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BER - Support OIDs with integers larger than 16383 - #307
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The current BER ObjectIdentifier (OID) encoding only support numbers between 0 and 16383. Any OIDs with larger values have their significant bits "truncated". This change supports BER encoding of OIDs containing numbers larger than 16383. BER encodes OIDs in 8-bit chunks (octet) in big-endian. The first two octets encode the object type (06) and the length. Next, the first two values of the OID are combined using a function (value1 * 40 + value2). Subsequent numbers are encoded as base 128 or in 7-bit chunks with each octet's most-significant bit signifying whether the number is complete (0) or requires consuming another chunk (1). For example, 16383 is encoded as 2 octets equaling (in hex) to `ff 7f`, whereas 16384 requires another octet `81 80 00`. This implementation keeps the existing logic and simply writes the number to the byte array if less than 127 (0x7F). If larger, it calculates the required number of 7-bit chunks to represent the number, then iteratively writes each required chunk to the byte array with the most-significant bit set to 1 until the final chunk is written with the most-significant bit set to 0. The includes some tests to verify the correct encoding output. The second and fourth tests will fail without the changes included in this commit.
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Looks good -- thanks for adding the tests. |
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The current BER ObjectIdentifier (OID) encoding only support numbers between 0 and 16383. Any OIDs with larger values have their significant bits "truncated". This change supports BER encoding of OIDs containing numbers larger than 16383.
BER encodes OIDs in 8-bit chunks (octet) in big-endian. The first two octets encode the object type (06) and the length. Next, the first two values of the OID are combined using a function (value1 * 40 + value2). Subsequent numbers are encoded as base 128 or in 7-bit chunks with each octet's most-significant bit signifying whether the number is complete (0) or requires consuming another chunk (1).
For example, 16383 is encoded as 2 octets equaling (in hex) to
ff 7f, whereas 16384 requires another octet81 80 00.This implementation keeps the existing logic and simply writes the number to the byte array if less than 127 (0x7F). If larger, it calculates the required number of 7-bit chunks to represent the number, then iteratively writes each required chunk to the byte array with the most-significant bit set to 1 until the final chunk is written with the most-significant bit set to 0.
The includes some tests to verify the correct encoding output. The second and fourth tests will fail without the changes included in this commit.
This fixes #306