/string.c

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/**********************************************************************

  string.c -

  $Author$
  created at: Mon Aug  9 17:12:58 JST 1993

  Copyright (C) 1993-2007 Yukihiro Matsumoto
  Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
  Copyright (C) 2000  Information-technology Promotion Agency, Japan

**********************************************************************/

#include "ruby/ruby.h"
#include "ruby/re.h"
#include "ruby/encoding.h"
#include "vm_core.h"
#include "internal.h"
#include "probes.h"
#include <assert.h>

#define BEG(no) (regs->beg[(no)])
#define END(no) (regs->end[(no)])

#include <math.h>
#include <ctype.h>

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#define numberof(array) (int)(sizeof(array) / sizeof((array)[0]))

#undef rb_str_new_cstr
#undef rb_tainted_str_new_cstr
#undef rb_usascii_str_new_cstr
#undef rb_external_str_new_cstr
#undef rb_locale_str_new_cstr
#undef rb_str_new2
#undef rb_str_new3
#undef rb_str_new4
#undef rb_str_new5
#undef rb_tainted_str_new2
#undef rb_usascii_str_new2
#undef rb_str_dup_frozen
#undef rb_str_buf_new_cstr
#undef rb_str_buf_new2
#undef rb_str_buf_cat2
#undef rb_str_cat2

static VALUE rb_str_clear(VALUE str);

VALUE rb_cString;
VALUE rb_cSymbol;

#define RUBY_MAX_CHAR_LEN 16
#define STR_TMPLOCK FL_USER7
#define STR_NOEMBED FL_USER1
#define STR_SHARED  FL_USER2 /* = ELTS_SHARED */
#define STR_ASSOC   FL_USER3
#define STR_SHARED_P(s) FL_ALL((s), STR_NOEMBED|ELTS_SHARED)
#define STR_ASSOC_P(s)  FL_ALL((s), STR_NOEMBED|STR_ASSOC)
#define STR_NOCAPA  (STR_NOEMBED|ELTS_SHARED|STR_ASSOC)
#define STR_NOCAPA_P(s) (FL_TEST((s),STR_NOEMBED) && FL_ANY((s),ELTS_SHARED|STR_ASSOC))
#define STR_UNSET_NOCAPA(s) do {\
    if (FL_TEST((s),STR_NOEMBED)) FL_UNSET((s),(ELTS_SHARED|STR_ASSOC));\
} while (0)


#define STR_SET_NOEMBED(str) do {\
    FL_SET((str), STR_NOEMBED);\
    STR_SET_EMBED_LEN((str), 0);\
} while (0)
#define STR_SET_EMBED(str) FL_UNSET((str), STR_NOEMBED)
#define STR_EMBED_P(str) (!FL_TEST((str), STR_NOEMBED))
#define STR_SET_EMBED_LEN(str, n) do { \
    long tmp_n = (n);\
    RBASIC(str)->flags &= ~RSTRING_EMBED_LEN_MASK;\
    RBASIC(str)->flags |= (tmp_n) << RSTRING_EMBED_LEN_SHIFT;\
} while (0)

#define STR_SET_LEN(str, n) do { \
    if (STR_EMBED_P(str)) {\
	STR_SET_EMBED_LEN((str), (n));\
    }\
    else {\
	RSTRING(str)->as.heap.len = (n);\
    }\
} while (0)

#define STR_DEC_LEN(str) do {\
    if (STR_EMBED_P(str)) {\
	long n = RSTRING_LEN(str);\
	n--;\
	STR_SET_EMBED_LEN((str), n);\
    }\
    else {\
	RSTRING(str)->as.heap.len--;\
    }\
} while (0)

#define RESIZE_CAPA(str,capacity) do {\
    if (STR_EMBED_P(str)) {\
	if ((capacity) > RSTRING_EMBED_LEN_MAX) {\
	    char *tmp = ALLOC_N(char, (capacity)+1);\
	    memcpy(tmp, RSTRING_PTR(str), RSTRING_LEN(str));\
	    RSTRING(str)->as.heap.ptr = tmp;\
	    RSTRING(str)->as.heap.len = RSTRING_LEN(str);\
            STR_SET_NOEMBED(str);\
	    RSTRING(str)->as.heap.aux.capa = (capacity);\
	}\
    }\
    else {\
	REALLOC_N(RSTRING(str)->as.heap.ptr, char, (capacity)+1);\
	if (!STR_NOCAPA_P(str))\
	    RSTRING(str)->as.heap.aux.capa = (capacity);\
    }\
} while (0)

#define is_ascii_string(str) (rb_enc_str_coderange(str) == ENC_CODERANGE_7BIT)
#define is_broken_string(str) (rb_enc_str_coderange(str) == ENC_CODERANGE_BROKEN)

#define STR_ENC_GET(str) rb_enc_from_index(ENCODING_GET(str))

static inline int
single_byte_optimizable(VALUE str)
{
    rb_encoding *enc;

    /* Conservative.  It may be ENC_CODERANGE_UNKNOWN. */
    if (ENC_CODERANGE(str) == ENC_CODERANGE_7BIT)
        return 1;

    enc = STR_ENC_GET(str);
    if (rb_enc_mbmaxlen(enc) == 1)
        return 1;

    /* Conservative.  Possibly single byte.
     * "\xa1" in Shift_JIS for example. */
    return 0;
}

VALUE rb_fs;

static inline const char *
search_nonascii(const char *p, const char *e)
{
#if SIZEOF_VALUE == 8
# define NONASCII_MASK 0x8080808080808080ULL
#elif SIZEOF_VALUE == 4
# define NONASCII_MASK 0x80808080UL
#endif
#ifdef NONASCII_MASK
    if ((int)sizeof(VALUE) * 2 < e - p) {
        const VALUE *s, *t;
        const VALUE lowbits = sizeof(VALUE) - 1;
        s = (const VALUE*)(~lowbits & ((VALUE)p + lowbits));
        while (p < (const char *)s) {
            if (!ISASCII(*p))
                return p;
            p++;
        }
        t = (const VALUE*)(~lowbits & (VALUE)e);
        while (s < t) {
            if (*s & NONASCII_MASK) {
                t = s;
                break;
            }
            s++;
        }
        p = (const char *)t;
    }
#endif
    while (p < e) {
        if (!ISASCII(*p))
            return p;
        p++;
    }
    return NULL;
}

static int
coderange_scan(const char *p, long len, rb_encoding *enc)
{
    const char *e = p + len;

    if (rb_enc_to_index(enc) == 0) {
        /* enc is ASCII-8BIT.  ASCII-8BIT string never be broken. */
        p = search_nonascii(p, e);
        return p ? ENC_CODERANGE_VALID : ENC_CODERANGE_7BIT;
    }

    if (rb_enc_asciicompat(enc)) {
        p = search_nonascii(p, e);
        if (!p) {
            return ENC_CODERANGE_7BIT;
        }
        while (p < e) {
            int ret = rb_enc_precise_mbclen(p, e, enc);
            if (!MBCLEN_CHARFOUND_P(ret)) {
                return ENC_CODERANGE_BROKEN;
            }
            p += MBCLEN_CHARFOUND_LEN(ret);
            if (p < e) {
                p = search_nonascii(p, e);
                if (!p) {
                    return ENC_CODERANGE_VALID;
                }
            }
        }
        if (e < p) {
            return ENC_CODERANGE_BROKEN;
        }
        return ENC_CODERANGE_VALID;
    }

    while (p < e) {
        int ret = rb_enc_precise_mbclen(p, e, enc);

        if (!MBCLEN_CHARFOUND_P(ret)) {
            return ENC_CODERANGE_BROKEN;
        }
        p += MBCLEN_CHARFOUND_LEN(ret);
    }
    if (e < p) {
        return ENC_CODERANGE_BROKEN;
    }
    return ENC_CODERANGE_VALID;
}

long
rb_str_coderange_scan_restartable(const char *s, const char *e, rb_encoding *enc, int *cr)
{
    const char *p = s;

    if (*cr == ENC_CODERANGE_BROKEN)
	return e - s;

