More efficient search in sparse fonts.

FONT_TO_PY.md

@@ -9,9 +9,9 @@ targets: the font file may be incorporated into a firmware build such that it
 occupies flash memory rather than scarce RAM. Python code built into firmware
 is known as frozen bytecode.
 
-## V0.3 notes
+## V0.31 notes
 
-8 Sept 2019
+10 Sept 2019
 
  1. Reduced output file size for sparse fonts. These result from large gaps
  between ordinal values of Unicode characters not in the standard ASCII set.

font_to_py.py

@@ -393,50 +393,56 @@ class Font(dict):
 STR01 = """# Code generated by font_to_py.py.
 # Font: {}{}
 # Cmd: {}
-version = '0.3'
+version = '0.31'
 
 """
 
 # Code emitted for charsets spanning a small range of ordinal values
 STR02 = """_mvfont = memoryview(_font)
+_mvi = memoryview(_index)
+ifb = lambda l : l[0] | (l[1] << 8)
 
 def get_ch(ch):
     oc = ord(ch)
-    idx_offs = 2 * (oc - {0} + 1) if oc >= {0} and oc <= {1} else 0
-    offset = int.from_bytes(_index[idx_offs : idx_offs + 2], 'little')
-    width = int.from_bytes(_font[offset:offset + 2], 'little')
+    ioff = 2 * (oc - {0} + 1) if oc >= {0} and oc <= {1} else 0
+    doff = ifb(_mvi[ioff : ])
+    width = ifb(_mvfont[doff : ])
 """
 
 # Code emiited for large charsets, assumed by build_arrays() to be sparse
 # Binary sort of sparse index.
 STRSP = """_mvfont = memoryview(_font)
 _mvsp = memoryview(_sparse)
+ifb = lambda l : l[0] | (l[1] << 8)
 
 def bs(lst, val):
     n = len(lst) // 4
     if n == 1:
-        v = int.from_bytes(lst[: 2], 'little')
-        return int.from_bytes(lst[2 : 4], 'little') if v == val else 0
+        return ifb(lst[2 : ]) if ifb(lst) == val else 0
     sp = (n // 2) * 4
-    res = bs(lst[: sp], val)
-    return res if res else bs(lst[sp :], val)
+    v = ifb(lst[sp - 4 : ])
+    if v == val:
+        return ifb(lst[sp - 2 : ])
+    if v > val:
+        return 0 if sp <= 4 else bs(lst[ : sp - 4], val)
+    return bs(lst[sp :], val)
 
 def get_ch(ch):
-    offset = bs(_mvsp, ord(ch))
-    width = int.from_bytes(_font[offset : offset + 2], 'little')
+    doff = bs(_mvsp, ord(ch))
+    width = ifb(_mvfont[doff : ])
 """
 
 # Code emitted for horizontally mapped fonts.
 STR02H ="""
-    next_offs = offset + 2 + ((width - 1)//8 + 1) * {0}
-    return _mvfont[offset + 2:next_offs], {0}, width
+    next_offs = doff + 2 + ((width - 1)//8 + 1) * {0}
+    return _mvfont[doff + 2:next_offs], {0}, width
  
 """
 
 # Code emitted for vertically mapped fonts.
 STR02V ="""
-    next_offs = offset + 2 + (({0} - 1)//8 + 1) * width
-    return _mvfont[offset + 2:next_offs], {0}, width
+    next_offs = doff + 2 + (({0} - 1)//8 + 1) * width
+    return _mvfont[doff + 2:next_offs], {0}, width
  
 """