Refactor QByteArray to allow for const data

Similar refactoring as done for QString. Make
shared_null read-only, and add support for
compile time generated QByteArrayData.

Add support for properly reserving capacity.

Change-Id: Ie4c41d4caac7b3b4bb1aef40c1c860a30b82edb8
Reviewed-on: http://codereview.qt.nokia.com/1484
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Olivier Goffart <olivier.goffart@nokia.com>

3 files changed, 285 insertions, 188 deletions

diff --git a/src/corelib/tools/qbytearray.cpp b/src/corelib/tools/qbytearray.cpp
index 767b71338f..0c5276f442 100644
--- a/src/corelib/tools/qbytearray.cpp
+++ b/src/corelib/tools/qbytearray.cpp
@@ -57,7 +57,7 @@
 #include <string.h>
 #include <stdlib.h>
 
-#define IS_RAW_DATA(d) ((d)->data != (d)->array)
+#define IS_RAW_DATA(d) ((d)->offset != 0)
 
 QT_BEGIN_NAMESPACE
 
@@ -546,7 +546,7 @@ QByteArray qUncompress(const uchar* data, int nbytes)
             qWarning("qUncompress: Input data is corrupted");
             return QByteArray();
         }
-        QByteArray::Data *p = static_cast<QByteArray::Data *>(qRealloc(d.data(), sizeof(QByteArray::Data) + alloc));
+        QByteArray::Data *p = static_cast<QByteArray::Data *>(qRealloc(d.data(), sizeof(QByteArray::Data) + alloc + 1));
         if (!p) {
             // we are not allowed to crash here when compiling with QT_NO_EXCEPTIONS
             qWarning("qUncompress: could not allocate enough memory to uncompress data");
@@ -554,8 +554,9 @@ QByteArray qUncompress(const uchar* data, int nbytes)
         }
         d.take(); // realloc was successful
         d.reset(p);
+        d->offset = 0;
 
-        int res = ::uncompress((uchar*)d->array, &len,
+        int res = ::uncompress((uchar*)d->data(), &len,
                                (uchar*)data+4, nbytes-4);
 
         switch (res) {
@@ -566,7 +567,7 @@ QByteArray qUncompress(const uchar* data, int nbytes)
                     qWarning("qUncompress: Input data is corrupted");
                     return QByteArray();
                 }
-                QByteArray::Data *p = static_cast<QByteArray::Data *>(qRealloc(d.data(), sizeof(QByteArray::Data) + len));
+                QByteArray::Data *p = static_cast<QByteArray::Data *>(qRealloc(d.data(), sizeof(QByteArray::Data) + len + 1));
                 if (!p) {
                     // we are not allowed to crash here when compiling with QT_NO_EXCEPTIONS
                     qWarning("qUncompress: could not allocate enough memory to uncompress data");
@@ -576,9 +577,11 @@ QByteArray qUncompress(const uchar* data, int nbytes)
                 d.reset(p);
             }
             d->ref = 1;
-            d->alloc = d->size = len;
-            d->data = d->array;
-            d->array[len] = 0;
+            d->size = len;
+            d->alloc = len;
+            d->capacityReserved = false;
+            d->offset = 0;
+            d->data()[len] = 0;
 
             return QByteArray(d.take(), 0, 0);
 
@@ -611,10 +614,10 @@ static inline char qToLower(char c)
         return c;
 }
 
-QByteArray::Data QByteArray::shared_null = {Q_BASIC_ATOMIC_INITIALIZER(1),
-                                                          0, 0, shared_null.array, {0} };
-QByteArray::Data QByteArray::shared_empty = { Q_BASIC_ATOMIC_INITIALIZER(1),
-                                              0, 0, shared_empty.array, {0} };
+QConstByteArrayData<1> QByteArray::shared_null = { { Q_REFCOUNT_INITIALIZER(-1),
+                                                  0, 0, 0, { 0 } }, { 0 } };
+QConstByteArrayData<1> QByteArray::shared_empty = { { Q_REFCOUNT_INITIALIZER(-1),
+                                                   0, 0, 0, { 0 } }, { 0 } };
 
 /*!
     \class QByteArray
@@ -896,15 +899,15 @@ QByteArray &QByteArray::operator=(const char *str)
 {
     Data *x;
     if (!str) {
-        x = &shared_null;
+        x = const_cast<Data *>(&shared_null.ba);
     } else if (!*str) {
-        x = &shared_empty;
+        x = const_cast<Data *>(&shared_empty.ba);
     } else {
         int len = qstrlen(str);
         if (d->ref != 1 || len > d->alloc || (len < d->size && len < d->alloc >> 1))
             realloc(len);
         x = d;
-        memcpy(x->data, str, len + 1); // include null terminator
+        memcpy(x->data(), str, len + 1); // include null terminator
         x->size = len;
     }
     x->ref.ref();
@@ -1294,19 +1297,20 @@ void QByteArray::chop(int n)
 QByteArray::QByteArray(const char *str)
 {
     if (!str) {
-        d = &shared_null;
+        d = const_cast<Data *>(&shared_null.ba);
     } else if (!*str) {
-        d = &shared_empty;
+        d = const_cast<Data *>(&shared_empty.ba);
     } else {
         int len = qstrlen(str);
-        d = static_cast<Data *>(qMalloc(sizeof(Data)+len));
+        d = static_cast<Data *>(qMalloc(sizeof(Data) + len + 1));
         Q_CHECK_PTR(d);
-        d->ref = 0;;
-        d->alloc = d->size = len;
-        d->data = d->array;
-        memcpy(d->array, str, len+1); // include null terminator
+        d->ref = 1;
+        d->size = len;
+        d->alloc = len;
+        d->capacityReserved = false;
+        d->offset = 0;
+        memcpy(d->data(), str, len+1); // include null terminator
     }
-    d->ref.ref();
 }
 