    if (rb_enc_to_index(enc) == 0) {
	/* enc is ASCII-8BIT.  ASCII-8BIT string never be broken. */
	p = search_nonascii(p, e);
	*cr = (!p && *cr != ENC_CODERANGE_VALID) ? ENC_CODERANGE_7BIT : ENC_CODERANGE_VALID;
	return e - s;
    }
    else if (rb_enc_asciicompat(enc)) {
	p = search_nonascii(p, e);
	if (!p) {
	    if (*cr != ENC_CODERANGE_VALID) *cr = ENC_CODERANGE_7BIT;
	    return e - s;
	}
	while (p < e) {
	    int ret = rb_enc_precise_mbclen(p, e, enc);
	    if (!MBCLEN_CHARFOUND_P(ret)) {
		*cr = MBCLEN_INVALID_P(ret) ? ENC_CODERANGE_BROKEN: ENC_CODERANGE_UNKNOWN;
		return p - s;
	    }
	    p += MBCLEN_CHARFOUND_LEN(ret);
	    if (p < e) {
		p = search_nonascii(p, e);
		if (!p) {
		    *cr = ENC_CODERANGE_VALID;
		    return e - s;
		}
	    }
	}
	*cr = e < p ? ENC_CODERANGE_BROKEN: ENC_CODERANGE_VALID;
	return p - s;
    }
    else {
	while (p < e) {
	    int ret = rb_enc_precise_mbclen(p, e, enc);
	    if (!MBCLEN_CHARFOUND_P(ret)) {
		*cr = MBCLEN_INVALID_P(ret) ? ENC_CODERANGE_BROKEN: ENC_CODERANGE_UNKNOWN;
		return p - s;
	    }
	    p += MBCLEN_CHARFOUND_LEN(ret);
	}
	*cr = e < p ? ENC_CODERANGE_BROKEN: ENC_CODERANGE_VALID;
	return p - s;
    }
}

static inline void
str_enc_copy(VALUE str1, VALUE str2)
{
    rb_enc_set_index(str1, ENCODING_GET(str2));
}

static void
rb_enc_cr_str_copy_for_substr(VALUE dest, VALUE src)
{
    /* this function is designed for copying encoding and coderange
     * from src to new string "dest" which is made from the part of src.
     */
    str_enc_copy(dest, src);
    if (RSTRING_LEN(dest) == 0) {
	if (!rb_enc_asciicompat(STR_ENC_GET(src)))
	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_VALID);
	else
	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
	return;
    }
    switch (ENC_CODERANGE(src)) {
      case ENC_CODERANGE_7BIT:
	ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
	break;
      case ENC_CODERANGE_VALID:
	if (!rb_enc_asciicompat(STR_ENC_GET(src)) ||
	    search_nonascii(RSTRING_PTR(dest), RSTRING_END(dest)))
	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_VALID);
	else
	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
	break;
      default:
	break;
    }
}

static void
rb_enc_cr_str_exact_copy(VALUE dest, VALUE src)
{
    str_enc_copy(dest, src);
    ENC_CODERANGE_SET(dest, ENC_CODERANGE(src));
}

int
rb_enc_str_coderange(VALUE str)
{
    int cr = ENC_CODERANGE(str);

    if (cr == ENC_CODERANGE_UNKNOWN) {
	rb_encoding *enc = STR_ENC_GET(str);
        cr = coderange_scan(RSTRING_PTR(str), RSTRING_LEN(str), enc);
        ENC_CODERANGE_SET(str, cr);
    }
    return cr;
}

int
rb_enc_str_asciionly_p(VALUE str)
{
    rb_encoding *enc = STR_ENC_GET(str);

    if (!rb_enc_asciicompat(enc))
        return FALSE;
    else if (rb_enc_str_coderange(str) == ENC_CODERANGE_7BIT)
        return TRUE;
    return FALSE;
}

static inline void
str_mod_check(VALUE s, const char *p, long len)
{
    if (RSTRING_PTR(s) != p || RSTRING_LEN(s) != len){
	rb_raise(rb_eRuntimeError, "string modified");
    }
}

size_t
rb_str_capacity(VALUE str)
{
    if (STR_EMBED_P(str)) {
	return RSTRING_EMBED_LEN_MAX;
    }
    else if (STR_NOCAPA_P(str)) {
	return RSTRING(str)->as.heap.len;
    }
    else {
	return RSTRING(str)->as.heap.aux.capa;
    }
}

static inline VALUE
str_alloc(VALUE klass)
{
    NEWOBJ_OF(str, struct RString, klass, T_STRING);

    str->as.heap.ptr = 0;
    str->as.heap.len = 0;
    str->as.heap.aux.capa = 0;

    return (VALUE)str;
}

static inline VALUE
empty_str_alloc(VALUE klass)
{
    if (RUBY_DTRACE_STRING_CREATE_ENABLED()) {
	RUBY_DTRACE_STRING_CREATE(0, rb_sourcefile(), rb_sourceline());
    }
    return str_alloc(klass);
}

static VALUE
str_new(VALUE klass, const char *ptr, long len)
{
    VALUE str;

    if (len < 0) {
	rb_raise(rb_eArgError, "negative string size (or size too big)");
    }

    if (RUBY_DTRACE_STRING_CREATE_ENABLED()) {
	RUBY_DTRACE_STRING_CREATE(len, rb_sourcefile(), rb_sourceline());
    }

    str = str_alloc(klass);
    if (len > RSTRING_EMBED_LEN_MAX) {
	RSTRING(str)->as.heap.aux.capa = len;
	RSTRING(str)->as.heap.ptr = ALLOC_N(char,len+1);
	STR_SET_NOEMBED(str);
    }
    else if (len == 0) {
	ENC_CODERANGE_SET(str, ENC_CODERANGE_7BIT);
    }
    if (ptr) {
	memcpy(RSTRING_PTR(str), ptr, len);
    }
    STR_SET_LEN(str, len);
    RSTRING_PTR(str)[len] = '\0';
    return str;
}

VALUE
rb_str_new(const char *ptr, long len)
{
    return str_new(rb_cString, ptr, len);
}

VALUE
rb_usascii_str_new(const char *ptr, long len)
{
    VALUE str = rb_str_new(ptr, len);
    ENCODING_CODERANGE_SET(str, rb_usascii_encindex(), ENC_CODERANGE_7BIT);
    return str;
}

VALUE
rb_enc_str_new(const char *ptr, long len, rb_encoding *enc)
{
    VALUE str = rb_str_new(ptr, len);
    rb_enc_associate(str, enc);
    return str;
}

VALUE
rb_str_new_cstr(const char *ptr)
{
    if (!ptr) {
	rb_raise(rb_eArgError, "NULL pointer given");
    }
    return rb_str_new(ptr, strlen(ptr));
}

RUBY_ALIAS_FUNCTION(rb_str_new2(const char *ptr), rb_str_new_cstr, (ptr))
#define rb_str_new2 rb_str_new_cstr

VALUE
rb_usascii_str_new_cstr(const char *ptr)
{
    VALUE str = rb_str_new2(ptr);
    ENCODING_CODERANGE_SET(str, rb_usascii_encindex(), ENC_CODERANGE_7BIT);
    return str;
}

RUBY_ALIAS_FUNCTION(rb_usascii_str_new2(const char *ptr), rb_usascii_str_new_cstr, (ptr))
#define rb_usascii_str_new2 rb_usascii_str_new_cstr

VALUE
rb_tainted_str_new(const char *ptr, long len)
{
    VALUE str = rb_str_new(ptr, len);

    OBJ_TAINT(str);
    return str;
}

VALUE
rb_tainted_str_new_cstr(const char *ptr)
{
    VALUE str = rb_str_new2(ptr);

    OBJ_TAINT(str);
    return str;
}

RUBY_ALIAS_FUNCTION(rb_tainted_str_new2(const char *ptr), rb_tainted_str_new_cstr, (ptr))
#define rb_tainted_str_new2 rb_tainted_str_new_cstr

