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|
# _pyquoting.py
"""Various helpers for string quoting/unquoting.
Here is pure Python that should match C code in _cquoting.
"""
import urllib, re
__all__ = [
"quote_literal", "quote_copy", "quote_bytea_raw",
"db_urlencode", "db_urldecode", "unescape",
"unquote_literal",
]
#
# SQL quoting
#
def quote_literal(s):
"""Quote a literal value for SQL.
If string contains '\\', extended E'' quoting is used,
otherwise standard quoting. Input value of None results
in string "null" without quotes.
Python implementation.
"""
if s == None:
return "null"
s = str(s).replace("'", "''")
s2 = s.replace("\\", "\\\\")
if len(s) != len(s2):
return "E'" + s2 + "'"
return "'" + s2 + "'"
def quote_copy(s):
"""Quoting for copy command. None is converted to \\N.
Python implementation.
"""
if s == None:
return "\\N"
s = str(s)
s = s.replace("\\", "\\\\")
s = s.replace("\t", "\\t")
s = s.replace("\n", "\\n")
s = s.replace("\r", "\\r")
return s
_bytea_map = None
def quote_bytea_raw(s):
"""Quoting for bytea parser. Returns None as None.
Python implementation.
"""
global _bytea_map
if s == None:
return None
if 1 and _bytea_map is None:
_bytea_map = {}
for i in xrange(256):
c = chr(i)
if i < 0x20 or i >= 0x7F:
_bytea_map[c] = "\\%03o" % i
elif c == "\\":
_bytea_map[c] = r"\\"
else:
_bytea_map[c] = c
return "".join([_bytea_map[c] for c in s])
#
# Database specific urlencode and urldecode.
#
def db_urlencode(dict):
"""Database specific urlencode.
Encode None as key without '='. That means that in "foo&bar=",
foo is NULL and bar is empty string.
Python implementation.
"""
elem_list = []
for k, v in dict.items():
if v is None:
elem = urllib.quote_plus(str(k))
else:
elem = urllib.quote_plus(str(k)) + '=' + urllib.quote_plus(str(v))
elem_list.append(elem)
return '&'.join(elem_list)
def db_urldecode(qs):
"""Database specific urldecode.
Decode key without '=' as None.
This also does not support one key several times.
Python implementation.
"""
res = {}
for elem in qs.split('&'):
if not elem:
continue
pair = elem.split('=', 1)
name = urllib.unquote_plus(pair[0])
# keep only one instance around
name = intern(str(name))
if len(pair) == 1:
res[name] = None
else:
res[name] = urllib.unquote_plus(pair[1])
return res
#
# Remove C-like backslash escapes
#
_esc_re = r"\\([0-7]{1,3}|.)"
_esc_rc = re.compile(_esc_re)
_esc_map = {
't': '\t',
'n': '\n',
'r': '\r',
'a': '\a',
'b': '\b',
"'": "'",
'"': '"',
'\\': '\\',
}
def _sub_unescape_c(m):
"""unescape single escape seq."""
v = m.group(1)
if (len(v) == 1) and (v < '0' or v > '7'):
try:
return _esc_map[v]
except KeyError:
return v
else:
return chr(int(v, 8))
def unescape(val):
"""Removes C-style escapes from string.
Python implementation.
"""
return _esc_rc.sub(_sub_unescape_c, val)
_esql_re = r"''|\\([0-7]{1,3}|.)"
_esql_rc = re.compile(_esql_re)
def _sub_unescape_sqlext(m):
"""Unescape extended-quoted string."""
if m.group() == "''":
return "'"
v = m.group(1)
if (len(v) == 1) and (v < '0' or v > '7'):
try:
return _esc_map[v]
except KeyError:
return v
return chr(int(v, 8))
def unquote_literal(val, stdstr = False):
"""Unquotes SQL string.
E'..' -> extended quoting.
'..' -> standard or extended quoting
null -> None
other -> returned as-is
"""
if val[0] == "'" and val[-1] == "'":
if stdstr:
return val[1:-1].replace("''", "'")
else:
return _esql_rc.sub(_sub_unescape_sqlext, val[1:-1])
elif len(val) > 2 and val[0] in ('E', 'e') and val[1] == "'" and val[-1] == "'":
return _esql_rc.sub(_sub_unescape_sqlext, val[2:-1])
elif len(val) >= 2 and val[0] == '$' and val[-1] == '$':
p1 = val.find('$', 1)
p2 = val.rfind('$', 1, -1)
if p1 > 0 and p2 > p1:
t1 = val[:p1+1]
t2 = val[p2:]
if t1 == t2:
return val[len(t1):-len(t1)]
raise Exception("Bad dollar-quoted string")
elif val.lower() == "null":
return None
return val
|
