hex2bin()

hex2bin()#

The hex2bin function converts a hexadecimal string (hex) into its binary representation, storing the result in a provided buffer (bf). It uses a decoding table to map hexadecimal characters to their corresponding values and processes the input string two characters at a time to produce binary bytes.

Prototype

PUBLIC char *hex2bin(
    char        *bf,
    int         bfsize,
    const char  *hex,
    size_t      hex_len,
    size_t      *out_len
);

Parameters

Parameter

Type

Description

bf

char *

Pointer to the output buffer where the binary data will be stored.

bfsize

int

The size of the output buffer in bytes.

hex

const char *

The input hexadecimal string to be converted.

hex_len

size_t

The length of the input hexadecimal string.

out_len

size_t *

Pointer to a variable where the length of the binary output will be stored. Can be NULL if not needed.

Return Value

  • Returns a pointer to the output buffer bf containing the binary data.

  • Returns NULL if an error occurs (e.g., invalid hex character or buffer overflow).

Notes

  • Hexadecimal Decoding:

    • The function uses a decoding table (base16_decoding_table1) to map valid hexadecimal characters (0-9, a-f, A-F) to their respective values.

    • If an invalid character is encountered, the function stops processing.

  • Buffer Size Check:

    • Ensures that the binary data does not exceed the size of the output buffer (bfsize).

  • Even/Odd Logic:

    • Even indices of the hexadecimal input are processed as the high nibble (4 bits) of the binary byte, and odd indices as the low nibble.

  • Output Length:

    • The total number of bytes written to the output buffer is stored in out_len if it is not NULL.

Example

char buffer[32];
size_t out_len;
const char *hex_string = "48656c6c6f20576f726c64"; // "Hello World" in hex
hex2bin(buffer, sizeof(buffer), hex_string, strlen(hex_string), &out_len);
// buffer now contains the binary representation of "Hello World"

Prototype

// Not applicable in JS

Prototype

# Not applicable in Python
Examples
// TODO C examples

// TODO JS examples

# TODO Python examples