;
+            case 1:     assert(k == 2); assert(d == 0xF4); break;
+            case 2:     assert(k == 2); assert(d == 0x80); break;
+            case 3:     assert(k == 2); assert(d == 0x91); break;
+            case 4:     assert(k == 2); assert(d == 0x96); break;
+            case 5:     assert(k == 1); assert(d == 0xE1); break;
+            case 6:     assert(k == 1); assert(d == 0x88); break;
+            case 7:     assert(k == 1); assert(d == 0xB4); break;
+            case 8:     assert(k == 0); assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 9);
+}
+
+/*****************************/
+
+extern (C) int _aApplyRdw2(in dchar[] aa, dg2_t dg)
+{   int result;
+
+    debug(apply) printf("_aApplyRdw2(), len = %d\n", aa.length);
+    for (size_t i = aa.length; i != 0; )
+    {   dchar d = aa[--i];
+        wchar w;
+
+        if (d <= 0xFFFF)
+            w = cast(wchar) d;
+        else
+        {
+            w = cast(wchar) ((((d - 0x10000) >> 10) & 0x3FF) + 0xD800);
+            result = dg(&i, cast(void *)&w);
+            if (result)
+                break;
+            w = cast(wchar) (((d - 0x10000) & 0x3FF) + 0xDC00);
+        }
+        result = dg(&i, cast(void *)&w);
+        if (result)
+            break;
+    }
+    return result;
+}
+
+unittest
+{
+    debug(apply) printf("_aApplyRdw2.unittest\n");
+
+    auto s = "hello"d[];
+    int i;
+
+    foreach_reverse(k, wchar d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        assert(k == 4 - i);
+        switch (i)
+        {
+            case 0:     assert(d == 'o'); break;
+            case 1:     assert(d == 'l'); break;
+            case 2:     assert(d == 'l'); break;
+            case 3:     assert(d == 'e'); break;
+            case 4:     assert(d == 'h'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+
+    s = "a\u1234\U00100456b";
+    i = 0;
+    foreach_reverse(k, wchar d; s)
+    {
+        //printf("i = %d, k = %d, d = %x\n", i, k, d);
+        switch (i)
+        {
+            case 0:     assert(k == 3); assert(d == 'b'); break;
+            case 1:     assert(k == 2); assert(d == 0xDBC1); break;
+            case 2:     assert(k == 2); assert(d == 0xDC56); break;
+            case 3:     assert(k == 1); assert(d == 0x1234); break;
+            case 4:     assert(k == 0); assert(d == 'a'); break;
+            default:    assert(0);
+        }
+        i++;
+    }
+    assert(i == 5);
+}