Jeremiah Mahler <jmmahler@xxxxxxxxx> writes:
> A common use case with strubfs is to set the buffer to a new value.
> This must be done in two steps: a reset followed by an add.
>
> strbuf_reset(buf);
> strbuf_add(buf, new_buf, len);
>
> In cases where the buffer is being built up in steps, these operations
> make sense and correctly convey what is being performed.
>
> strbuf_reset(buf);
> strbuf_add(buf, data1, len1);
> strbuf_add(buf, data2, len2);
> strbuf_add(buf, data3, len3);
>
> However, in other cases, it can be confusing and is not very concise.
>
> strbuf_reset(buf);
> strbuf_add(buf, default, len1);
>
> if (cond1) {
> strbuf_reset(buf);
> strbuf_add(buf, data2, len2);
> }
>
> if (cond2) {
> strbuf_reset(buf);
> strbuf_add(buf, data3, len3);
> }
>
> Add strbuf_set operations so that it can be re-written in a clear and
> concise way.
>
> strbuf_set(buf, default len1);
>
> if (cond1) {
> strbuf_set(buf, data2, len2);
> }
>
> if (cond2) {
> strbuf_set(buf, data3, len3);
> }
Or even more concisely without making unnecessary internal calls to
strbuf_reset():
strbuf_reset(buf);
if (cond2)
strbuf_add(buf, data3, len3);
else if (cond1)
strbuf_add(buf, data2, len2);
else
strbuf_add(buf, default, len2);
;-)
I am on the fence.
I have this suspicion that the addition of strbuf_set() would *only*
help when the original written with reset-and-then-add sequence was
suboptimal to begin with, and it helps *only* how the code reads,
without correcting the fact that it is still doing unnecessary
"first set to a value to be discarded and then reset to set the
right value", sweeping the issue under the rug.
Repeated reset-and-then-add on the same strbuf used to be something
that may indicate that the code is doing unnecessary work. Now,
repeated uses of strbuf_set on the same strbuf replaced that pattern
to be watched for to spot wasteful code paths.
I dunno...
> Signed-off-by: Jeremiah Mahler <jmmahler@xxxxxxxxx>
> ---
> Documentation/technical/api-strbuf.txt | 18 ++++++++++++++++++
> strbuf.c | 21 +++++++++++++++++++++
> strbuf.h | 13 +++++++++++++
> 3 files changed, 52 insertions(+)
>
> diff --git a/Documentation/technical/api-strbuf.txt b/Documentation/technical/api-strbuf.txt
> index f9c06a7..ae9c9cc 100644
> --- a/Documentation/technical/api-strbuf.txt
> +++ b/Documentation/technical/api-strbuf.txt
> @@ -149,6 +149,24 @@ Functions
> than zero if the first buffer is found, respectively, to be less than,
> to match, or be greater than the second buffer.
>
> +* Setting the buffer
> +
> +`strbuf_set`::
> +
> + Replace content with data of a given length.
> +
> +`strbuf_setstr`::
> +
> + Replace content with data from a NUL-terminated string.
> +
> +`strbuf_setf`::
> +
> + Replace content with a formatted string.
> +
> +`strbuf_setbuf`::
> +
> + Replace content with data from another buffer.
> +
> * Adding data to the buffer
>
> NOTE: All of the functions in this section will grow the buffer as necessary.
> diff --git a/strbuf.c b/strbuf.c
> index ac62982..9d64b00 100644
> --- a/strbuf.c
> +++ b/strbuf.c
> @@ -189,6 +189,27 @@ void strbuf_splice(struct strbuf *sb, size_t pos, size_t len,
> strbuf_setlen(sb, sb->len + dlen - len);
> }
>
> +void strbuf_set(struct strbuf *sb, const void *data, size_t len)
> +{
> + strbuf_reset(sb);
> + strbuf_add(sb, data, len);
> +}
> +
> +void strbuf_setf(struct strbuf *sb, const char *fmt, ...)
> +{
> + va_list ap;
> + strbuf_reset(sb);
> + va_start(ap, fmt);
> + strbuf_vaddf(sb, fmt, ap);
> + va_end(ap);
> +}
> +
> +void strbuf_setbuf(struct strbuf *sb, const struct strbuf *sb2)
> +{
> + strbuf_reset(sb);
> + strbuf_add(sb, sb2->buf, sb2->len);
> +}
> +
> void strbuf_insert(struct strbuf *sb, size_t pos, const void *data, size_t len)
> {
> strbuf_splice(sb, pos, 0, data, len);
> diff --git a/strbuf.h b/strbuf.h
> index e9ad03e..5041c35 100644
> --- a/strbuf.h
> +++ b/strbuf.h
> @@ -101,6 +101,19 @@ static inline struct strbuf **strbuf_split(const struct strbuf *sb,
> */
> extern void strbuf_list_free(struct strbuf **);
>
> +/*----- set buffer to data -----*/
> +extern void strbuf_set(struct strbuf *sb, const void *data, size_t len);
> +
> +static inline void strbuf_setstr(struct strbuf *sb, const char *s)
> +{
> + strbuf_set(sb, s, strlen(s));
> +}
> +
> +__attribute__((format (printf,2,3)))
> +extern void strbuf_setf(struct strbuf *sb, const char *fmt, ...);
> +
> +extern void strbuf_setbuf(struct strbuf *sb, const struct strbuf *sb2);
> +
> /*----- add data in your buffer -----*/
> static inline void strbuf_addch(struct strbuf *sb, int c)
> {
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