 /*!
@@ -1323,19 +1327,20 @@ QByteArray::QByteArray(const char *str)
 QByteArray::QByteArray(const char *data, int size)
 {
     if (!data) {
-        d = &shared_null;
+        d = const_cast<Data *>(&shared_null.ba);
     } else if (size <= 0) {
-        d = &shared_empty;
+        d = const_cast<Data *>(&shared_empty.ba);
     } else {
-        d = static_cast<Data *>(qMalloc(sizeof(Data) + size));
+        d = static_cast<Data *>(qMalloc(sizeof(Data) + size + 1));
         Q_CHECK_PTR(d);
-        d->ref = 0;
-        d->alloc = d->size = size;
-        d->data = d->array;
-        memcpy(d->array, data, size);
-        d->array[size] = '\0';
+        d->ref = 1;
+        d->size = size;
+        d->alloc = size;
+        d->capacityReserved = false;
+        d->offset = 0;
+        memcpy(d->data(), data, size);
+        d->data()[size] = '\0';
     }
-    d->ref.ref();
 }
 
 /*!
@@ -1348,17 +1353,18 @@ QByteArray::QByteArray(const char *data, int size)
 QByteArray::QByteArray(int size, char ch)
 {
     if (size <= 0) {
-        d = &shared_null;
+        d = const_cast<Data *>(&shared_null.ba);
     } else {
-        d = static_cast<Data *>(qMalloc(sizeof(Data)+size));
+        d = static_cast<Data *>(qMalloc(sizeof(Data) + size + 1));
         Q_CHECK_PTR(d);
-        d->ref = 0;
-        d->alloc = d->size = size;
-        d->data = d->array;
-        d->array[size] = '\0';
-        memset(d->array, ch, size);
+        d->ref = 1;
+        d->size = size;
+        d->alloc = size;
+        d->capacityReserved = false;
+        d->offset = 0;
+        memset(d->data(), ch, size);
+        d->data()[size] = '\0';
     }
-    d->ref.ref();
 }
 
 /*!
@@ -1369,12 +1375,14 @@ QByteArray::QByteArray(int size, char ch)
 
 QByteArray::QByteArray(int size, Qt::Initialization)
 {
-    d = static_cast<Data *>(qMalloc(sizeof(Data)+size));
+    d = static_cast<Data *>(qMalloc(sizeof(Data) + size + 1));
     Q_CHECK_PTR(d);
     d->ref = 1;
-    d->alloc = d->size = size;
-    d->data = d->array;
-    d->array[size] = '\0';
+    d->size = size;
+    d->alloc = size;
+    d->capacityReserved = false;
+    d->offset = 0;
+    d->data()[size] = '\0';
 }
 
 /*!
@@ -1392,13 +1400,20 @@ QByteArray::QByteArray(int size, Qt::Initialization)
 
 void QByteArray::resize(int size)
 {
-    if (size <= 0) {
-        Data *x = &shared_empty;
-        x->ref.ref();
+    if (size < 0)
+        size = 0;
+
+    if (d->offset && d->ref == 1 && size < d->size) {
+        d->size = size;
+        return;
+    }
+
+    if (size == 0 && !d->capacityReserved) {
+        Data *x = const_cast<Data *>(&shared_empty.ba);
         if (!d->ref.deref())
             qFree(d);
         d = x;
-    } else if (d == &shared_null) {
+    } else if (d == &shared_null.ba || d == &shared_empty.ba) {
         //
         // Optimize the idiom:
         //    QByteArray a;
@@ -1407,22 +1422,21 @@ void QByteArray::resize(int size)
         // which is used in place of the Qt 3 idiom:
         //    QByteArray a(sz);
         //
-        Data *x = static_cast<Data *>(qMalloc(sizeof(Data)+size));
+        Data *x = static_cast<Data *>(qMalloc(sizeof(Data) + size + 1));
         Q_CHECK_PTR(x);
         x->ref = 1;
-        x->alloc = x->size = size;
-        x->data = x->array;
-        x->array[size] = '\0';
-        (void) d->ref.deref(); // cannot be 0, x points to shared_null
+        x->size = size;
+        x->alloc = size;
+        x->capacityReserved = false;
+        x->offset = 0;
+        x->data()[size] = '\0';
         d = x;
     } else {
-        if (d->ref != 1 || size > d->alloc || (size < d->size && size < d->alloc >> 1))
+        if (d->ref != 1 || size > d->alloc || (!d->capacityReserved && size < d->size && size < d->alloc >> 1))
             realloc(qAllocMore(size, sizeof(Data)));
         if (d->alloc >= size) {
             d->size = size;
-            if (d->data == d->array) {
-                d->array[size] = '\0';
-            }
+            d->data()[size] = '\0';
         }
     }
 }
@@ -1442,29 +1456,30 @@ QByteArray &QByteArray::fill(char ch, int size)
 {
     resize(size < 0 ? d->size : size);
     if (d->size)
-        memset(d->data, ch, d->size);
+        memset(d->data(), ch, d->size);
     return *this;
 }
 
