Move the UTF conversion methods to qstringconverter

Separate them from the qutfcodec, so that the codec
can later on be moved out of Qt Core.

Fix the QUtf methods to take qsizetype instead of int
for length arguments.

This also makes it possible to not build QTextCodec into
the bootstrap lib anymore.

Change-Id: I0b4f83139d61b19c651520a2f3a5012aa7e85cb8
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 323 insertions, 0 deletions

diff --git a/src/corelib/text/qstringconverter_p.h b/src/corelib/text/qstringconverter_p.h
new file mode 100644
index 0000000000..5764979542
--- /dev/null
+++ b/src/corelib/text/qstringconverter_p.h
@@ -0,0 +1,323 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Copyright (C) 2018 Intel Corporation.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QSTRINGCONVERTER_P_H
+#define QSTRINGCONVERTER_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtCore/qstring.h>
+#include <QtCore/qendian.h>
+#include <QtCore/qstringconverter.h>
+
+QT_BEGIN_NAMESPACE
+
+struct QUtf8BaseTraits
+{
+    static const bool isTrusted = false;
+    static const bool allowNonCharacters = true;
+    static const bool skipAsciiHandling = false;
+    static const int Error = -1;
+    static const int EndOfString = -2;
+
+    static bool isValidCharacter(uint u)
+    { return int(u) >= 0; }
+
+    static void appendByte(uchar *&ptr, uchar b)
+    { *ptr++ = b; }
+
+    static uchar peekByte(const uchar *ptr, int n = 0)
+    { return ptr[n]; }
+
+    static qptrdiff availableBytes(const uchar *ptr, const uchar *end)
+    { return end - ptr; }
+
+    static void advanceByte(const uchar *&ptr, int n = 1)
+    { ptr += n; }
+
+    static void appendUtf16(ushort *&ptr, ushort uc)
+    { *ptr++ = uc; }
+
+    static void appendUcs4(ushort *&ptr, uint uc)
+    {
+        appendUtf16(ptr, QChar::highSurrogate(uc));
+        appendUtf16(ptr, QChar::lowSurrogate(uc));
+    }
+
+    static ushort peekUtf16(const ushort *ptr, int n = 0)
+    { return ptr[n]; }
+
+    static qptrdiff availableUtf16(const ushort *ptr, const ushort *end)
+    { return end - ptr; }
+
+    static void advanceUtf16(const ushort *&ptr, int n = 1)
+    { ptr += n; }
+
+    // it's possible to output to UCS-4 too
+    static void appendUtf16(uint *&ptr, ushort uc)
+    { *ptr++ = uc; }
+
+    static void appendUcs4(uint *&ptr, uint uc)
+    { *ptr++ = uc; }
+};
+
+struct QUtf8BaseTraitsNoAscii : public QUtf8BaseTraits
+{
+    static const bool skipAsciiHandling = true;
+};
+
+namespace QUtf8Functions
+{
+    /// returns 0 on success; errors can only happen if \a u is a surrogate:
+    /// Error if \a u is a low surrogate;
+    /// if \a u is a high surrogate, Error if the next isn't a low one,
+    /// EndOfString if we run into the end of the string.
+    template <typename Traits, typename OutputPtr, typename InputPtr> inline
+    int toUtf8(ushort u, OutputPtr &dst, InputPtr &src, InputPtr end)
+    {
+        if (!Traits::skipAsciiHandling && u < 0x80) {
+            // U+0000 to U+007F (US-ASCII) - one byte
+            Traits::appendByte(dst, uchar(u));
+            return 0;
+        } else if (u < 0x0800) {
+            // U+0080 to U+07FF - two bytes
+            // first of two bytes
+            Traits::appendByte(dst, 0xc0 | uchar(u >> 6));
+        } else {
+            if (!QChar::isSurrogate(u)) {
+                // U+0800 to U+FFFF (except U+D800-U+DFFF) - three bytes
+                if (!Traits::allowNonCharacters && QChar::isNonCharacter(u))
+                    return Traits::Error;
+
+                // first of three bytes
+                Traits::appendByte(dst, 0xe0 | uchar(u >> 12));
+            } else {
+                // U+10000 to U+10FFFF - four bytes
+                // need to get one extra codepoint
+                if (Traits::availableUtf16(src, end) == 0)
+                    return Traits::EndOfString;
+
+                ushort low = Traits::peekUtf16(src);
+                if (!QChar::isHighSurrogate(u))
+                    return Traits::Error;
+                if (!QChar::isLowSurrogate(low))
+                    return Traits::Error;
+
+                Traits::advanceUtf16(src);
+                uint ucs4 = QChar::surrogateToUcs4(u, low);
+
+                if (!Traits::allowNonCharacters && QChar::isNonCharacter(ucs4))
+                    return Traits::Error;
+
+                // first byte
+                Traits::appendByte(dst, 0xf0 | (uchar(ucs4 >> 18) & 0xf));
+
+                // second of four bytes
+                Traits::appendByte(dst, 0x80 | (uchar(ucs4 >> 12) & 0x3f));
+
+                // for the rest of the bytes
+                u = ushort(ucs4);
+            }
+
+            // second to last byte
+            Traits::appendByte(dst, 0x80 | (uchar(u >> 6) & 0x3f));
+        }
+
+        // last byte
+        Traits::appendByte(dst, 0x80 | (u & 0x3f));
+        return 0;
+    }
+
+    inline bool isContinuationByte(uchar b)
+    {
+        return (b & 0xc0) == 0x80;
+    }
+
+    /// returns the number of characters consumed (including \a b) in case of success;
