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| -rw-r--r-- | doc/README.dissector | 40 |
1 files changed, 36 insertions, 4 deletions
diff --git a/doc/README.dissector b/doc/README.dissector index 778ef0775f..70a6875d1b 100644 --- a/doc/README.dissector +++ b/doc/README.dissector @@ -2301,13 +2301,45 @@ is expected to create a new tvbuff of type TVBUFF_SUBSET which contains the payload portion of the protocol (that is, the bytes that are relevant to the next dissector). -The syntax for creating a new TVBUFF_SUBSET is: +To create a new TVBUFF_SUBSET that begins at a specified offset in a +parent tvbuff, and runs to the end of the parent tvbuff, the routine +tvbuff_new_subset_remaining() is used: -next_tvb = tvb_new_subset_length_caplen(tvb, offset, length, reported_length) + next_tvb = tvb_new_subset_remaining(tvb, offset); -or, in the common case where it should just run to the end of the packet, +Where: + tvb is the tvbuff that the dissector has been working on. It + can be a tvbuff of any type. + + next_tvb is the new TVBUFF_SUBSET. + + offset is the byte offset of 'tvb' at which the new tvbuff + should start. The first byte is the 0th byte. + +To create a new TVBUFF_SUBSET that begins at a specified offset in a +parent tvbuff, with a specified number of bytes in the payload, the +routine tvbuff_new_subset_length() is used: + + next_tvb = tvb_new_subset_length(tvb, offset, reported_length); + +Where: + tvb is the tvbuff that the dissector has been working on. It + can be a tvbuff of any type. + + next_tvb is the new TVBUFF_SUBSET. + + offset is the byte offset of 'tvb' at which the new tvbuff + should start. The first byte is the 0th byte. + + reported_length is the number of bytes that the current protocol + says should be in the payload. + +In the few cases where the number of bytes available in the new subset +must be explicitly specified, rather than being calculated based on the +number of bytes in the payload, the routine tvb_new_subset_length_caplen() +is used: -next_tvb = tvb_new_subset_remaining(tvb, offset) + next_tvb = tvb_new_subset_length_caplen(tvb, offset, length, reported_length); Where: tvb is the tvbuff that the dissector has been working on. It |