// SPDX-License-Identifier: GPL-2.0
#include <string.h>
#include <stdlib.h>
#include "util/string2.h"

#include "demangle-ocaml.h"

#include <linux/ctype.h>

static const char *caml_prefix = "caml";
static const size_t caml_prefix_len = 4;

/* mangled OCaml symbols start with "caml" followed by an upper-case letter */
static bool
ocaml_is_mangled(const char *sym)
{
        return 0 == strncmp(sym, caml_prefix, caml_prefix_len)
                && isupper(sym[caml_prefix_len]);
}

/*
 * input:
 *     sym: a symbol which may have been mangled by the OCaml compiler
 * return:
 *     if the input doesn't look like a mangled OCaml symbol, NULL is returned
 *     otherwise, a newly allocated string containing the demangled symbol is returned
 */
char *
ocaml_demangle_sym(const char *sym)
{
        char *result;
        int j = 0;
        int i;
        int len;

        if (!ocaml_is_mangled(sym)) {
                return NULL;
        }

        len = strlen(sym);

        /* the demangled symbol is always smaller than the mangled symbol */
        result = malloc(len + 1);
        if (!result)
                return NULL;

        /* skip "caml" prefix */
        i = caml_prefix_len;

        while (i < len) {
                if (sym[i] == '_' && sym[i + 1] == '_') {
                        /* "__" -> "." */
                        result[j++] = '.';
                        i += 2;
                }
                else if (sym[i] == '$' && isxdigit(sym[i + 1]) && isxdigit(sym[i + 2])) {
                        /* "$xx" is a hex-encoded character */
                        result[j++] = (hex(sym[i + 1]) << 4) | hex(sym[i + 2]);
                        i += 3;
                }
                else {
                        result[j++] = sym[i++];
                }
        }
        result[j] = '\0';

        return result;
}