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Format Bytes as a Hex and ASCII Dump

WaymoSoftware Engineer · Onsite
MediumSoftware EngineerOnsiteCoding & Algorithms

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This problem tests string manipulation, modular arithmetic, and careful handling of formatting constraints to produce a standardized hexadecimal memory dump.

Problem Statement

Implement a function format_hex_dump(data: bytes, width: int = 16) -> str that converts a byte string into a formatted hex dump. Each line represents a chunk of width bytes.

Formatting Rules

  1. Offset: The start of each line must show the 8-digit hexadecimal offset (e.g., 00000000).
  2. Hex Columns: Follow the offset with space-separated hex values. If a line has fewer than width bytes, pad the missing columns with spaces to maintain alignment. Use two lowercase hex digits per byte.
  3. ASCII Column: Add a vertical bar | after the hex section, followed by the printable ASCII representation of the bytes. If a byte is not a printable ASCII character (defined as space 0x20 through tilde 0x7E), display a period . instead.
  4. Alignment: Ensure the ASCII section is always the same width, even if the last line is partial.

Constraints

  • width will be a multiple of 4, typically 16.
  • Input data length can be from 0 to 10,000 bytes.

Example

Input: data = b'Hello, World!', width = 8

Output:

00000000  48 65 6c 6c 6f 2c 20 57  |Hello, W|
00000008  6f 72 6c 64 21           |orld!   |

Edge Cases

  • Empty input b''.
  • Data length exactly divisible by width vs. remainder cases.
  • Handling non-printable characters (e.g., 0x00, 0x1F, 0x7F).

Hints

Hint 1

Process the byte array in slices of size `width` and track the current offset counter.

Hint 2

For each slice, generate hex strings using `'{:02x}'.format(b)` and convert characters to '.' if they are outside the range 32-126.

Hint 3

To pad the hex section, calculate the number of missing bytes and add three spaces (two for hex digits plus one separator) for each missing byte.

Follow-up questions

  • How would you modify this to handle streaming input where data is provided in chunks rather than a single byte array?
  • If you needed to output this to a file instead of a string to save memory, what design changes would you implement?
  • How would the logic change if you wanted to display the hex in groups of 4 bytes instead of individually?