comparison mercurial/encoding.py @ 21856:d24969ee272f

encoding: add 'trim' to trim multi-byte characters at most specified columns

Newly added 'trim' is used to trim multi-byte characters at most
specified columns correctly: directly slicing byte sequence should be
replaced with 'encoding.trim', because the former may split at
intermediate multi-byte sequence.

Slicing unicode sequence ('uslice') and concatenation with ellipsis
('concat') are defined as function, to make enhancement in subsequent
patch easier.

21854:ba3bc6474bbf

    for x in xrange(start + c, len(s)):
        t = s[start:x]
        if colwidth(t) == c:
            return t

def lower(s):
    "best-effort encoding-aware case-folding of local string s"
    try:
        s.decode('ascii') # throw exception for non-ASCII character
        return s.lower()

21856:d24969ee272f

    for x in xrange(start + c, len(s)):
        t = s[start:x]
        if colwidth(t) == c:
            return t

def trim(s, width, ellipsis=''):
    """Trim string 's' to at most 'width' columns (including 'ellipsis').

    >>> ellipsis = '+++'
    >>> from mercurial import encoding
    >>> encoding.encoding = 'utf-8'
    >>> t= '1234567890'
    >>> print trim(t, 12, ellipsis=ellipsis)
    1234567890
    >>> print trim(t, 10, ellipsis=ellipsis)
    1234567890
    >>> print trim(t, 8, ellipsis=ellipsis)
    12345+++
    >>> print trim(t, 8)
    12345678
    >>> print trim(t, 3, ellipsis=ellipsis)
    +++
    >>> print trim(t, 1, ellipsis=ellipsis)
    +
    >>> u = u'\u3042\u3044\u3046\u3048\u304a' # 2 x 5 = 10 columns
    >>> t = u.encode(encoding.encoding)
    >>> print trim(t, 12, ellipsis=ellipsis)
    \xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88\xe3\x81\x8a
    >>> print trim(t, 10, ellipsis=ellipsis)
    \xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88\xe3\x81\x8a
    >>> print trim(t, 8, ellipsis=ellipsis)
    \xe3\x81\x82\xe3\x81\x84+++
    >>> print trim(t, 5)
    \xe3\x81\x82\xe3\x81\x84
    >>> print trim(t, 4, ellipsis=ellipsis)
    +++
    >>> t = '\x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa' # invalid byte sequence
    >>> print trim(t, 12, ellipsis=ellipsis)
    \x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa
    >>> print trim(t, 10, ellipsis=ellipsis)
    \x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa
    >>> print trim(t, 8, ellipsis=ellipsis)
    \x11\x22\x33\x44\x55+++
    >>> print trim(t, 8)
    \x11\x22\x33\x44\x55\x66\x77\x88
    >>> print trim(t, 3, ellipsis=ellipsis)
    +++
    >>> print trim(t, 1, ellipsis=ellipsis)
    +
    """
    try:
        u = s.decode(encoding)
    except UnicodeDecodeError:
        if len(s) <= width: # trimming is not needed
            return s
        width -= len(ellipsis)
        if width <= 0: # no enough room even for ellipsis
            return ellipsis[:width + len(ellipsis)]
        return s[:width] + ellipsis

    if ucolwidth(u) <= width: # trimming is not needed
        return s

    width -= len(ellipsis)
    if width <= 0: # no enough room even for ellipsis
        return ellipsis[:width + len(ellipsis)]

    uslice = lambda i: u[:-i]
    concat = lambda s: s + ellipsis
    for i in xrange(1, len(u)):
        usub = uslice(i)
        if ucolwidth(usub) <= width:
            return concat(usub.encode(encoding))
    return ellipsis # no enough room for multi-column characters

def lower(s):
    "best-effort encoding-aware case-folding of local string s"
    try:
        s.decode('ascii') # throw exception for non-ASCII character
        return s.lower()