 void QByteArray::realloc(int alloc)
 {
-    if (d->ref != 1 || d->data != d->array) {
-        Data *x = static_cast<Data *>(qMalloc(sizeof(Data) + alloc));
+    if (d->ref != 1 || d->offset) {
+        Data *x = static_cast<Data *>(qMalloc(sizeof(Data) + alloc + 1));
         Q_CHECK_PTR(x);
-        x->size = qMin(alloc, d->size);
-        ::memcpy(x->array, d->data, x->size);
-        x->array[x->size] = '\0';
         x->ref = 1;
+        x->size = qMin(alloc, d->size);
         x->alloc = alloc;
-        x->data = x->array;
+        x->capacityReserved = d->capacityReserved;
+        x->offset = 0;
+        ::memcpy(x->data(), d->data(), x->size);
+        x->data()[x->size] = '\0';
         if (!d->ref.deref())
             qFree(d);
         d = x;
     } else {
-        Data *x = static_cast<Data *>(qRealloc(d, sizeof(Data) + alloc));
+        Data *x = static_cast<Data *>(qRealloc(d, sizeof(Data) + alloc + 1));
         Q_CHECK_PTR(x);
         x->alloc = alloc;
-        x->data = x->array;
+        x->offset = 0;
         d = x;
     }
 }
@@ -1486,7 +1501,7 @@ void QByteArray::expand(int i)
 QByteArray QByteArray::nulTerminated() const
 {
     // is this fromRawData?
-    if (d->data == d->array)
+    if (!d->offset)
         return *this;           // no, then we're sure we're zero terminated
 
     QByteArray copy(*this);
@@ -1517,9 +1532,9 @@ QByteArray QByteArray::nulTerminated() const
 
 QByteArray &QByteArray::prepend(const QByteArray &ba)
 {
-    if ((d == &shared_null || d == &shared_empty) && !IS_RAW_DATA(ba.d)) {
+    if ((d == &shared_null.ba || d == &shared_empty.ba) && !IS_RAW_DATA(ba.d)) {
         *this = ba;
-    } else if (ba.d != &shared_null) {
+    } else if (ba.d != &shared_null.ba) {
         QByteArray tmp = *this;
         *this = ba;
         append(tmp);
@@ -1550,10 +1565,10 @@ QByteArray &QByteArray::prepend(const char *str, int len)
     if (str) {
         if (d->ref != 1 || d->size + len > d->alloc)
             realloc(qAllocMore(d->size + len, sizeof(Data)));
-        memmove(d->data+len, d->data, d->size);
-        memcpy(d->data, str, len);
+        memmove(d->data()+len, d->data(), d->size);
+        memcpy(d->data(), str, len);
         d->size += len;
-        d->data[d->size] = '\0';
+        d->data()[d->size] = '\0';
     }
     return *this;
 }
@@ -1568,10 +1583,10 @@ QByteArray &QByteArray::prepend(char ch)
 {
     if (d->ref != 1 || d->size + 1 > d->alloc)
         realloc(qAllocMore(d->size + 1, sizeof(Data)));
-    memmove(d->data+1, d->data, d->size);
-    d->data[0] = ch;
+    memmove(d->data()+1, d->data(), d->size);
+    d->data()[0] = ch;
     ++d->size;
-    d->data[d->size] = '\0';
+    d->data()[d->size] = '\0';
     return *this;
 }
 
@@ -1601,14 +1616,14 @@ QByteArray &QByteArray::prepend(char ch)
 
 QByteArray &QByteArray::append(const QByteArray &ba)
 {
-    if ((d == &shared_null || d == &shared_empty) && !IS_RAW_DATA(ba.d)) {
+    if ((d == &shared_null.ba || d == &shared_empty.ba) && !IS_RAW_DATA(ba.d)) {
         *this = ba;
-    } else if (ba.d != &shared_null) {
+    } else if (ba.d != &shared_null.ba) {
         if (d->ref != 1 || d->size + ba.d->size > d->alloc)
             realloc(qAllocMore(d->size + ba.d->size, sizeof(Data)));
-        memcpy(d->data + d->size, ba.d->data, ba.d->size);
+        memcpy(d->data() + d->size, ba.d->data(), ba.d->size);
         d->size += ba.d->size;
-        d->data[d->size] = '\0';
+        d->data()[d->size] = '\0';
     }
     return *this;
 }
@@ -1640,7 +1655,7 @@ QByteArray& QByteArray::append(const char *str)
         int len = qstrlen(str);
         if (d->ref != 1 || d->size + len > d->alloc)
             realloc(qAllocMore(d->size + len, sizeof(Data)));
-        memcpy(d->data + d->size, str, len + 1); // include null terminator
+        memcpy(d->data() + d->size, str, len + 1); // include null terminator
         d->size += len;
     }
     return *this;
@@ -1665,9 +1680,9 @@ QByteArray &QByteArray::append(const char *str, int len)
     if (str && len) {
         if (d->ref != 1 || d->size + len > d->alloc)
             realloc(qAllocMore(d->size + len, sizeof(Data)));
-        memcpy(d->data + d->size, str, len); // include null terminator
+        memcpy(d->data() + d->size, str, len); // include null terminator
         d->size += len;
-        d->data[d->size] = '\0';
+        d->data()[d->size] = '\0';
     }
     return *this;
 }
@@ -1682,8 +1697,8 @@ QByteArray& QByteArray::append(char ch)
 {
     if (d->ref != 1 || d->size + 1 > d->alloc)
         realloc(qAllocMore(d->size + 1, sizeof(Data)));
-    d->data[d->size++] = ch;
-    d->data[d->size] = '\0';
+    d->data()[d->size++] = ch;
+    d->data()[d->size] = '\0';
     return *this;
 }
 
