/ext/zlib/zlib.c

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/*
 * zlib.c - An interface for zlib.
 *
 *   Copyright (C) UENO Katsuhiro 2000-2003
 *
 * $Id$
 */

#include <ruby.h>
#include <zlib.h>
#include <time.h>
#include <ruby/encoding.h>

#define RUBY_ZLIB_VERSION  "0.6.0"


#define OBJ_IS_FREED(val)  (RBASIC(val)->flags == 0)

#ifndef GZIP_SUPPORT
#define GZIP_SUPPORT  1
#endif

/* from zutil.h */
#ifndef DEF_MEM_LEVEL
#if MAX_MEM_LEVEL >= 8
#define DEF_MEM_LEVEL  8
#else
#define DEF_MEM_LEVEL  MAX_MEM_LEVEL
#endif
#endif


/*--------- Prototypes --------*/

static NORETURN(void raise_zlib_error(int, const char*));
static VALUE rb_zlib_version(VALUE);
static VALUE do_checksum(int, VALUE*, uLong (*)(uLong, const Bytef*, uInt));
static VALUE rb_zlib_adler32(int, VALUE*, VALUE);
static VALUE rb_zlib_crc32(int, VALUE*, VALUE);
static VALUE rb_zlib_crc_table(VALUE);
static voidpf zlib_mem_alloc(voidpf, uInt, uInt);
static void zlib_mem_free(voidpf, voidpf);
static void finalizer_warn(const char*);

struct zstream;
struct zstream_funcs;
static void zstream_init(struct zstream*, const struct zstream_funcs*);
static void zstream_expand_buffer(struct zstream*);
static void zstream_expand_buffer_into(struct zstream*, int);
static void zstream_append_buffer(struct zstream*, const Bytef*, int);
static VALUE zstream_detach_buffer(struct zstream*);
static VALUE zstream_shift_buffer(struct zstream*, int);
static void zstream_buffer_ungets(struct zstream*, const Bytef*, int);
static void zstream_buffer_ungetbyte(struct zstream*, int);
static void zstream_append_input(struct zstream*, const Bytef*, unsigned int);
static void zstream_discard_input(struct zstream*, unsigned int);
static void zstream_reset_input(struct zstream*);
static void zstream_passthrough_input(struct zstream*);
static VALUE zstream_detach_input(struct zstream*);
static void zstream_reset(struct zstream*);
static VALUE zstream_end(struct zstream*);
static void zstream_run(struct zstream*, Bytef*, uInt, int);
static VALUE zstream_sync(struct zstream*, Bytef*, uInt);
static void zstream_mark(struct zstream*);
static void zstream_free(struct zstream*);
static VALUE zstream_new(VALUE, const struct zstream_funcs*);
static struct zstream *get_zstream(VALUE);
static void zstream_finalize(struct zstream*);

static VALUE rb_zstream_end(VALUE);
static VALUE rb_zstream_reset(VALUE);
static VALUE rb_zstream_finish(VALUE);
static VALUE rb_zstream_flush_next_in(VALUE);
static VALUE rb_zstream_flush_next_out(VALUE);
static VALUE rb_zstream_avail_out(VALUE);
static VALUE rb_zstream_set_avail_out(VALUE, VALUE);
static VALUE rb_zstream_avail_in(VALUE);
static VALUE rb_zstream_total_in(VALUE);
static VALUE rb_zstream_total_out(VALUE);
static VALUE rb_zstream_data_type(VALUE);
static VALUE rb_zstream_adler(VALUE);
static VALUE rb_zstream_finished_p(VALUE);
static VALUE rb_zstream_closed_p(VALUE);

static VALUE rb_deflate_s_allocate(VALUE);
static VALUE rb_deflate_initialize(int, VALUE*, VALUE);
static VALUE rb_deflate_init_copy(VALUE, VALUE);
static VALUE deflate_run(VALUE);
static VALUE rb_deflate_s_deflate(int, VALUE*, VALUE);
static void do_deflate(struct zstream*, VALUE, int);
static VALUE rb_deflate_deflate(int, VALUE*, VALUE);
static VALUE rb_deflate_addstr(VALUE, VALUE);
static VALUE rb_deflate_flush(int, VALUE*, VALUE);
static VALUE rb_deflate_params(VALUE, VALUE, VALUE);
static VALUE rb_deflate_set_dictionary(VALUE, VALUE);

static VALUE inflate_run(VALUE);
static VALUE rb_inflate_s_allocate(VALUE);
static VALUE rb_inflate_initialize(int, VALUE*, VALUE);
static VALUE rb_inflate_s_inflate(VALUE, VALUE);
static void do_inflate(struct zstream*, VALUE);
static VALUE rb_inflate_inflate(VALUE, VALUE);
static VALUE rb_inflate_addstr(VALUE, VALUE);
static VALUE rb_inflate_sync(VALUE, VALUE);
static VALUE rb_inflate_sync_point_p(VALUE);
static VALUE rb_inflate_set_dictionary(VALUE, VALUE);

#if GZIP_SUPPORT
struct gzfile;
static void gzfile_mark(struct gzfile*);
static void gzfile_free(struct gzfile*);
static VALUE gzfile_new(VALUE, const struct zstream_funcs*, void (*) _((struct gzfile*)));
static void gzfile_reset(struct gzfile*);
static void gzfile_close(struct gzfile*, int);
static void gzfile_write_raw(struct gzfile*);
static VALUE gzfile_read_raw_partial(VALUE);
static VALUE gzfile_read_raw_rescue(VALUE);
static VALUE gzfile_read_raw(struct gzfile*);
static int gzfile_read_raw_ensure(struct gzfile*, int);
static char *gzfile_read_raw_until_zero(struct gzfile*, long);
static unsigned int gzfile_get16(const unsigned char*);
static unsigned long gzfile_get32(const unsigned char*);
static void gzfile_set32(unsigned long n, unsigned char*);
static void gzfile_make_header(struct gzfile*);
static void gzfile_make_footer(struct gzfile*);
static void gzfile_read_header(struct gzfile*);
static void gzfile_check_footer(struct gzfile*);
static void gzfile_write(struct gzfile*, Bytef*, uInt);
static long gzfile_read_more(struct gzfile*);
static void gzfile_calc_crc(struct gzfile*, VALUE);
static VALUE gzfile_read(struct gzfile*, int);
static VALUE gzfile_read_all(struct gzfile*);
static void gzfile_ungets(struct gzfile*, const Bytef*, int);
static void gzfile_ungetbyte(struct gzfile*, int);
static VALUE gzfile_writer_end_run(VALUE);
static void gzfile_writer_end(struct gzfile*);
static VALUE gzfile_reader_end_run(VALUE);
static void gzfile_reader_end(struct gzfile*);
static void gzfile_reader_rewind(struct gzfile*);
static VALUE gzfile_reader_get_unused(struct gzfile*);
static struct gzfile *get_gzfile(VALUE);
static VALUE gzfile_ensure_close(VALUE);
static VALUE rb_gzfile_s_wrap(int, VALUE*, VALUE);
static VALUE gzfile_s_open(int, VALUE*, VALUE, const char*);

static VALUE rb_gzfile_to_io(VALUE);
static VALUE rb_gzfile_crc(VALUE);
static VALUE rb_gzfile_mtime(VALUE);
static VALUE rb_gzfile_level(VALUE);
static VALUE rb_gzfile_os_code(VALUE);
static VALUE rb_gzfile_orig_name(VALUE);
static VALUE rb_gzfile_comment(VALUE);
static VALUE rb_gzfile_lineno(VALUE);
static VALUE rb_gzfile_set_lineno(VALUE, VALUE);
static VALUE rb_gzfile_set_mtime(VALUE, VALUE);
static VALUE rb_gzfile_set_orig_name(VALUE, VALUE);
static VALUE rb_gzfile_set_comment(VALUE, VALUE);
static VALUE rb_gzfile_close(VALUE);
static VALUE rb_gzfile_finish(VALUE);
static VALUE rb_gzfile_closed_p(VALUE);
static VALUE rb_gzfile_eof_p(VALUE);
static VALUE rb_gzfile_sync(VALUE);
static VALUE rb_gzfile_set_sync(VALUE, VALUE);
static VALUE rb_gzfile_total_in(VALUE);
static VALUE rb_gzfile_total_out(VALUE);
static VALUE rb_gzfile_path(VALUE);

