path: root/lineread.c
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* Add cleaner line-by-line reading primitivesDavid Gibson2022-07-061-0/+115
Two places in passt need to read files line by line (one parsing resolv.conf, the other parsing /proc/net/*. They can't use fgets() because in glibc that can allocate memory. Instead they use an implementation line_read() in util.c. This has some problems: * It has two completely separate modes of operation, one buffering and one not, the relation between these and how they're activated is subtle and confusing * At least in non-buffered mode, it will mishandle an empty line, folding them onto the start of the next non-empty line * In non-buffered mode it will use lseek() which prevents using this on non-regular files (we don't need that at present, but it's a surprising limitation) * It has a lot of difficult to read pointer mangling Add a new cleaner implementation of allocation-free line-by-line reading in lineread.c. This one always buffers, using a state structure to keep track of what we need. This is larger than I'd like, but it turns out handling all the edge cases of line-by-line reading in C is surprisingly hard. This just adds the code, subsequent patches will change the existing users of line_read() to the new implementation. Signed-off-by: David Gibson <david@gibson.dropbear.id.au>