@@ -1724,7 +1739,7 @@ static inline QByteArray &qbytearray_insert(QByteArray *ba,
 QByteArray &QByteArray::insert(int i, const QByteArray &ba)
 {
     QByteArray copy(ba);
-    return qbytearray_insert(this, i, copy.d->data, copy.d->size);
+    return qbytearray_insert(this, i, copy.d->data(), copy.d->size);
 }
 
 /*!
@@ -1812,7 +1827,7 @@ QByteArray &QByteArray::remove(int pos, int len)
     if (pos + len >= d->size) {
         resize(pos);
     } else {
-        memmove(d->data + pos, d->data + pos + len, d->size - pos - len);
+        memmove(d->data() + pos, d->data() + pos + len, d->size - pos - len);
         resize(d->size - len);
     }
     return *this;
@@ -1832,7 +1847,7 @@ QByteArray &QByteArray::replace(int pos, int len, const QByteArray &after)
 {
     if (len == after.d->size && (pos + len <= d->size)) {
         detach();
-        memmove(d->data + pos, after.d->data, len*sizeof(char));
+        memmove(d->data() + pos, after.d->data(), len*sizeof(char));
         return *this;
     } else {
         QByteArray copy(after);
@@ -1869,7 +1884,7 @@ QByteArray &QByteArray::replace(int pos, int len, const char *after, int alen)
 {
     if (len == alen && (pos + len <= d->size)) {
         detach();
-        memcpy(d->data + pos, after, len*sizeof(char));
+        memcpy(d->data() + pos, after, len*sizeof(char));
         return *this;
     } else {
         remove(pos, len);
@@ -1936,13 +1951,13 @@ QByteArray &QByteArray::replace(const char *before, int bsize, const char *after
     // protect against before or after being part of this
     const char *a = after;
     const char *b = before;
-    if (after >= d->data && after < d->data + d->size) {
+    if (after >= d->data() && after < d->data() + d->size) {
         char *copy = (char *)malloc(asize);
         Q_CHECK_PTR(copy);
         memcpy(copy, after, asize);
         a = copy;
     }
-    if (before >= d->data && before < d->data + d->size) {
+    if (before >= d->data() && before < d->data() + d->size) {
         char *copy = (char *)malloc(bsize);
         Q_CHECK_PTR(copy);
         memcpy(copy, before, bsize);
@@ -2019,7 +2034,7 @@ QByteArray &QByteArray::replace(const char *before, int bsize, const char *after
                 resize(newlen);
                 len = newlen;
             }
-            d = this->d->data;
+            d = this->d->data();
 
             while(pos) {
                 pos--;
@@ -2192,19 +2207,19 @@ QByteArray QByteArray::repeated(int times) const
     if (result.d->alloc != resultSize)
         return QByteArray(); // not enough memory
 
-    memcpy(result.d->data, d->data, d->size);
+    memcpy(result.d->data(), d->data(), d->size);
 
     int sizeSoFar = d->size;
-    char *end = result.d->data + sizeSoFar;
+    char *end = result.d->data() + sizeSoFar;
 
     const int halfResultSize = resultSize >> 1;
     while (sizeSoFar <= halfResultSize) {
-        memcpy(end, result.d->data, sizeSoFar);
+        memcpy(end, result.d->data(), sizeSoFar);
         end += sizeSoFar;
         sizeSoFar <<= 1;
     }
-    memcpy(end, result.d->data, resultSize - sizeSoFar);
-    result.d->data[resultSize] = '\0';
+    memcpy(end, result.d->data(), resultSize - sizeSoFar);
+    result.d->data()[resultSize] = '\0';
     result.d->size = resultSize;
     return result;
 }
@@ -2231,13 +2246,13 @@ int QByteArray::indexOf(const QByteArray &ba, int from) const
     if (ol == 0)
         return from;
     if (ol == 1)
-        return indexOf(*ba.d->data, from);
+        return indexOf(*ba.d->data(), from);
 
     const int l = d->size;
     if (from > d->size || ol + from > l)
         return -1;
 
-    return qFindByteArray(d->data, d->size, from, ba.d->data, ol);
+    return qFindByteArray(d->data(), d->size, from, ba.d->data(), ol);
 }
 
 /*! \fn int QByteArray::indexOf(const QString &str, int from) const
@@ -2279,7 +2294,7 @@ int QByteArray::indexOf(const char *c, int from) const
     if (ol == 0)
         return from;
 
-    return qFindByteArray(d->data, d->size, from, c, ol);
+    return qFindByteArray(d->data(), d->size, from, c, ol);
 }
 
 /*!
@@ -2300,11 +2315,11 @@ int QByteArray::indexOf(char ch, int from) const
     if (from < 0)
         from = qMax(from + d->size, 0);
     if (from < d->size) {
-        const char *n = d->data + from - 1;
-        const char *e = d->data + d->size;
+        const char *n = d->data() + from - 1;
+        const char *e = d->data() + d->size;
         while (++n != e)
         if (*n == ch)
-            return  n - d->data;
+            return  n - d->data();
     }
     return -1;
 }
@@ -2361,9 +2376,9 @@ int QByteArray::lastIndexOf(const QByteArray &ba, int from) const
 {
     const int ol = ba.d->size;
     if (ol == 1)
-        return lastIndexOf(*ba.d->data, from);
+        return lastIndexOf(*ba.d->data(), from);
 
