diff options
Diffstat (limited to 'src/corelib/tools')
| -rw-r--r-- | src/corelib/tools/qstring.cpp | 30 |
1 files changed, 27 insertions, 3 deletions
diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp index eea41ea3d7..1b6ff3c5df 100644 --- a/src/corelib/tools/qstring.cpp +++ b/src/corelib/tools/qstring.cpp @@ -8808,13 +8808,37 @@ QString QString::toHtmlEscaped() const Creating a QString from it is free in this case, and the generated string data is stored in the read-only segment of the compiled object file. + For compilers not supporting the creation of compile time strings, QStringLiteral will fall back to + QLatin1String. + + The result of the QStringLiteral expression can be cast into a QString. + + If you have code looking like: + \code + if (node.hasAttribute("http-contents-length")) //... + \endcode + One temporary QString will be created to be passed as the hasAttribute function parameter. + This can be quite expensive, as it involves a memory allocation and the copy and the conversion + of the data into QString's internal encoding. + + This can be avoided by doing + \code + if (node.hasAttribute(QStringLiteral("http-contents-length"))) //... + \endcode + Then the QString's internal data will be generated at compile time and no conversion or allocation + will occur at runtime + Using QStringLiteral instead of a double quoted ascii literal can significantly speed up creation of QString's from data known at compile time. - If the compiler is c++0x enabled the string \a str can actually contain unicode data. + If the compiler is C++11 enabled the string \a str can actually contain unicode data. - For compilers not supporting the creation of compile time strings, QStringLiteral will fall back to - QLatin1String. + \note There are still a few cases in which QLatin1String is more efficient than QStringLiteral: + If it is passed to a function that has an overload that takes the QLatin1String directly, without + conversion to QString. For instance, this is the case of QString::operator== + \code + if (attribute.name() == QLatin1String("http-contents-length")) //... + \endcode */ QT_END_NAMESPACE |