VALUE
rb_str_conv_enc_opts(VALUE str, rb_encoding *from, rb_encoding *to, int ecflags, VALUE ecopts)
{
    rb_econv_t *ec;
    rb_econv_result_t ret;
    long len;
    VALUE newstr;
    const unsigned char *sp;
    unsigned char *dp;

    if (!to) return str;
    if (!from) from = rb_enc_get(str);
    if (from == to) return str;
    if ((rb_enc_asciicompat(to) && ENC_CODERANGE(str) == ENC_CODERANGE_7BIT) ||
	to == rb_ascii8bit_encoding()) {
	if (STR_ENC_GET(str) != to) {
	    str = rb_str_dup(str);
	    rb_enc_associate(str, to);
	}
	return str;
    }

    len = RSTRING_LEN(str);
    newstr = rb_str_new(0, len);

  retry:
    ec = rb_econv_open_opts(from->name, to->name, ecflags, ecopts);
    if (!ec) return str;

    sp = (unsigned char*)RSTRING_PTR(str);
    dp = (unsigned char*)RSTRING_PTR(newstr);
    ret = rb_econv_convert(ec, &sp, (unsigned char*)RSTRING_END(str),
			   &dp, (unsigned char*)RSTRING_END(newstr), 0);
    rb_econv_close(ec);
    switch (ret) {
      case econv_destination_buffer_full:
	/* destination buffer short */
	len = len < 2 ? 2 : len * 2;
	rb_str_resize(newstr, len);
	goto retry;

      case econv_finished:
	len = dp - (unsigned char*)RSTRING_PTR(newstr);
	rb_str_set_len(newstr, len);
	rb_enc_associate(newstr, to);
	return newstr;

      default:
	/* some error, return original */
	return str;
    }
}

VALUE
rb_str_conv_enc(VALUE str, rb_encoding *from, rb_encoding *to)
{
    return rb_str_conv_enc_opts(str, from, to, 0, Qnil);
}

VALUE
rb_external_str_new_with_enc(const char *ptr, long len, rb_encoding *eenc)
{
    VALUE str;

    str = rb_tainted_str_new(ptr, len);
    if (eenc == rb_usascii_encoding() &&
	rb_enc_str_coderange(str) != ENC_CODERANGE_7BIT) {
	rb_enc_associate(str, rb_ascii8bit_encoding());
	return str;
    }
    rb_enc_associate(str, eenc);
    return rb_str_conv_enc(str, eenc, rb_default_internal_encoding());
}

VALUE
rb_external_str_new(const char *ptr, long len)
{
    return rb_external_str_new_with_enc(ptr, len, rb_default_external_encoding());
}

VALUE
rb_external_str_new_cstr(const char *ptr)
{
    return rb_external_str_new_with_enc(ptr, strlen(ptr), rb_default_external_encoding());
}

VALUE
rb_locale_str_new(const char *ptr, long len)
{
    return rb_external_str_new_with_enc(ptr, len, rb_locale_encoding());
}

VALUE
rb_locale_str_new_cstr(const char *ptr)
{
    return rb_external_str_new_with_enc(ptr, strlen(ptr), rb_locale_encoding());
}

VALUE
rb_filesystem_str_new(const char *ptr, long len)
{
    return rb_external_str_new_with_enc(ptr, len, rb_filesystem_encoding());
}

VALUE
rb_filesystem_str_new_cstr(const char *ptr)
{
    return rb_external_str_new_with_enc(ptr, strlen(ptr), rb_filesystem_encoding());
}

VALUE
rb_str_export(VALUE str)
{
    return rb_str_conv_enc(str, STR_ENC_GET(str), rb_default_external_encoding());
}

VALUE
rb_str_export_locale(VALUE str)
{
    return rb_str_conv_enc(str, STR_ENC_GET(str), rb_locale_encoding());
}

VALUE
rb_str_export_to_enc(VALUE str, rb_encoding *enc)
{
    return rb_str_conv_enc(str, STR_ENC_GET(str), enc);
}

static VALUE
str_replace_shared_without_enc(VALUE str2, VALUE str)
{
    if (RSTRING_LEN(str) <= RSTRING_EMBED_LEN_MAX) {
	STR_SET_EMBED(str2);
	memcpy(RSTRING_PTR(str2), RSTRING_PTR(str), RSTRING_LEN(str)+1);
	STR_SET_EMBED_LEN(str2, RSTRING_LEN(str));
    }
    else {
	str = rb_str_new_frozen(str);
	FL_SET(str2, STR_NOEMBED);
	RSTRING(str2)->as.heap.len = RSTRING_LEN(str);
	RSTRING(str2)->as.heap.ptr = RSTRING_PTR(str);
	RSTRING(str2)->as.heap.aux.shared = str;
	FL_SET(str2, ELTS_SHARED);
    }
    return str2;
}

static VALUE
str_replace_shared(VALUE str2, VALUE str)
{
    str_replace_shared_without_enc(str2, str);
    rb_enc_cr_str_exact_copy(str2, str);
    return str2;
}

static VALUE
str_new_shared(VALUE klass, VALUE str)
{
    return str_replace_shared(str_alloc(klass), str);
}

static VALUE
str_new3(VALUE klass, VALUE str)
{
    return str_new_shared(klass, str);
}

VALUE
rb_str_new_shared(VALUE str)
{
    VALUE str2 = str_new3(rb_obj_class(str), str);

    OBJ_INFECT(str2, str);
    return str2;
}

RUBY_ALIAS_FUNCTION(rb_str_new3(VALUE str), rb_str_new_shared, (str))
#define rb_str_new3 rb_str_new_shared

static VALUE
str_new4(VALUE klass, VALUE str)
{
    VALUE str2;

    str2 = str_alloc(klass);
    STR_SET_NOEMBED(str2);
    RSTRING(str2)->as.heap.len = RSTRING_LEN(str);
    RSTRING(str2)->as.heap.ptr = RSTRING_PTR(str);
    if (STR_SHARED_P(str)) {
	VALUE shared = RSTRING(str)->as.heap.aux.shared;
	assert(OBJ_FROZEN(shared));
	FL_SET(str2, ELTS_SHARED);
	RSTRING(str2)->as.heap.aux.shared = shared;
    }
    else {
	FL_SET(str, ELTS_SHARED);
	RSTRING(str)->as.heap.aux.shared = str2;
    }
    rb_enc_cr_str_exact_copy(str2, str);
    OBJ_INFECT(str2, str);
    return str2;
}

VALUE
rb_str_new_frozen(VALUE orig)
{
    VALUE klass, str;

    if (OBJ_FROZEN(orig)) return orig;
    klass = rb_obj_class(orig);
    if (STR_SHARED_P(orig) && (str = RSTRING(orig)->as.heap.aux.shared)) {
	long ofs;
	assert(OBJ_FROZEN(str));
	ofs = RSTRING_LEN(str) - RSTRING_LEN(orig);
	if ((ofs > 0) || (klass != RBASIC(str)->klass) ||
	    ((RBASIC(str)->flags ^ RBASIC(orig)->flags) & (FL_TAINT|FL_UNTRUSTED)) ||
	    ENCODING_GET(str) != ENCODING_GET(orig)) {
	    str = str_new3(klass, str);
	    RSTRING(str)->as.heap.ptr += ofs;
	    RSTRING(str)->as.heap.len -= ofs;
	    rb_enc_cr_str_exact_copy(str, orig);
	    OBJ_INFECT(str, orig);
	}
    }
    else if (STR_EMBED_P(orig)) {
	str = str_new(klass, RSTRING_PTR(orig), RSTRING_LEN(orig));
	rb_enc_cr_str_exact_copy(str, orig);
	OBJ_INFECT(str, orig);
    }
    else if (STR_ASSOC_P(orig)) {
	VALUE assoc = RSTRING(orig)->as.heap.aux.shared;
	FL_UNSET(orig, STR_ASSOC);
	str = str_new4(klass, orig);
	FL_SET(str, STR_ASSOC);
	RSTRING(str)->as.heap.aux.shared = assoc;
    }
    else {
	str = str_new4(klass, orig);
    }
    OBJ_FREEZE(str);
    return str;
}

RUBY_ALIAS_FUNCTION(rb_str_new4(VALUE orig), rb_str_new_frozen, (orig))
#define rb_str_new4 rb_str_new_frozen

VALUE
rb_str_new_with_class(VALUE obj, const char *ptr, long len)
{
    return str_new(rb_obj_class(obj), ptr, len);
}

RUBY_ALIAS_FUNCTION(rb_str_new5(VALUE obj, const char *ptr, long len),
	   rb_str_new_with_class, (obj, ptr, len))
#define rb_str_new5 rb_str_new_with_class

static VALUE
str_new_empty(VALUE str)
{
    VALUE v = rb_str_new5(str, 0, 0);
    rb_enc_copy(v, str);
    OBJ_INFECT(v, str);
    return v;
}