static VALUE rb_gzwriter_s_allocate(VALUE);
static VALUE rb_gzwriter_s_open(int, VALUE*, VALUE);
static VALUE rb_gzwriter_initialize(int, VALUE*, VALUE);
static VALUE rb_gzwriter_flush(int, VALUE*, VALUE);
static VALUE rb_gzwriter_write(VALUE, VALUE);
static VALUE rb_gzwriter_putc(VALUE, VALUE);

static VALUE rb_gzreader_s_allocate(VALUE);
static VALUE rb_gzreader_s_open(int, VALUE*, VALUE);
static VALUE rb_gzreader_initialize(int, VALUE*, VALUE);
static VALUE rb_gzreader_rewind(VALUE);
static VALUE rb_gzreader_unused(VALUE);
static VALUE rb_gzreader_read(int, VALUE*, VALUE);
static VALUE rb_gzreader_getc(VALUE);
static VALUE rb_gzreader_readchar(VALUE);
static VALUE rb_gzreader_each_byte(VALUE);
static VALUE rb_gzreader_ungetc(VALUE, VALUE);
static VALUE rb_gzreader_ungetbyte(VALUE, VALUE);
static void gzreader_skip_linebreaks(struct gzfile*);
static VALUE gzreader_gets(int, VALUE*, VALUE);
static VALUE rb_gzreader_gets(int, VALUE*, VALUE);
static VALUE rb_gzreader_readline(int, VALUE*, VALUE);
static VALUE rb_gzreader_each(int, VALUE*, VALUE);
static VALUE rb_gzreader_readlines(int, VALUE*, VALUE);
#endif /* GZIP_SUPPORT */


void Init_zlib(void);

int rb_io_extract_encoding_option(VALUE opt, rb_encoding **enc_p, rb_encoding **enc2_p);
VALUE rb_str_conv_enc_opts(VALUE, rb_encoding*, rb_encoding*, int, VALUE);

/*--------- Exceptions --------*/

static VALUE cZError, cStreamEnd, cNeedDict;
static VALUE cStreamError, cDataError, cMemError, cBufError, cVersionError;

static void
raise_zlib_error(int err, const char *msg)
{
    VALUE exc;

    if (!msg) {
	msg = zError(err);
    }

    switch(err) {
      case Z_STREAM_END:
	exc = rb_exc_new2(cStreamEnd, msg);
	break;
      case Z_NEED_DICT:
	exc = rb_exc_new2(cNeedDict, msg);
	break;
      case Z_STREAM_ERROR:
	exc = rb_exc_new2(cStreamError, msg);
	break;
      case Z_DATA_ERROR:
	exc = rb_exc_new2(cDataError, msg);
	break;
      case Z_BUF_ERROR:
	exc = rb_exc_new2(cBufError, msg);
	break;
      case Z_VERSION_ERROR:
	exc = rb_exc_new2(cVersionError, msg);
	break;
      case Z_MEM_ERROR:
	exc = rb_exc_new2(cMemError, msg);
	break;
      case Z_ERRNO:
	rb_sys_fail(msg);
	/* no return */
      default:
      {
	  char buf[BUFSIZ];
	  snprintf(buf, BUFSIZ, "unknown zlib error %d: %s", err, msg);
	  exc = rb_exc_new2(cZError, buf);
      }
    }

    rb_exc_raise(exc);
}


/*--- Warning (in finalizer) ---*/

static void
finalizer_warn(const char *msg)
{
    fprintf(stderr, "zlib(finalizer): %s\n", msg);
}


/*-------- module Zlib --------*/

/*
 * Returns the string which represents the version of zlib library.
 */
static VALUE
rb_zlib_version(VALUE klass)
{
    VALUE str;

    str = rb_str_new2(zlibVersion());
    OBJ_TAINT(str);  /* for safe */
    return str;
}

static VALUE
do_checksum(argc, argv, func)
    int argc;
    VALUE *argv;
    uLong (*func)(uLong, const Bytef*, uInt);
{
    VALUE str, vsum;
    unsigned long sum;

    rb_scan_args(argc, argv, "02", &str, &vsum);

    if (!NIL_P(vsum)) {
	sum = NUM2ULONG(vsum);
    }
    else if (NIL_P(str)) {
	sum = 0;
    }
    else {
	sum = func(0, Z_NULL, 0);
    }

    if (NIL_P(str)) {
	sum = func(sum, Z_NULL, 0);
    }
    else {
	StringValue(str);
	sum = func(sum, (Bytef*)RSTRING_PTR(str), RSTRING_LEN(str));
    }
    return rb_uint2inum(sum);
}

/*
 * call-seq: Zlib.adler32(string, adler)
 *
 * Calculates Adler-32 checksum for +string+, and returns updated value of
 * +adler+. If +string+ is omitted, it returns the Adler-32 initial value. If
 * +adler+ is omitted, it assumes that the initial value is given to +adler+.
 *
 * FIXME: expression.
 */
static VALUE
rb_zlib_adler32(int argc, VALUE *argv, VALUE klass)
{
    return do_checksum(argc, argv, adler32);
}

#ifdef HAVE_ADLER32_COMBINE
/*
 * call-seq: Zlib.adler32_combine(adler1, adler2, len2)
 *
 * Combine two Adler-32 check values in to one.  +alder1+ is the first Adler-32
 * value, +adler2+ is the second Adler-32 value.  +len2+ is the length of the
 * string used to generate +adler2+.
 *
 */
static VALUE
rb_zlib_adler32_combine(VALUE klass, VALUE adler1, VALUE adler2, VALUE len2)
{
  return ULONG2NUM(
	adler32_combine(NUM2ULONG(adler1), NUM2ULONG(adler2), NUM2LONG(len2)));
}
#else
#define rb_zlib_adler32_combine rb_f_notimplement
#endif

/*
 * call-seq: Zlib.crc32(string, adler)
 *
 * Calculates CRC checksum for +string+, and returns updated value of +crc+. If
 * +string+ is omitted, it returns the CRC initial value. If +crc+ is omitted, it
 * assumes that the initial value is given to +crc+.
 *
 * FIXME: expression.
 */
static VALUE
rb_zlib_crc32(int argc, VALUE *argv, VALUE klass)
{
    return do_checksum(argc, argv, crc32);
}

#ifdef HAVE_CRC32_COMBINE
/*
 * call-seq: Zlib.crc32_combine(crc1, crc2, len2)
 *
 * Combine two CRC-32 check values in to one.  +crc1+ is the first CRC-32
 * value, +crc2+ is the second CRC-32 value.  +len2+ is the length of the
 * string used to generate +crc2+.
 *
 */
static VALUE
rb_zlib_crc32_combine(VALUE klass, VALUE crc1, VALUE crc2, VALUE len2)
{
  return ULONG2NUM(
	crc32_combine(NUM2ULONG(crc1), NUM2ULONG(crc2), NUM2LONG(len2)));
}
#else
#define rb_zlib_crc32_combine rb_f_notimplement
#endif

/*
 * Returns the table for calculating CRC checksum as an array.
 */
static VALUE
rb_zlib_crc_table(VALUE obj)
{
    const unsigned long *crctbl;
    VALUE dst;
    int i;

    crctbl = get_crc_table();
    dst = rb_ary_new2(256);

    for (i = 0; i < 256; i++) {
	rb_ary_push(dst, rb_uint2inum(crctbl[i]));
    }
    return dst;
}



/*-------- zstream - internal APIs --------*/

struct zstream {
    unsigned long flags;
    VALUE buf;
    long buf_filled;
    VALUE input;
    z_stream stream;
    const struct zstream_funcs {
	int (*reset)(z_streamp);
	int (*end)(z_streamp);
	int (*run)(z_streamp, int);
    } *func;
};