-    return lastIndexOfHelper(d->data, d->size, ba.d->data, ol, from);
+    return lastIndexOfHelper(d->data(), d->size, ba.d->data(), ol, from);
 }
 
 /*! \fn int QByteArray::lastIndexOf(const QString &str, int from) const
@@ -2400,7 +2415,7 @@ int QByteArray::lastIndexOf(const char *str, int from) const
     if (ol == 1)
         return lastIndexOf(*str, from);
 
-    return lastIndexOfHelper(d->data, d->size, str, ol, from);
+    return lastIndexOfHelper(d->data(), d->size, str, ol, from);
 }
 
 /*!
@@ -2424,8 +2439,8 @@ int QByteArray::lastIndexOf(char ch, int from) const
     else if (from > d->size)
         from = d->size-1;
     if (from >= 0) {
-        const char *b = d->data;
-        const char *n = d->data + from + 1;
+        const char *b = d->data();
+        const char *n = d->data() + from + 1;
         while (n-- != b)
             if (*n == ch)
                 return  n - b;
@@ -2479,8 +2494,8 @@ int QByteArray::count(const char *str) const
 int QByteArray::count(char ch) const
 {
     int num = 0;
-    const char *i = d->data + d->size;
-    const char *b = d->data;
+    const char *i = d->data() + d->size;
+    const char *b = d->data();
     while (i != b)
         if (*--i == ch)
             ++num;
@@ -2509,7 +2524,7 @@ bool QByteArray::startsWith(const QByteArray &ba) const
         return true;
     if (d->size < ba.d->size)
         return false;
-    return memcmp(d->data, ba.d->data, ba.d->size) == 0;
+    return memcmp(d->data(), ba.d->data(), ba.d->size) == 0;
 }
 
 /*! \overload
@@ -2524,7 +2539,7 @@ bool QByteArray::startsWith(const char *str) const
     int len = qstrlen(str);
     if (d->size < len)
         return false;
-    return qstrncmp(d->data, str, len) == 0;
+    return qstrncmp(d->data(), str, len) == 0;
 }
 
 /*! \overload
@@ -2536,7 +2551,7 @@ bool QByteArray::startsWith(char ch) const
 {
     if (d->size == 0)
         return false;
-    return d->data[0] == ch;
+    return d->data()[0] == ch;
 }
 
 /*!
@@ -2554,7 +2569,7 @@ bool QByteArray::endsWith(const QByteArray &ba) const
         return true;
     if (d->size < ba.d->size)
         return false;
-    return memcmp(d->data + d->size - ba.d->size, ba.d->data, ba.d->size) == 0;
+    return memcmp(d->data() + d->size - ba.d->size, ba.d->data(), ba.d->size) == 0;
 }
 
 /*! \overload
@@ -2569,7 +2584,7 @@ bool QByteArray::endsWith(const char *str) const
     int len = qstrlen(str);
     if (d->size < len)
         return false;
-    return qstrncmp(d->data + d->size - len, str, len) == 0;
+    return qstrncmp(d->data() + d->size - len, str, len) == 0;
 }
 
 /*! \overload
@@ -2581,7 +2596,7 @@ bool QByteArray::endsWith(char ch) const
 {
     if (d->size == 0)
         return false;
-    return d->data[d->size - 1] == ch;
+    return d->data()[d->size - 1] == ch;
 }
 
 /*!
@@ -2603,7 +2618,7 @@ QByteArray QByteArray::left(int len)  const
         return *this;
     if (len < 0)
         len = 0;
-    return QByteArray(d->data, len);
+    return QByteArray(d->data(), len);
 }
 
 /*!
@@ -2625,7 +2640,7 @@ QByteArray QByteArray::right(int len) const
         return *this;
     if (len < 0)
         len = 0;
-    return QByteArray(d->data + d->size - len, len);
+    return QByteArray(d->data() + d->size - len, len);
 }
 
 /*!
@@ -2644,7 +2659,7 @@ QByteArray QByteArray::right(int len) const
 
 QByteArray QByteArray::mid(int pos, int len) const
 {
-    if (d == &shared_null || d == &shared_empty || pos >= d->size)
+    if (d == &shared_null.ba || d == &shared_empty.ba || pos >= d->size)
         return QByteArray();
     if (len < 0)
         len = d->size - pos;
@@ -2656,7 +2671,7 @@ QByteArray QByteArray::mid(int pos, int len) const
         len = d->size - pos;
     if (pos == 0 && len == d->size)
         return *this;
-    return QByteArray(d->data + pos, len);
+    return QByteArray(d->data() + pos, len);
 }
 
 /*!
@@ -2715,7 +2730,7 @@ void QByteArray::clear()
 {
     if (!d->ref.deref())
         qFree(d);
-    d = &shared_null;
+    d = const_cast<Data *>(&shared_null.ba);
     d->ref.ref();
 }
 
