#define PERL_NO_GET_CONTEXT
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#ifdef PERLIO_LAYERS

#include "perliol.h"

static const char code_point_warning[] =
 "Strings with code points over 0xFF may not be mapped into in-memory file handles\n";

typedef struct {
    struct _PerlIO base;	/* Base "class" info */
    SV *var;
    Off_t posn;
} PerlIOScalar;

IV
PerlIOScalar_eof(pTHX_ PerlIO * f)
{
    if (PerlIOBase(f)->flags & PERLIO_F_CANREAD) {
        PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
        STRLEN len;
        (void)SvPV(s->var, len);
        return len - (STRLEN)(s->posn) <= 0;
    }
    return 1;
}

static IV
PerlIOScalar_pushed(pTHX_ PerlIO * f, const char *mode, SV * arg,
		    PerlIO_funcs * tab)
{
    IV code;
    PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
    /* If called (normally) via open() then arg is ref to scalar we are
     * using, otherwise arg (from binmode presumably) is either NULL
     * or the _name_ of the scalar
     */
    if (arg && SvOK(arg)) {
	if (SvROK(arg)) {
	    if (SvREADONLY(SvRV(arg)) && !SvIsCOW(SvRV(arg))
	     && mode && *mode != 'r') {
		if (ckWARN(WARN_LAYER))
		    Perl_warner(aTHX_ packWARN(WARN_LAYER), "%s", PL_no_modify);
		SETERRNO(EINVAL, SS_IVCHAN);
		return -1;
	    }
	    s->var = SvREFCNT_inc(SvRV(arg));
	    SvGETMAGIC(s->var);
	    if (!SvPOK(s->var) && SvOK(s->var))
		(void)SvPV_nomg_const_nolen(s->var);
	}
	else {
	    s->var =
		SvREFCNT_inc(perl_get_sv
			     (SvPV_nolen(arg), GV_ADD | GV_ADDMULTI));
	}
    }
    else {
	s->var = newSVpvs("");
    }
    SvUPGRADE(s->var, SVt_PV);

    code = PerlIOBase_pushed(aTHX_ f, mode, Nullsv, tab);
    if (!SvOK(s->var) || (PerlIOBase(f)->flags) & PERLIO_F_TRUNCATE)
    {
	sv_force_normal(s->var);
	SvCUR_set(s->var, 0);
	if (SvPOK(s->var)) *SvPVX(s->var) = 0;
    }
    if (SvUTF8(s->var) && !sv_utf8_downgrade(s->var, TRUE)) {
	if (ckWARN(WARN_UTF8))
	    Perl_warner(aTHX_ packWARN(WARN_UTF8), code_point_warning);
	SETERRNO(EINVAL, SS_IVCHAN);
	SvREFCNT_dec(s->var);
	s->var = Nullsv;
	return -1;
    }
    if ((PerlIOBase(f)->flags) & PERLIO_F_APPEND)
	s->posn = SvOK(s->var) ? sv_len(s->var) : 0;
    else
	s->posn = 0;
    SvSETMAGIC(s->var);
    return code;
}

static IV
PerlIOScalar_popped(pTHX_ PerlIO * f)
{
    PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
    if (s->var) {
	SvREFCNT_dec(s->var);
	s->var = Nullsv;
    }
    return 0;
}

static IV
PerlIOScalar_close(pTHX_ PerlIO * f)
{
    IV code = PerlIOBase_close(aTHX_ f);
    PerlIOBase(f)->flags &= ~(PERLIO_F_RDBUF | PERLIO_F_WRBUF);
    return code;
}

static IV
PerlIOScalar_fileno(pTHX_ PerlIO * f)
{
    PERL_UNUSED_ARG(f);
    return -1;
}

static IV
PerlIOScalar_seek(pTHX_ PerlIO * f, Off_t offset, int whence)
{
    PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
    Off_t new_posn;

    switch (whence) {
    case SEEK_SET:
	new_posn = offset;
	break;
    case SEEK_CUR:
	new_posn = offset + s->posn;
	break;
    case SEEK_END:
      {
	STRLEN oldcur;
	(void)SvPV(s->var, oldcur);
	new_posn = offset + oldcur;
	break;
      }
    default:
        SETERRNO(EINVAL, SS_IVCHAN);
        return -1;
    }
    if (new_posn < 0) {
        if (ckWARN(WARN_LAYER))
	    Perl_warner(aTHX_ packWARN(WARN_LAYER), "Offset outside string");
	SETERRNO(EINVAL, SS_IVCHAN);
	return -1;
    }
    s->posn = new_posn;
    return 0;
}

static Off_t
PerlIOScalar_tell(pTHX_ PerlIO * f)
{
    PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
    return s->posn;
}