#define ZSTREAM_FLAG_READY      0x1
#define ZSTREAM_FLAG_IN_STREAM  0x2
#define ZSTREAM_FLAG_FINISHED   0x4
#define ZSTREAM_FLAG_CLOSING    0x8
#define ZSTREAM_FLAG_UNUSED     0x10

#define ZSTREAM_READY(z)       ((z)->flags |= ZSTREAM_FLAG_READY)
#define ZSTREAM_IS_READY(z)    ((z)->flags & ZSTREAM_FLAG_READY)
#define ZSTREAM_IS_FINISHED(z) ((z)->flags & ZSTREAM_FLAG_FINISHED)
#define ZSTREAM_IS_CLOSING(z)  ((z)->flags & ZSTREAM_FLAG_CLOSING)

/* I think that more better value should be found,
   but I gave up finding it. B) */
#define ZSTREAM_INITIAL_BUFSIZE       1024
#define ZSTREAM_AVAIL_OUT_STEP_MAX   16384
#define ZSTREAM_AVAIL_OUT_STEP_MIN    2048

static const struct zstream_funcs deflate_funcs = {
    deflateReset, deflateEnd, deflate,
};

static const struct zstream_funcs inflate_funcs = {
    inflateReset, inflateEnd, inflate,
};


static voidpf
zlib_mem_alloc(voidpf opaque, uInt items, uInt size)
{
    return xmalloc(items * size);
}

static void
zlib_mem_free(voidpf opaque, voidpf address)
{
    xfree(address);
}

static void
zstream_init(struct zstream *z, const struct zstream_funcs *func)
{
    z->flags = 0;
    z->buf = Qnil;
    z->buf_filled = 0;
    z->input = Qnil;
    z->stream.zalloc = zlib_mem_alloc;
    z->stream.zfree = zlib_mem_free;
    z->stream.opaque = Z_NULL;
    z->stream.msg = Z_NULL;
    z->stream.next_in = Z_NULL;
    z->stream.avail_in = 0;
    z->stream.next_out = Z_NULL;
    z->stream.avail_out = 0;
    z->func = func;
}

#define zstream_init_deflate(z)   zstream_init((z), &deflate_funcs)
#define zstream_init_inflate(z)   zstream_init((z), &inflate_funcs)

static void
zstream_expand_buffer(struct zstream *z)
{
    long inc;

    if (NIL_P(z->buf)) {
	    /* I uses rb_str_new here not rb_str_buf_new because
	       rb_str_buf_new makes a zero-length string. */
	z->buf = rb_str_new(0, ZSTREAM_INITIAL_BUFSIZE);
	z->buf_filled = 0;
	z->stream.next_out = (Bytef*)RSTRING_PTR(z->buf);
	z->stream.avail_out = ZSTREAM_INITIAL_BUFSIZE;
	RBASIC(z->buf)->klass = 0;
	return;
    }

    if (RSTRING_LEN(z->buf) - z->buf_filled >= ZSTREAM_AVAIL_OUT_STEP_MAX) {
	/* to keep other threads from freezing */
	z->stream.avail_out = ZSTREAM_AVAIL_OUT_STEP_MAX;
    }
    else {
	inc = z->buf_filled / 2;
	if (inc < ZSTREAM_AVAIL_OUT_STEP_MIN) {
	    inc = ZSTREAM_AVAIL_OUT_STEP_MIN;
	}
	rb_str_resize(z->buf, z->buf_filled + inc);
	z->stream.avail_out = (inc < ZSTREAM_AVAIL_OUT_STEP_MAX) ?
	    inc : ZSTREAM_AVAIL_OUT_STEP_MAX;
    }
    z->stream.next_out = (Bytef*)RSTRING_PTR(z->buf) + z->buf_filled;
}

static void
zstream_expand_buffer_into(struct zstream *z, int size)
{
    if (NIL_P(z->buf)) {
	/* I uses rb_str_new here not rb_str_buf_new because
	   rb_str_buf_new makes a zero-length string. */
	z->buf = rb_str_new(0, size);
	z->buf_filled = 0;
	z->stream.next_out = (Bytef*)RSTRING_PTR(z->buf);
	z->stream.avail_out = size;
	RBASIC(z->buf)->klass = 0;
    }
    else if (z->stream.avail_out != size) {
	rb_str_resize(z->buf, z->buf_filled + size);
	z->stream.next_out = (Bytef*)RSTRING_PTR(z->buf) + z->buf_filled;
	z->stream.avail_out = size;
    }
}

static void
zstream_append_buffer(struct zstream *z, const Bytef *src, int len)
{
    if (NIL_P(z->buf)) {
	z->buf = rb_str_buf_new(len);
	rb_str_buf_cat(z->buf, (const char*)src, len);
	z->buf_filled = len;
	z->stream.next_out = (Bytef*)RSTRING_PTR(z->buf);
	z->stream.avail_out = 0;
	RBASIC(z->buf)->klass = 0;
	return;
    }

    if (RSTRING_LEN(z->buf) < z->buf_filled + len) {
	rb_str_resize(z->buf, z->buf_filled + len);
	z->stream.avail_out = 0;
    }
    else {
	if (z->stream.avail_out >= (uInt)len) {
	    z->stream.avail_out -= len;
	}
	else {
	    z->stream.avail_out = 0;
	}
    }
    memcpy(RSTRING_PTR(z->buf) + z->buf_filled, src, len);
    z->buf_filled += len;
    z->stream.next_out = (Bytef*)RSTRING_PTR(z->buf) + z->buf_filled;
}

#define zstream_append_buffer2(z,v) \
    zstream_append_buffer((z),(Bytef*)RSTRING_PTR(v),RSTRING_LEN(v))

static VALUE
zstream_detach_buffer(struct zstream *z)
{
    VALUE dst;

    if (NIL_P(z->buf)) {
	dst = rb_str_new(0, 0);
    }
    else {
	dst = z->buf;
	rb_str_resize(dst, z->buf_filled);
	RBASIC(dst)->klass = rb_cString;
    }

    z->buf = Qnil;
    z->buf_filled = 0;
    z->stream.next_out = 0;
    z->stream.avail_out = 0;
    return dst;
}

static VALUE
zstream_shift_buffer(struct zstream *z, int len)
{
    VALUE dst;

    if (z->buf_filled <= len) {
	return zstream_detach_buffer(z);
    }

    dst = rb_str_subseq(z->buf, 0, len);
    RBASIC(dst)->klass = rb_cString;
    z->buf_filled -= len;
    memmove(RSTRING_PTR(z->buf), RSTRING_PTR(z->buf) + len,
	    z->buf_filled);
    z->stream.next_out = (Bytef*)RSTRING_PTR(z->buf) + z->buf_filled;
    z->stream.avail_out = RSTRING_LEN(z->buf) - z->buf_filled;
    if (z->stream.avail_out > ZSTREAM_AVAIL_OUT_STEP_MAX) {
	z->stream.avail_out = ZSTREAM_AVAIL_OUT_STEP_MAX;
    }

    return dst;
}

static void
zstream_buffer_ungets(struct zstream *z, const Bytef *b, int len)
{
    if (NIL_P(z->buf) || RSTRING_LEN(z->buf) - z->buf_filled == 0) {
	zstream_expand_buffer_into(z, len);
    }

    memmove(RSTRING_PTR(z->buf) + len, RSTRING_PTR(z->buf), z->buf_filled);
    memmove(RSTRING_PTR(z->buf), b, len);
    z->buf_filled+=len;
    if (z->stream.avail_out > 0) {
	z->stream.next_out+=len;
	z->stream.avail_out-=len;
    }
}

static void
zstream_buffer_ungetbyte(struct zstream *z, int c)
{
    if (NIL_P(z->buf) || RSTRING_LEN(z->buf) - z->buf_filled == 0) {
	zstream_expand_buffer(z);
    }

    memmove(RSTRING_PTR(z->buf) + 1, RSTRING_PTR(z->buf), z->buf_filled);
    RSTRING_PTR(z->buf)[0] = (char)c;
    z->buf_filled++;
    if (z->stream.avail_out > 0) {
	z->stream.next_out++;
	z->stream.avail_out--;
    }
}

static void
zstream_append_input(struct zstream *z, const Bytef *src, unsigned int len)
{
    if (len <= 0) return;

    if (NIL_P(z->input)) {
	z->input = rb_str_buf_new(len);
	rb_str_buf_cat(z->input, (const char*)src, len);
	RBASIC(z->input)->klass = 0;
    }
    else {
	rb_str_buf_cat(z->input, (const char*)src, len);
    }
}

