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Filename : scan_args.h
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#ifndef RBIMPL_SCAN_ARGS_H                           /*-*-C++-*-vi:se ft=cpp:*/
#define RBIMPL_SCAN_ARGS_H
/**
 * @file
 * @author     Ruby developers <ruby-core@ruby-lang.org>
 * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
 *             Permission  is hereby  granted,  to  either redistribute  and/or
 *             modify this file, provided that  the conditions mentioned in the
 *             file COPYING are met.  Consult the file for details.
 * @warning    Symbols   prefixed  with   either  `RBIMPL`   or  `rbimpl`   are
 *             implementation details.   Don't take  them as canon.  They could
 *             rapidly appear then vanish.  The name (path) of this header file
 *             is also an  implementation detail.  Do not expect  it to persist
 *             at the place it is now.  Developers are free to move it anywhere
 *             anytime at will.
 * @note       To  ruby-core:  remember  that   this  header  can  be  possibly
 *             recursively included  from extension  libraries written  in C++.
 *             Do not  expect for  instance `__VA_ARGS__` is  always available.
 *             We assume C99  for ruby itself but we don't  assume languages of
 *             extension libraries. They could be written in C++98.
 * @brief      Compile-time static implementation of ::rb_scan_args().
 *
 * This  is a  beast.  It  statically analyses  the argument  spec string,  and
 * expands the assignment of variables into dedicated codes.
 */
#include "ruby/internal/attr/diagnose_if.h"
#include "ruby/internal/attr/error.h"
#include "ruby/internal/attr/forceinline.h"
#include "ruby/internal/attr/noreturn.h"
#include "ruby/internal/config.h"
#include "ruby/internal/dllexport.h"
#include "ruby/internal/has/attribute.h"
#include "ruby/internal/intern/array.h" /* rb_ary_new_from_values */
#include "ruby/internal/intern/error.h" /* rb_error_arity */
#include "ruby/internal/intern/hash.h"  /* rb_hash_dup */
#include "ruby/internal/intern/proc.h"  /* rb_block_proc */
#include "ruby/internal/iterator.h"     /* rb_block_given_p / rb_keyword_given_p */
#include "ruby/internal/static_assert.h"
#include "ruby/internal/stdbool.h"
#include "ruby/internal/value.h"
#include "ruby/assert.h"

#define RB_SCAN_ARGS_PASS_CALLED_KEYWORDS 0
#define RB_SCAN_ARGS_KEYWORDS 1
#define RB_SCAN_ARGS_LAST_HASH_KEYWORDS 3
#define RB_NO_KEYWORDS 0
#define RB_PASS_KEYWORDS 1
#define RB_PASS_CALLED_KEYWORDS rb_keyword_given_p()
/* rb_scan_args() format allows ':' for optional hash */
#define HAVE_RB_SCAN_ARGS_OPTIONAL_HASH 1

RBIMPL_SYMBOL_EXPORT_BEGIN()
int rb_scan_args(int, const VALUE*, const char*, ...);
int rb_scan_args_kw(int, int, const VALUE*, const char*, ...);

RBIMPL_ATTR_ERROR(("bad scan arg format"))
void rb_scan_args_bad_format(const char*);

RBIMPL_ATTR_ERROR(("variable argument length doesn't match"))
void rb_scan_args_length_mismatch(const char*,int);

RBIMPL_SYMBOL_EXPORT_END()

/* If we could use constexpr the following macros could be inline functions
 * ... but sadly we cannot. */

#define rb_scan_args_isdigit(c) (RBIMPL_CAST((unsigned char)((c)-'0'))<10)

#define rb_scan_args_count_end(fmt, ofs, vari) \
    ((fmt)[ofs] ? -1 : (vari))

#define rb_scan_args_count_block(fmt, ofs, vari) \
    ((fmt)[ofs]!='&' ? \
     rb_scan_args_count_end(fmt, ofs, vari) : \
     rb_scan_args_count_end(fmt, (ofs)+1, (vari)+1))

#define rb_scan_args_count_hash(fmt, ofs, vari) \
    ((fmt)[ofs]!=':' ? \
     rb_scan_args_count_block(fmt, ofs, vari) : \
     rb_scan_args_count_block(fmt, (ofs)+1, (vari)+1))

