Patrick Steinhardt <ps@xxxxxx> writes:
> While the strbuf interface already provides functions to read a line
> into it that completely replaces its current contents, we do not have an
> interface that allows for appending lines without discarding current
> contents.
>
> Add a new function `strbuf_appendwholeline` that reads a line including
> its terminating character into a strbuf non-destructively. This is a
> preparatory step for git-update-ref(1) reading standard input line-wise
> instead of as a block.
Hmph. If we were to gain more uses of this function over time, the
necessity for an extra strbuf_addbuf() becomes annoying. I wonder
if we should be doing this patch the other way around, i.e. move the
whole implementation, except for the early
if (feof(fp))
return EOF;
strbuf_reset(sb);
part, and call it strbuf_addwholeline(), and strbuf_getwholeline()
becomes a thin wrapper around it that resets the incoming buffer
before calling strbuf_addwholeline(). The logic to determine EOF
would need to be updated if we go that route (i.e. instead of
checking sb->len is zero in the !HAVE_GETDELIM side of the
implementation, we need to see if the number is the same as before)
but it should be minor.
There is a stale comment in the HAVE_GETDELIM side of the curent
implementation, by the way. I think our xrealloc no longer tries
to "recover" from ENOMEM.
Having said all that, I am fine with this version, at least for now.
> +int strbuf_appendwholeline(struct strbuf *sb, FILE *fp, int term)
> +{
> + struct strbuf line = STRBUF_INIT;
> + if (strbuf_getwholeline(&line, fp, term))
> + return EOF;
So, if caller wants to read the stream until it runs out, it can do
strbuf_init(&sb);
while (strbuf_appendwholeline(&sb, fp, '\n') != EOF)
; /* keep going */
If the caller knows how many lines to read, EOF-return can be used
only for error checking, e.g.
strbuf_init(&sb);
for (count = 0; count < 5; count++)
if (strbuf_appendwholeline(&sb, fp, '\n') == EOF)
die("cannot grab 5 lines");
It becomes cumbersome if the input lines are terminated, though.
The caller wouldn't be using strbuf_appendwholeline() interface,
e.g.
strbuf_init(&accum);
while ((strbuf_getwholeline(&sb, fp, '\n') != EOF) &&
strcmp(sb.buf, "done\n"))
strbuf_addbuf(&accum, &sb);
Anyway, I was primarily wondering if returning EOF, which perfectly
makes sense for getwholeline(), still makes sense for addwholeline(),
and it seems that it is still useful.
> + strbuf_addbuf(sb, &line);
> + strbuf_release(&line);
> + return 0;
> +}
> +
> static int strbuf_getdelim(struct strbuf *sb, FILE *fp, int term)
> {
> if (strbuf_getwholeline(sb, fp, term))
> diff --git a/strbuf.h b/strbuf.h
> index ce8e49c0b2..411063ca76 100644
> --- a/strbuf.h
> +++ b/strbuf.h
> @@ -502,6 +502,12 @@ int strbuf_getline(struct strbuf *sb, FILE *file);
> */
> int strbuf_getwholeline(struct strbuf *sb, FILE *file, int term);
>
> +/**
> + * Like `strbuf_getwholeline`, but appends the line instead of
> + * resetting the buffer first.
> + */
> +int strbuf_appendwholeline(struct strbuf *sb, FILE *file, int term);
> +
> /**
> * Like `strbuf_getwholeline`, but operates on a file descriptor.
> * It reads one character at a time, so it is very slow. Do not
