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Difference between revisions of "User:Rick.barkhouse.oracle.com/VTD"
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[[Image:Vtd_layout.jpg]] | [[Image:Vtd_layout.jpg]] | ||
| − | + | * Big endian | |
| − | + | * Starting offset: 30 bits (b29 ~ b0) maximum value is 2^30 -1 = 1G -1 | |
| − | + | * Length: 20 bits (b51 ~ b32) maximum value is 2^20-1 = 1M -1 | |
| − | + | ** For some token type | |
| − | + | *** Prefix length: 9 bits (b51~ b43) max value 511 | |
| − | + | *** Q-name length: 11 bits (b42 ~ b 32) max value 1023 | |
| − | + | * Depth: 8 bits (b59~b52) max value is 2^8-1 = 255 | |
| − | + | * Token type: 4 bits (b63~b60) | |
| − | + | * Reserved bit: 2 bits (b31: b30) | |
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==VTD-XML Core Concepts== | ==VTD-XML Core Concepts== | ||
Revision as of 12:43, 14 December 2012
VTD-XML Investigation
VTD-XML (http://vtd-xml.sourceforge.net/) is a high-performance XML processing model that deals with XML in a binary form, instead of the traditional text form. VTD stands for Virtual Token Descriptor.
VTD-XML parses an XML document and builds an internal data structure representing the entire XML document in byte[] form. Each "token" of the XML document is represented as the following 64-bit integer:
- Big endian
- Starting offset: 30 bits (b29 ~ b0) maximum value is 2^30 -1 = 1G -1
- Length: 20 bits (b51 ~ b32) maximum value is 2^20-1 = 1M -1
- For some token type
- Prefix length: 9 bits (b51~ b43) max value 511
- Q-name length: 11 bits (b42 ~ b 32) max value 1023
- For some token type
- Depth: 8 bits (b59~b52) max value is 2^8-1 = 255
- Token type: 4 bits (b63~b60)
- Reserved bit: 2 bits (b31: b30)
VTD-XML Core Concepts
Unmarshalling a VTD-XML document
VTDGen vg = new VTDGen(); // from existing byte[] // true indicates namespace aware vg.setDoc(byte[]); vg.parse(true); // - or - // from file vg.parseFile("old.xml",false)