static SSize_t
PerlIOScalar_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
{
    if (!f)
	return 0;
    if (!(PerlIOBase(f)->flags & PERLIO_F_CANREAD)) {
	PerlIOBase(f)->flags |= PERLIO_F_ERROR;
	SETERRNO(EBADF, SS_IVCHAN);
	Perl_PerlIO_save_errno(aTHX_ f);
	return 0;
    }
    {
	PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
	SV *sv = s->var;
	char *p;
	STRLEN len;
        STRLEN got;
	p = SvPV(sv, len);
	if (SvUTF8(sv)) {
	    if (sv_utf8_downgrade(sv, TRUE)) {
	        p = SvPV_nomg(sv, len);
	    }
	    else {
	        if (ckWARN(WARN_UTF8))
		    Perl_warner(aTHX_ packWARN(WARN_UTF8), code_point_warning);
	        SETERRNO(EINVAL, SS_IVCHAN);
	        return -1;
	    }
	}
        /* I assume that Off_t is at least as large as len (which 
         * seems safe) and that the size of the buffer in our SV is
         * always less than half the size of the address space
         */
        assert(sizeof(Off_t) >= sizeof(len));
        assert((Off_t)len >= 0);
        if ((Off_t)len <= s->posn)
	    return 0;
	got = len - (STRLEN)(s->posn);
	if ((STRLEN)got > (STRLEN)count)
	    got = (STRLEN)count;
	Copy(p + (STRLEN)(s->posn), vbuf, got, STDCHAR);
	s->posn += (Off_t)got;
	return (SSize_t)got;
    }
}

static SSize_t
PerlIOScalar_write(pTHX_ PerlIO * f, const void *vbuf, Size_t count)
{
    if (PerlIOBase(f)->flags & PERLIO_F_CANWRITE) {
	Off_t offset;
	PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
	SV *sv = s->var;
	char *dst;
	SvGETMAGIC(sv);
	if (!SvROK(sv)) sv_force_normal(sv);
	if (SvOK(sv)) SvPV_force_nomg_nolen(sv);
	if (SvUTF8(sv) && !sv_utf8_downgrade(sv, TRUE)) {
	    if (ckWARN(WARN_UTF8))
	        Perl_warner(aTHX_ packWARN(WARN_UTF8), code_point_warning);
	    SETERRNO(EINVAL, SS_IVCHAN);
	    return 0;
	}
	if ((PerlIOBase(f)->flags) & PERLIO_F_APPEND) {
	    dst = SvGROW(sv, SvCUR(sv) + count + 1);
	    offset = SvCUR(sv);
	    s->posn = offset + count;
	}
	else {
	    STRLEN const cur = SvCUR(sv);

            /* ensure we don't try to create ridiculously large
             * SVs on small platforms
             */
#if Size_t_size < Off_t_size
            if (s->posn > SSize_t_MAX) {
#ifdef EFBIG
                SETERRNO(EFBIG, SS_BUFFEROVF);
#else
                SETERRNO(ENOSPC, SS_BUFFEROVF);
#endif
                return 0;
            }
#endif

	    if ((STRLEN)s->posn > cur) {
		dst = SvGROW(sv, (STRLEN)s->posn + count + 1);
		Zero(SvPVX(sv) + cur, (STRLEN)s->posn - cur, char);
	    }
	    else if ((s->posn + count) >= cur)
		dst = SvGROW(sv, (STRLEN)s->posn + count + 1);
	    else
		dst = SvPVX(sv);
	    offset = s->posn;
	    s->posn += count;
	}
	Move(vbuf, dst + offset, count, char);
	if ((STRLEN) s->posn > SvCUR(sv)) {
	    SvCUR_set(sv, (STRLEN)s->posn);
	    dst[(STRLEN) s->posn] = 0;
	}
	SvPOK_on(sv);
	SvSETMAGIC(sv);
	return count;
    }
    else
	return 0;
}

static IV
PerlIOScalar_fill(pTHX_ PerlIO * f)
{
    PERL_UNUSED_ARG(f);
    return -1;
}

static IV
PerlIOScalar_flush(pTHX_ PerlIO * f)
{
    PERL_UNUSED_ARG(f);
    return 0;
}

static STDCHAR *
PerlIOScalar_get_base(pTHX_ PerlIO * f)
{
    PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
    if (PerlIOBase(f)->flags & PERLIO_F_CANREAD) {
	SvGETMAGIC(s->var);
	return (STDCHAR *) SvPV_nolen(s->var);
    }
    return (STDCHAR *) NULL;
}

static STDCHAR *
PerlIOScalar_get_ptr(pTHX_ PerlIO * f)
{
    if (PerlIOBase(f)->flags & PERLIO_F_CANREAD) {
	PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
	return PerlIOScalar_get_base(aTHX_ f) + s->posn;
    }
    return (STDCHAR *) NULL;
}