#define zstream_append_input2(z,v)\
    zstream_append_input((z), (Bytef*)RSTRING_PTR(v), RSTRING_LEN(v))

static void
zstream_discard_input(struct zstream *z, unsigned int len)
{
    if (NIL_P(z->input) || (unsigned int)RSTRING_LEN(z->input) <= len) {
	z->input = Qnil;
    }
    else {
	memmove(RSTRING_PTR(z->input), RSTRING_PTR(z->input) + len,
		RSTRING_LEN(z->input) - len);
	rb_str_resize(z->input, RSTRING_LEN(z->input) - len);
    }
}

static void
zstream_reset_input(struct zstream *z)
{
    z->input = Qnil;
}

static void
zstream_passthrough_input(struct zstream *z)
{
    if (!NIL_P(z->input)) {
	zstream_append_buffer2(z, z->input);
	z->input = Qnil;
    }
}

static VALUE
zstream_detach_input(struct zstream *z)
{
    VALUE dst;

    if (NIL_P(z->input)) {
	dst = rb_str_new(0, 0);
    }
    else {
	dst = z->input;
	RBASIC(dst)->klass = rb_cString;
    }
    z->input = Qnil;
    RBASIC(dst)->klass = rb_cString;
    return dst;
}

static void
zstream_reset(struct zstream *z)
{
    int err;

    err = z->func->reset(&z->stream);
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }
    z->flags = ZSTREAM_FLAG_READY;
    z->buf = Qnil;
    z->buf_filled = 0;
    z->stream.next_out = 0;
    z->stream.avail_out = 0;
    zstream_reset_input(z);
}

static VALUE
zstream_end(struct zstream *z)
{
    int err;

    if (!ZSTREAM_IS_READY(z)) {
	rb_warning("attempt to close uninitialized zstream; ignored.");
	return Qnil;
    }
    if (z->flags & ZSTREAM_FLAG_IN_STREAM) {
	rb_warning("attempt to close unfinished zstream; reset forced.");
	zstream_reset(z);
    }

    zstream_reset_input(z);
    err = z->func->end(&z->stream);
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }
    z->flags = 0;
    return Qnil;
}

static void
zstream_run(struct zstream *z, Bytef *src, uInt len, int flush)
{
    uInt n;
    int err;
    volatile VALUE guard = Qnil;

    if (NIL_P(z->input) && len == 0) {
	z->stream.next_in = (Bytef*)"";
	z->stream.avail_in = 0;
    }
    else {
	zstream_append_input(z, src, len);
	z->stream.next_in = (Bytef*)RSTRING_PTR(z->input);
	z->stream.avail_in = RSTRING_LEN(z->input);
	/* keep reference to `z->input' so as not to be garbage collected
	   after zstream_reset_input() and prevent `z->stream.next_in'
	   from dangling. */
	guard = z->input;
    }

    if (z->stream.avail_out == 0) {
	zstream_expand_buffer(z);
    }

    for (;;) {
	/* VC allocates err and guard to same address.  accessing err and guard
	   in same scope prevents it. */
	RB_GC_GUARD(guard);
	n = z->stream.avail_out;
	err = z->func->run(&z->stream, flush);
	z->buf_filled += n - z->stream.avail_out;
	rb_thread_schedule();

	if (err == Z_STREAM_END) {
	    z->flags &= ~ZSTREAM_FLAG_IN_STREAM;
	    z->flags |= ZSTREAM_FLAG_FINISHED;
	    break;
	}
	if (err != Z_OK) {
	    if (flush != Z_FINISH && err == Z_BUF_ERROR
		&& z->stream.avail_out > 0) {
		z->flags |= ZSTREAM_FLAG_IN_STREAM;
		break;
	    }
	    zstream_reset_input(z);
	    if (z->stream.avail_in > 0) {
		zstream_append_input(z, z->stream.next_in, z->stream.avail_in);
	    }
	    raise_zlib_error(err, z->stream.msg);
	}
	if (z->stream.avail_out > 0) {
	    z->flags |= ZSTREAM_FLAG_IN_STREAM;
	    break;
	}
	zstream_expand_buffer(z);
    }

    zstream_reset_input(z);
    if (z->stream.avail_in > 0) {
	zstream_append_input(z, z->stream.next_in, z->stream.avail_in);
        guard = Qnil; /* prevent tail call to make guard effective */
    }
}

static VALUE
zstream_sync(struct zstream *z, Bytef *src, uInt len)
{
    VALUE rest;
    int err;

    if (!NIL_P(z->input)) {
	z->stream.next_in = (Bytef*)RSTRING_PTR(z->input);
	z->stream.avail_in = RSTRING_LEN(z->input);
	err = inflateSync(&z->stream);
	if (err == Z_OK) {
	    zstream_discard_input(z,
				  RSTRING_LEN(z->input) - z->stream.avail_in);
	    zstream_append_input(z, src, len);
	    return Qtrue;
	}
	zstream_reset_input(z);
	if (err != Z_DATA_ERROR) {
	    rest = rb_str_new((char*)z->stream.next_in, z->stream.avail_in);
	    raise_zlib_error(err, z->stream.msg);
	}
    }

    if (len <= 0) return Qfalse;

    z->stream.next_in = src;
    z->stream.avail_in = len;
    err = inflateSync(&z->stream);
    if (err == Z_OK) {
	zstream_append_input(z, z->stream.next_in, z->stream.avail_in);
	return Qtrue;
    }
    if (err != Z_DATA_ERROR) {
	rest = rb_str_new((char*)z->stream.next_in, z->stream.avail_in);
	raise_zlib_error(err, z->stream.msg);
    }
    return Qfalse;
}

static void
zstream_mark(struct zstream *z)
{
    rb_gc_mark(z->buf);
    rb_gc_mark(z->input);
}

static void
zstream_finalize(struct zstream *z)
{
    int err = z->func->end(&z->stream);
    if (err == Z_STREAM_ERROR)
	finalizer_warn("the stream state was inconsistent.");
    if (err == Z_DATA_ERROR)
	finalizer_warn("the stream was freed prematurely.");
}

static void
zstream_free(struct zstream *z)
{
    if (ZSTREAM_IS_READY(z)) {
	zstream_finalize(z);
    }
    xfree(z);
}

static VALUE
zstream_new(VALUE klass, const struct zstream_funcs *funcs)
{
    VALUE obj;
    struct zstream *z;

    obj = Data_Make_Struct(klass, struct zstream,
			   zstream_mark, zstream_free, z);
    zstream_init(z, funcs);
    return obj;
}

#define zstream_deflate_new(klass)  zstream_new((klass), &deflate_funcs)
#define zstream_inflate_new(klass)  zstream_new((klass), &inflate_funcs)

static struct zstream *
get_zstream(VALUE obj)
{
    struct zstream *z;

    Data_Get_Struct(obj, struct zstream, z);
    if (!ZSTREAM_IS_READY(z)) {
	rb_raise(cZError, "stream is not ready");
    }
    return z;
}


