QByteArray: Add append/prepend/insert overload

Use-case is fast insertion of copies of a character,
avoiding any temporary heap allocations

Change-Id: Ie5517d88429fbd4c58dbe5729de7c468d5d9a279
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Sérgio Martins <sergio.martins@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 53 insertions, 0 deletions

diff --git a/src/corelib/tools/qbytearray.cpp b/src/corelib/tools/qbytearray.cpp
index 447e84b3d4..241c255b5d 100644
--- a/src/corelib/tools/qbytearray.cpp
+++ b/src/corelib/tools/qbytearray.cpp
@@ -1713,6 +1713,14 @@ QByteArray &QByteArray::prepend(const char *str, int len)
     return *this;
 }
 
+/*! \fn QByteArray &QByteArray::prepend(int count, char ch)
+
+    \overload
+    \since 5.7
+
+    Prepends \a count copies of character \a ch to this byte array.
+*/
+
 /*!
     \overload
 
@@ -1825,6 +1833,17 @@ QByteArray &QByteArray::append(const char *str, int len)
     return *this;
 }
 
+/*! \fn QByteArray &QByteArray::append(int count, char ch)
+
+    \overload
+    \since 5.7
+
+    Appends \a count copies of character \a ch to this byte
+    array and returns a reference to this byte array.
+
+    If \a count is negative or zero nothing is appended to the byte array.
+*/
+
 /*!
     \overload
 
@@ -1941,6 +1960,33 @@ QByteArray &QByteArray::insert(int i, char ch)
     return qbytearray_insert(this, i, &ch, 1);
 }
 
+/*! \fn QByteArray &QByteArray::insert(int i, int count, char ch)
+
+    \overload
+    \since 5.7
+
+    Inserts \a count copies of character \a ch at index position \a i in the
+    byte array.
+
+    If \a i is greater than size(), the array is first extended using resize().
+*/
+
+QByteArray &QByteArray::insert(int i, int count, char ch)
+{
+    if (i < 0 || count <= 0)
+        return *this;
+
+    int oldsize = size();
+    resize(qMax(i, oldsize) + count);
+    char *dst = d->data();
+    if (i > oldsize)
+        ::memset(dst + oldsize, 0x20, i - oldsize);
+    else if (i < oldsize)
+        ::memmove(dst + i + count, dst + i, oldsize - i);
+    ::memset(dst + i, ch, count);
+    return *this;
+}
+
 /*!
     Removes \a len bytes from the array, starting at index position \a
     pos, and returns a reference to the array.
diff --git a/src/corelib/tools/qbytearray.h b/src/corelib/tools/qbytearray.h
index f0032227e8..cf310b3b1a 100644
--- a/src/corelib/tools/qbytearray.h
+++ b/src/corelib/tools/qbytearray.h
@@ -285,14 +285,17 @@ public:
     QByteArray rightJustified(int width, char fill = ' ', bool truncate = false) const Q_REQUIRED_RESULT;
 
     QByteArray &prepend(char c);
+    QByteArray &prepend(int count, char c);
     QByteArray &prepend(const char *s);
     QByteArray &prepend(const char *s, int len);
     QByteArray &prepend(const QByteArray &a);
     QByteArray &append(char c);
+    QByteArray &append(int count, char c);
     QByteArray &append(const char *s);
     QByteArray &append(const char *s, int len);
     QByteArray &append(const QByteArray &a);
     QByteArray &insert(int i, char c);
+    QByteArray &insert(int i, int count, char c);
     QByteArray &insert(int i, const char *s);
     QByteArray &insert(int i, const char *s, int len);
     QByteArray &insert(int i, const QByteArray &a);
@@ -568,6 +571,10 @@ inline QByteArray::const_iterator QByteArray::cend() const
 { return d->data() + d->size; }
 inline QByteArray::const_iterator QByteArray::constEnd() const
 { return d->data() + d->size; }
+inline QByteArray &QByteArray::append(int n, char ch)
+{ return insert(d->size, n, ch); }
+inline QByteArray &QByteArray::prepend(int n, char ch)
+{ return insert(0, n, ch); }
 inline QByteArray &QByteArray::operator+=(char c)
 { return append(c); }
 inline QByteArray &QByteArray::operator+=(const char *s)