#define STR_BUF_MIN_SIZE 128

VALUE
rb_str_buf_new(long capa)
{
    VALUE str = str_alloc(rb_cString);

    if (capa < STR_BUF_MIN_SIZE) {
	capa = STR_BUF_MIN_SIZE;
    }
    FL_SET(str, STR_NOEMBED);
    RSTRING(str)->as.heap.aux.capa = capa;
    RSTRING(str)->as.heap.ptr = ALLOC_N(char, capa+1);
    RSTRING(str)->as.heap.ptr[0] = '\0';

    return str;
}

VALUE
rb_str_buf_new_cstr(const char *ptr)
{
    VALUE str;
    long len = strlen(ptr);

    str = rb_str_buf_new(len);
    rb_str_buf_cat(str, ptr, len);

    return str;
}

RUBY_ALIAS_FUNCTION(rb_str_buf_new2(const char *ptr), rb_str_buf_new_cstr, (ptr))
#define rb_str_buf_new2 rb_str_buf_new_cstr

VALUE
rb_str_tmp_new(long len)
{
    return str_new(0, 0, len);
}

void *
rb_alloc_tmp_buffer(volatile VALUE *store, long len)
{
    VALUE s = rb_str_tmp_new(len);
    *store = s;
    return RSTRING_PTR(s);
}

void
rb_free_tmp_buffer(volatile VALUE *store)
{
    VALUE s = *store;
    *store = 0;
    if (s) rb_str_clear(s);
}

void
rb_str_free(VALUE str)
{
    if (!STR_EMBED_P(str) && !STR_SHARED_P(str)) {
	xfree(RSTRING(str)->as.heap.ptr);
    }
}

RUBY_FUNC_EXPORTED size_t
rb_str_memsize(VALUE str)
{
    if (!STR_EMBED_P(str) && !STR_SHARED_P(str)) {
	return RSTRING(str)->as.heap.aux.capa;
    }
    else {
	return 0;
    }
}

VALUE
rb_str_to_str(VALUE str)
{
    return rb_convert_type(str, T_STRING, "String", "to_str");
}

static inline void str_discard(VALUE str);

void
rb_str_shared_replace(VALUE str, VALUE str2)
{
    rb_encoding *enc;
    int cr;
    if (str == str2) return;
    enc = STR_ENC_GET(str2);
    cr = ENC_CODERANGE(str2);
    str_discard(str);
    OBJ_INFECT(str, str2);
    if (RSTRING_LEN(str2) <= RSTRING_EMBED_LEN_MAX) {
	STR_SET_EMBED(str);
	memcpy(RSTRING_PTR(str), RSTRING_PTR(str2), RSTRING_LEN(str2)+1);
	STR_SET_EMBED_LEN(str, RSTRING_LEN(str2));
        rb_enc_associate(str, enc);
        ENC_CODERANGE_SET(str, cr);
	return;
    }
    STR_SET_NOEMBED(str);
    STR_UNSET_NOCAPA(str);
    RSTRING(str)->as.heap.ptr = RSTRING_PTR(str2);
    RSTRING(str)->as.heap.len = RSTRING_LEN(str2);
    if (STR_NOCAPA_P(str2)) {
	FL_SET(str, RBASIC(str2)->flags & STR_NOCAPA);
	RSTRING(str)->as.heap.aux.shared = RSTRING(str2)->as.heap.aux.shared;
    }
    else {
	RSTRING(str)->as.heap.aux.capa = RSTRING(str2)->as.heap.aux.capa;
    }
    STR_SET_EMBED(str2);	/* abandon str2 */
    RSTRING_PTR(str2)[0] = 0;
    STR_SET_EMBED_LEN(str2, 0);
    rb_enc_associate(str, enc);
    ENC_CODERANGE_SET(str, cr);
}

static ID id_to_s;

VALUE
rb_obj_as_string(VALUE obj)
{
    VALUE str;

    if (RB_TYPE_P(obj, T_STRING)) {
	return obj;
    }
    str = rb_funcall(obj, id_to_s, 0);
    if (!RB_TYPE_P(str, T_STRING))
	return rb_any_to_s(obj);
    if (OBJ_TAINTED(obj)) OBJ_TAINT(str);
    return str;
}

static VALUE
str_replace(VALUE str, VALUE str2)
{
    long len;

    len = RSTRING_LEN(str2);
    if (STR_ASSOC_P(str2)) {
	str2 = rb_str_new4(str2);
    }
    if (STR_SHARED_P(str2)) {
	VALUE shared = RSTRING(str2)->as.heap.aux.shared;
	assert(OBJ_FROZEN(shared));
	STR_SET_NOEMBED(str);
	RSTRING(str)->as.heap.len = len;
	RSTRING(str)->as.heap.ptr = RSTRING_PTR(str2);
	FL_SET(str, ELTS_SHARED);
	FL_UNSET(str, STR_ASSOC);
	RSTRING(str)->as.heap.aux.shared = shared;
    }
    else {
	str_replace_shared(str, str2);
    }

    OBJ_INFECT(str, str2);
    rb_enc_cr_str_exact_copy(str, str2);
    return str;
}

static VALUE
str_duplicate(VALUE klass, VALUE str)
{
    VALUE dup = str_alloc(klass);
    str_replace(dup, str);
    return dup;
}

VALUE
rb_str_dup(VALUE str)
{
    return str_duplicate(rb_obj_class(str), str);
}

VALUE
rb_str_resurrect(VALUE str)
{
    if (RUBY_DTRACE_STRING_CREATE_ENABLED()) {
	RUBY_DTRACE_STRING_CREATE(RSTRING_LEN(str),
				  rb_sourcefile(), rb_sourceline());
    }
    return str_replace(str_alloc(rb_cString), str);
}

/*
 *  call-seq:
 *     String.new(str="")   -> new_str
 *
 *  Returns a new string object containing a copy of <i>str</i>.
 */

static VALUE
rb_str_init(int argc, VALUE *argv, VALUE str)
{
    VALUE orig;

    if (argc > 0 && rb_scan_args(argc, argv, "01", &orig) == 1)
	rb_str_replace(str, orig);
    return str;
}

static inline long
enc_strlen(const char *p, const char *e, rb_encoding *enc, int cr)
{
    long c;
    const char *q;

    if (rb_enc_mbmaxlen(enc) == rb_enc_mbminlen(enc)) {
        return (e - p + rb_enc_mbminlen(enc) - 1) / rb_enc_mbminlen(enc);
    }
    else if (rb_enc_asciicompat(enc)) {
        c = 0;
	if (cr == ENC_CODERANGE_7BIT || cr == ENC_CODERANGE_VALID) {
	    while (p < e) {
		if (ISASCII(*p)) {
		    q = search_nonascii(p, e);
		    if (!q)
			return c + (e - p);
		    c += q - p;
		    p = q;
		}
		p += rb_enc_fast_mbclen(p, e, enc);
		c++;
	    }
	}
	else {
	    while (p < e) {
		if (ISASCII(*p)) {
		    q = search_nonascii(p, e);
		    if (!q)
			return c + (e - p);
		    c += q - p;
		    p = q;
		}
		p += rb_enc_mbclen(p, e, enc);
		c++;
	    }
	}
        return c;
    }

    for (c=0; p<e; c++) {
        p += rb_enc_mbclen(p, e, enc);
    }
    return c;
}

long
rb_enc_strlen(const char *p, const char *e, rb_encoding *enc)
{
    return enc_strlen(p, e, enc, ENC_CODERANGE_UNKNOWN);
}

long
rb_enc_strlen_cr(const char *p, const char *e, rb_encoding *enc, int *cr)
{
    long c;
    const char *q;
    int ret;

    *cr = 0;
    if (rb_enc_mbmaxlen(enc) == rb_enc_mbminlen(enc)) {
	return (e - p + rb_enc_mbminlen(enc) - 1) / rb_enc_mbminlen(enc);
    }
    else if (rb_enc_asciicompat(enc)) {
	c = 0;
	while (p < e) {
	    if (ISASCII(*p)) {
		q = search_nonascii(p, e);
		if (!q) {
		    if (!*cr) *cr = ENC_CODERANGE_7BIT;
		    return c + (e - p);
		}
		c += q - p;
		p = q;
	    }
	    ret = rb_enc_precise_mbclen(p, e, enc);
	    if (MBCLEN_CHARFOUND_P(ret)) {
		*cr |= ENC_CODERANGE_VALID;
		p += MBCLEN_CHARFOUND_LEN(ret);
	    }
	    else {
		*cr = ENC_CODERANGE_BROKEN;
		p++;
	    }
	    c++;
	}
	if (!*cr) *cr = ENC_CODERANGE_7BIT;
	return c;
    }

    for (c=0; p<e; c++) {
	ret = rb_enc_precise_mbclen(p, e, enc);
	if (MBCLEN_CHARFOUND_P(ret)) {
	    *cr |= ENC_CODERANGE_VALID;
	    p += MBCLEN_CHARFOUND_LEN(ret);
	}
	else {
	    *cr = ENC_CODERANGE_BROKEN;
            if (p + rb_enc_mbminlen(enc) <= e)
                p += rb_enc_mbminlen(enc);
            else
                p = e;
	}
    }
    if (!*cr) *cr = ENC_CODERANGE_7BIT;
    return c;
}