@@ -3106,10 +3121,10 @@ QByteArray QByteArray::simplified() const
     if (d->size == 0)
         return *this;
     QByteArray result(d->size, Qt::Uninitialized);
-    const char *from = d->data;
+    const char *from = d->data();
     const char *fromend = from + d->size;
     int outc=0;
-    char *to = result.d->data;
+    char *to = result.d->data();
     for (;;) {
         while (from!=fromend && isspace(uchar(*from)))
             from++;
@@ -3145,7 +3160,7 @@ QByteArray QByteArray::trimmed() const
 {
     if (d->size == 0)
         return *this;
-    const char *s = d->data;
+    const char *s = d->data();
     if (!isspace(uchar(*s)) && !isspace(uchar(s[d->size-1])))
         return *this;
     int start = 0;
@@ -3158,8 +3173,7 @@ QByteArray QByteArray::trimmed() const
     }
     int l = end - start + 1;
     if (l <= 0) {
-        shared_empty.ref.ref();
-        return QByteArray(&shared_empty, 0, 0);
+        return QByteArray(const_cast<Data *>(&shared_empty.ba), 0, 0);
     }
     return QByteArray(s+start, l);
 }
@@ -3190,8 +3204,8 @@ QByteArray QByteArray::leftJustified(int width, char fill, bool truncate) const
     if (padlen > 0) {
         result.resize(len+padlen);
         if (len)
-            memcpy(result.d->data, d->data, len);
-        memset(result.d->data+len, fill, padlen);
+            memcpy(result.d->data(), d->data(), len);
+        memset(result.d->data()+len, fill, padlen);
     } else {
         if (truncate)
             result = left(width);
@@ -3227,8 +3241,8 @@ QByteArray QByteArray::rightJustified(int width, char fill, bool truncate) const
     if (padlen > 0) {
         result.resize(len+padlen);
         if (len)
-            memcpy(result.d->data+padlen, data(), len);
-        memset(result.d->data, fill, padlen);
+            memcpy(result.d->data()+padlen, data(), len);
+        memset(result.d->data(), fill, padlen);
     } else {
         if (truncate)
             result = left(width);
@@ -3238,7 +3252,7 @@ QByteArray QByteArray::rightJustified(int width, char fill, bool truncate) const
     return result;
 }
 
-bool QByteArray::isNull() const { return d == &shared_null; }
+bool QByteArray::isNull() const { return d == &shared_null.ba; }
 
 
 /*!
@@ -3562,13 +3576,13 @@ QByteArray QByteArray::toBase64() const
     char *out = tmp.data();
     while (i < d->size) {
 	int chunk = 0;
-	chunk |= int(uchar(d->data[i++])) << 16;
+        chunk |= int(uchar(d->data()[i++])) << 16;
 	if (i == d->size) {
 	    padlen = 2;
 	} else {
-	    chunk |= int(uchar(d->data[i++])) << 8;
+            chunk |= int(uchar(d->data()[i++])) << 8;
 	    if (i == d->size) padlen = 1;
-	    else chunk |= int(uchar(d->data[i++]));
+            else chunk |= int(uchar(d->data()[i++]));
 	}
 
 	int j = (chunk & 0x00fc0000) >> 18;
@@ -3864,17 +3878,20 @@ QByteArray QByteArray::number(double n, char f, int prec)
 
 QByteArray QByteArray::fromRawData(const char *data, int size)
 {
-    Data *x = static_cast<Data *>(qMalloc(sizeof(Data)));
-    Q_CHECK_PTR(x);
-    if (data) {
-        x->data = const_cast<char *>(data);
+    Data *x;
+    if (!data) {
+        x = const_cast<Data *>(&shared_null.ba);
+    } else if (!size) {
+        x = const_cast<Data *>(&shared_empty.ba);
     } else {
-        x->data = x->array;
-        size = 0;
+        x = static_cast<Data *>(qMalloc(sizeof(Data) + 1));
+        Q_CHECK_PTR(x);
+        x->ref = 1;
+        x->size = size;
+        x->alloc = 0;
+        x->capacityReserved = false;
+        x->offset = data - (x->d + sizeof(qptrdiff));
     }
-    x->ref = 1;
-    x->alloc = x->size = size;
-    *x->array = '\0';
     return QByteArray(x, 0, 0);
 }
 
@@ -3898,13 +3915,13 @@ QByteArray &QByteArray::setRawData(const char *data, uint size)
         *this = fromRawData(data, size);
     } else {
         if (data) {
-            d->data = const_cast<char *>(data);
+            d->size = size;
+            d->offset = data - (d->d + sizeof(qptrdiff));
         } else {
-            d->data = d->array;
-            size = 0;
+            d->offset = 0;
+            d->size = 0;
+            *d->data() = 0;
         }
-        d->alloc = d->size = size;
-        *d->array = '\0';
     }
     return *this;
 }
@@ -4013,7 +4030,7 @@ QByteArray QByteArray::toHex() const
 {
     QByteArray hex(d->size * 2, Qt::Uninitialized);
     char *hexData = hex.data();
-    const uchar *data = (const uchar *)d->data;
+    const uchar *data = (const uchar *)d->data();
     for (int i = 0; i < d->size; ++i) {
         int j = (data[i] >> 4) & 0xf;
         if (j <= 9)
diff --git a/src/corelib/tools/qbytearray.h b/src/corelib/tools/qbytearray.h
index 26cf2af59c..dbac302d05 100644
--- a/src/corelib/tools/qbytearray.h
+++ b/src/corelib/tools/qbytearray.h
@@ -42,7 +42,7 @@
 #ifndef QBYTEARRAY_H
 #define QBYTEARRAY_H
 
-#include <QtCore/qatomic.h>
+#include <QtCore/qrefcount.h>
 #include <QtCore/qnamespace.h>
 
