Added dbgcat.py for extracted raw data from block devices

dbgcat.py is basically the same as dbgblock.py except:

- dbgcat.py pipes the block's contents directly to stdout.

  The intention is to enable external tools with Unix pipes while
  letting dbgcat.py take care of block address decoding:

    $ ./scripts/dbgcat.py disk -b4096 0x1.8 -n8 | grep littlefs
    littlefs

- Unlike dbgblock.py, dbgcat.py accepts multiple block addresses,
  concatenating the data that resides at those blocks.

  This is dbgCAT.py after all.

scripts/dbgcat.py

@@ -0,0 +1,165 @@
+#!/usr/bin/env python3
+
+import os
+
+
+# some ways of block geometry representations
+# 512      -> 512
+# 512x16   -> (512, 16)
+# 0x200x10 -> (512, 16)
+def bdgeom(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
+
+    if 'x' in s:
+        s, s_ = s.split('x', 1)
+        return (int(s, b), int(s_, b))
+    else:
+        return int(s, b)
+
+# parse some rbyd addr encodings
+# 0xa       -> [0xa]
+# 0xa.c     -> [(0xa, 0xc)]
+# 0x{a,b}   -> [0xa, 0xb]
+# 0x{a,b}.c -> [(0xa, 0xc), (0xb, 0xc)]
+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 crc32c(data, crc=0):
+    crc ^= 0xffffffff
+    for b in data:
+        crc ^= b
+        for j in range(8):
+            crc = (crc >> 1) ^ ((crc & 1) * 0x82f63b78)
+    return 0xffffffff ^ crc
+
+def main(disk, blocks=None, *,
+        block_size=None,
+        block_count=None,
+        off=None,
+        size=None):
+    # is bd geometry specified?
+    if isinstance(block_size, tuple):
+        block_size, block_count_ = block_size
+        if block_count is None:
+            block_count = block_count_
+
+    # flatten block, default to block 0
+    if not blocks:
+        blocks = [[0]]
+    blocks = [block for blocks_ in blocks for block in blocks_]
+
+    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()
+
+        # blocks may also encode offsets
+        blocks, offs, size = (
+            [block[0] if isinstance(block, tuple) else block
+                for block in blocks],
+            [off[0] if isinstance(off, tuple)
+                    else off if off is not None
+                    else size[0] if isinstance(size, tuple) and len(size) > 1
+                    else block[1] if isinstance(block, tuple)
+                    else None
+                for block in blocks],
+            size[1] - size[0] if isinstance(size, tuple) and len(size) > 1
+                else size[0] if isinstance(size, tuple)
+                else size if size is not None
+                else off[1] - off[0] if isinstance(off, tuple) and len(off) > 1
+                else block_size)
+
+        # cat the blocks
+        for block, off in zip(blocks, offs):
+            f.seek((block * block_size) + (off or 0))
+            data = f.read(size)
+            sys.stdout.buffer.write(data)
+        sys.stdout.flush()
+
+if __name__ == "__main__":
+    import argparse
+    import sys
+    parser = argparse.ArgumentParser(
+        description="Cat data from a block device.",
+        allow_abbrev=False)
+    parser.add_argument(
+        'disk',
+        help="File containing the block device.")
+    parser.add_argument(
+        'blocks',
+        nargs='*',
+        type=rbydaddr,
+        help="Block address.")
+    parser.add_argument(
+        '-b', '--block-size',
+        type=bdgeom,
+        help="Block size/geometry in bytes.")
+    parser.add_argument(
+        '--block-count',
+        type=lambda x: int(x, 0),
+        help="Block count in blocks.")
+    parser.add_argument(
+        '--off',
+        type=lambda x: tuple(
+            int(x, 0) if x.strip() else None
+            for x in x.split(',')),
+        help="Show a specific offset, may be a range.")
+    parser.add_argument(
+        '-n', '--size',
+        type=lambda x: tuple(
+            int(x, 0) if x.strip() else None
+            for x in x.split(',')),
+        help="Show this many bytes, may be a range.")
+    sys.exit(main(**{k: v
+        for k, v in vars(parser.parse_intermixed_args()).items()
+        if v is not None}))