+    /// returns negative in case of error: Traits::Error or Traits::EndOfString
+    template <typename Traits, typename OutputPtr, typename InputPtr> inline
+    int fromUtf8(uchar b, OutputPtr &dst, InputPtr &src, InputPtr end)
+    {
+        int charsNeeded;
+        uint min_uc;
+        uint uc;
+
+        if (!Traits::skipAsciiHandling && b < 0x80) {
+            // US-ASCII
+            Traits::appendUtf16(dst, b);
+            return 1;
+        }
+
+        if (!Traits::isTrusted && Q_UNLIKELY(b <= 0xC1)) {
+            // an UTF-8 first character must be at least 0xC0
+            // however, all 0xC0 and 0xC1 first bytes can only produce overlong sequences
+            return Traits::Error;
+        } else if (b < 0xe0) {
+            charsNeeded = 2;
+            min_uc = 0x80;
+            uc = b & 0x1f;
+        } else if (b < 0xf0) {
+            charsNeeded = 3;
+            min_uc = 0x800;
+            uc = b & 0x0f;
+        } else if (b < 0xf5) {
+            charsNeeded = 4;
+            min_uc = 0x10000;
+            uc = b & 0x07;
+        } else {
+            // the last Unicode character is U+10FFFF
+            // it's encoded in UTF-8 as "\xF4\x8F\xBF\xBF"
+            // therefore, a byte higher than 0xF4 is not the UTF-8 first byte
+            return Traits::Error;
+        }
+
+        int bytesAvailable = Traits::availableBytes(src, end);
+        if (Q_UNLIKELY(bytesAvailable < charsNeeded - 1)) {
+            // it's possible that we have an error instead of just unfinished bytes
+            if (bytesAvailable > 0 && !isContinuationByte(Traits::peekByte(src, 0)))
+                return Traits::Error;
+            if (bytesAvailable > 1 && !isContinuationByte(Traits::peekByte(src, 1)))
+                return Traits::Error;
+            return Traits::EndOfString;
+        }
+
+        // first continuation character
+        b = Traits::peekByte(src, 0);
+        if (!isContinuationByte(b))
+            return Traits::Error;
+        uc <<= 6;
+        uc |= b & 0x3f;
+
+        if (charsNeeded > 2) {
+            // second continuation character
+            b = Traits::peekByte(src, 1);
+            if (!isContinuationByte(b))
+                return Traits::Error;
+            uc <<= 6;
+            uc |= b & 0x3f;
+
+            if (charsNeeded > 3) {
+                // third continuation character
+                b = Traits::peekByte(src, 2);
+                if (!isContinuationByte(b))
+                    return Traits::Error;
+                uc <<= 6;
+                uc |= b & 0x3f;
+            }
+        }
+
+        // we've decoded something; safety-check it
+        if (!Traits::isTrusted) {
+            if (uc < min_uc)
+                return Traits::Error;
+            if (QChar::isSurrogate(uc) || uc > QChar::LastValidCodePoint)
+                return Traits::Error;
+            if (!Traits::allowNonCharacters && QChar::isNonCharacter(uc))
+                return Traits::Error;
+        }
+
+        // write the UTF-16 sequence
+        if (!QChar::requiresSurrogates(uc)) {
+            // UTF-8 decoded and no surrogates are required
+            // detach if necessary
+            Traits::appendUtf16(dst, ushort(uc));
+        } else {
+            // UTF-8 decoded to something that requires a surrogate pair
+            Traits::appendUcs4(dst, uc);
+        }
+
+        Traits::advanceByte(src, charsNeeded - 1);
+        return charsNeeded;
+    }
+}
+
+enum DataEndianness
+{
+    DetectEndianness,
+    BigEndianness,
+    LittleEndianness
+};
+
+struct QUtf8
+{
+    static QChar *convertToUnicode(QChar *, const char *, qsizetype) noexcept;
+    static QString convertToUnicode(const char *, qsizetype);
+    static QString convertToUnicode(const char *, qsizetype, QStringConverter::State *);
+    static QByteArray convertFromUnicode(const QChar *, qsizetype);
+    static QByteArray convertFromUnicode(const QChar *, qsizetype, QStringConverter::State *);
+    struct ValidUtf8Result {
+        bool isValidUtf8;
+        bool isValidAscii;
+    };
+    static ValidUtf8Result isValidUtf8(const char *, qsizetype);
+    static int compareUtf8(const char *, qsizetype, const QChar *, qsizetype);
+    static int compareUtf8(const char *, qsizetype, QLatin1String s);
+};
+
+struct QUtf16
+{
+    static QString convertToUnicode(const char *, qsizetype, QStringConverter::State *, DataEndianness = DetectEndianness);
+    static QByteArray convertFromUnicode(const QChar *, qsizetype, QStringConverter::State *, DataEndianness = DetectEndianness);
+};
+
+struct QUtf32
+{
+    static QString convertToUnicode(const char *, qsizetype, QStringConverter::State *, DataEndianness = DetectEndianness);
+    static QByteArray convertFromUnicode(const QChar *, qsizetype, QStringConverter::State *, DataEndianness = DetectEndianness);
+};
+
+/*
+ Converts from different utf encodings looking at a possible byte order mark at the
+ beginning of the string. If no BOM exists, utf-8 is assumed.
+ */
+Q_CORE_EXPORT QString qFromUtfEncoded(const QByteArray &ba);
+
+QT_END_NAMESPACE
+
+#endif // QSTRINGCONVERTER_P_H