 #include <string.h>
@@ -119,18 +119,65 @@ class QString;
 class QDataStream;
 template <typename T> class QList;
 
+struct QByteArrayData
+{
+    QtPrivate::RefCount ref;
+    int size;
+    uint alloc : 31;
+    uint capacityReserved : 1;
+    union {
+        qptrdiff offset; // will always work as we add/subtract from a ushort ptr
+        char d[sizeof(qptrdiff)];
+    };
+    inline char *data() { return d + sizeof(qptrdiff) + offset; }
+    inline const char *data() const { return d + sizeof(qptrdiff) + offset; }
+};
+
+template<int n> struct QConstByteArrayData
+{
+    const QByteArrayData ba;
+    const char data[n];
+};
+
+template<int N> struct QConstByteArrayDataPtr
+{
+    const QConstByteArrayData<N> *ptr;
+};
+
+
+#if defined(Q_COMPILER_LAMBDA)
+#  define QByteArrayLiteral(str) ([]() { \
+        enum { Size = sizeof(str) }; \
+        static const QConstByteArrayData<Size> qbytearray_literal = \
+        { { Q_REFCOUNT_INITIALIZER(-1), Size -1, 0, 0, { 0 } }, str }; \
+        QConstByteArrayDataPtr<Size> holder = { &qbytearray_literal }; \
+    return holder; }())
+
+#elif defined(Q_CC_GNU)
+// We need to create a QByteArrayData in the .rodata section of memory
+// and the only way to do that is to create a "static const" variable.
+// To do that, we need the __extension__ {( )} trick which only GCC supports
+
+#  define QByteArrayLiteral(str) \
+    __extension__ ({ \
+        enum { Size = sizeof(str) }; \
+        static const QConstByteArrayData<Size> qbytearray_literal = \
+        { { Q_REFCOUNT_INITIALIZER(-1), Size -1, 0, 0, { 0 } }, str }; \
+        QConstByteArrayDataPtr<Size> holder = { &qbytearray_literal }; \
+        holder; })
+#endif
+
+#ifndef QByteArrayLiteral
+// no lambdas, not GCC, use const char * instead
+
+# define QByteArrayLiteral(str) (str)
+#endif
+
+
 class Q_CORE_EXPORT QByteArray
 {
 private:
-    struct Data {
-        QBasicAtomicInt ref;
-        int alloc, size;
-        // ### Qt 5.0: We need to add the missing capacity bit
-        // (like other tool classes have), to maintain the
-        // reserved memory on resize.
-        char *data;
-        char array[1];
-    };
+    typedef QByteArrayData Data;
 
 public:
     inline QByteArray();
@@ -330,10 +377,17 @@ public:
     int length() const { return d->size; }
     bool isNull() const;
 
+    template <int n>
+    inline QByteArray(const QConstByteArrayData<n> &dd)
+        : d(const_cast<QByteArrayData *>(&dd.str)) {}
+    template <int N>
+    Q_DECL_CONSTEXPR inline QByteArray(QConstByteArrayDataPtr<N> dd)
+        : d(const_cast<QByteArrayData *>(&dd.ptr->ba)) {}
+
 private:
     operator QNoImplicitBoolCast() const;
-    static Data shared_null;
-    static Data shared_empty;
+    static QConstByteArrayData<1> shared_null;
+    static QConstByteArrayData<1> shared_empty;
     Data *d;
     QByteArray(Data *dd, int /*dummy*/, int /*dummy*/) : d(dd) {}
     void realloc(int alloc);
@@ -348,34 +402,34 @@ public:
     inline DataPtr &data_ptr() { return d; }
 };
 
-inline QByteArray::QByteArray(): d(&shared_null) { d->ref.ref(); }
+inline QByteArray::QByteArray(): d(const_cast<Data *>(&shared_null.ba)) { d->ref.ref(); }
 inline QByteArray::~QByteArray() { if (!d->ref.deref()) qFree(d); }
 inline int QByteArray::size() const
 { return d->size; }
 
 inline char QByteArray::at(int i) const
-{ Q_ASSERT(i >= 0 && i < size()); return d->data[i]; }
+{ Q_ASSERT(i >= 0 && i < size()); return d->data()[i]; }
 inline char QByteArray::operator[](int i) const
-{ Q_ASSERT(i >= 0 && i < size()); return d->data[i]; }
+{ Q_ASSERT(i >= 0 && i < size()); return d->data()[i]; }
 inline char QByteArray::operator[](uint i) const
-{ Q_ASSERT(i < uint(size())); return d->data[i]; }
+{ Q_ASSERT(i < uint(size())); return d->data()[i]; }
 
 inline bool QByteArray::isEmpty() const
 { return d->size == 0; }
 #ifndef QT_NO_CAST_FROM_BYTEARRAY
 inline QByteArray::operator const char *() const
-{ return d->data; }
+{ return d->data(); }
 inline QByteArray::operator const void *() const
-{ return d->data; }
+{ return d->data(); }
 #endif
 inline char *QByteArray::data()
-{ detach(); return d->data; }
+{ detach(); return d->data(); }
 inline const char *QByteArray::data() const
-{ return d->data; }
+{ return d->data(); }
 inline const char *QByteArray::constData() const
-{ return d->data; }
+{ return d->data(); }
 inline void QByteArray::detach()
-{ if (d->ref != 1 || d->data != d->array) realloc(d->size); }
+{ if (d->ref != 1 || d->offset) realloc(d->size); }
 inline bool QByteArray::isDetached() const
 { return d->ref == 1; }
 inline QByteArray::QByteArray(const QByteArray &a) : d(a.d)
@@ -385,10 +439,10 @@ inline int QByteArray::capacity() const
 { return d->alloc; }
 
