hex.h File Reference

Tiny no-stdlib hex encode / decode / nibble helpers (one shared copy). More...

#include <stddef.h>
#include <stdint.h>

Go to the source code of this file.

Functions
char	det_hex_digit (int nibble, bool upper=false)
	Nibble 0..15 -> hex char (lowercase, or uppercase when upper).
int	det_hex_val (char c)
	Hex digit -> 0..15, or -1 if c is not a hex digit (either case).
void	det_hex_encode (const uint8_t *in, size_t n, char *out, bool upper=false)
	Encode n bytes as 2*n hex chars + NUL into out (needs cap >= 2*n+1).
int	det_hex_decode (const char *in, size_t hexlen, uint8_t *out, size_t out_cap)
	Decode exactly hexlen hex chars into out (hexlen/2 bytes).

Detailed Description

Tiny no-stdlib hex encode / decode / nibble helpers (one shared copy).

Hex was open-coded in ~10 places (CSRF token, WebDAV XX, provisioning, audit-log hash, device-id, HTTP auth, OAuth2 percent-encode). These header-only inline helpers are the single home for it, mirroring numparse.h - no <stdlib.h>, no heap, and zero link cost when unused.

Author

Douglas Quigg (dstroy0)

Date

2026

Definition in file hex.h.

Function Documentation

det_hex_digit()

char det_hex_digit ( int  nibble, bool  upper = false  )

inline

Nibble 0..15 -> hex char (lowercase, or uppercase when upper).

Definition at line 24 of file hex.h.

det_hex_val()

int det_hex_val ( char  c )

inline

Hex digit -> 0..15, or -1 if c is not a hex digit (either case).

Definition at line 31 of file hex.h.

Referenced by det_hex_decode(), and detws_prov_form_field().

det_hex_encode()

void det_hex_encode ( const uint8_t *  in, size_t  n, char *  out, bool  upper = false  )

inline

Encode n bytes as 2*n hex chars + NUL into out (needs cap >= 2*n+1).

Parameters

upper

uppercase A-F when true, else lowercase a-f.

Definition at line 46 of file hex.h.

det_hex_decode()

int det_hex_decode ( const char *  in, size_t  hexlen, uint8_t *  out, size_t  out_cap  )

inline

Decode exactly hexlen hex chars into out (hexlen/2 bytes).

Returns

byte count, or -1 on odd length / overflow (> out_cap) / non-hex input.

Definition at line 61 of file hex.h.

References det_hex_val().