74543a0423
Most of the callers of packet_read_line just read into a
static 1000-byte buffer (callers which handle arbitrary
binary data already use LARGE_PACKET_MAX). This works fine
in practice, because:
1. The only variable-sized data in these lines is a ref
name, and refs tend to be a lot shorter than 1000
characters.
2. When sending ref lines, git-core always limits itself
to 1000 byte packets.
However, the only limit given in the protocol specification
in Documentation/technical/protocol-common.txt is
LARGE_PACKET_MAX; the 1000 byte limit is mentioned only in
pack-protocol.txt, and then only describing what we write,
not as a specific limit for readers.
This patch lets us bump the 1000-byte limit to
LARGE_PACKET_MAX. Even though git-core will never write a
packet where this makes a difference, there are two good
reasons to do this:
1. Other git implementations may have followed
protocol-common.txt and used a larger maximum size. We
don't bump into it in practice because it would involve
very long ref names.
2. We may want to increase the 1000-byte limit one day.
Since packets are transferred before any capabilities,
it's difficult to do this in a backwards-compatible
way. But if we bump the size of buffer the readers can
handle, eventually older versions of git will be
obsolete enough that we can justify bumping the
writers, as well. We don't have plans to do this
anytime soon, but there is no reason not to start the
clock ticking now.
Just bumping all of the reading bufs to LARGE_PACKET_MAX
would waste memory. Instead, since most readers just read
into a temporary buffer anyway, let's provide a single
static buffer that all callers can use. We can further wrap
this detail away by having the packet_read_line wrapper just
use the buffer transparently and return a pointer to the
static storage. That covers most of the cases, and the
remaining ones already read into their own LARGE_PACKET_MAX
buffers.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
72 lines
2.5 KiB
C
72 lines
2.5 KiB
C
#ifndef PKTLINE_H
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#define PKTLINE_H
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#include "git-compat-util.h"
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#include "strbuf.h"
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/*
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* Write a packetized stream, where each line is preceded by
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* its length (including the header) as a 4-byte hex number.
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* A length of 'zero' means end of stream (and a length of 1-3
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* would be an error).
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*
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* This is all pretty stupid, but we use this packetized line
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* format to make a streaming format possible without ever
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* over-running the read buffers. That way we'll never read
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* into what might be the pack data (which should go to another
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* process entirely).
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*
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* The writing side could use stdio, but since the reading
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* side can't, we stay with pure read/write interfaces.
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*/
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void packet_flush(int fd);
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void packet_write(int fd, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
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void packet_buf_flush(struct strbuf *buf);
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void packet_buf_write(struct strbuf *buf, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
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/*
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* Read a packetized line from the descriptor into the buffer, which must be at
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* least size bytes long. The return value specifies the number of bytes read
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* into the buffer.
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*
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* If options does not contain PACKET_READ_GENTLE_ON_EOF, we will die under any
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* of the following conditions:
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*
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* 1. Read error from descriptor.
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*
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* 2. Protocol error from the remote (e.g., bogus length characters).
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*
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* 3. Receiving a packet larger than "size" bytes.
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*
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* 4. Truncated output from the remote (e.g., we expected a packet but got
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* EOF, or we got a partial packet followed by EOF).
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*
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* If options does contain PACKET_READ_GENTLE_ON_EOF, we will not die on
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* condition 4 (truncated input), but instead return -1. However, we will still
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* die for the other 3 conditions.
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*
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* If options contains PACKET_READ_CHOMP_NEWLINE, a trailing newline (if
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* present) is removed from the buffer before returning.
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*/
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#define PACKET_READ_GENTLE_ON_EOF (1u<<0)
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#define PACKET_READ_CHOMP_NEWLINE (1u<<1)
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int packet_read(int fd, char *buffer, unsigned size, int options);
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/*
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* Convenience wrapper for packet_read that is not gentle, and sets the
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* CHOMP_NEWLINE option. The return value is NULL for a flush packet,
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* and otherwise points to a static buffer (that may be overwritten by
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* subsequent calls). If the size parameter is not NULL, the length of the
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* packet is written to it.
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*/
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char *packet_read_line(int fd, int *size);
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#define DEFAULT_PACKET_MAX 1000
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#define LARGE_PACKET_MAX 65520
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extern char packet_buffer[LARGE_PACKET_MAX];
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int packet_get_line(struct strbuf *out, char **src_buf, size_t *src_len);
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#endif
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