#define rb_scan_args_count_trail(fmt, ofs, vari) \
    (!rb_scan_args_isdigit((fmt)[ofs]) ? \
     rb_scan_args_count_hash(fmt, ofs, vari) : \
     rb_scan_args_count_hash(fmt, (ofs)+1, (vari)+((fmt)[ofs]-'0')))

#define rb_scan_args_count_var(fmt, ofs, vari) \
    ((fmt)[ofs]!='*' ? \
     rb_scan_args_count_trail(fmt, ofs, vari) : \
     rb_scan_args_count_trail(fmt, (ofs)+1, (vari)+1))

#define rb_scan_args_count_opt(fmt, ofs, vari) \
    (!rb_scan_args_isdigit((fmt)[ofs]) ? \
     rb_scan_args_count_var(fmt, ofs, vari) : \
     rb_scan_args_count_var(fmt, (ofs)+1, (vari)+(fmt)[ofs]-'0'))

#define rb_scan_args_count_lead(fmt, ofs, vari) \
    (!rb_scan_args_isdigit((fmt)[ofs]) ? \
     rb_scan_args_count_var(fmt, ofs, vari) : \
     rb_scan_args_count_opt(fmt, (ofs)+1, (vari)+(fmt)[ofs]-'0'))

#define rb_scan_args_count(fmt) rb_scan_args_count_lead(fmt, 0, 0)

#if RBIMPL_HAS_ATTRIBUTE(diagnose_if)
# /* Assertions done in the attribute. */
# define rb_scan_args_verify(fmt, varc) RBIMPL_ASSERT_NOTHING
#else
# /* At  one sight  it _seems_  the expressions  below could  be written  using
#  * static assrtions.  The reality is no, they don't.  Because fmt is a string
#  * literal, any operations  against fmt cannot produce  the "integer constant
#  * expression"s, as  defined in ISO/IEC  9899:2018 section 6.6  paragraph #6.
#  * Static assertions  need such  integer constant  expressions as  defined in
#  * ISO/IEC 9899:2018 section 6.7.10 paragraph #3.
#  *
#  * GCC nonetheless constant-folds this into no-op, though. */
# define rb_scan_args_verify(fmt, varc) \
    (sizeof(char[1-2*(rb_scan_args_count(fmt)<0)])!=1 ? \
     rb_scan_args_bad_format(fmt) : \
     sizeof(char[1-2*(rb_scan_args_count(fmt)!=(varc))])!=1 ? \
     rb_scan_args_length_mismatch(fmt, varc) : \
     RBIMPL_ASSERT_NOTHING)
#endif

static inline bool
rb_scan_args_keyword_p(int kw_flag, VALUE last)
{
    switch (kw_flag) {
      case RB_SCAN_ARGS_PASS_CALLED_KEYWORDS:
        return !! rb_keyword_given_p();
      case RB_SCAN_ARGS_KEYWORDS:
        return true;
      case RB_SCAN_ARGS_LAST_HASH_KEYWORDS:
        return RB_TYPE_P(last, T_HASH);
      default:
        return false;
    }
}

RBIMPL_ATTR_FORCEINLINE()
static bool
rb_scan_args_lead_p(const char *fmt)
{
    return rb_scan_args_isdigit(fmt[0]);
}

RBIMPL_ATTR_FORCEINLINE()
static int
rb_scan_args_n_lead(const char *fmt)
{
    return (rb_scan_args_lead_p(fmt) ? fmt[0]-'0' : 0);
}

RBIMPL_ATTR_FORCEINLINE()
static bool
rb_scan_args_opt_p(const char *fmt)
{
    return (rb_scan_args_lead_p(fmt) && rb_scan_args_isdigit(fmt[1]));
}

RBIMPL_ATTR_FORCEINLINE()
static int
rb_scan_args_n_opt(const char *fmt)
{
    return (rb_scan_args_opt_p(fmt) ? fmt[1]-'0' : 0);
}

RBIMPL_ATTR_FORCEINLINE()
static int
rb_scan_args_var_idx(const char *fmt)
{
    return (!rb_scan_args_lead_p(fmt) ? 0 : !rb_scan_args_isdigit(fmt[1]) ? 1 : 2);
}

RBIMPL_ATTR_FORCEINLINE()
static bool
rb_scan_args_f_var(const char *fmt)
{
    return (fmt[rb_scan_args_var_idx(fmt)]=='*');
}

