13 Nov
2019
13 Nov
'19
6:24 a.m.
On Tue, Nov 12, 2019 at 11:41:51PM +0100, Robert Clausecker wrote:
Oh please no. One of the things we've hopefully
all learned from Pascal
is that length-prefixed strings suck because you can't perform anything
useful without copying the entire string. Rob Pike and friends showed
how to get strings and vectors right in the Go language where you have a
builtin slice type which is essentially a structure
struct slice(type) {
type *data;
size_t len, cap;
};
where data points to a buffer, len is the length of meaningful data in
that buffer and cap is the total buffer size.
We did something similar in BitKeeper but we added a spicy little twist.
We encoded len and cap in one word by making cap increase in powers of
2 only (which means you need log(n) bits for cap). So it was a data
structure that scaled both up and down.
We used it everywhere in BitKeeper, it was super handy.
http://repos.bkbits.net/bk/dev/src/libc/utils/lines.c?PAGE=anno&REV=56c…