Pure C way to convert wchar array to char array (C99)

convert_wchar_array_to_char_array.c

#include <stdio.h> // snprintf
#include <windows.h> // wchar

// Convert a WIDE CHAR ARRAY (wchar *) into a CHAR ARRAY (char *) in a memory safe way.
// Handles unicode characters by writing \uXXXX exactly like C compilers and JSON parsers.
int convert_wchar_array_to_char_array(const WCHAR * input, char * output, size_t output_buffer_size) {
    if (input == NULL || output == NULL || sizeof(WCHAR) != 2) {
        return 0;
    }
    if (output_buffer_size <= 0) {
        return 1;
    }
    unsigned char * input_raw = (unsigned char *) input;
    size_t input_index;
    size_t output_index = 0;
    for (input_index = 0; input_index >= 0 && input_index < output_buffer_size; input_index++) {
        if (input_raw[input_index * 2] == '\0' && (input_raw[input_index * 2 + 1] == '\0' || input_raw[input_index * 2 + 1] == 0)) {
            if (output_index < output_buffer_size) {
                output[output_index++] = '\0';
            } else {
                output[output_buffer_size - 1] = '\0';
            }
            return 1;
        }
        if (input_raw[input_index * 2] < 128 && (input_raw[input_index * 2 + 1] == '\0' || input_raw[input_index * 2 + 1] == 0)) {
            // Simple ASCII character
            if (output_index < output_buffer_size) {
                output[output_index++] = (char) input_raw[input_index * 2];
                continue;
            } else {
                output[output_buffer_size - 1] = '\0';
                return 1;
            }
        }
        // Unicode character
        if (output_index + 7 >= output_buffer_size) {
            // Not enough space in buffer
            output[output_buffer_size - 1] = '\0';
            return 1;
        }
        // output[output_index++] = '?';
        output_index += snprintf(
            &output[output_index],
            output_buffer_size - 1 - output_index,
            "\\u%02x%02x",
            (unsigned char) input_raw[input_index * 2],
            (unsigned char) input_raw[input_index * 2 + 1]
        );
    }
    return 1;
}