From: Jeff Hostetler Date: Fri, 09 Aug 2019 17:13:25 GMT Subject: Re: [PATCH v2 5/7] quote: add sq_quote_argv_pretty_ltrim Message-ID: <5651286b-cd28-68ba-4743-98d546dfa3b0@jeffhostetler.com> In-Reply-To: <60c7b26c-e598-182b-421e-bdf5c0a8ac9f@web.de> On 8/8/2019 6:49 PM, René Scharfe wrote: > Am 08.08.19 um 21:04 schrieb Jeff Hostetler: >> On 8/8/2019 2:05 PM, Junio C Hamano wrote: >>> Having made the primary purpose of the helper clearer leads me to >>> wonder if "do not add SP before the first element, i.e. argv[0]", is >>> really what we want.  If we always clear the *dst strbuf before >>> starting to serialize argv[] into it, then the behaviour would make >>> sense, but we do not---we are "appending". >>> >>> As long as we are appending, would we be better off doing something >>> sillily magical like this instead, I have to wonder? >>> >>>     void sq_append_strings_quoted(struct strbuf *buf, const char **av) >>>     { >>>         int i; >>> >>>         for (i = 0; av[i]; i++) { >>>             if (buf->len) >>>                 strbuf_addch(buf, ' '); >>>             sq_quote_buf_pretty(buf, argv[0]); >>>         } >>>     } >>> >>> That is, "if we are appending to an existing string, have SP to >>> separate the first element from that existing string; treat the >>> remaining elements the same way (if the buffer is empty, there is no >>> point adding SP at the beginning)". >> >> I don't think that would do what we want.  We don't know what the >> caller's expectations are.  In my uses in commits 6/7 and 7/7 I >> already added the leading chars I wanted in the strbuf before calling >> sq_quote_argv_pretty_ltrim() and assumed the output would be a true >> append.  For example: >> >> +    strbuf_addf(&buf_payload, "alias:%s argv:[", alias); >> +    sq_quote_argv_pretty_ltrim(&buf_payload, argv); >> +    strbuf_addch(&buf_payload, ']'); >> >> I like your suggestion of putting my new function in the _append_ >> category.  I think I'll add the 3rd arg to this and then it will >> be completely specified and I can get rid of the _ltrim suffix. > > Two observations: > > If callers want to add something before a joined delimited list, they > already can with a strbuf_add* call. No need to add that feature to > a function that joins lists. > > And repetitions of repetitions (loops) are boring. > > Apologies in advance for any coffee stains on your monitor, but > here's how I would start, probably followed by attempts to inline the > functions that become trivial wrappers: Um, yeah, I must say that I didn't expect the conversation to turn to map-style functions and a change in design styles. I think it would be better to have that conversation in a different patch series and not mix it with my trace2 janitoring. I'm going to push a V3 that does just the minimum to have a sq_ function that joins the args with a space delimiter (and without the leading space) and re-write the existing function to call it after adding the legacy leading space. This will let existing callers continue to work as is. And they can be converted if/when anyone wants to dig into them. > > --- > quote.c | 18 ++++-------------- > strbuf.c | 20 +++++++++++++------- > strbuf.h | 8 ++++++++ > 3 files changed, 25 insertions(+), 21 deletions(-) > > diff --git a/quote.c b/quote.c > index 7f2aa6faa4..f422188852 100644 > --- a/quote.c > +++ b/quote.c > @@ -74,24 +74,14 @@ void sq_quotef(struct strbuf *dst, const char *fmt, ...) > > void sq_quote_argv(struct strbuf *dst, const char **argv) > { > - int i; > - > - /* Copy into destination buffer. */ > - strbuf_grow(dst, 255); > - for (i = 0; argv[i]; ++i) { > - strbuf_addch(dst, ' '); > - sq_quote_buf(dst, argv[i]); > - } > + strbuf_addch(dst, ' '); > + strbuf_map_join_argv(dst, argv, sq_quote_buf, " "); > } > > void sq_quote_argv_pretty(struct strbuf *dst, const char **argv) > { > - int i; > - > - for (i = 0; argv[i]; i++) { > - strbuf_addch(dst, ' '); > - sq_quote_buf_pretty(dst, argv[i]); > - } > + strbuf_addch(dst, ' '); If I'm reading this correctly, this has slightly different behavior than the original version. Perhaps: if (argv[0]) strbuf_addch(dst, ' '); > + strbuf_map_join_argv(dst, argv, sq_quote_buf_pretty, " "); > } > > static char *sq_dequote_step(char *arg, char **next) > diff --git a/strbuf.c b/strbuf.c > index d30f916858..d337853b53 100644 > --- a/strbuf.c > +++ b/strbuf.c > @@ -304,17 +304,23 @@ void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2) > strbuf_setlen(sb, sb->len + sb2->len); > } > > +void strbuf_map_join_argv(struct strbuf *sb, const char **argv, > + void (*fn)(struct strbuf *, const char *), > + const char *separator) > +{ > + while (*argv) { > + fn(sb, *argv++); > + if (*argv) > + strbuf_addstr(sb, separator); > + } > +} > + > const char *strbuf_join_argv(struct strbuf *buf, > int argc, const char **argv, char delim) > { > - if (!argc) > - return buf->buf; > + char separator[] = { delim, '\0' }; > > - strbuf_addstr(buf, *argv); > - while (--argc) { > - strbuf_addch(buf, delim); > - strbuf_addstr(buf, *(++argv)); > - } > + strbuf_map_join_argv(buf, argv, strbuf_addstr, separator); > > return buf->buf; > } > diff --git a/strbuf.h b/strbuf.h > index f62278a0be..7adeff94a7 100644 > --- a/strbuf.h > +++ b/strbuf.h > @@ -297,6 +297,14 @@ static inline void strbuf_addstr(struct strbuf *sb, const char *s) > */ > void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2); > > +/** > + * Apply `fn` to `sb` and each element of the NULL-terminated array > + * `argv`. Add `separator` between these invocations. > + */ > +void strbuf_map_join_argv(struct strbuf *sb, const char **argv, > + void (*fn)(struct strbuf *, const char *), > + const char *separator); > + > /** > * Join the arguments into a buffer. `delim` is put between every > * two arguments. > -- > 2.22.0 >