#ifdef NONASCII_MASK
#define is_utf8_lead_byte(c) (((c)&0xC0) != 0x80)

/*
 * UTF-8 leading bytes have either 0xxxxxxx or 11xxxxxx
 * bit represention. (see http://en.wikipedia.org/wiki/UTF-8)
 * Therefore, following pseudo code can detect UTF-8 leading byte.
 *
 * if (!(byte & 0x80))
 *   byte |= 0x40;          // turn on bit6
 * return ((byte>>6) & 1);  // bit6 represent it's leading byte or not.
 *
 * This function calculate every bytes in the argument word `s'
 * using the above logic concurrently. and gather every bytes result.
 */
static inline VALUE
count_utf8_lead_bytes_with_word(const VALUE *s)
{
    VALUE d = *s;

    /* Transform into bit0 represent UTF-8 leading or not. */
    d |= ~(d>>1);
    d >>= 6;
    d &= NONASCII_MASK >> 7;

    /* Gather every bytes. */
    d += (d>>8);
    d += (d>>16);
#if SIZEOF_VALUE == 8
    d += (d>>32);
#endif
    return (d&0xF);
}
#endif

static long
str_strlen(VALUE str, rb_encoding *enc)
{
    const char *p, *e;
    long n;
    int cr;

    if (single_byte_optimizable(str)) return RSTRING_LEN(str);
    if (!enc) enc = STR_ENC_GET(str);
    p = RSTRING_PTR(str);
    e = RSTRING_END(str);
    cr = ENC_CODERANGE(str);
#ifdef NONASCII_MASK
    if (ENC_CODERANGE(str) == ENC_CODERANGE_VALID &&
        enc == rb_utf8_encoding()) {

	VALUE len = 0;
	if ((int)sizeof(VALUE) * 2 < e - p) {
	    const VALUE *s, *t;
	    const VALUE lowbits = sizeof(VALUE) - 1;
	    s = (const VALUE*)(~lowbits & ((VALUE)p + lowbits));
	    t = (const VALUE*)(~lowbits & (VALUE)e);
	    while (p < (const char *)s) {
		if (is_utf8_lead_byte(*p)) len++;
		p++;
	    }
	    while (s < t) {
		len += count_utf8_lead_bytes_with_word(s);
		s++;
	    }
	    p = (const char *)s;
	}
	while (p < e) {
	    if (is_utf8_lead_byte(*p)) len++;
	    p++;
	}
	return (long)len;
    }
#endif
    n = rb_enc_strlen_cr(p, e, enc, &cr);
    if (cr) {
        ENC_CODERANGE_SET(str, cr);
    }
    return n;
}

long
rb_str_strlen(VALUE str)
{
    return str_strlen(str, STR_ENC_GET(str));
}

/*
 *  call-seq:
 *     str.length   -> integer
 *     str.size     -> integer
 *
 *  Returns the character length of <i>str</i>.
 */

VALUE
rb_str_length(VALUE str)
{
    long len;

    len = str_strlen(str, STR_ENC_GET(str));
    return LONG2NUM(len);
}

/*
 *  call-seq:
 *     str.bytesize  -> integer
 *
 *  Returns the length of +str+ in bytes.
 *
 *    "\x80\u3042".bytesize  #=> 4
 *    "hello".bytesize       #=> 5
 */

static VALUE
rb_str_bytesize(VALUE str)
{
    return LONG2NUM(RSTRING_LEN(str));
}

/*
 *  call-seq:
 *     str.empty?   -> true or false
 *
 *  Returns <code>true</code> if <i>str</i> has a length of zero.
 *
 *     "hello".empty?   #=> false
 *     " ".empty?       #=> false
 *     "".empty?        #=> true
 */

static VALUE
rb_str_empty(VALUE str)
{
    if (RSTRING_LEN(str) == 0)
	return Qtrue;
    return Qfalse;
}

/*
 *  call-seq:
 *     str + other_str   -> new_str
 *
 *  Concatenation---Returns a new <code>String</code> containing
 *  <i>other_str</i> concatenated to <i>str</i>.
 *
 *     "Hello from " + self.to_s   #=> "Hello from main"
 */

VALUE
rb_str_plus(VALUE str1, VALUE str2)
{
    VALUE str3;
    rb_encoding *enc;

    StringValue(str2);
    enc = rb_enc_check(str1, str2);
    str3 = rb_str_new(0, RSTRING_LEN(str1)+RSTRING_LEN(str2));
    memcpy(RSTRING_PTR(str3), RSTRING_PTR(str1), RSTRING_LEN(str1));
    memcpy(RSTRING_PTR(str3) + RSTRING_LEN(str1),
	   RSTRING_PTR(str2), RSTRING_LEN(str2));
    RSTRING_PTR(str3)[RSTRING_LEN(str3)] = '\0';

    if (OBJ_TAINTED(str1) || OBJ_TAINTED(str2))
	OBJ_TAINT(str3);
    ENCODING_CODERANGE_SET(str3, rb_enc_to_index(enc),
			   ENC_CODERANGE_AND(ENC_CODERANGE(str1), ENC_CODERANGE(str2)));
    return str3;
}

/*
 *  call-seq:
 *     str * integer   -> new_str
 *
 *  Copy --- Returns a new String containing +integer+ copies of the receiver.
 *  +integer+ must be greater than or equal to 0.
 *
 *     "Ho! " * 3   #=> "Ho! Ho! Ho! "
 *     "Ho! " * 0   #=> ""
 */

VALUE
rb_str_times(VALUE str, VALUE times)
{
    VALUE str2;
    long n, len;
    char *ptr2;

    len = NUM2LONG(times);
    if (len < 0) {
	rb_raise(rb_eArgError, "negative argument");
    }
    if (len && LONG_MAX/len <  RSTRING_LEN(str)) {
	rb_raise(rb_eArgError, "argument too big");
    }

    str2 = rb_str_new5(str, 0, len *= RSTRING_LEN(str));
    ptr2 = RSTRING_PTR(str2);
    if (len) {
        n = RSTRING_LEN(str);
        memcpy(ptr2, RSTRING_PTR(str), n);
        while (n <= len/2) {
            memcpy(ptr2 + n, ptr2, n);
            n *= 2;
        }
        memcpy(ptr2 + n, ptr2, len-n);
    }
    ptr2[RSTRING_LEN(str2)] = '\0';
    OBJ_INFECT(str2, str);
    rb_enc_cr_str_copy_for_substr(str2, str);

    return str2;
}

/*
 *  call-seq:
 *     str % arg   -> new_str
 *
 *  Format---Uses <i>str</i> as a format specification, and returns the result
 *  of applying it to <i>arg</i>. If the format specification contains more than
 *  one substitution, then <i>arg</i> must be an <code>Array</code> or <code>Hash</code>
 *  containing the values to be substituted. See <code>Kernel::sprintf</code> for
 *  details of the format string.
 *
 *     "%05d" % 123                              #=> "00123"
 *     "%-5s: %08x" % [ "ID", self.object_id ]   #=> "ID   : 200e14d6"
 *     "foo = %{foo}" % { :foo => 'bar' }        #=> "foo = bar"
 */

static VALUE
rb_str_format_m(VALUE str, VALUE arg)
{
    volatile VALUE tmp = rb_check_array_type(arg);

    if (!NIL_P(tmp)) {
	return rb_str_format(RARRAY_LENINT(tmp), RARRAY_PTR(tmp), str);
    }
    return rb_str_format(1, &arg, str);
}

static inline void
str_modifiable(VALUE str)
{
    if (FL_TEST(str, STR_TMPLOCK)) {
	rb_raise(rb_eRuntimeError, "can't modify string; temporarily locked");
    }
    rb_check_frozen(str);
    if (!OBJ_UNTRUSTED(str) && rb_safe_level() >= 4)
	rb_raise(rb_eSecurityError, "Insecure: can't modify string");
}

static inline int
str_independent(VALUE str)
{
    str_modifiable(str);
    if (!STR_SHARED_P(str)) return 1;
    if (STR_EMBED_P(str)) return 1;
    return 0;
}

static void
str_make_independent_expand(VALUE str, long expand)
{
    char *ptr;
    long len = RSTRING_LEN(str);
    long capa = len + expand;

    if (len > capa) len = capa;
    ptr = ALLOC_N(char, capa + 1);
    if (RSTRING_PTR(str)) {
	memcpy(ptr, RSTRING_PTR(str), len);
    }
    STR_SET_NOEMBED(str);
    STR_UNSET_NOCAPA(str);
    ptr[len] = 0;
    RSTRING(str)->as.heap.ptr = ptr;
    RSTRING(str)->as.heap.len = len;
    RSTRING(str)->as.heap.aux.capa = capa;
}