static SSize_t
PerlIOScalar_get_cnt(pTHX_ PerlIO * f)
{
    if (PerlIOBase(f)->flags & PERLIO_F_CANREAD) {
	PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
	STRLEN len;
	(void)SvPV(s->var,len);
	if ((Off_t)len > s->posn)
	    return len - (STRLEN)s->posn;
	else
	    return 0;
    }
    return 0;
}

static Size_t
PerlIOScalar_bufsiz(pTHX_ PerlIO * f)
{
    if (PerlIOBase(f)->flags & PERLIO_F_CANREAD) {
	PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
	SvGETMAGIC(s->var);
	return SvCUR(s->var);
    }
    return 0;
}

static void
PerlIOScalar_set_ptrcnt(pTHX_ PerlIO * f, STDCHAR * ptr, SSize_t cnt)
{
    PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
    STRLEN len;
    PERL_UNUSED_ARG(ptr);
    (void)SvPV(s->var,len);
    s->posn = len - cnt;
}

static PerlIO *
PerlIOScalar_open(pTHX_ PerlIO_funcs * self, PerlIO_list_t * layers, IV n,
		  const char *mode, int fd, int imode, int perm,
		  PerlIO * f, int narg, SV ** args)
{
    SV *arg = (narg > 0) ? *args : PerlIOArg;
    PERL_UNUSED_ARG(fd);
    PERL_UNUSED_ARG(imode);
    PERL_UNUSED_ARG(perm);
    if (SvROK(arg) || SvPOK(arg)) {
	if (!f) {
	    f = PerlIO_allocate(aTHX);
	}
	if ( (f = PerlIO_push(aTHX_ f, self, mode, arg)) ) {
	    PerlIOBase(f)->flags |= PERLIO_F_OPEN;
	}
	return f;
    }
    return NULL;
}

static SV *
PerlIOScalar_arg(pTHX_ PerlIO * f, CLONE_PARAMS * param, int flags)
{
    PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
    SV *var = s->var;
    if (flags & PERLIO_DUP_CLONE)
	var = PerlIO_sv_dup(aTHX_ var, param);
    else if (flags & PERLIO_DUP_FD) {
	/* Equivalent (guesses NI-S) of dup() is to create a new scalar */
	var = newSVsv(var);
    }
    else {
	var = SvREFCNT_inc(var);
    }
    return newRV_noinc(var);
}

static PerlIO *
PerlIOScalar_dup(pTHX_ PerlIO * f, PerlIO * o, CLONE_PARAMS * param,
		 int flags)
{
    /* Duplication causes the scalar layer to be pushed on to clone, caus-
       ing the cloned scalar to be set to the empty string by
       PerlIOScalar_pushed.  So set aside our scalar temporarily. */
    PerlIOScalar * const os = PerlIOSelf(o, PerlIOScalar);
    PerlIOScalar *fs = NULL; /* avoid "may be used uninitialized" warning */
    SV * const var = os->var;
    os->var = newSVpvs("");
    if ((f = PerlIOBase_dup(aTHX_ f, o, param, flags))) {
	fs = PerlIOSelf(f, PerlIOScalar);
	/* var has been set by implicit push, so replace it */
	SvREFCNT_dec(fs->var);
    }
    SvREFCNT_dec(os->var);
    os->var = var;
    if (f) {
	SV * const rv = PerlIOScalar_arg(aTHX_ o, param, flags);
	fs->var = SvREFCNT_inc(SvRV(rv));
	SvREFCNT_dec(rv);
	fs->posn = os->posn;
    }
    return f;
}

static PERLIO_FUNCS_DECL(PerlIO_scalar) = {
    sizeof(PerlIO_funcs),
    "scalar",
    sizeof(PerlIOScalar),
    PERLIO_K_BUFFERED | PERLIO_K_RAW,
    PerlIOScalar_pushed,
    PerlIOScalar_popped,
    PerlIOScalar_open,
    PerlIOBase_binmode,
    PerlIOScalar_arg,
    PerlIOScalar_fileno,
    PerlIOScalar_dup,
    PerlIOScalar_read,
    NULL, /* unread */
    PerlIOScalar_write,
    PerlIOScalar_seek,
    PerlIOScalar_tell,
    PerlIOScalar_close,
    PerlIOScalar_flush,
    PerlIOScalar_fill,
    PerlIOScalar_eof,
    PerlIOBase_error,
    PerlIOBase_clearerr,
    PerlIOBase_setlinebuf,
    PerlIOScalar_get_base,
    PerlIOScalar_bufsiz,
    PerlIOScalar_get_ptr,
    PerlIOScalar_get_cnt,
    PerlIOScalar_set_ptrcnt,
};


#endif /* Layers available */

MODULE = PerlIO::scalar	PACKAGE = PerlIO::scalar

PROTOTYPES: ENABLE

BOOT:
{
#ifdef PERLIO_LAYERS
 PerlIO_define_layer(aTHX_ PERLIO_FUNCS_CAST(&PerlIO_scalar));
#endif
}