[Python-Dev] Simplify lnotab? (AST branch update) (original) (raw)

Phillip J. Eby pje at telecommunity.com
Fri Oct 14 17:20:45 CEST 2005

At 08:07 PM 10/14/2005 +1300, Greg Ewing wrote:

Phillip J. Eby wrote:

> A more > compact scheme is possible, by using two tables - a bytecode->line > number table, and a line number-> file table. > > If you have to encode multiple files, you just offset their line numbers > by the size of the other files, More straightforwardly, the second table could just be a bytecode -> file number mapping.

That would use more space in any case involving multiple files.

In the case of only one file, it would contain just a single entry, so it probably wouldn't even be worth the bother of special-casing that.

A line->file mapping would also have only one entry in that case.

You could save a bit more by having two kinds of line number table, "small" (16-bit entries) and "large" (32-bit entries) depending on the size of the code object and range of line numbers. The small one would be sufficient for almost all code objects, so the most common case would use only about 4 bytes per line of code. That's only twice as much as the current scheme uses.

That'd probably work.

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