SF.net SVN: matplotlib: [3727] trunk/matplotlib/lib/matplotlib/afm.py

[<jo...@us...>]

Revision: 3727
          http://matplotlib.svn.sourceforge.net/matplotlib/?rev=3727&view=rev
Author:   jouni
Date:     2007-08-21 12:42:28 -0700 (Tue, 21 Aug 2007)

Log Message:
-----------
Run a simple sanity check to avoid attempting to parse non-AFM files as AFM.

Modified Paths:
--------------
    trunk/matplotlib/lib/matplotlib/afm.py

Modified: trunk/matplotlib/lib/matplotlib/afm.py
===================================================================
--- trunk/matplotlib/lib/matplotlib/afm.py	2007-08-21 19:10:02 UTC (rev 3726)
+++ trunk/matplotlib/lib/matplotlib/afm.py	2007-08-21 19:42:28 UTC (rev 3727)
@@ -53,7 +53,27 @@
     else: return True
 
 
+def _sanity_check(fh):
+    """
+    Check if the file at least looks like AFM. 
+    If not, raise RuntimeError.
+    """
 
+    # Remember the file position in case the caller wants to
+    # do something else with the file.
+    pos = fh.tell()
+    try:
+        line = fh.readline()
+    finally:
+        fh.seek(pos, 0)
+
+    # AFM spec, Section 4: The StartFontMetrics keyword [followed by a
+    # version number] must be the first line in the file, and the
+    # EndFontMetrics keyword must be the last non-empty line in the
+    # file. We just check the first line.
+    if not line.startswith('StartFontMetrics'):
+        raise RuntimeError('Not an AFM file')
+
 def _parse_header(fh):
     """
     Reads the font metrics header (up to the char metrics) and returns
@@ -255,6 +275,7 @@
     dkernpairs : a parse_kern_pairs dict, possibly {}
     dcomposite : a parse_composites dict , possibly {}
     """
+    _sanity_check(fh)
     dhead =  _parse_header(fh)
     dcmetrics =  _parse_char_metrics(fh)
     doptional = _parse_optional(fh)


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