view contrib/debugcmdserver.py @ 39814:d059cb669632

wireprotov2: allow multiple fields to follow revision maps

The *data wire protocol commands emit a series of CBOR values.
Because revision/delta data may be large, their data is emitted
outside the map as a top-level bytestring value.

Before this commit, we'd emit a single optional bytestring
value after the revision descriptor map. This got the job done.
But it was limiting in that we could only send a single field.
And, it required the consumer to know that the presence of a
key in the map implied the existence of a following bytestring
value.

This commit changes the encoding strategy so top-level bytestring
values in the stream are explicitly denoted in a "fieldsfollowing"
key. This key contains an array defining what fields that follow
and the expected size of each field.

By defining things this way, we can easily send N bytestring
values without any ambiguity about their order. In addition,
clients only need to know how to parse ``fieldsfollowing`` to
know if extra values are present.

Because this breaks backwards compatibility, we've bumped the version
number of the wire protocol version 2 API endpoint.

Differential Revision: https://phab.mercurial-scm.org/D4620

#!/usr/bin/env python
#
# Dumps output generated by Mercurial's command server in a formatted style to a
# given file or stderr if '-' is specified. Output is also written in its raw
# format to stdout.
#
# $ ./hg serve --cmds pipe | ./contrib/debugcmdserver.py -
# o, 52   -> 'capabilities: getencoding runcommand\nencoding: UTF-8'

from __future__ import absolute_import, print_function
import struct
import sys

if len(sys.argv) != 2:
    print('usage: debugcmdserver.py FILE')
    sys.exit(1)

outputfmt = '>cI'
outputfmtsize = struct.calcsize(outputfmt)

if sys.argv[1] == '-':
    log = sys.stderr
else:
    log = open(sys.argv[1], 'a')

def read(size):
    data = sys.stdin.read(size)
    if not data:
        raise EOFError
    sys.stdout.write(data)
    sys.stdout.flush()
    return data

try:
    while True:
        header = read(outputfmtsize)
        channel, length = struct.unpack(outputfmt, header)
        log.write('%s, %-4d' % (channel, length))
        if channel in 'IL':
            log.write(' -> waiting for input\n')
        else:
            data = read(length)
            log.write(' -> %r\n' % data)
        log.flush()
except EOFError:
    pass
finally:
    if log != sys.stderr:
        log.close()