internal static ZipIOExtraFieldElement Parse(BinaryReader reader, ZipIOZip64ExtraFieldUsage zip64extraFieldUsage)
{
// we can safely parse the Id and Size here
// since the minimum size is checked from the caller (ZipIoExtraField)
UInt16 id = reader.ReadUInt16();
UInt16 size = reader.ReadUInt16();
ZipIOExtraFieldElement newElement;
if (id == ZipIOExtraFieldZip64Element.ConstantFieldId) // Found Zip64 Extra Field element
{
newElement = new ZipIOExtraFieldZip64Element();
((ZipIOExtraFieldZip64Element)newElement).Zip64ExtraFieldUsage = zip64extraFieldUsage;
}
else if (id == ZipIOExtraFieldPaddingElement.ConstantFieldId) // Found potential Padding Extra Field element
{
// Even if the id matches Padding Extra Element id, we cannot be sure if it is Microsoft defined one
// until its signature is verified
// This extra field matches Padding Extra Element id, but it is not big enough to be ours
if (size < ZipIOExtraFieldPaddingElement.MinimumFieldDataSize)
{
// Treat it as an unknown Extra Field element
newElement = new ZipIOExtraFieldElement(id);
}
else
{
// Sniff bytes to check it it matches our Padding extra field signature
byte[] sniffedBytes = reader.ReadBytes(ZipIOExtraFieldPaddingElement.SignatureSize);
if (ZipIOExtraFieldPaddingElement.MatchesPaddingSignature(sniffedBytes))
{
// Signature matches the Padding Extra Field signature
newElement = new ZipIOExtraFieldPaddingElement();
}
else
{
// Signature doesn't match; treat it a an unknown Extra Field element
newElement = new ZipIOExtraFieldElement(id, sniffedBytes);
}
}
}
else
{
newElement = new ZipIOExtraFieldElement(id);
}
// Parse the data field of the Extra Field element
newElement.ParseDataField(reader, size);
return(newElement);
}
internal static ZipIOExtraFieldElement Parse(BinaryReader reader, ZipIOZip64ExtraFieldUsage zip64extraFieldUsage)
{
// we can safely parse the Id and Size here
// since the minimum size is checked from the caller (ZipIoExtraField)
UInt16 id = reader.ReadUInt16();
UInt16 size = reader.ReadUInt16();
ZipIOExtraFieldElement newElement;
if (id == ZipIOExtraFieldZip64Element.ConstantFieldId) // Found Zip64 Extra Field element
{
newElement = new ZipIOExtraFieldZip64Element();
((ZipIOExtraFieldZip64Element) newElement).Zip64ExtraFieldUsage = zip64extraFieldUsage;
}
else if (id == ZipIOExtraFieldPaddingElement.ConstantFieldId) // Found potential Padding Extra Field element
{
// Even if the id matches Padding Extra Element id, we cannot be sure if it is Microsoft defined one
// until its signature is verified
// This extra field matches Padding Extra Element id, but it is not big enough to be ours
if (size < ZipIOExtraFieldPaddingElement.MinimumFieldDataSize)
{
// Treat it as an unknown Extra Field element
newElement = new ZipIOExtraFieldElement(id);
}
else
{
// Sniff bytes to check it it matches our Padding extra field signature
byte[] sniffedBytes = reader.ReadBytes(ZipIOExtraFieldPaddingElement.SignatureSize);
if (ZipIOExtraFieldPaddingElement.MatchesPaddingSignature(sniffedBytes))
{
// Signature matches the Padding Extra Field signature
newElement = new ZipIOExtraFieldPaddingElement();
}
else
{
// Signature doesn't match; treat it a an unknown Extra Field element
newElement = new ZipIOExtraFieldElement(id, sniffedBytes);
}
}
}
else
{
newElement = new ZipIOExtraFieldElement(id);
}
// Parse the data field of the Extra Field element
newElement.ParseDataField(reader, size);
return newElement;
}
internal static ZipIOExtraField ParseRecord(BinaryReader reader, ZipIOZip64ExtraFieldUsage zip64extraFieldUsage, ushort expectedExtraFieldSize)
{
// most of the files are not ZIP 64, and instead of trying to parse it we should create new empty record
if (expectedExtraFieldSize == 0)
{
if (zip64extraFieldUsage != ZipIOZip64ExtraFieldUsage.None)
{
// in case there is an expectation by the caller for a non empty record we should throw
throw new FileFormatException(SR.Get(SRID.CorruptedData));
}
// We are creating Extra Fields for the existing Local File Header,
// so no need to create a new padding field
return(CreateNew(false));
}
ZipIOExtraField extraField = new ZipIOExtraField();
// Parse all Extra elements from Extra Field
while (expectedExtraFieldSize > 0)
{
if (expectedExtraFieldSize < ZipIOExtraFieldElement.MinimumSize)
{
throw new FileFormatException(SR.Get(SRID.CorruptedData));
}
ZipIOExtraFieldElement newElement = ZipIOExtraFieldElement.Parse(reader, zip64extraFieldUsage);
ZipIOExtraFieldZip64Element zip64Element = newElement as ZipIOExtraFieldZip64Element;
ZipIOExtraFieldPaddingElement paddingElement = newElement as ZipIOExtraFieldPaddingElement;
// if we have found the Zip 64 record. let's remember it
if (zip64Element != null)
{
if (extraField._zip64Element != null)
{
// multiple ZIP 64 extra fields are not allowed
throw new FileFormatException(SR.Get(SRID.CorruptedData));
}
extraField._zip64Element = zip64Element;
}
else if (paddingElement != null)
{
if (extraField._paddingElement != null)
{
// multiple padding extra fields are not allowed
throw new FileFormatException(SR.Get(SRID.CorruptedData));
}
extraField._paddingElement = paddingElement;
}
else
{
if (extraField._extraFieldElements == null)
{
extraField._extraFieldElements = new ArrayList(3); // we expect to see a few records there, as it sould have been produced by other authoring systems.
}
// any other instances of extra fields with the same id are allowed
extraField._extraFieldElements.Add(newElement);
}
checked { expectedExtraFieldSize -= newElement.Size; }
}
// if we didn't end up at the exact expected position, we are treating this as a corrupted file
if (expectedExtraFieldSize != 0)
{
throw new FileFormatException(SR.Get(SRID.CorruptedData));
}
// As we treat the ZIP 64 extra field as optional for all version >= 4.5
// we need to explicitly consider a case when it is missing
if (extraField._zip64Element == null)
{
extraField._zip64Element = ZipIOExtraFieldZip64Element.CreateNew();
}
/////////////////////////////////////////////////////////////////////
// extraField.Validate();
// an instance Validate function is removed to fix FxCop violation, please add it back
// if extra validation steps are required
//
// we are checking for uniqueness of the Zip 64 header ID in the Parse function.
// Although it might be a good idea to check for record id uniqueness in general,
// we are treating the rest of the field as a bag of bits, so it is probably not worth it to
// search for other duplicate ID especially as appnote considers ID duplication a possibility
// and even suggest a work around for file producers.
/////////////////////////////////////////////////////////////////////
return(extraField);
}