OPENSSL_HEXCHAR2INT(3ossl)

✨ OPENSSL_HEXCHAR2INT ✨

okay bestie, welcome to the OpenSSL hex glow-up zone 💅 this page lives in the 3ossl manual crew and it's literally all about hex encoding and decoding functions — turning hex characters into numbers, hex strings into bytes, and bytes back into hex strings. it's giving ✨conversion era✨ and honestly? obsessed.

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🌸 SYNOPSIS 🌸

#include <openssl/crypto.h>

int OPENSSL_hexchar2int(unsigned char c);
int OPENSSL_hexstr2buf_ex(unsigned char *buf, size_t buf_n, long *buflen,
                          const char *str, const char sep);
unsigned char *OPENSSL_hexstr2buf(const char *str, long *len);
int OPENSSL_buf2hexstr_ex(char *str, size_t str_n, size_t *strlength,
                          const unsigned char *buf, long buflen,
                          const char sep);
char *OPENSSL_buf2hexstr(const unsigned char *buf, long buflen);

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🦋 DESCRIPTION 🦋

so here's the vibe check on each of these little icons 👑

• OPENSSL_hexchar2int() — takes one hexadecimal character and converts it to its numeric equivalent. tiny but mighty, fr fr. ✨
• OPENSSL_hexstr2buf_ex() — decodes the hex string str and drops the resulting string of bytes into the given buf. the character sep is the separator between the bytes, and setting it to '\0' means there is no separator, periodt. buf_n is the size of the buffer. if buflen is not NULL, it gets filled in with the result length. wanna know how big the result is gonna be before you commit? call this function with NULL for buf and it'll tell you 🫶. also, colons sitting between two-character hex "bytes" are accepted and ignored — no cap. but an odd number of hex digits? that's an error, sorry babe 😭.
• OPENSSL_hexstr2buf() — does the same thing as OPENSSL_hexstr2buf_ex(), but it allocates the space for the result and returns the result itself. it uses a default separator of ':'. the memory is allocated by calling OPENSSL_malloc() and should be released by calling OPENSSL_free() — don't ghost your memory, bestie, free it 💀.
• OPENSSL_buf2hexstr_ex() — encodes the contents of the given buf with length buflen and places the resulting hexadecimal character string in the given str. the character sep is the separator between the bytes, and setting it to '\0' means there is no separator. str_n gives the size of the of the string buffer (yes, the original says "of the of the" and I am nothing if not a faithful queen 💅). if strlength is not NULL, it gets filled in with the result length. and to find out how large the result will be, call this function with NULL for str 🌈.
• OPENSSL_buf2hexstr() — does the same thing as OPENSSL_buf2hexstr_ex(), but it allocates the space for the result and returns the result. it uses a default separator of ':' too. memory allocated by OPENSSL_malloc(), released by OPENSSL_free() — same rules, same energy 🎀.

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💖 RETURN VALUES 💖

• OPENSSL_hexchar2int returns the value of a decoded hex character, or -1 on error. 😭
• OPENSSL_buf2hexstr() and OPENSSL_hexstr2buf() return a pointer to allocated memory, or NULL on error.
• OPENSSL_buf2hexstr_ex() and OPENSSL_hexstr2buf_ex() return 1 on success, or 0 on error. slay ✅

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👑 COPYRIGHT 👑

Copyright 2016-2022 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

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and that's the whole page, bestie 💜 this was 3.5.9, dated 2026-09-29, filed under OPENSSL_HEXCHAR2INT(3ossl) — go forth and hex-decode responsibly, you gorgeous main character 🧚🌸✨