RBIMPL_ATTR_FORCEINLINE()
static int
rb_scan_args_trail_idx(const char *fmt)
{
    const int idx = rb_scan_args_var_idx(fmt);
    return idx+(fmt[idx]=='*');
}

RBIMPL_ATTR_FORCEINLINE()
static int
rb_scan_args_n_trail(const char *fmt)
{
    const int idx = rb_scan_args_trail_idx(fmt);
    return (rb_scan_args_isdigit(fmt[idx]) ? fmt[idx]-'0' : 0);
}

RBIMPL_ATTR_FORCEINLINE()
static int
rb_scan_args_hash_idx(const char *fmt)
{
    const int idx = rb_scan_args_trail_idx(fmt);
    return idx+rb_scan_args_isdigit(fmt[idx]);
}

RBIMPL_ATTR_FORCEINLINE()
static bool
rb_scan_args_f_hash(const char *fmt)
{
    return (fmt[rb_scan_args_hash_idx(fmt)]==':');
}

RBIMPL_ATTR_FORCEINLINE()
static int
rb_scan_args_block_idx(const char *fmt)
{
    const int idx = rb_scan_args_hash_idx(fmt);
    return idx+(fmt[idx]==':');
}

RBIMPL_ATTR_FORCEINLINE()
static bool
rb_scan_args_f_block(const char *fmt)
{
    return (fmt[rb_scan_args_block_idx(fmt)]=='&');
}

# if 0
RBIMPL_ATTR_FORCEINLINE()
static int
rb_scan_args_end_idx(const char *fmt)
{
    const int idx = rb_scan_args_block_idx(fmt);
    return idx+(fmt[idx]=='&');
}
# endif

/* NOTE: Use `char *fmt` instead of `const char *fmt` because of clang's bug*/
/* https://bugs.llvm.org/show_bug.cgi?id=38095 */
# define rb_scan_args0(argc, argv, fmt, varc, vars) \
    rb_scan_args_set(RB_SCAN_ARGS_PASS_CALLED_KEYWORDS, argc, argv, \
                     rb_scan_args_n_lead(fmt), \
                     rb_scan_args_n_opt(fmt), \
                     rb_scan_args_n_trail(fmt), \
                     rb_scan_args_f_var(fmt), \
                     rb_scan_args_f_hash(fmt), \
                     rb_scan_args_f_block(fmt), \
                     (rb_scan_args_verify(fmt, varc), vars), (char *)fmt, varc)
# define rb_scan_args_kw0(kw_flag, argc, argv, fmt, varc, vars) \
    rb_scan_args_set(kw_flag, argc, argv, \
                     rb_scan_args_n_lead(fmt), \
                     rb_scan_args_n_opt(fmt), \
                     rb_scan_args_n_trail(fmt), \
                     rb_scan_args_f_var(fmt), \
                     rb_scan_args_f_hash(fmt), \
                     rb_scan_args_f_block(fmt), \
                     (rb_scan_args_verify(fmt, varc), vars), (char *)fmt, varc)

RBIMPL_ATTR_FORCEINLINE()
static int
rb_scan_args_set(int kw_flag, int argc, const VALUE *argv,
                 int n_lead, int n_opt, int n_trail,
                 bool f_var, bool f_hash, bool f_block,
                 VALUE *vars[], RB_UNUSED_VAR(const char *fmt), RB_UNUSED_VAR(int varc))
    RBIMPL_ATTR_DIAGNOSE_IF(rb_scan_args_count(fmt) <  0,    "bad scan arg format",                    "error")
    RBIMPL_ATTR_DIAGNOSE_IF(rb_scan_args_count(fmt) != varc, "variable argument length doesn't match", "error")
{
    int i, argi = 0, vari = 0;
    VALUE *var, hash = Qnil;
#define rb_scan_args_next_param() vars[vari++]
    const int n_mand = n_lead + n_trail;

    /* capture an option hash - phase 1: pop from the argv */
    if (f_hash && argc > 0) {
        VALUE last = argv[argc - 1];
        if (rb_scan_args_keyword_p(kw_flag, last)) {
            hash = rb_hash_dup(last);
            argc--;
        }
    }

    if (argc < n_mand) {
        goto argc_error;
    }

    /* capture leading mandatory arguments */
    for (i = 0; i < n_lead; i++) {
        var = rb_scan_args_next_param();
        if (var) *var = argv[argi];
        argi++;
    }