/* ------------------------------------------------------------------------- */

/*
 * Document-class: Zlib::ZStream
 *
 * Zlib::ZStream is the abstract class for the stream which handles the
 * compressed data. The operations are defined in the subclasses:
 * Zlib::Deflate for compression, and Zlib::Inflate for decompression.
 *
 * An instance of Zlib::ZStream has one stream (struct zstream in the source)
 * and two variable-length buffers which associated to the input (next_in) of
 * the stream and the output (next_out) of the stream. In this document,
 * "input buffer" means the buffer for input, and "output buffer" means the
 * buffer for output.
 *
 * Data input into an instance of Zlib::ZStream are temporally stored into
 * the end of input buffer, and then data in input buffer are processed from
 * the beginning of the buffer until no more output from the stream is
 * produced (i.e. until avail_out > 0 after processing).  During processing,
 * output buffer is allocated and expanded automatically to hold all output
 * data.
 *
 * Some particular instance methods consume the data in output buffer and
 * return them as a String.
 *
 * Here is an ascii art for describing above:
 *
 *    +================ an instance of Zlib::ZStream ================+
 *    ||                                                            ||
 *    ||     +--------+          +-------+          +--------+      ||
 *    ||  +--| output |<---------|zstream|<---------| input  |<--+  ||
 *    ||  |  | buffer |  next_out+-------+next_in   | buffer |   |  ||
 *    ||  |  +--------+                             +--------+   |  ||
 *    ||  |                                                      |  ||
 *    +===|======================================================|===+
 *        |                                                      |
 *        v                                                      |
 *    "output data"                                         "input data"
 *
 * If an error occurs during processing input buffer, an exception which is a
 * subclass of Zlib::Error is raised.  At that time, both input and output
 * buffer keep their conditions at the time when the error occurs.
 *
 * == Method Catalogue
 *
 * Many of the methods in this class are fairly low-level and unlikely to be
 * of interest to users.  In fact, users are unlikely to use this class
 * directly; rather they will be interested in Zlib::Inflate and
 * Zlib::Deflate.
 *
 * The higher level methods are listed below.
 *
 * - #total_in
 * - #total_out
 * - #data_type
 * - #adler
 * - #reset
 * - #finish
 * - #finished?
 * - #close
 * - #closed?
 */

/*
 * Closes the stream. All operations on the closed stream will raise an
 * exception.
 */
static VALUE
rb_zstream_end(VALUE obj)
{
    zstream_end(get_zstream(obj));
    return Qnil;
}

/*
 * Resets and initializes the stream. All data in both input and output buffer
 * are discarded.
 */
static VALUE
rb_zstream_reset(VALUE obj)
{
    zstream_reset(get_zstream(obj));
    return Qnil;
}

/*
 * Finishes the stream and flushes output buffer. See Zlib::Deflate#finish and
 * Zlib::Inflate#finish for details of this behavior.
 */
static VALUE
rb_zstream_finish(VALUE obj)
{
    struct zstream *z = get_zstream(obj);
    VALUE dst;

    zstream_run(z, (Bytef*)"", 0, Z_FINISH);
    dst = zstream_detach_buffer(z);

    OBJ_INFECT(dst, obj);
    return dst;
}

/*
 * Flushes input buffer and returns all data in that buffer.
 */
static VALUE
rb_zstream_flush_next_in(VALUE obj)
{
    struct zstream *z;
    VALUE dst;

    Data_Get_Struct(obj, struct zstream, z);
    dst = zstream_detach_input(z);
    OBJ_INFECT(dst, obj);
    return dst;
}

/*
 * Flushes output buffer and returns all data in that buffer.
 */
static VALUE
rb_zstream_flush_next_out(VALUE obj)
{
    struct zstream *z;
    VALUE dst;

    Data_Get_Struct(obj, struct zstream, z);
    dst = zstream_detach_buffer(z);
    OBJ_INFECT(dst, obj);
    return dst;
}

/*
 * Returns number of bytes of free spaces in output buffer.  Because the free
 * space is allocated automatically, this method returns 0 normally.
 */
static VALUE
rb_zstream_avail_out(VALUE obj)
{
    struct zstream *z;
    Data_Get_Struct(obj, struct zstream, z);
    return rb_uint2inum(z->stream.avail_out);
}

/*
 * Allocates +size+ bytes of free space in the output buffer. If there are more
 * than +size+ bytes already in the buffer, the buffer is truncated. Because 
 * free space is allocated automatically, you usually don't need to use this
 * method.
 */
static VALUE
rb_zstream_set_avail_out(VALUE obj, VALUE size)
{
    struct zstream *z = get_zstream(obj);

    Check_Type(size, T_FIXNUM);
    zstream_expand_buffer_into(z, FIX2INT(size));
    return size;
}

/*
 * Returns bytes of data in the input buffer. Normally, returns 0.
 */
static VALUE
rb_zstream_avail_in(VALUE obj)
{
    struct zstream *z;
    Data_Get_Struct(obj, struct zstream, z);
    return INT2FIX(NIL_P(z->input) ? 0 : (int)(RSTRING_LEN(z->input)));
}

/*
 * Returns the total bytes of the input data to the stream.  FIXME
 */
static VALUE
rb_zstream_total_in(VALUE obj)
{
    return rb_uint2inum(get_zstream(obj)->stream.total_in);
}

/*
 * Returns the total bytes of the output data from the stream.  FIXME
 */
static VALUE
rb_zstream_total_out(VALUE obj)
{
    return rb_uint2inum(get_zstream(obj)->stream.total_out);
}

/*
 * Guesses the type of the data which have been inputed into the stream. The
 * returned value is either <tt>Zlib::BINARY</tt>, <tt>Zlib::ASCII</tt>, or
 * <tt>Zlib::UNKNOWN</tt>.
 */
static VALUE
rb_zstream_data_type(VALUE obj)
{
    return INT2FIX(get_zstream(obj)->stream.data_type);
}

/*
 * Returns the adler-32 checksum.
 */
static VALUE
rb_zstream_adler(VALUE obj)
{
	return rb_uint2inum(get_zstream(obj)->stream.adler);
}

/*
 * Returns true if the stream is finished.
 */
static VALUE
rb_zstream_finished_p(VALUE obj)
{
    return ZSTREAM_IS_FINISHED(get_zstream(obj)) ? Qtrue : Qfalse;
}

/*
 * Returns true if the stream is closed.
 */
static VALUE
rb_zstream_closed_p(VALUE obj)
{
    struct zstream *z;
    Data_Get_Struct(obj, struct zstream, z);
    return ZSTREAM_IS_READY(z) ? Qfalse : Qtrue;
}


/* ------------------------------------------------------------------------- */

/*
 * Document-class: Zlib::Deflate
 *
 * Zlib::Deflate is the class for compressing data.  See Zlib::Stream for more
 * information.
 */

#define FIXNUMARG(val, ifnil) \
    (NIL_P((val)) ? (ifnil) \
    : ((void)Check_Type((val), T_FIXNUM), FIX2INT((val))))

#define ARG_LEVEL(val)     FIXNUMARG((val), Z_DEFAULT_COMPRESSION)
#define ARG_WBITS(val)     FIXNUMARG((val), MAX_WBITS)
#define ARG_MEMLEVEL(val)  FIXNUMARG((val), DEF_MEM_LEVEL)
#define ARG_STRATEGY(val)  FIXNUMARG((val), Z_DEFAULT_STRATEGY)
#define ARG_FLUSH(val)     FIXNUMARG((val), Z_NO_FLUSH)


static VALUE
rb_deflate_s_allocate(VALUE klass)
{
    return zstream_deflate_new(klass);
}

