From: Phillip Wood Date: Mon, 10 Nov 2025 16:27:38 GMT Subject: Re: [PATCH v6 1/4] interpret-trailers: factor out buffer-based processing to process_trailers() Message-ID: In-Reply-To: On 05/11/2025 16:57, Junio C Hamano wrote: > Li Chen writes: > >> From: Li Chen >> >> Extracted trailer processing into a helper that accumulates output in >> a strbuf before writing. >> >> Updated interpret_trailers() to reuse the helper, buffer output, and >> clean up both input and output buffers after writing. > > Imperative? > >> >> Signed-off-by: Li Chen >> --- >> builtin/interpret-trailers.c | 51 ++++++++++++++++++++---------------- >> 1 file changed, 29 insertions(+), 22 deletions(-) >> >> diff --git a/builtin/interpret-trailers.c b/builtin/interpret-trailers.c >> index 41b0750e5a..4c90580fff 100644 >> --- a/builtin/interpret-trailers.c >> +++ b/builtin/interpret-trailers.c >> @@ -136,32 +136,21 @@ static void read_input_file(struct strbuf *sb, const char *file) >> strbuf_complete_line(sb); >> } >> >> -static void interpret_trailers(const struct process_trailer_options *opts, >> - struct list_head *new_trailer_head, >> - const char *file) >> +static void process_trailers(const struct process_trailer_options *opts, >> + struct list_head *new_trailer_head, >> + struct strbuf *sb, struct strbuf *out) > > So we gained *out strbuf; in the preimage below I see fwrite(), > fprintf(), etc. to outfile that is either stdout or tempfile, but > presumably the output all will be captured in the strbuf instead, > which makes sense. It is a bit curious what the new paramater sb > is, but this is a file-scope static helper, so it does not strictly > require documenting. Having a comment would still be nicer, though, > unlike "struct process_trailer_options" that is very limited > purpose, "strbuf" can be used for any string processing, so a good > variable name like "out" that conveys what it is used for by > implication is good, but "sb", which is obvious abbreviation for > "Str Buf", conveys no useful information. This patch is based on my suggestion[1]. I had intended to rename "sb" to "in" but forgot to do so before posting that diff. Here's my signoff which Li should add before their own Signed-off-by: Phillip Wood Thanks Phillip [1] https://lore.kernel.org/git/7d12b046-365f-441c-af8e-8a39d61efbbd@gmail.com >> { >> LIST_HEAD(head); >> - struct strbuf sb = STRBUF_INIT; >> - struct strbuf trailer_block_sb = STRBUF_INIT; > > We no longer need a separate strbuf only for trailer block; we will > see why before we read through this helper function, hopefully. > >> struct trailer_block *trailer_block; >> - FILE *outfile = stdout; >> - >> - trailer_config_init(); >> >> - read_input_file(&sb, file); >> - >> - if (opts->in_place) >> - outfile = create_in_place_tempfile(file); > > OK, so the original code read the input (either "file", or standard > input) into a tempfile and prepared the output file stream. > Presumably it is now the responsibility of the caller of this new > function. Initializing the trailer configuration is also what the > caller of this function is reponsible for, as well. > > So this answers one of the questions I had upon starting to read > this function, i.e. "what is sb?" It holds the input string, which > is what? Something that look like a commit message that has title, > body and then a trailer block? We may want to give the parameter a > better name? I dunno (as this is file-scope static, as long as it > is obvious to the local caller, it may be OK, but on the other hand, > the caller needs to differenciate two strbuf parameters to the > helper function, one used for input and the other output, so if you > are calling the latter "out", perhaps you would want to call it > "in", or "input", perhaps?) > >> - trailer_block = parse_trailers(opts, sb.buf, &head); >> + trailer_block = parse_trailers(opts, sb->buf, &head); > > So we parse existing trailers from the input strbuf that is supplied > by the caller. The rest of this hunk is rewriting FILE* I/O with > strbuf addition. > >> @@ -173,22 +162,40 @@ static void interpret_trailers(const struct process_trailer_options *opts, >> } >> >> /* Print trailer block. */ >> - format_trailers(opts, &head, &trailer_block_sb); >> + format_trailers(opts, &head, out); >> free_trailers(&head); >> - fwrite(trailer_block_sb.buf, 1, trailer_block_sb.len, outfile); >> - strbuf_release(&trailer_block_sb); > > The format_trailers() helper function appends appends to the strbuf > that is given to it, so instead of using an extra strbuf (and then > appending that to the output), we just pass our output strbuf to it, > which is why we no longer need the trailer_block_sb strbuf anymore. > Makes sense. > >> /* Print the lines after the trailer block as is. */ >> if (!opts->only_trailers) >> - fwrite(sb.buf + trailer_block_end(trailer_block), 1, >> - sb.len - trailer_block_end(trailer_block), outfile); >> + strbuf_add(out, sb->buf + trailer_block_end(trailer_block), >> + sb->len - trailer_block_end(trailer_block)); >> trailer_block_release(trailer_block); >> +} > > And again, FILE* I/O is replaced with appending to the output strbuf > in the rest of this helper function. Good. > >> +static void interpret_trailers(const struct process_trailer_options *opts, >> + struct list_head *new_trailer_head, >> + const char *file) > > So the original caller of interpret_trailers() now call this outer > shell, which has the same name and the same function signature as > the original. Our new process_trailers() helper assumes a handful > of preparatory steps are already done by the caller, so what we are > going read here will be mostly those preparation, a call to our new > helper, and then printing the result to "file" or standard output. > >> +{ >> + struct strbuf sb = STRBUF_INIT; >> + struct strbuf out = STRBUF_INIT; >> + FILE *outfile = stdout; >> + >> + trailer_config_init(); >> + >> + read_input_file(&sb, file); >> + if (opts->in_place) >> + outfile = create_in_place_tempfile(file); > > And these are exactly the lines we lost from the new helper. > Looking good. > >> + process_trailers(opts, new_trailer_head, &sb, &out); > > And our call. "out" should have what we wanted to output to > outfile, so ... > >> + fwrite(out.buf, out.len, 1, outfile); > > ... we write it out. Good. For a single long string that can never > have NUL in it, I'd personally find it more natural to call fputs(), > though. Use of fwrite() makes readers unnecessarily wonder if there > is something unusual (like needing to be able to handle NULs in the > buffer). > >> if (opts->in_place) >> if (rename_tempfile(&trailers_tempfile, file)) >> die_errno(_("could not rename temporary file to %s"), file); >> >> strbuf_release(&sb); >> + strbuf_release(&out); > > OK. We could release out a bit earlier, immediately after fwrite(). > > Looking mostly good. > >> } >> >> int cmd_interpret_trailers(int argc, >