    /* capture optional arguments */
    for (i = 0; i < n_opt; i++) {
        var = rb_scan_args_next_param();
        if (argi < argc - n_trail) {
            if (var) *var = argv[argi];
            argi++;
        }
        else {
            if (var) *var = Qnil;
        }
    }

    /* capture variable length arguments */
    if (f_var) {
        int n_var = argc - argi - n_trail;

        var = rb_scan_args_next_param();
        if (0 < n_var) {
            if (var) *var = rb_ary_new_from_values(n_var, &argv[argi]);
            argi += n_var;
        }
        else {
            if (var) *var = rb_ary_new();
        }
    }

    /* capture trailing mandatory arguments */
    for (i = 0; i < n_trail; i++) {
        var = rb_scan_args_next_param();
        if (var) *var = argv[argi];
        argi++;
    }

    /* capture an option hash - phase 2: assignment */
    if (f_hash) {
        var = rb_scan_args_next_param();
        if (var) *var = hash;
    }

    /* capture iterator block */
    if (f_block) {
        var = rb_scan_args_next_param();
        if (rb_block_given_p()) {
            *var = rb_block_proc();
        }
        else {
            *var = Qnil;
        }
    }

    if (argi == argc) {
        return argc;
    }

  argc_error:
    rb_error_arity(argc, n_mand, f_var ? UNLIMITED_ARGUMENTS : n_mand + n_opt);
    UNREACHABLE_RETURN(-1);
#undef rb_scan_args_next_param
}

#if ! defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P)
# /* skip */

#elif ! defined(HAVE_VA_ARGS_MACRO)
# /* skip */

#elif ! defined(__OPTIMIZE__)
# /* skip */

#elif defined(HAVE___VA_OPT__)
# define rb_scan_args(argc, argvp, fmt, ...)                  \
    __builtin_choose_expr(                                    \
        __builtin_constant_p(fmt),                            \
        rb_scan_args0(                                        \
            argc, argvp, fmt,                                 \
            (sizeof((VALUE*[]){__VA_ARGS__})/sizeof(VALUE*)), \
            ((VALUE*[]){__VA_ARGS__})),                       \
        (rb_scan_args)(argc, argvp, fmt __VA_OPT__(, __VA_ARGS__)))
# define rb_scan_args_kw(kw_flag, argc, argvp, fmt, ...)      \
    __builtin_choose_expr(                                    \
        __builtin_constant_p(fmt),                            \
        rb_scan_args_kw0(                                     \
            kw_flag, argc, argvp, fmt,                        \
            (sizeof((VALUE*[]){__VA_ARGS__})/sizeof(VALUE*)), \
            ((VALUE*[]){__VA_ARGS__})),                       \
        (rb_scan_args_kw)(kw_flag, argc, argvp, fmt __VA_OPT__(, __VA_ARGS__)))

#elif defined(__STRICT_ANSI__)
# /* skip */

#elif defined(__GNUC__)
# define rb_scan_args(argc, argvp, fmt, ...)                  \
    __builtin_choose_expr(                                    \
        __builtin_constant_p(fmt),                            \
        rb_scan_args0(                                        \
            argc, argvp, fmt,                                 \
            (sizeof((VALUE*[]){__VA_ARGS__})/sizeof(VALUE*)), \
            ((VALUE*[]){__VA_ARGS__})),                       \
        (rb_scan_args)(argc, argvp, fmt, __VA_ARGS__))
# define rb_scan_args_kw(kw_flag, argc, argvp, fmt, ...)      \
    __builtin_choose_expr(                                    \
        __builtin_constant_p(fmt),                            \
        rb_scan_args_kw0(                                     \
            kw_flag, argc, argvp, fmt,                        \
            (sizeof((VALUE*[]){__VA_ARGS__})/sizeof(VALUE*)), \
            ((VALUE*[]){__VA_ARGS__})),                       \
        (rb_scan_args_kw)(kw_flag, argc, argvp, fmt, __VA_ARGS__ /**/))
#endif

#endif /* RBIMPL_SCAN_ARGS_H */