/*
 * call-seq: Zlib::Deflate.new(level=nil, windowBits=nil, memlevel=nil, strategy=nil)
 *
 * Creates a new deflate stream for compression. See zlib.h for details of
 * each argument. If an argument is nil, the default value of that argument is
 * used.
 *
 * TODO: document better!
 */
static VALUE
rb_deflate_initialize(int argc, VALUE *argv, VALUE obj)
{
    struct zstream *z;
    VALUE level, wbits, memlevel, strategy;
    int err;

    rb_scan_args(argc, argv, "04", &level, &wbits, &memlevel, &strategy);
    Data_Get_Struct(obj, struct zstream, z);

    err = deflateInit2(&z->stream, ARG_LEVEL(level), Z_DEFLATED,
		       ARG_WBITS(wbits), ARG_MEMLEVEL(memlevel),
		       ARG_STRATEGY(strategy));
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }
    ZSTREAM_READY(z);

    return obj;
}

/*
 * Duplicates the deflate stream.
 */
static VALUE
rb_deflate_init_copy(VALUE self, VALUE orig)
{
    struct zstream *z1, *z2;
    int err;

    Data_Get_Struct(self, struct zstream, z1);
    z2 = get_zstream(orig);

    err = deflateCopy(&z1->stream, &z2->stream);
    if (err != Z_OK) {
	raise_zlib_error(err, 0);
    }
    z1->input = NIL_P(z2->input) ? Qnil : rb_str_dup(z2->input);
    z1->buf   = NIL_P(z2->buf)   ? Qnil : rb_str_dup(z2->buf);
    z1->buf_filled = z2->buf_filled;
    z1->flags = z2->flags;

    return self;
}

static VALUE
deflate_run(VALUE args)
{
    struct zstream *z = (struct zstream*)((VALUE*)args)[0];
    VALUE src = ((VALUE*)args)[1];

    zstream_run(z, (Bytef*)RSTRING_PTR(src), RSTRING_LEN(src), Z_FINISH);
    return zstream_detach_buffer(z);
}

/*
 * call-seq: Zlib::Deflate.deflate(string[, level])
 *
 * Compresses the given +string+. Valid values of level are
 * <tt>Zlib::NO_COMPRESSION</tt>, <tt>Zlib::BEST_SPEED</tt>,
 * <tt>Zlib::BEST_COMPRESSION</tt>, <tt>Zlib::DEFAULT_COMPRESSION</tt>, and an
 * integer from 0 to 9.
 *
 * This method is almost equivalent to the following code:
 *
 *   def deflate(string, level)
 *     z = Zlib::Deflate.new(level)
 *     dst = z.deflate(string, Zlib::FINISH)
 *     z.close
 *     dst
 *   end
 *
 * TODO: what's default value of +level+?
 *
 */
static VALUE
rb_deflate_s_deflate(int argc, VALUE *argv, VALUE klass)
{
    struct zstream z;
    VALUE src, level, dst, args[2];
    int err, lev;

    rb_scan_args(argc, argv, "11", &src, &level);

    lev = ARG_LEVEL(level);
    StringValue(src);
    zstream_init_deflate(&z);
    err = deflateInit(&z.stream, lev);
    if (err != Z_OK) {
	raise_zlib_error(err, z.stream.msg);
    }
    ZSTREAM_READY(&z);

    args[0] = (VALUE)&z;
    args[1] = src;
    dst = rb_ensure(deflate_run, (VALUE)args, zstream_end, (VALUE)&z);

    OBJ_INFECT(dst, src);
    return dst;
}

static void
do_deflate(struct zstream *z, VALUE src, int flush)
{
    if (NIL_P(src)) {
	zstream_run(z, (Bytef*)"", 0, Z_FINISH);
	return;
    }
    StringValue(src);
    if (flush != Z_NO_FLUSH || RSTRING_LEN(src) > 0) { /* prevent BUF_ERROR */
	zstream_run(z, (Bytef*)RSTRING_PTR(src), RSTRING_LEN(src), flush);
    }
}

/*
 * call-seq: deflate(string[, flush])
 *
 * Inputs +string+ into the deflate stream and returns the output from the
 * stream.  On calling this method, both the input and the output buffers of
 * the stream are flushed. If +string+ is nil, this method finishes the
 * stream, just like Zlib::ZStream#finish.
 *
 * The value of +flush+ should be either <tt>Zlib::NO_FLUSH</tt>,
 * <tt>Zlib::SYNC_FLUSH</tt>, <tt>Zlib::FULL_FLUSH</tt>, or
 * <tt>Zlib::FINISH</tt>. See zlib.h for details.
 *
 * TODO: document better!
 */
static VALUE
rb_deflate_deflate(int argc, VALUE *argv, VALUE obj)
{
    struct zstream *z = get_zstream(obj);
    VALUE src, flush, dst;

    rb_scan_args(argc, argv, "11", &src, &flush);
    OBJ_INFECT(obj, src);
    do_deflate(z, src, ARG_FLUSH(flush));
    dst = zstream_detach_buffer(z);

    OBJ_INFECT(dst, obj);
    return dst;
}

/*
 * call-seq: << string
 *
 * Inputs +string+ into the deflate stream just like Zlib::Deflate#deflate, but
 * returns the Zlib::Deflate object itself.  The output from the stream is
 * preserved in output buffer.
 */
static VALUE
rb_deflate_addstr(VALUE obj, VALUE src)
{
    OBJ_INFECT(obj, src);
    do_deflate(get_zstream(obj), src, Z_NO_FLUSH);
    return obj;
}

/*
 * call-seq: flush(flush)
 *
 * This method is equivalent to <tt>deflate('', flush)</tt>.  If flush is omitted,
 * <tt>Zlib::SYNC_FLUSH</tt> is used as flush.  This method is just provided
 * to improve the readability of your Ruby program.
 *
 * TODO: document better!
 */
static VALUE
rb_deflate_flush(int argc, VALUE *argv, VALUE obj)
{
    struct zstream *z = get_zstream(obj);
    VALUE v_flush, dst;
    int flush;

    rb_scan_args(argc, argv, "01", &v_flush);
    flush = FIXNUMARG(v_flush, Z_SYNC_FLUSH);
    if (flush != Z_NO_FLUSH) {  /* prevent Z_BUF_ERROR */
	zstream_run(z, (Bytef*)"", 0, flush);
    }
    dst = zstream_detach_buffer(z);

    OBJ_INFECT(dst, obj);
    return dst;
}

/*
 * call-seq: params(level, strategy)
 * 
 * Changes the parameters of the deflate stream. See zlib.h for details. The
 * output from the stream by changing the params is preserved in output
 * buffer.
 *
 * TODO: document better!
 */
static VALUE
rb_deflate_params(VALUE obj, VALUE v_level, VALUE v_strategy)
{
    struct zstream *z = get_zstream(obj);
    int level, strategy;
    int err;

    level = ARG_LEVEL(v_level);
    strategy = ARG_STRATEGY(v_strategy);

    zstream_run(z, (Bytef*)"", 0, Z_SYNC_FLUSH);
    err = deflateParams(&z->stream, level, strategy);
    while (err == Z_BUF_ERROR) {
	rb_warning("deflateParams() returned Z_BUF_ERROR");
	zstream_expand_buffer(z);
	err = deflateParams(&z->stream, level, strategy);
    }
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }

    return Qnil;
}

/*
 * call-seq: set_dictionary(string)
 *
 * Sets the preset dictionary and returns +string+. This method is available
 * just only after Zlib::Deflate.new or Zlib::ZStream#reset method was called.
 * See zlib.h for details.
 *
 * TODO: document better!
 */
static VALUE
rb_deflate_set_dictionary(VALUE obj, VALUE dic)
{
    struct zstream *z = get_zstream(obj);
    VALUE src = dic;
    int err;

    OBJ_INFECT(obj, dic);
    StringValue(src);
    err = deflateSetDictionary(&z->stream,
			       (Bytef*)RSTRING_PTR(src), RSTRING_LEN(src));
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }

    return dic;
}


/* ------------------------------------------------------------------------- */

/*
 * Document-class: Zlib::Inflate
 *
 * Zlib:Inflate is the class for decompressing compressed data.  Unlike
 * Zlib::Deflate, an instance of this class is not able to duplicate (clone,
 * dup) itself.
 */



static VALUE
rb_inflate_s_allocate(VALUE klass)
{
    return zstream_inflate_new(klass);
}

