misc: Add scripts to report VMS tile offsets

misc/vms-dump-opt.py

@@ -0,0 +1,19 @@
+import struct
+import sys
+
+jpeg = 0
+last = float('inf')
+
+with open(sys.argv[1]) as fh:
+    while True:
+        buf = fh.read(40)
+        if not buf:
+            break
+        val = struct.unpack('<q32x', buf)[0]
+
+        if val < last:
+            print '=====', jpeg
+            jpeg += 1
+        last = val
+
+        print val

misc/vms-jpeg-find-tiles.py

@@ -0,0 +1,58 @@
+import struct
+import sys
+
+class EOFError(Exception):
+    pass
+
+
+def decode(fh, fmt):
+    count = struct.calcsize(fmt)
+    buf = fh.read(count)
+    if not buf:
+        raise EOFError
+    elif len(buf) < count:
+        raise IOError('Short read')
+    return struct.unpack(fmt, buf)
+
+
+with open(sys.argv[1]) as fh:
+    try:
+        # Walk header
+        marker_byte = 0
+        while marker_byte != 0xda:  # SOS
+            flag, marker_byte = decode(fh, '2B')
+            if flag != 0xff:
+                raise ValueError('Expected marker, found something else')
+            if marker_byte == 0xd8:
+                # SOI; no marker segment
+                continue
+            count = decode(fh, '>H')[0]
+            fh.seek(count - 2, 1)
+
+        # Walk entropy-coded data
+        base = fh.tell()
+        print base
+        while True:
+            buf = fh.read(4 << 10)
+            if not buf:
+                break
+            off = 0
+            while True:
+                off = buf.find('\xff', off)
+                if off == -1:
+                    break
+                elif off == len(buf) - 1:
+                    ch = fh.read(1)
+                    if len(ch) != 1:
+                        raise IOError('Short read')
+                    buf += ch
+                marker_byte = struct.unpack('B', buf[off + 1])[0]
+                if marker_byte >= 0xd0 and marker_byte <= 0xd7:
+                    print base + off + 2
+                off += 2
+            base += len(buf)
+    except EOFError:
+        pass
+    except Exception:
+        print 'At {}:'.format(fh.tell())
+        raise