isxdigitint

isxdigitint is a term used in some codebases to refer to a function that determines whether a given integral value corresponds to a hexadecimal digit. It is not part of the C standard library, and its exact name and behavior may vary between projects. In practice, such a function is typically designed to return a nonzero value when its input represents a character in the set 0–9, a–f, or A–F.

A common convention for the signature is int isxdigitint(int ch); the function takes an int parameter and returns an integer where a nonzero value indicates a hexadecimal digit and zero indicates that it is not. The intended characters aligned with this check are the ASCII digits and letters used in hexadecimal notation.

Because isxdigitint is not standardized, its implementation details can differ. When bridging to standard libraries, some implementations wrap the standard isxdigit function from <ctype.h>, ensuring that the input is treated as an unsigned char value or handling EOF appropriately. In other cases, isxdigitint may implement the check directly via range comparisons to '0'–'9', 'a'–'f', and 'A'–'F'.

Implementation tip: a portable direct check might resemble returning (ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'f') || (ch >= 'A' && ch <= 'F'), often after casting ch to unsigned char to avoid undefined behavior with negative values.

Usage considerations include consistency with the project’s coding standards and awareness that isxdigitint is not a standard function. Alternatives include using the standard isxdigit from <ctype.h> or providing a documented custom equivalent. See also: isxdigit, ctype.h.