json_out.h

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/*
 * SPDX-License-Identifier: LGPL-3.0-or-later
 * Copyright (c) 2026 Cryptnox SA
 */

 
#ifndef JSON_OUT_H
#define JSON_OUT_H
 
#include <stddef.h>
#include <stdio.h>

static inline size_t json_escape(char *out, size_t n, const char *val)
{
    if ((out == NULL) || (n == 0U)) { return 0U; }
    out[0] = '\0';
    if (val == NULL) { return 0U; }
 
    size_t w = 0U;
    for (const char *p = val; *p != '\0'; p++) {
        const unsigned char c = (unsigned char)*p;
        /* Room for the worst case (6) plus the NUL before committing to anything,
         * so the output never ends half way through an escape sequence. */
        if ((w + 7U) > n) { break; }
        if ((c == '"') || (c == '\\')) {
            out[w++] = '\\';
            out[w++] = (char)c;
        } else if (c < 0x20U) {
            const int k = snprintf(&out[w], n - w, "\\u%04x", (unsigned)c);
            if (k < 0) { break; }
            w += (size_t)k;
        } else {
            out[w++] = (char)c;
        }
    }
    out[w] = '\0';
    return w;
}
 
#endif /* JSON_OUT_H */