nakulbhat/hexdtmf

Purpose and executable entry point

hexdtmf is a POSIX C command-line program that converts hexadecimal-style keypad digits to/from WAV-encoded DTMF audio. The process begins in src/main.c, with shared program declarations in include/main.h. Makefile builds the hexdtmf executable using GCC.

CLI parsing and mode selection

Argument parsing determines the top-level encode or decode operation plus input/output, timing, compatibility, verbosity, and help options. This is isolated in:

• src/args.c

• include/args.h

• src/main.c

The parsed options form the boundary between command-line/user I/O concerns and audio processing.

Encode pipeline

Encode mode accepts digits from positional arguments, a file, or standard input, then produces a WAV file or writes WAV bytes to its selected output. The encoder is responsible for mapping supported values (0–9, A–D, plus E/F or compatibility */#) to DTMF row/column frequency pairs, generating timed tone and gap samples, and serializing WAV output.

• src/encoder.c

• include/encoder.h

• src/main.c

Tone and gap durations supplied through CLI options directly control generated sample timing.

Decode pipeline

Decode mode consumes a WAV stream/file, identifies DTMF tone segments, resolves their two component frequencies to keypad digits, and emits text to stdout or an output file. WAV parsing and signal/digit recovery are encapsulated behind:

• src/decoder.c

• include/decoder.h

• src/main.c

This component owns the audio-input boundary and must tolerate binary WAV data arriving via stdin as well as files.

Digit representation and compatibility boundary

The application uses an extended hexadecimal-oriented representation: E represents * and F represents # by default. The compatibility option changes external representation to literal * and #. That translation applies at the CLI-facing encode/decode boundary rather than changing the underlying DTMF frequency model.

• src/args.c

• src/encoder.c

• src/decoder.c

User feedback and failures

Usage/help rendering is separated from core processing in:

• src/help.c

• include/help.h

src/main.c coordinates help/version-style control paths, validates operation selection, calls the appropriate codec path, and returns process status. Verbose mode is a diagnostic/control-flow concern exposed through parsed arguments.

Runtime and external dependencies

The program targets Linux/macOS-style POSIX environments and relies on the C runtime, standard streams/files, GCC, and Make. It has no indicated network service, database, web runtime, or third-party runtime dependency. WAV files and stdin/stdout are its primary integration interfaces.