#define str_make_independent(str) str_make_independent_expand((str), 0L)

void
rb_str_modify(VALUE str)
{
    if (!str_independent(str))
	str_make_independent(str);
    ENC_CODERANGE_CLEAR(str);
}

void
rb_str_modify_expand(VALUE str, long expand)
{
    if (expand < 0) {
	rb_raise(rb_eArgError, "negative expanding string size");
    }
    if (!str_independent(str)) {
	str_make_independent_expand(str, expand);
    }
    else if (expand > 0) {
	long len = RSTRING_LEN(str);
	long capa = len + expand;
	if (!STR_EMBED_P(str)) {
	    REALLOC_N(RSTRING(str)->as.heap.ptr, char, capa+1);
	    RSTRING(str)->as.heap.aux.capa = capa;
	}
	else if (capa > RSTRING_EMBED_LEN_MAX) {
	    str_make_independent_expand(str, expand);
	}
    }
    ENC_CODERANGE_CLEAR(str);
}

/* As rb_str_modify(), but don't clear coderange */
static void
str_modify_keep_cr(VALUE str)
{
    if (!str_independent(str))
	str_make_independent(str);
    if (ENC_CODERANGE(str) == ENC_CODERANGE_BROKEN)
	/* Force re-scan later */
	ENC_CODERANGE_CLEAR(str);
}

static inline void
str_discard(VALUE str)
{
    str_modifiable(str);
    if (!STR_SHARED_P(str) && !STR_EMBED_P(str)) {
	xfree(RSTRING_PTR(str));
	RSTRING(str)->as.heap.ptr = 0;
	RSTRING(str)->as.heap.len = 0;
    }
}

void
rb_str_associate(VALUE str, VALUE add)
{
    /* sanity check */
    rb_check_frozen(str);
    if (STR_ASSOC_P(str)) {
	/* already associated */
	rb_ary_concat(RSTRING(str)->as.heap.aux.shared, add);
    }
    else {
	if (STR_SHARED_P(str)) {
	    VALUE assoc = RSTRING(str)->as.heap.aux.shared;
	    str_make_independent(str);
	    if (STR_ASSOC_P(assoc)) {
		assoc = RSTRING(assoc)->as.heap.aux.shared;
		rb_ary_concat(assoc, add);
		add = assoc;
	    }
	}
	else if (STR_EMBED_P(str)) {
	    str_make_independent(str);
	}
	else if (RSTRING(str)->as.heap.aux.capa != RSTRING_LEN(str)) {
	    RESIZE_CAPA(str, RSTRING_LEN(str));
	}
	FL_SET(str, STR_ASSOC);
	RBASIC(add)->klass = 0;
	RSTRING(str)->as.heap.aux.shared = add;
    }
}

VALUE
rb_str_associated(VALUE str)
{
    if (STR_SHARED_P(str)) str = RSTRING(str)->as.heap.aux.shared;
    if (STR_ASSOC_P(str)) {
	return RSTRING(str)->as.heap.aux.shared;
    }
    return Qfalse;
}

void
rb_must_asciicompat(VALUE str)
{
    rb_encoding *enc = rb_enc_get(str);
    if (!rb_enc_asciicompat(enc)) {
	rb_raise(rb_eEncCompatError, "ASCII incompatible encoding: %s", rb_enc_name(enc));
    }
}

VALUE
rb_string_value(volatile VALUE *ptr)
{
    VALUE s = *ptr;
    if (!RB_TYPE_P(s, T_STRING)) {
	s = rb_str_to_str(s);
	*ptr = s;
    }
    return s;
}

char *
rb_string_value_ptr(volatile VALUE *ptr)
{
    VALUE str = rb_string_value(ptr);
    return RSTRING_PTR(str);
}

char *
rb_string_value_cstr(volatile VALUE *ptr)
{
    VALUE str = rb_string_value(ptr);
    char *s = RSTRING_PTR(str);
    long len = RSTRING_LEN(str);

    if (!s || memchr(s, 0, len)) {
	rb_raise(rb_eArgError, "string contains null byte");
    }
    if (s[len]) {
	rb_str_modify(str);
	s = RSTRING_PTR(str);
	s[RSTRING_LEN(str)] = 0;
    }
    return s;
}

VALUE
rb_check_string_type(VALUE str)
{
    str = rb_check_convert_type(str, T_STRING, "String", "to_str");
    return str;
}

/*
 *  call-seq:
 *     String.try_convert(obj) -> string or nil
 *
 *  Try to convert <i>obj</i> into a String, using to_str method.
 *  Returns converted string or nil if <i>obj</i> cannot be converted
 *  for any reason.
 *
 *     String.try_convert("str")     #=> "str"
 *     String.try_convert(/re/)      #=> nil
 */
static VALUE
rb_str_s_try_convert(VALUE dummy, VALUE str)
{
    return rb_check_string_type(str);
}

static char*
str_nth_len(const char *p, const char *e, long *nthp, rb_encoding *enc)
{
    long nth = *nthp;
    if (rb_enc_mbmaxlen(enc) == 1) {
        p += nth;
    }
    else if (rb_enc_mbmaxlen(enc) == rb_enc_mbminlen(enc)) {
        p += nth * rb_enc_mbmaxlen(enc);
    }
    else if (rb_enc_asciicompat(enc)) {
        const char *p2, *e2;
        int n;

        while (p < e && 0 < nth) {
            e2 = p + nth;
            if (e < e2) {
                *nthp = nth;
                return (char *)e;
            }
            if (ISASCII(*p)) {
                p2 = search_nonascii(p, e2);
                if (!p2) {
		    nth -= e2 - p;
		    *nthp = nth;
                    return (char *)e2;
                }
                nth -= p2 - p;
                p = p2;
            }
            n = rb_enc_mbclen(p, e, enc);
            p += n;
            nth--;
        }
        *nthp = nth;
        if (nth != 0) {
            return (char *)e;
        }
        return (char *)p;
    }
    else {
        while (p < e && nth--) {
            p += rb_enc_mbclen(p, e, enc);
        }
    }
    if (p > e) p = e;
    *nthp = nth;
    return (char*)p;
}

char*
rb_enc_nth(const char *p, const char *e, long nth, rb_encoding *enc)
{
    return str_nth_len(p, e, &nth, enc);
}

static char*
str_nth(const char *p, const char *e, long nth, rb_encoding *enc, int singlebyte)
{
    if (singlebyte)
	p += nth;
    else {
	p = str_nth_len(p, e, &nth, enc);
    }
    if (!p) return 0;
    if (p > e) p = e;
    return (char *)p;
}

/* char offset to byte offset */
static long
str_offset(const char *p, const char *e, long nth, rb_encoding *enc, int singlebyte)
{
    const char *pp = str_nth(p, e, nth, enc, singlebyte);
    if (!pp) return e - p;
    return pp - p;
}

long
rb_str_offset(VALUE str, long pos)
{
    return str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
		      STR_ENC_GET(str), single_byte_optimizable(str));
}

#ifdef NONASCII_MASK
static char *
str_utf8_nth(const char *p, const char *e, long *nthp)
{
    long nth = *nthp;
    if ((int)SIZEOF_VALUE * 2 < e - p && (int)SIZEOF_VALUE * 2 < nth) {
	const VALUE *s, *t;
	const VALUE lowbits = sizeof(VALUE) - 1;
	s = (const VALUE*)(~lowbits & ((VALUE)p + lowbits));
	t = (const VALUE*)(~lowbits & (VALUE)e);
	while (p < (const char *)s) {
	    if (is_utf8_lead_byte(*p)) nth--;
	    p++;
	}
	do {
	    nth -= count_utf8_lead_bytes_with_word(s);
	    s++;
	} while (s < t && (int)sizeof(VALUE) <= nth);
	p = (char *)s;
    }
    while (p < e) {
	if (is_utf8_lead_byte(*p)) {
	    if (nth == 0) break;
	    nth--;
	}
	p++;
    }
    *nthp = nth;
    return (char *)p;
}

static long
str_utf8_offset(const char *p, const char *e, long nth)
{
    const char *pp = str_utf8_nth(p, e, &nth);
    return pp - p;
}
#endif