/*
 * call-seq: Zlib::Inflate.new(window_bits)
 *
 * Creates a new inflate stream for decompression. See zlib.h for details
 * of the argument.  If +window_bits+ is +nil+, the default value is used.
 *
 * TODO: document better!
 */
static VALUE
rb_inflate_initialize(int argc, VALUE *argv, VALUE obj)
{
    struct zstream *z;
    VALUE wbits;
    int err;

    rb_scan_args(argc, argv, "01", &wbits);
    Data_Get_Struct(obj, struct zstream, z);

    err = inflateInit2(&z->stream, ARG_WBITS(wbits));
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }
    ZSTREAM_READY(z);

    return obj;
}

static VALUE
inflate_run(VALUE args)
{
    struct zstream *z = (struct zstream*)((VALUE*)args)[0];
    VALUE src = ((VALUE*)args)[1];

    zstream_run(z, (Bytef*)RSTRING_PTR(src), RSTRING_LEN(src), Z_SYNC_FLUSH);
    zstream_run(z, (Bytef*)"", 0, Z_FINISH);  /* for checking errors */
    return zstream_detach_buffer(z);
}

/*
 * call-seq: Zlib::Inflate.inflate(string)
 *
 * Decompresses +string+. Raises a Zlib::NeedDict exception if a preset
 * dictionary is needed for decompression.
 *
 * This method is almost equivalent to the following code:
 *
 *   def inflate(string)
 *     zstream = Zlib::Inflate.new
 *     buf = zstream.inflate(string)
 *     zstream.finish
 *     zstream.close
 *     buf
 *   end
 *
 */
static VALUE
rb_inflate_s_inflate(VALUE obj, VALUE src)
{
    struct zstream z;
    VALUE dst, args[2];
    int err;

    StringValue(src);
    zstream_init_inflate(&z);
    err = inflateInit(&z.stream);
    if (err != Z_OK) {
	raise_zlib_error(err, z.stream.msg);
    }
    ZSTREAM_READY(&z);

    args[0] = (VALUE)&z;
    args[1] = src;
    dst = rb_ensure(inflate_run, (VALUE)args, zstream_end, (VALUE)&z);

    OBJ_INFECT(dst, src);
    return dst;
}

static void
do_inflate(struct zstream *z, VALUE src)
{
    if (NIL_P(src)) {
	zstream_run(z, (Bytef*)"", 0, Z_FINISH);
	return;
    }
    StringValue(src);
    if (RSTRING_LEN(src) > 0) { /* prevent Z_BUF_ERROR */
	zstream_run(z, (Bytef*)RSTRING_PTR(src), RSTRING_LEN(src), Z_SYNC_FLUSH);
    }
}

/*
 * call-seq: inflate(string)
 *
 * Inputs +string+ into the inflate stream and returns the output from the
 * stream.  Calling this method, both the input and the output buffer of the
 * stream are flushed.  If string is +nil+, this method finishes the stream,
 * just like Zlib::ZStream#finish.
 *
 * Raises a Zlib::NeedDict exception if a preset dictionary is needed to
 * decompress.  Set the dictionary by Zlib::Inflate#set_dictionary and then
 * call this method again with an empty string.  (<i>???</i>)
 *
 * TODO: document better!
 */
static VALUE
rb_inflate_inflate(VALUE obj, VALUE src)
{
    struct zstream *z = get_zstream(obj);
    VALUE dst;

    OBJ_INFECT(obj, src);

    if (ZSTREAM_IS_FINISHED(z)) {
	if (NIL_P(src)) {
	    dst = zstream_detach_buffer(z);
	}
	else {
	    StringValue(src);
	    zstream_append_buffer2(z, src);
	    dst = rb_str_new(0, 0);
	}
    }
    else {
	do_inflate(z, src);
	dst = zstream_detach_buffer(z);
	if (ZSTREAM_IS_FINISHED(z)) {
	    zstream_passthrough_input(z);
	}
    }

    OBJ_INFECT(dst, obj);
    return dst;
}

/*
 * call-seq: << string
 *
 * Inputs +string+ into the inflate stream just like Zlib::Inflate#inflate, but
 * returns the Zlib::Inflate object itself.  The output from the stream is
 * preserved in output buffer.
 */
static VALUE
rb_inflate_addstr(VALUE obj, VALUE src)
{
    struct zstream *z = get_zstream(obj);

    OBJ_INFECT(obj, src);

    if (ZSTREAM_IS_FINISHED(z)) {
	if (!NIL_P(src)) {
	    StringValue(src);
	    zstream_append_buffer2(z, src);
	}
    }
    else {
	do_inflate(z, src);
	if (ZSTREAM_IS_FINISHED(z)) {
	    zstream_passthrough_input(z);
	}
    }

    return obj;
}

/*
 * call-seq: sync(string)
 *
 * Inputs +string+ into the end of input buffer and skips data until a full
 * flush point can be found.  If the point is found in the buffer, this method
 * flushes the buffer and returns false.  Otherwise it returns +true+ and the
 * following data of full flush point is preserved in the buffer.
 */
static VALUE
rb_inflate_sync(VALUE obj, VALUE src)
{
    struct zstream *z = get_zstream(obj);

    OBJ_INFECT(obj, src);
    StringValue(src);
    return zstream_sync(z, (Bytef*)RSTRING_PTR(src), RSTRING_LEN(src));
}

/*
 * Quoted verbatim from original documentation:
 *
 *   What is this?
 *
 * <tt>:)</tt>
 */
static VALUE
rb_inflate_sync_point_p(VALUE obj)
{
    struct zstream *z = get_zstream(obj);
    int err;

    err = inflateSyncPoint(&z->stream);
    if (err == 1) {
	return Qtrue;
    }
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }
    return Qfalse;
}

/*
 * Sets the preset dictionary and returns +string+.  This method is available just
 * only after a Zlib::NeedDict exception was raised.  See zlib.h for details.
 *
 * TODO: document better!
 */
static VALUE
rb_inflate_set_dictionary(VALUE obj, VALUE dic)
{
    struct zstream *z = get_zstream(obj);
    VALUE src = dic;
    int err;

    OBJ_INFECT(obj, dic);
    StringValue(src);
    err = inflateSetDictionary(&z->stream,
			       (Bytef*)RSTRING_PTR(src), RSTRING_LEN(src));
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }

    return dic;
}



#if GZIP_SUPPORT

/* NOTE: Features for gzip files of Ruby/zlib are written from scratch
 *       and using undocumented feature of zlib, negative wbits.
 *       I don't think gzFile APIs of zlib are good for Ruby.
 */

/*------- .gz file header --------*/

#define GZ_MAGIC1             0x1f
#define GZ_MAGIC2             0x8b
#define GZ_METHOD_DEFLATE     8
#define GZ_FLAG_MULTIPART     0x2
#define GZ_FLAG_EXTRA         0x4
#define GZ_FLAG_ORIG_NAME     0x8
#define GZ_FLAG_COMMENT       0x10
#define GZ_FLAG_ENCRYPT       0x20
#define GZ_FLAG_UNKNOWN_MASK  0xc0

#define GZ_EXTRAFLAG_FAST     0x4
#define GZ_EXTRAFLAG_SLOW     0x2

/* from zutil.h */
#define OS_MSDOS    0x00
#define OS_AMIGA    0x01
#define OS_VMS      0x02
#define OS_UNIX     0x03
#define OS_ATARI    0x05
#define OS_OS2      0x06
#define OS_MACOS    0x07
#define OS_TOPS20   0x0a
#define OS_WIN32    0x0b

#define OS_VMCMS    0x04
#define OS_ZSYSTEM  0x08
#define OS_CPM      0x09
#define OS_QDOS     0x0c
#define OS_RISCOS   0x0d
#define OS_UNKNOWN  0xff

#ifndef OS_CODE
#define OS_CODE  OS_UNIX
#endif

static ID id_write, id_read, id_readpartial, id_flush, id_seek, id_close, id_path;
static VALUE cGzError, cNoFooter, cCRCError, cLengthError;



