Added dbgblock.py for quicker hex dumps

This script is basically the same as xxd, but with the other debug
script's block address format:

  $ ./scripts/dbgblock.py disk -B4096 1
  block 0x1, size 20
  off       data
  00000000: 00 00 00 00 00 03 00 08 6c 69 74 74 6c 65 66 73  ........littlefs
  00000010: 40 03 00 0c 80 04 00 02 02 00 d0 03 00 16 c0 04  @...............
  ...

scripts/dbgblock.py

@@ -0,0 +1,125 @@
+#!/usr/bin/env python3
+
+import os
+
+
+# parse some rbyd addr encodings
+# 0xa     -> [0xa]
+# 0xa.b   -> ([0xa], b)
+# 0x{a,b} -> [0xa, 0xb]
+def rbydaddr(s):
+    s = s.strip()
+    b = 10
+    if s.startswith('0x') or s.startswith('0X'):
+        s = s[2:]
+        b = 16
+    elif s.startswith('0o') or s.startswith('0O'):
+        s = s[2:]
+        b = 8
+    elif s.startswith('0b') or s.startswith('0B'):
+        s = s[2:]
+        b = 2
+
+    trunk = None
+    if '.' in s:
+        s, s_ = s.split('.', 1)
+        trunk = int(s_, b)
+
+    if s.startswith('{') and '}' in s:
+        ss = s[1:s.find('}')].split(',')
+    else:
+        ss = [s]
+
+    addr = []
+    for s in ss:
+        if trunk is not None:
+            addr.append((int(s, b), trunk))
+        else:
+            addr.append(int(s, b))
+
+    return addr
+
+def xxd(data, width=16):
+    for i in range(0, len(data), width):
+        yield '%-*s %-*s' % (
+            3*width,
+            ' '.join('%02x' % b for b in data[i:i+width]),
+            width,
+            ''.join(
+                b if b >= ' ' and b <= '~' else '.'
+                for b in map(chr, data[i:i+width])))
+
+def main(disk, block=None, *,
+        block_size=None,
+        seek=None,
+        size=None):
+    # flatten block, default to block 0
+    if not block:
+        block = [0]
+
+    if len(block) > 1:
+        print("error: More than one block address?")
+        sys.exit(-1)
+
+    block = block[0]
+
+    with open(disk, 'rb') as f:
+        # if block_size is omitted, assume the block device is one big block
+        if block_size is None:
+            f.seek(0, os.SEEK_END)
+            block_size = f.tell()
+
+        # block may also encode an offset
+        block, off, size = (
+            block[0] if isinstance(block, tuple) else block,
+            seek if seek is not None
+                else block[1] if isinstance(block, tuple)
+                else None,
+            size if size is not None else block_size)
+
+        print('block %s, size %d' % (
+            '0x%x.%x' % (block, off)
+                if off is not None
+                else '0x%x' % block,
+            size))
+
+        # read the block
+        f.seek((block * block_size) + (off or 0))
+        data = f.read(size)
+
+        # print header
+        print('%-8s  %s' % ('off', 'data'))
+
+        # render the hex view
+        for o, line in enumerate(xxd(data)):
+            print('%08x: %s' % ((off or 0) + 16*o, line))
+
+if __name__ == "__main__":
+    import argparse
+    import sys
+    parser = argparse.ArgumentParser(
+        description="Debug block devices.",
+        allow_abbrev=False)
+    parser.add_argument(
+        'disk',
+        help="File containing the block device.")
+    parser.add_argument(
+        'block',
+        nargs='?',
+        type=rbydaddr,
+        help="Block address.")
+    parser.add_argument(
+        '-B', '--block-size',
+        type=lambda x: int(x, 0),
+        help="Block size in bytes.")
+    parser.add_argument(
+        '-s', '--seek',
+        type=lambda x: int(x, 0),
+        help="Start at this offset.")
+    parser.add_argument(
+        '-n', '--size',
+        type=lambda x: int(x, 0),
+        help="Show this many bytes.")
+    sys.exit(main(**{k: v
+        for k, v in vars(parser.parse_intermixed_args()).items()
+        if v is not None}))