/* byte offset to char offset */
long
rb_str_sublen(VALUE str, long pos)
{
    if (single_byte_optimizable(str) || pos < 0)
        return pos;
    else {
	char *p = RSTRING_PTR(str);
        return enc_strlen(p, p + pos, STR_ENC_GET(str), ENC_CODERANGE(str));
    }
}

VALUE
rb_str_subseq(VALUE str, long beg, long len)
{
    VALUE str2;

    if (RSTRING_LEN(str) == beg + len &&
        RSTRING_EMBED_LEN_MAX < len) {
        str2 = rb_str_new_shared(rb_str_new_frozen(str));
        rb_str_drop_bytes(str2, beg);
    }
    else {
        str2 = rb_str_new5(str, RSTRING_PTR(str)+beg, len);
	RB_GC_GUARD(str);
    }

    rb_enc_cr_str_copy_for_substr(str2, str);
    OBJ_INFECT(str2, str);

    return str2;
}

static char *
rb_str_subpos(VALUE str, long beg, long *lenp)
{
    long len = *lenp;
    long slen = -1L;
    long blen = RSTRING_LEN(str);
    rb_encoding *enc = STR_ENC_GET(str);
    char *p, *s = RSTRING_PTR(str), *e = s + blen;

    if (len < 0) return 0;
    if (!blen) {
	len = 0;
    }
    if (single_byte_optimizable(str)) {
	if (beg > blen) return 0;
	if (beg < 0) {
	    beg += blen;
	    if (beg < 0) return 0;
	}
	if (beg + len > blen)
	    len = blen - beg;
	if (len < 0) return 0;
	p = s + beg;
	goto end;
    }
    if (beg < 0) {
	if (len > -beg) len = -beg;
	if (-beg * rb_enc_mbmaxlen(enc) < RSTRING_LEN(str) / 8) {
	    beg = -beg;
	    while (beg-- > len && (e = rb_enc_prev_char(s, e, e, enc)) != 0);
	    p = e;
	    if (!p) return 0;
	    while (len-- > 0 && (p = rb_enc_prev_char(s, p, e, enc)) != 0);
	    if (!p) return 0;
	    len = e - p;
	    goto end;
	}
	else {
	    slen = str_strlen(str, enc);
	    beg += slen;
	    if (beg < 0) return 0;
	    p = s + beg;
	    if (len == 0) goto end;
	}
    }
    else if (beg > 0 && beg > RSTRING_LEN(str)) {
	return 0;
    }
    if (len == 0) {
	if (beg > str_strlen(str, enc)) return 0;
	p = s + beg;
    }
#ifdef NONASCII_MASK
    else if (ENC_CODERANGE(str) == ENC_CODERANGE_VALID &&
        enc == rb_utf8_encoding()) {
        p = str_utf8_nth(s, e, &beg);
        if (beg > 0) return 0;
        len = str_utf8_offset(p, e, len);
    }
#endif
    else if (rb_enc_mbmaxlen(enc) == rb_enc_mbminlen(enc)) {
	int char_sz = rb_enc_mbmaxlen(enc);

	p = s + beg * char_sz;
	if (p > e) {
	    return 0;
	}
        else if (len * char_sz > e - p)
            len = e - p;
        else
	    len *= char_sz;
    }
    else if ((p = str_nth_len(s, e, &beg, enc)) == e) {
	if (beg > 0) return 0;
	len = 0;
    }
    else {
	len = str_offset(p, e, len, enc, 0);
    }
  end:
    *lenp = len;
    RB_GC_GUARD(str);
    return p;
}

VALUE
rb_str_substr(VALUE str, long beg, long len)
{
    VALUE str2;
    char *p = rb_str_subpos(str, beg, &len);

    if (!p) return Qnil;
    if (len > RSTRING_EMBED_LEN_MAX && p + len == RSTRING_END(str)) {
	str2 = rb_str_new4(str);
	str2 = str_new3(rb_obj_class(str2), str2);
	RSTRING(str2)->as.heap.ptr += RSTRING(str2)->as.heap.len - len;
	RSTRING(str2)->as.heap.len = len;
    }
    else {
	str2 = rb_str_new5(str, p, len);
	rb_enc_cr_str_copy_for_substr(str2, str);
	OBJ_INFECT(str2, str);
	RB_GC_GUARD(str);
    }

    return str2;
}

VALUE
rb_str_freeze(VALUE str)
{
    if (STR_ASSOC_P(str)) {
	VALUE ary = RSTRING(str)->as.heap.aux.shared;
	OBJ_FREEZE(ary);
    }
    return rb_obj_freeze(str);
}

RUBY_ALIAS_FUNCTION(rb_str_dup_frozen(VALUE str), rb_str_new_frozen, (str))
#define rb_str_dup_frozen rb_str_new_frozen

VALUE
rb_str_locktmp(VALUE str)
{
    if (FL_TEST(str, STR_TMPLOCK)) {
	rb_raise(rb_eRuntimeError, "temporal locking already locked string");
    }
    FL_SET(str, STR_TMPLOCK);
    return str;
}

VALUE
rb_str_unlocktmp(VALUE str)
{
    if (!FL_TEST(str, STR_TMPLOCK)) {
	rb_raise(rb_eRuntimeError, "temporal unlocking already unlocked string");
    }
    FL_UNSET(str, STR_TMPLOCK);
    return str;
}

void
rb_str_set_len(VALUE str, long len)
{
    long capa;

    str_modifiable(str);
    if (STR_SHARED_P(str)) {
	rb_raise(rb_eRuntimeError, "can't set length of shared string");
    }
    if (len > (capa = (long)rb_str_capacity(str))) {
	rb_bug("probable buffer overflow: %ld for %ld", len, capa);
    }
    STR_SET_LEN(str, len);
    RSTRING_PTR(str)[len] = '\0';
}

VALUE
rb_str_resize(VALUE str, long len)
{
    long slen;
    int independent;

    if (len < 0) {
	rb_raise(rb_eArgError, "negative string size (or size too big)");
    }

    independent = str_independent(str);
    ENC_CODERANGE_CLEAR(str);
    slen = RSTRING_LEN(str);
    if (len != slen) {
	if (STR_EMBED_P(str)) {
	    if (len <= RSTRING_EMBED_LEN_MAX) {
		STR_SET_EMBED_LEN(str, len);
		RSTRING(str)->as.ary[len] = '\0';
		return str;
	    }
	    str_make_independent_expand(str, len - slen);
	    STR_SET_NOEMBED(str);
	}
	else if (len <= RSTRING_EMBED_LEN_MAX) {
	    char *ptr = RSTRING(str)->as.heap.ptr;
	    STR_SET_EMBED(str);
	    if (slen > len) slen = len;
	    if (slen > 0) MEMCPY(RSTRING(str)->as.ary, ptr, char, slen);
	    RSTRING(str)->as.ary[len] = '\0';
	    STR_SET_EMBED_LEN(str, len);
	    if (independent) xfree(ptr);
	    return str;
	}
	else if (!independent) {
	    str_make_independent_expand(str, len - slen);
	}
	else if (slen < len || slen - len > 1024) {
	    REALLOC_N(RSTRING(str)->as.heap.ptr, char, len+1);
	}
	if (!STR_NOCAPA_P(str)) {
	    RSTRING(str)->as.heap.aux.capa = len;
	}
	RSTRING(str)->as.heap.len = len;
	RSTRING(str)->as.heap.ptr[len] = '\0';	/* sentinel */
    }
    return str;
}

static VALUE
str_buf_cat(VALUE str, const char *ptr, long len)
{
    long capa, total, off = -1;

    if (ptr >= RSTRING_PTR(str) && ptr <= RSTRING_END(str)) {
        off = ptr - RSTRING_PTR(str);
    }
    rb_str_modify(str);
    if (len == 0) return 0;
    if (STR_ASSOC_P(str)) {
	FL_UNSET(str, STR_ASSOC);
	capa = RSTRING(str)->as.heap.aux.capa = RSTRING_LEN(str);
    }
    else if (STR_EMBED_P(str)) {
	capa = RSTRING_EMBED_LEN_MAX;
    }
    else {
	capa = RSTRING(str)->as.heap.aux.capa;
    }
    if (RSTRING_LEN(str) >= LONG_MAX - len) {
	rb_raise(rb_eArgError, "string sizes too big");
    }
    total = RSTRING_LEN(str)+len;
    if (capa <= total) {
	while (total > capa) {
	    if (capa + 1 >= LONG_MAX / 2) {
		capa = (total + 4095) / 4096;
		break;
	    }
	    capa = (capa + 1) * 2;
	}
	RESIZE_CAPA(str, capa);
    }
    if (off != -1) {
        ptr = RSTRING_PTR(str) + off;
    }
    memcpy(RSTRING_PTR(str) + RSTRING_LEN(str), ptr, len);
    STR_SET_LEN(str, total);
    RSTRING_PTR(str)[total] = '\0'; /* sentinel */

    return str;
}

#define str_buf_cat2(str, ptr) str_buf_cat((str), (ptr), strlen(ptr))

