private static (ReadOnlyMemory <byte>, ReadOnlyMemory <byte>) ExtractVersionInformationBlocks(ReadOnlySpan <byte> symbol)
{
byte[] first = new byte[18];
byte[] second = new byte[18];
int sideLength = 4 * QRSymbol.GetVersion(symbol) + 17;
for (int i = 0; i < 6; i++)
{
for (int j = 0; j < 3; j++)
{
first[i * 3 + j] = symbol[(sideLength - 9 - j) + (5 - i) * sideLength];
}
}
for (int i = 0; i < 6; i++)
{
for (int j = 0; j < 3; j++)
{
second[i * 3 + j] = symbol[(sideLength - 9 - j) * sideLength + (5 - i)];
}
}
return(new ReadOnlyMemory <byte>(first), new ReadOnlyMemory <byte>(second));
}
private static (ReadOnlyMemory <byte>, ReadOnlyMemory <byte>) ExtractFormatInformationBlocks(ReadOnlySpan <byte> symbol)
{
byte[] first = new byte[15];
byte[] second = new byte[15];
int sideLength = 4 * QRSymbol.GetVersion(symbol) + 17;
for (int i = 0; i < 6; i++)
{
first[i] = symbol[8 * sideLength + i];
}
first[6] = symbol[7 + 8 * sideLength];
first[7] = symbol[8 + 8 * sideLength];
first[8] = symbol[8 + 7 * sideLength];
for (int i = 5; i >= 0; i--)
{
first[14 - i] = symbol[8 + i * sideLength];
}
for (int i = 0; i < 7; i++)
{
second[i] = symbol[8 + (sideLength - 1 - i) * sideLength];
}
for (int i = 0; i < 8; i++)
{
second[14 - i] = symbol[(sideLength - 1 - i) + 8 * sideLength];
}
return(new ReadOnlyMemory <byte>(first), new ReadOnlyMemory <byte>(second));
}
public static VersionInformation CreateFrom(ReadOnlySpan <byte> symbol)
{
int version = QRSymbol.GetVersion(symbol);
if (version >= 7)
{
(var firstVersion, var secondVersion) = DecodeVersionInformationBlocks(ExtractVersionInformationBlocks(symbol));
if (firstVersion != secondVersion)
{
throw new Exception($"Decoded Version Information is not consistent.{Environment.NewLine}First:{firstVersion}{Environment.NewLine}Second:{secondVersion}");
}
else if (firstVersion != version)
{
throw new Exception($"Decoded Version Information does not match with the symbol's size{Environment.NewLine}Decoded:{firstVersion}{Environment.NewLine}Derived from size:{version}");
}
}
return(new VersionInformation(version));
}