/*-------- gzfile internal APIs --------*/

struct gzfile {
    struct zstream z;
    VALUE io;
    int level;
    time_t mtime;       /* for header */
    int os_code;        /* for header */
    VALUE orig_name;    /* for header; must be a String */
    VALUE comment;      /* for header; must be a String */
    unsigned long crc;
    int lineno;
    int ungetc;
    void (*end)(struct gzfile *);
    rb_encoding *enc;
    rb_encoding *enc2;
    rb_econv_t *ec;
    int ecflags;
    VALUE ecopts;
    char *cbuf;
    VALUE path;
};
#define GZFILE_CBUF_CAPA 10

#define GZFILE_FLAG_SYNC             ZSTREAM_FLAG_UNUSED
#define GZFILE_FLAG_HEADER_FINISHED  (ZSTREAM_FLAG_UNUSED << 1)
#define GZFILE_FLAG_FOOTER_FINISHED  (ZSTREAM_FLAG_UNUSED << 2)

#define GZFILE_IS_FINISHED(gz) \
    (ZSTREAM_IS_FINISHED(&gz->z) && (gz)->z.buf_filled == 0)

#define GZFILE_READ_SIZE  2048


static void
gzfile_mark(struct gzfile *gz)
{
    rb_gc_mark(gz->io);
    rb_gc_mark(gz->orig_name);
    rb_gc_mark(gz->comment);
    zstream_mark(&gz->z);
    rb_gc_mark(gz->ecopts);
    rb_gc_mark(gz->path);
}

static void
gzfile_free(struct gzfile *gz)
{
    struct zstream *z = &gz->z;

    if (ZSTREAM_IS_READY(z)) {
	if (z->func == &deflate_funcs) {
	    finalizer_warn("Zlib::GzipWriter object must be closed explicitly.");
	}
	zstream_finalize(z);
    }
    if (gz->cbuf) {
	xfree(gz->cbuf);
    }
    xfree(gz);
}

static VALUE
gzfile_new(klass, funcs, endfunc)
    VALUE klass;
    const struct zstream_funcs *funcs;
    void (*endfunc)(struct gzfile *);
{
    VALUE obj;
    struct gzfile *gz;

    obj = Data_Make_Struct(klass, struct gzfile, gzfile_mark, gzfile_free, gz);
    zstream_init(&gz->z, funcs);
    gz->io = Qnil;
    gz->level = 0;
    gz->mtime = 0;
    gz->os_code = OS_CODE;
    gz->orig_name = Qnil;
    gz->comment = Qnil;
    gz->crc = crc32(0, Z_NULL, 0);
    gz->lineno = 0;
    gz->ungetc = 0;
    gz->end = endfunc;
    gz->enc = rb_default_external_encoding();
    gz->enc2 = 0;
    gz->ec = NULL;
    gz->ecflags = 0;
    gz->ecopts = Qnil;
    gz->cbuf = 0;
    gz->path = Qnil;

    return obj;
}

#define gzfile_writer_new(gz) gzfile_new((gz),&deflate_funcs,gzfile_writer_end)
#define gzfile_reader_new(gz) gzfile_new((gz),&inflate_funcs,gzfile_reader_end)

static void
gzfile_reset(struct gzfile *gz)
{
    zstream_reset(&gz->z);
    gz->crc = crc32(0, Z_NULL, 0);
    gz->lineno = 0;
    gz->ungetc = 0;
    if (gz->ec) {
	rb_econv_close(gz->ec);
	gz->ec = rb_econv_open_opts(gz->enc2->name, gz->enc->name,
				    gz->ecflags, gz->ecopts);
    }
}

static void
gzfile_close(struct gzfile *gz, int closeflag)
{
    VALUE io = gz->io;

    gz->end(gz);
    gz->io = Qnil;
    gz->orig_name = Qnil;
    gz->comment = Qnil;
    if (closeflag && rb_respond_to(io, id_close)) {
	rb_funcall(io, id_close, 0);
    }
}

static void
gzfile_write_raw(struct gzfile *gz)
{
    VALUE str;

    if (gz->z.buf_filled > 0) {
	str = zstream_detach_buffer(&gz->z);
	OBJ_TAINT(str);  /* for safe */
	rb_funcall(gz->io, id_write, 1, str);
	if ((gz->z.flags & GZFILE_FLAG_SYNC)
	    && rb_respond_to(gz->io, id_flush))
	    rb_funcall(gz->io, id_flush, 0);
    }
}

static VALUE
gzfile_read_raw_partial(VALUE arg)
{
    struct gzfile *gz = (struct gzfile*)arg;
    VALUE str;

    str = rb_funcall(gz->io, id_readpartial, 1, INT2FIX(GZFILE_READ_SIZE));
    Check_Type(str, T_STRING);
    return str;
}

static VALUE
gzfile_read_raw_rescue(VALUE arg)
{
    struct gzfile *gz = (struct gzfile*)arg;
    VALUE str = Qnil;
    if (rb_obj_is_kind_of(rb_errinfo(), rb_eNoMethodError)) {
        str = rb_funcall(gz->io, id_read, 1, INT2FIX(GZFILE_READ_SIZE));
        if (!NIL_P(str)) {
            Check_Type(str, T_STRING);
        }
    }
    return str; /* return nil when EOFError */
}

static VALUE
gzfile_read_raw(struct gzfile *gz)
{
    return rb_rescue2(gzfile_read_raw_partial, (VALUE)gz,
                      gzfile_read_raw_rescue, (VALUE)gz,
                      rb_eEOFError, rb_eNoMethodError, (VALUE)0);
}

static int
gzfile_read_raw_ensure(struct gzfile *gz, int size)
{
    VALUE str;

    while (NIL_P(gz->z.input) || RSTRING_LEN(gz->z.input) < size) {
	str = gzfile_read_raw(gz);
	if (NIL_P(str)) return Qfalse;
	zstream_append_input2(&gz->z, str);
    }
    return Qtrue;
}

static char *
gzfile_read_raw_until_zero(struct gzfile *gz, long offset)
{
    VALUE str;
    char *p;

    for (;;) {
	p = memchr(RSTRING_PTR(gz->z.input) + offset, '\0',
		   RSTRING_LEN(gz->z.input) - offset);
	if (p) break;
	str = gzfile_read_raw(gz);
	if (NIL_P(str)) {
	    rb_raise(cGzError, "unexpected end of file");
	}
	offset = RSTRING_LEN(gz->z.input);
	zstream_append_input2(&gz->z, str);
    }
    return p;
}

static unsigned int
gzfile_get16(const unsigned char *src)
{
    unsigned int n;
    n  = *(src++) & 0xff;
    n |= (*(src++) & 0xff) << 8;
    return n;
}

static unsigned long
gzfile_get32(const unsigned char *src)
{
    unsigned long n;
    n  = *(src++) & 0xff;
    n |= (*(src++) & 0xff) << 8;
    n |= (*(src++) & 0xff) << 16;
    n |= (*(src++) & 0xffU) << 24;
    return n;
}

static void
gzfile_set32(unsigned long n, unsigned char *dst)
{
    *(dst++) = n & 0xff;
    *(dst++) = (n >> 8) & 0xff;
    *(dst++) = (n >> 16) & 0xff;
    *dst     = (n >> 24) & 0xff;
}

static void
gzfile_make_header(struct gzfile *gz)
{
    Bytef buf[10];  /* the size of gzip header */
    unsigned char flags = 0, extraflags = 0;

    if (!NIL_P(gz->orig_name)) {
	flags |= GZ_FLAG_ORIG_NAME;
    }
    if (!NIL_P(gz->comment)) {
	flags |= GZ_FLAG_COMMENT;
    }
    if (gz->mtime == 0) {
	gz->mtime = time(0);
    }

    if (gz->level == Z_BEST_SPEED) {
	extraflags |= GZ_EXTRAFLAG_FAST;
    }
    else if (gz->level == Z_BEST_COMPRESSION) {
	extraflags |= GZ_EXTRAFLAG_SLOW;
    …