#!/usr/bin/env python
from struct import unpack


##  Matrix operations
##
MATRIX_IDENTITY = (1, 0, 0, 1, 0, 0)

def mult_matrix((a1,b1,c1,d1,e1,f1), (a0,b0,c0,d0,e0,f0)):
  '''Multiplies two matrices.'''
  return (a0*a1+c0*b1,    b0*a1+d0*b1,
          a0*c1+c0*d1,    b0*c1+d0*d1,
          a0*e1+c0*f1+e0, b0*e1+d0*f1+f0)

def translate_matrix((a,b,c,d,e,f), (x,y)):
  return (a,b,c,d,e+x,f+y)
  
def apply_matrix((a,b,c,d,e,f), (x,y)):
  '''Applies a matrix to coordinates.'''
  return (a*x+c*y+e, b*x+d*y+f)

def apply_matrix_norm((a,b,c,d,e,f), (p,q)):
  '''equiv to apply_matrix(M, (p,q)) - apply_matrix(M, (0,0))'''
  return (a*p+c*q, b*p+d*q)


##  Utilities
##
def choplist(n, seq):
  '''Groups every n elements of the list.'''
  r = []
  for x in seq:
    r.append(x)
    if len(r) == n:
      yield tuple(r)
      r = []
  return

def nunpack(s, default=0):
  '''Unpacks up to 4 bytes big endian.'''
  l = len(s)
  if not l:
    return default
  elif l == 1:
    return ord(s)
  elif l == 2:
    return unpack('>H', s)[0]
  elif l == 3:
    return unpack('>L', '\x00'+s)[0]
  elif l == 4:
    return unpack('>L', s)[0]
  else:
    return TypeError('invalid length: %d' % l)

PDFDocEncoding = ''.join( unichr(x) for x in (
  0x0000, 0x0001, 0x0002, 0x0003, 0x0004, 0x0005, 0x0006, 0x0007,
  0x0008, 0x0009, 0x000a, 0x000b, 0x000c, 0x000d, 0x000e, 0x000f,
  0x0010, 0x0011, 0x0012, 0x0013, 0x0014, 0x0015, 0x0017, 0x0017,
  0x02d8, 0x02c7, 0x02c6, 0x02d9, 0x02dd, 0x02db, 0x02da, 0x02dc,
  0x0020, 0x0021, 0x0022, 0x0023, 0x0024, 0x0025, 0x0026, 0x0027,
  0x0028, 0x0029, 0x002a, 0x002b, 0x002c, 0x002d, 0x002e, 0x002f,
  0x0030, 0x0031, 0x0032, 0x0033, 0x0034, 0x0035, 0x0036, 0x0037,
  0x0038, 0x0039, 0x003a, 0x003b, 0x003c, 0x003d, 0x003e, 0x003f,
  0x0040, 0x0041, 0x0042, 0x0043, 0x0044, 0x0045, 0x0046, 0x0047,
  0x0048, 0x0049, 0x004a, 0x004b, 0x004c, 0x004d, 0x004e, 0x004f,
  0x0050, 0x0051, 0x0052, 0x0053, 0x0054, 0x0055, 0x0056, 0x0057,
  0x0058, 0x0059, 0x005a, 0x005b, 0x005c, 0x005d, 0x005e, 0x005f,
  0x0060, 0x0061, 0x0062, 0x0063, 0x0064, 0x0065, 0x0066, 0x0067,
  0x0068, 0x0069, 0x006a, 0x006b, 0x006c, 0x006d, 0x006e, 0x006f,
  0x0070, 0x0071, 0x0072, 0x0073, 0x0074, 0x0075, 0x0076, 0x0077,
  0x0078, 0x0079, 0x007a, 0x007b, 0x007c, 0x007d, 0x007e, 0x0000,
  0x2022, 0x2020, 0x2021, 0x2026, 0x2014, 0x2013, 0x0192, 0x2044,
  0x2039, 0x203a, 0x2212, 0x2030, 0x201e, 0x201c, 0x201d, 0x2018,
  0x2019, 0x201a, 0x2122, 0xfb01, 0xfb02, 0x0141, 0x0152, 0x0160,
  0x0178, 0x017d, 0x0131, 0x0142, 0x0153, 0x0161, 0x017e, 0x0000,
  0x20ac, 0x00a1, 0x00a2, 0x00a3, 0x00a4, 0x00a5, 0x00a6, 0x00a7,
  0x00a8, 0x00a9, 0x00aa, 0x00ab, 0x00ac, 0x0000, 0x00ae, 0x00af,
  0x00b0, 0x00b1, 0x00b2, 0x00b3, 0x00b4, 0x00b5, 0x00b6, 0x00b7,
  0x00b8, 0x00b9, 0x00ba, 0x00bb, 0x00bc, 0x00bd, 0x00be, 0x00bf,
  0x00c0, 0x00c1, 0x00c2, 0x00c3, 0x00c4, 0x00c5, 0x00c6, 0x00c7,
  0x00c8, 0x00c9, 0x00ca, 0x00cb, 0x00cc, 0x00cd, 0x00ce, 0x00cf,
  0x00d0, 0x00d1, 0x00d2, 0x00d3, 0x00d4, 0x00d5, 0x00d6, 0x00d7,
  0x00d8, 0x00d9, 0x00da, 0x00db, 0x00dc, 0x00dd, 0x00de, 0x00df,
  0x00e0, 0x00e1, 0x00e2, 0x00e3, 0x00e4, 0x00e5, 0x00e6, 0x00e7,
  0x00e8, 0x00e9, 0x00ea, 0x00eb, 0x00ec, 0x00ed, 0x00ee, 0x00ef,
  0x00f0, 0x00f1, 0x00f2, 0x00f3, 0x00f4, 0x00f5, 0x00f6, 0x00f7,
  0x00f8, 0x00f9, 0x00fa, 0x00fb, 0x00fc, 0x00fd, 0x00fe, 0x00ff,
))
def decode_text(s):
  if s.startswith('\xfe\xff'):
    return unicode(s[2:], 'utf-16be', 'ignore')
  else:
    return ''.join( PDFDocEncoding[ord(c)] for c in s )

# enc(x): encode string in SGML/XML/HTML
def enc(x, codec='ascii'):
  x = x.replace('&','&amp;').replace('>','&gt;').replace('<','&lt;').replace('"','&quot;')
  return x.encode(codec, 'xmlcharrefreplace')