- Qt 6.8
- Qt Core
- C++ Classes
- QStaticByteArrayMatcher
- Qt 6.8.1 Reference Documentation

# QStaticByteArrayMatcher Class

template <size_t N> class QStaticByteArrayMatcher

The QStaticByteArrayMatcher class is a compile-time version of QByteArrayMatcher. More...

Header: | `#include <QStaticByteArrayMatcher>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Core)` `target_link_libraries(mytarget PRIVATE Qt6::Core)`
qmake: | `QT += core`

- List of all members, including inherited members

## Public Functions

qsizetype | indexIn(const QByteArray &haystack, qsizetype from = 0) const
qsizetype | indexIn(const char *haystack, qsizetype hlen, qsizetype from = 0) const
QByteArray | pattern() const

## Related Non-Members

QStaticByteArrayMatcher<N> | qMakeStaticByteArrayMatcher(const char (&)[N] pattern)

## Detailed Description

This class is useful when you have a sequence of bytes that you want to repeatedly match against some byte arrays (perhaps in a loop), or when you want to search for the same sequence of bytes multiple times in the same byte array. Using a matcher object and indexIn() is faster than matching a plain QByteArray with QByteArray::indexOf(), in particular if repeated matching takes place.

Unlike QByteArrayMatcher, this class calculates the internal representation at compile-time, so it can even benefit if you are doing one-off byte array matches.

Create the QStaticByteArrayMatcher by calling qMakeStaticByteArrayMatcher(), passing it the C string literal you want to search for. Store the return value of that function in a `static const auto` variable, so you don't need to pass the `N` template parameter explicitly:

     static const auto matcher = qMakeStaticByteArrayMatcher("needle");

Then call indexIn() on the QByteArray in which you want to search, just like with QByteArrayMatcher.

Since this class is designed to do all the up-front calculations at compile-time, it does not offer a setPattern() method.

See also QByteArrayMatcher and QStringMatcher.

## Member Function Documentation

### `[noexcept]` qsizetype QStaticByteArrayMatcher::indexIn(const QByteArray &haystack, qsizetype from = 0) const

Searches the char string haystack, from byte position from (default 0, i.e. from the first byte), for the byte array pattern() that was set in the constructor.

Returns the position where the pattern() matched in haystack, or -1 if no match was found.

### `[noexcept]` qsizetype QStaticByteArrayMatcher::indexIn(const char *haystack, qsizetype hlen, qsizetype from = 0) const

Searches the char string haystack, which has length hlen, from byte position from (default 0, i.e. from the first byte), for the byte array pattern() that was set in the constructor.

Returns the position where the pattern() matched in haystack, or -1 if no match was found.

### QByteArray QStaticByteArrayMatcher::pattern() const

Returns the byte array pattern that this byte array matcher will search for.

See also QByteArrayMatcher::setPattern().

## Related Non-Members

### `[constexpr noexcept]` template <size_t N> QStaticByteArrayMatcher<N> qMakeStaticByteArrayMatcher(const char (&)[N] pattern)

Return a QStaticByteArrayMatcher with the correct `N` determined automatically from the pattern passed.

To take full advantage of this function, assign the result to an `auto` variable:

     static const auto matcher = qMakeStaticByteArrayMatcher("needle");