Convert function to qt notation

Damian7546

Hi,
Please help how convert this line: buffer.writeBigInt64LE(BigInt(number)) to qt ?
JS:

function int64LE(number) {
  const buffer = Buffer.alloc(8)
  buffer.writeBigInt64LE(BigInt(number))
  return buffer
}

qt:

QByteArray int64LE(quint64 number)
{
    QByteArray buffer[8];
    ......
    return buffer;

}

Gaobo

Maybe you can ask chatgpt.....
This answer is from deepseek:

To convert the JavaScript function int64LE to Qt, you need to create a QByteArray that holds the little-endian byte representation of a 64-bit signed integer. Here's the step-by-step solution:

Resize the QByteArray to hold 8 bytes (64 bits).
Cast the input quint64 number to qint64 to handle it as a signed integer.
Extract each byte in little-endian order by masking and shifting the value.
Store each byte in the QByteArray.

QByteArray UtilsEssp::int64LE(quint64 number)
{
    QByteArray buffer;
    buffer.resize(8); // Allocate 8 bytes
    qint64 value = static_cast<qint64>(number); // Treat as signed

    // Extract each byte in little-endian order
    for (int i = 0; i < 8; ++i) {
        buffer[i] = static_cast<char>(value & 0xFF);
        value >>= 8;
    }

    return buffer;
}

Explanation:

Resizing the Buffer: buffer.resize(8) ensures the QByteArray has space for 8 bytes.
Casting to Signed: static_cast<qint64>(number) converts the unsigned input to a signed 64-bit integer, preserving the bit pattern.
Little-Endian Extraction: The loop iterates 8 times, each time taking the least significant byte using value & 0xFF, then right-shifting value by 8 bits. This fills the QByteArray from the least significant byte to the most significant, achieving little-endian order.

This approach mirrors the original JavaScript functionality by directly manipulating the byte representation, ensuring compatibility with systems expecting a signed 64-bit integer in little-endian format.

Gaobo

This post is deleted!

Christian Ehrlicher

Why manually when there are helper functions?
https://doc.qt.io/qt-6/qtendian.html

Oh, now deleted for unknown reasons.

Gaobo

Maybe you can ask chatgpt.....
This answer is from deepseek:

To convert the JavaScript function int64LE to Qt, you need to create a QByteArray that holds the little-endian byte representation of a 64-bit signed integer. Here's the step-by-step solution:

Resize the QByteArray to hold 8 bytes (64 bits).
Cast the input quint64 number to qint64 to handle it as a signed integer.
Extract each byte in little-endian order by masking and shifting the value.
Store each byte in the QByteArray.

QByteArray UtilsEssp::int64LE(quint64 number)
{
    QByteArray buffer;
    buffer.resize(8); // Allocate 8 bytes
    qint64 value = static_cast<qint64>(number); // Treat as signed

    // Extract each byte in little-endian order
    for (int i = 0; i < 8; ++i) {
        buffer[i] = static_cast<char>(value & 0xFF);
        value >>= 8;
    }

    return buffer;
}

Explanation:

Resizing the Buffer: buffer.resize(8) ensures the QByteArray has space for 8 bytes.
Casting to Signed: static_cast<qint64>(number) converts the unsigned input to a signed 64-bit integer, preserving the bit pattern.
Little-Endian Extraction: The loop iterates 8 times, each time taking the least significant byte using value & 0xFF, then right-shifting value by 8 bits. This fills the QByteArray from the least significant byte to the most significant, achieving little-endian order.

This approach mirrors the original JavaScript functionality by directly manipulating the byte representation, ensuring compatibility with systems expecting a signed 64-bit integer in little-endian format.