VALUE
rb_str_buf_cat(VALUE str, const char *ptr, long len)
{
    if (len == 0) return str;
    if (len < 0) {
	rb_raise(rb_eArgError, "negative string size (or size too big)");
    }
    return str_buf_cat(str, ptr, len);
}

VALUE
rb_str_buf_cat2(VALUE str, const char *ptr)
{
    return rb_str_buf_cat(str, ptr, strlen(ptr));
}

VALUE
rb_str_cat(VALUE str, const char *ptr, long len)
{
    if (len < 0) {
	rb_raise(rb_eArgError, "negative string size (or size too big)");
    }
    if (STR_ASSOC_P(str)) {
	char *p;
	rb_str_modify_expand(str, len);
	p = RSTRING(str)->as.heap.ptr;
	memcpy(p + RSTRING(str)->as.heap.len, ptr, len);
	len = RSTRING(str)->as.heap.len += len;
	p[len] = '\0'; /* sentinel */
	return str;
    }

    return rb_str_buf_cat(str, ptr, len);
}

VALUE
rb_str_cat2(VALUE str, const char *ptr)
{
    return rb_str_cat(str, ptr, strlen(ptr));
}

static VALUE
rb_enc_cr_str_buf_cat(VALUE str, const char *ptr, long len,
    int ptr_encindex, int ptr_cr, int *ptr_cr_ret)
{
    int str_encindex = ENCODING_GET(str);
    int res_encindex;
    int str_cr, res_cr;

    str_cr = ENC_CODERANGE(str);

    if (str_encindex == ptr_encindex) {
        if (str_cr == ENC_CODERANGE_UNKNOWN)
            ptr_cr = ENC_CODERANGE_UNKNOWN;
        else if (ptr_cr == ENC_CODERANGE_UNKNOWN) {
            ptr_cr = coderange_scan(ptr, len, rb_enc_from_index(ptr_encindex));
        }
    }
    else {
        rb_encoding *str_enc = rb_enc_from_index(str_encindex);
        rb_encoding *ptr_enc = rb_enc_from_index(ptr_encindex);
        if (!rb_enc_asciicompat(str_enc) || !rb_enc_asciicompat(ptr_enc)) {
            if (len == 0)
                return str;
            if (RSTRING_LEN(str) == 0) {
                rb_str_buf_cat(str, ptr, len);
                ENCODING_CODERANGE_SET(str, ptr_encindex, ptr_cr);
                return str;
            }
            goto incompatible;
        }
	if (ptr_cr == ENC_CODERANGE_UNKNOWN) {
	    ptr_cr = coderange_scan(ptr, len, ptr_enc);
	}
        if (str_cr == ENC_CODERANGE_UNKNOWN) {
            if (ENCODING_IS_ASCII8BIT(str) || ptr_cr != ENC_CODERANGE_7BIT) {
                str_cr = rb_enc_str_coderange(str);
            }
        }
    }
    if (ptr_cr_ret)
        *ptr_cr_ret = ptr_cr;

    if (str_encindex != ptr_encindex &&
        str_cr != ENC_CODERANGE_7BIT &&
        ptr_cr != ENC_CODERANGE_7BIT) {
      incompatible:
        rb_raise(rb_eEncCompatError, "incompatible character encodings: %s and %s",
            rb_enc_name(rb_enc_from_index(str_encindex)),
            rb_enc_name(rb_enc_from_index(ptr_encindex)));
    }

    if (str_cr == ENC_CODERANGE_UNKNOWN) {
        res_encindex = str_encindex;
        res_cr = ENC_CODERANGE_UNKNOWN;
    }
    else if (str_cr == ENC_CODERANGE_7BIT) {
        if (ptr_cr == ENC_CODERANGE_7BIT) {
            res_encindex = str_encindex;
            res_cr = ENC_CODERANGE_7BIT;
        }
        else {
            res_encindex = ptr_encindex;
            res_cr = ptr_cr;
        }
    }
    else if (str_cr == ENC_CODERANGE_VALID) {
        res_encindex = str_encindex;
	if (ptr_cr == ENC_CODERANGE_7BIT || ptr_cr == ENC_CODERANGE_VALID)
	    res_cr = str_cr;
	else
	    res_cr = ptr_cr;
    }
    else { /* str_cr == ENC_CODERANGE_BROKEN */
        res_encindex = str_encindex;
        res_cr = str_cr;
        if (0 < len) res_cr = ENC_CODERANGE_UNKNOWN;
    }

    if (len < 0) {
	rb_raise(rb_eArgError, "negative string size (or size too big)");
    }
    str_buf_cat(str, ptr, len);
    ENCODING_CODERANGE_SET(str, res_encindex, res_cr);
    return str;
}

VALUE
rb_enc_str_buf_cat(VALUE str, const char *ptr, long len, rb_encoding *ptr_enc)
{
    return rb_enc_cr_str_buf_cat(str, ptr, len,
        rb_enc_to_index(ptr_enc), ENC_CODERANGE_UNKNOWN, NULL);
}

VALUE
rb_str_buf_cat_ascii(VALUE str, const char *ptr)
{
    /* ptr must reference NUL terminated ASCII string. */
    int encindex = ENCODING_GET(str);
    rb_encoding *enc = rb_enc_from_index(encindex);
    if (rb_enc_asciicompat(enc)) {
        return rb_enc_cr_str_buf_cat(str, ptr, strlen(ptr),
            encindex, ENC_CODERANGE_7BIT, 0);
    }
    else {
        char *buf = ALLOCA_N(char, rb_enc_mbmaxlen(enc));
        while (*ptr) {
            unsigned int c = (unsigned char)*ptr;
            int len = rb_enc_codelen(c, enc);
            rb_enc_mbcput(c, buf, enc);
            rb_enc_cr_str_buf_cat(str, buf, len,
                encindex, ENC_CODERANGE_VALID, 0);
            ptr++;
        }
        return str;
    }
}

VALUE
rb_str_buf_append(VALUE str, VALUE str2)
{
    int str2_cr;

    str2_cr = ENC_CODERANGE(str2);

    rb_enc_cr_str_buf_cat(str, RSTRING_PTR(str2), RSTRING_LEN(str2),
        ENCODING_GET(str2), str2_cr, &str2_cr);

    OBJ_INFECT(str, str2);
    ENC_CODERANGE_SET(str2, str2_cr);

    return str;
}

VALUE
rb_str_append(VALUE str, VALUE str2)
{
    rb_encoding *enc;
    int cr, cr2;
    long len2;

    StringValue(str2);
    if ((len2 = RSTRING_LEN(str2)) > 0 && STR_ASSOC_P(str)) {
        long len = RSTRING_LEN(str) + len2;
        enc = rb_enc_check(str, str2);
        cr = ENC_CODERANGE(str);
        if ((cr2 = ENC_CODERANGE(str2)) > cr) cr = cr2;
        rb_str_modify_expand(str, len2);
        memcpy(RSTRING(str)->as.heap.ptr + RSTRING(str)->as.heap.len,
               RSTRING_PTR(str2), len2+1);
        RSTRING(str)->as.heap.len = len;
        rb_enc_associate(str, enc);
        ENC_CODERANGE_SET(str, cr);
        OBJ_INFECT(str, str2);
        return str;
    }
    return rb_str_buf_append(str, str2);
}

/*
 *  call-seq:
 *     str << integer       -> str
 *     str.concat(integer)  -> str
 *     str << obj           -> str
 *     str.concat(obj)      -> str
 *
 *  Append---Concatenates the given object to <i>str</i>. If the object is a
 *  <code>Integer</code>, it is considered as a codepoint,…