Add appendicies on big numbers #32
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rohanmahy
reviewed
Jan 21, 2026
| By this, a value like 0 or 1 encoded as major type 0 is clearly distinct from the same value encoded as tag 2. | ||
| However, text in {{Section 3.4.3 of -cbor}} overrides this and makes these values equivalent. | ||
| This text affects the CBOR data model. | ||
| No other serliazation requirement in {{-cbor}} or this document affects the data model. |
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| No other serliazation requirement in {{-cbor}} or this document affects the data model. | |
| No other serialization requirement in {{-cbor}} or this document affects the data model. |
rohanmahy
reviewed
Jan 21, 2026
| However, text in {{Section 3.4.3 of -cbor}} overrides this and makes these values equivalent. | ||
| This text affects the CBOR data model. | ||
| No other serliazation requirement in {{-cbor}} or this document affects the data model. | ||
| Only this one. |
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This is a sentence fragment. Please remove, or attach to the previous sentence.
rohanmahy
reviewed
Jan 21, 2026
| That is, there is no data model in all of CBOR where these integer spaces are distinct. | ||
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| It is not in the scope of this document to update the text of {{Section 3.4.3 of -cbor}} | ||
| This text is only describing a common assumption of the meaing the text in {{Section 3.4.3 of -cbor}}. |
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| This text is only describing a common assumption of the meaing the text in {{Section 3.4.3 of -cbor}}. | |
| This text is only describing a common assumption of the meaning of the text in {{Section 3.4.3 of -cbor}}. |
rohanmahy
reviewed
Jan 21, 2026
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| Some programming environments have good support for big numbers (e.g., Python, Ruby and Go) and some do not (e.g., C, C++ and Rust). | ||
| However, even in environments that support big numbers, support for native integer sizes (e.g., 64-bit integers) is much more efficient. | ||
| It is thus reasonable for a CBOR library to provide a separate API for handling native integers size from the one handling big numbers. |
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did you mean native-sized or just native?
Suggested change
| It is thus reasonable for a CBOR library to provide a separate API for handling native integers size from the one handling big numbers. | |
| It is thus reasonable for a CBOR library to provide a separate API for handling native-sized integers from the one handling big numbers. |
rohanmahy
reviewed
Jan 21, 2026
| However, even in environments that support big numbers, support for native integer sizes (e.g., 64-bit integers) is much more efficient. | ||
| It is thus reasonable for a CBOR library to provide a separate API for handling native integers size from the one handling big numbers. | ||
| When doing this, the big number API must encode the values in the range of major types 0 and 1 as major type 0 and 1, not tag 2 and 3. | ||
| Similar the decoding facilities handling big numbers must accept major types 0 and 1 even though it returns there values as big numbers. |
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| Similar the decoding facilities handling big numbers must accept major types 0 and 1 even though it returns there values as big numbers. | |
| Similarly, the decoding facilities handling big numbers must accept major types 0 and 1 even though those facilities present that range of values to the application as big numbers. |
rohanmahy
reviewed
Jan 21, 2026
| When doing this, the big number API must encode the values in the range of major types 0 and 1 as major type 0 and 1, not tag 2 and 3. | ||
| Similar the decoding facilities handling big numbers must accept major types 0 and 1 even though it returns there values as big numbers. | ||
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| Alternately, some CBOR libraries may choose to return tags 2 and 3 in raw byte string form because this is very simple compared. |
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| Alternately, some CBOR libraries may choose to return tags 2 and 3 in raw byte string form because this is very simple compared. | |
| Alternately, some CBOR libraries may choose to return tags 2 and 3 in raw byte string form because this is very simple compared to implementing Big Numbers completely. |
rohanmahy
reviewed
Jan 21, 2026
| Alternately, some CBOR libraries may choose to return tags 2 and 3 in raw byte string form because this is very simple compared. | ||
| A full unified big number API incurs a few complications such as having to do big number increment and decrement by one for CBOR’s offset-by-one of negative values. | ||
| They also have to do the unification with major types 0 and 1. | ||
| Note also that major type 1 can express negative numbers beyond the range of native integers common and also have to be handled. |
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| Note also that major type 1 can express negative numbers beyond the range of native integers common and also have to be handled. | |
| Note also that major type 1 can express negative numbers well beyond the range of common native integers.. |
rohanmahy
approved these changes
Jan 21, 2026
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These explain how big number unification affects the data model and how one might implement big numbers.