 inline void QByteArray::reserve(int asize)
-{ if (d->ref != 1 || asize > d->alloc) realloc(asize); }
+{ if (d->ref != 1 || asize > d->alloc) realloc(asize); d->capacityReserved = true; }
 
 inline void QByteArray::squeeze()
-{ if (d->size < d->alloc) realloc(d->size); }
+{ if (d->size < d->alloc) realloc(d->size); d->capacityReserved = false; }
 
 class Q_CORE_EXPORT QByteRef {
     QByteArray &a;
@@ -398,25 +452,25 @@ class Q_CORE_EXPORT QByteRef {
     friend class QByteArray;
 public:
     inline operator char() const
-        { return i < a.d->size ? a.d->data[i] : char(0); }
+        { return i < a.d->size ? a.d->data()[i] : char(0); }
     inline QByteRef &operator=(char c)
         { if (i >= a.d->size) a.expand(i); else a.detach();
-          a.d->data[i] = c;  return *this; }
+          a.d->data()[i] = c;  return *this; }
     inline QByteRef &operator=(const QByteRef &c)
         { if (i >= a.d->size) a.expand(i); else a.detach();
-          a.d->data[i] = c.a.d->data[c.i];  return *this; }
+          a.d->data()[i] = c.a.d->data()[c.i];  return *this; }
     inline bool operator==(char c) const
-    { return a.d->data[i] == c; }
+    { return a.d->data()[i] == c; }
     inline bool operator!=(char c) const
-    { return a.d->data[i] != c; }
+    { return a.d->data()[i] != c; }
     inline bool operator>(char c) const
-    { return a.d->data[i] > c; }
+    { return a.d->data()[i] > c; }
     inline bool operator>=(char c) const
-    { return a.d->data[i] >= c; }
+    { return a.d->data()[i] >= c; }
     inline bool operator<(char c) const
-    { return a.d->data[i] < c; }
+    { return a.d->data()[i] < c; }
     inline bool operator<=(char c) const
-    { return a.d->data[i] <= c; }
+    { return a.d->data()[i] <= c; }
 };
 
 inline QByteRef QByteArray::operator[](int i)
@@ -424,17 +478,17 @@ inline QByteRef QByteArray::operator[](int i)
 inline QByteRef QByteArray::operator[](uint i)
 { return QByteRef(*this, i); }
 inline QByteArray::iterator QByteArray::begin()
-{ detach(); return d->data; }
+{ detach(); return d->data(); }
 inline QByteArray::const_iterator QByteArray::begin() const
-{ return d->data; }
+{ return d->data(); }
 inline QByteArray::const_iterator QByteArray::constBegin() const
-{ return d->data; }
+{ return d->data(); }
 inline QByteArray::iterator QByteArray::end()
-{ detach(); return d->data + d->size; }
+{ detach(); return d->data() + d->size; }
 inline QByteArray::const_iterator QByteArray::end() const
-{ return d->data + d->size; }
+{ return d->data() + d->size; }
 inline QByteArray::const_iterator QByteArray::constEnd() const
-{ return d->data + d->size; }
+{ return d->data() + d->size; }
 inline QByteArray &QByteArray::operator+=(char c)
 { return append(c); }
 inline QByteArray &QByteArray::operator+=(const char *s)
diff --git a/tests/auto/qbytearray/tst_qbytearray.cpp b/tests/auto/qbytearray/tst_qbytearray.cpp
index e2f64b84f8..78b655419e 100644
--- a/tests/auto/qbytearray/tst_qbytearray.cpp
+++ b/tests/auto/qbytearray/tst_qbytearray.cpp
@@ -145,6 +145,8 @@ private slots:
     void byteRefDetaching() const;
 
     void reserve();
+
+    void literals();
 };
 
 tst_QByteArray::tst_QByteArray()
@@ -1527,14 +1529,38 @@ void tst_QByteArray::reserve()
     QVERIFY(qba.capacity() == capacity);
     char *data = qba.data();
 
-    // FIXME count from 0 to make it fail
-    for (int i = 1; i < capacity; i++) {
+    for (int i = 0; i < capacity; i++) {
         qba.resize(i);
         QVERIFY(capacity == qba.capacity());
         QVERIFY(data == qba.data());
     }
 }
 
+void tst_QByteArray::literals()
+{
+#if defined(Q_COMPILER_LAMBDA) || defined(Q_CC_GNU)
+    QByteArray str(QByteArrayLiteral("abcd"));
+
+    QVERIFY(str.length() == 4);
+    QVERIFY(str == "abcd");
+    QVERIFY(str.data_ptr()->ref == -1);
+    QVERIFY(str.data_ptr()->offset == 0);
+
+    const char *s = str.constData();
+    QByteArray str2 = str;
+    QVERIFY(str2.constData() == s);
+
+    // detach on non const access
+    QVERIFY(str.data() != s);
+
+    QVERIFY(str2.constData() == s);
+    QVERIFY(str2.data() != s);
+
+#else
+    QSKIP("Only tested on c++0x compliant compiler or gcc", SkipAll);
+#endif
+}
+
 const char globalChar = '1';
 
 QTEST_APPLESS_MAIN(tst_QByteArray)