On Tue, Jan 2, 2018 at 4:18 PM, Brandon Williams <bmwill@xxxxxxxxxx> wrote:
> The current pkt-line API encodes the status of a pkt-line read in the
> length of the read content. An error is indicated with '-1', a flush
> with '0' (which can be confusing since a return value of '0' can also
> indicate an empty pkt-line), and a positive integer for the length of
> the read content otherwise. This doesn't leave much room for allowing
> the addition of additional special packets in the future.
>
> To solve this introduce 'packet_read_with_status()' which reads a packet
> and returns the status of the read encoded as an 'enum packet_status'
> type. This allows for easily identifying between special and normal
> packets as well as errors. It also enables easily adding a new special
> packet in the future.
>
> Signed-off-by: Brandon Williams <bmwill@xxxxxxxxxx>
> ---
> pkt-line.c | 55 ++++++++++++++++++++++++++++++++++++++++++-------------
> pkt-line.h | 15 +++++++++++++++
> 2 files changed, 57 insertions(+), 13 deletions(-)
>
> diff --git a/pkt-line.c b/pkt-line.c
> index 2827ca772..8d7cd389f 100644
> --- a/pkt-line.c
> +++ b/pkt-line.c
> @@ -280,28 +280,33 @@ static int packet_length(const char *linelen)
> return (val < 0) ? val : (val << 8) | hex2chr(linelen + 2);
> }
>
> -int packet_read(int fd, char **src_buf, size_t *src_len,
> - char *buffer, unsigned size, int options)
> +enum packet_read_status packet_read_with_status(int fd, char **src_buffer, size_t *src_len,
> + char *buffer, unsigned size, int *pktlen,
> + int options)
> {
> - int len, ret;
> + int len;
> char linelen[4];
>
> - ret = get_packet_data(fd, src_buf, src_len, linelen, 4, options);
> - if (ret < 0)
> - return ret;
> + if (get_packet_data(fd, src_buffer, src_len, linelen, 4, options) < 0)
> + return PACKET_READ_EOF;
> +
> len = packet_length(linelen);
> if (len < 0)
> die("protocol error: bad line length character: %.4s", linelen);
> - if (!len) {
> +
> + if (len == 0) {
> packet_trace("0000", 4, 0);
> - return 0;
> + return PACKET_READ_FLUSH;
> + } else if (len >= 1 && len <= 3) {
> + die("protocol error: bad line length character: %.4s", linelen);
I wonder how much libified code we want here already, maybe we could
have PACKET_READ_ERROR as a return value here instead of die()ing.
There could also be an option that tells this code to die on error, this reminds
me of the repository discovery as well as the refs code, both of which have
this pattern.
Currently this series is only upgrading commands that use the network
anyway, so I guess die()ing in an ls-remote or fetch is no big deal,
but it could
be interesting to keep going once we have more of the partial clone
stuff working
(e.g. remote assisted log/blame would want to gracefully fall back instead of
die()ing without any useful output, I would think.)
> }
> +
> len -= 4;
> - if (len >= size)
> + if ((len < 0) || ((unsigned)len >= size))
> die("protocol error: bad line length %d", len);
> - ret = get_packet_data(fd, src_buf, src_len, buffer, len, options);
> - if (ret < 0)
> - return ret;
> +
> + if (get_packet_data(fd, src_buffer, src_len, buffer, len, options) < 0)
> + return PACKET_READ_EOF;
>
> if ((options & PACKET_READ_CHOMP_NEWLINE) &&
> len && buffer[len-1] == '\n')
> @@ -309,7 +314,31 @@ int packet_read(int fd, char **src_buf, size_t *src_len,
>
> buffer[len] = 0;
> packet_trace(buffer, len, 0);
> - return len;
> + *pktlen = len;
> + return PACKET_READ_NORMAL;
> +}
> +
> +int packet_read(int fd, char **src_buffer, size_t *src_len,
> + char *buffer, unsigned size, int options)
> +{
> + enum packet_read_status status;
> + int pktlen;
> +
> + status = packet_read_with_status(fd, src_buffer, src_len,
> + buffer, size, &pktlen,
> + options);
> + switch (status) {
> + case PACKET_READ_EOF:
> + pktlen = -1;
> + break;
> + case PACKET_READ_NORMAL:
> + break;
> + case PACKET_READ_FLUSH:
> + pktlen = 0;
> + break;
> + }
> +
> + return pktlen;
> }
>
> static char *packet_read_line_generic(int fd,
> diff --git a/pkt-line.h b/pkt-line.h
> index 3dad583e2..06c468927 100644
> --- a/pkt-line.h
> +++ b/pkt-line.h
> @@ -65,6 +65,21 @@ int write_packetized_from_buf(const char *src_in, size_t len, int fd_out);
> int packet_read(int fd, char **src_buffer, size_t *src_len, char
> *buffer, unsigned size, int options);
>
> +/*
> + * Read a packetized line into a buffer like the 'packet_read()' function but
> + * returns an 'enum packet_read_status' which indicates the status of the read.
> + * The number of bytes read will be assigined to *pktlen if the status of the
> + * read was 'PACKET_READ_NORMAL'.
> + */
> +enum packet_read_status {
> + PACKET_READ_EOF = -1,
> + PACKET_READ_NORMAL,
> + PACKET_READ_FLUSH,
> +};
> +enum packet_read_status packet_read_with_status(int fd, char **src_buffer, size_t *src_len,
> + char *buffer, unsigned size, int *pktlen,
> + int options);
> +
> /*
> * Convenience wrapper for packet_read that is not gentle, and sets the
> * CHOMP_NEWLINE option. The return value is NULL for a flush packet,
> --
> 2.15.1.620.gb9897f4670-goog
>
