Enhancement for mmap_read: Consistency with standard file read

[elwynd]

BPO	16358
Nosy	@jcea
Superseder	bpo-12021: mmap.read requires an argument

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2012-10-29.16:31:15.323>
created_at = <Date 2012-10-29.16:20:11.136>
labels = ['type-feature', 'library']
title = 'Enhancement for mmap_read: Consistency with standard file read'
updated_at = <Date 2012-10-29.23:58:02.285>
user = 'https://bugs.python.org/elwynd'

bugs.python.org fields:

activity = <Date 2012-10-29.23:58:02.285>
actor = 'jcea'
assignee = 'none'
closed = True
closed_date = <Date 2012-10-29.16:31:15.323>
closer = 'r.david.murray'
components = ['Library (Lib)']
creation = <Date 2012-10-29.16:20:11.136>
creator = 'elwynd'
dependencies = []
files = []
hgrepos = []
issue_num = 16358
keywords = []
message_count = 1.0
messages = ['174123']
nosy_count = 2.0
nosy_names = ['jcea', 'elwynd']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '12021'
type = 'enhancement'
url = 'https://bugs.python.org/issue16358'
versions = ['Python 2.6', 'Python 3.1', 'Python 2.7', 'Python 3.2', 'Python 3.3', 'Python 3.4']

[elwynd]

Enhancement requested for module mmap:
Alter the interface of mmap.read from
mmap.read(num)
to
mmap.read([num])
reading the whole file if no argument provided.

The read function in the mmap module (Modules/mmapmodule.c) *requires* an argument whereas for the standard file read function the argument is optional and the function reads the remainder of the file if absent.

The mmap module knows how big the file is, so it should be no problem to internally use the remaining length if no argument is supplied.

This would avoid having to write (for example)
f = mmap.mmap(file_desc, file_size)
b = f.read(file_size)
j = json.loads(b)

instead of
f = mmap.mmap(file_desc, file_size)
j = json.load(f)