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Merged
rtissera merged 1 commit into from
Sep 10, 2026
Merged

Share one subcode inflater across the CD codecs #189

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9 changes: 9 additions & 0 deletions src/codec_zlib.h
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Original file line number Diff line number Diff line change
Expand Up @@ -51,12 +51,21 @@ struct _zlib_codec_data
* against a 254KB peak for a three-codec CD file. Heap-allocated rather
* than inline because chd_file embeds every codec's state by value. */
tinfl_decompressor * inflater;
/* Set when `inflater` is owned by the chd_file rather than by this codec.
* The CD codecs' subcode inflaters are one shared object - a hunk is
* decoded by exactly one CD codec, and tinfl_init() runs on entry to
* every decompress, so nothing carries across - and only the owner
* frees it. */
int borrowed;
#endif
};

/* zlib compression codec */
chd_error zlib_codec_init(void *codec, uint32_t hunkbytes);
void zlib_codec_free(void *codec);
#ifndef CHDR_SYSTEM_ZLIB
void zlib_codec_lend(void *codec, void *owner);
#endif
chd_error zlib_codec_decompress(void *codec, const uint8_t *src, uint32_t complen, uint8_t *dest, uint32_t destlen);

#endif /* LIBCHDR_CODEC_ZLIB_H */
69 changes: 69 additions & 0 deletions src/libchdr_chd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -326,6 +326,17 @@ struct _chd_file
avhuff_codec_data avhuff; /* avhuff codec data */
} codec_data;

#if WANT_SUBCODE && !defined(CHDR_SYSTEM_ZLIB)
/* One inflater for every CD codec's subcode stream. cdzl, cdlz and cdfl
* each used to allocate their own, but a hunk is decoded by exactly one
* CD codec and zlib_codec_decompress() runs tinfl_init() on entry, so
* nothing carries from one to the next - three tinfl_decompressor
* instances where one does. At CD geometry that is 16752 bytes back on a
* file using all three, 9.3% of its peak. cdzs is not here: its subcode
* goes through zstd. */
zlib_codec_data subcode_shared;
#endif

uint8_t * file_cache; /* cache of underlying file */

/* Compressed read-ahead. libchdr issues one seek+read per hunk, and
Expand Down Expand Up @@ -436,6 +447,9 @@ static chd_error header_read(chd_file *chd);
#endif
#endif

#if WANT_SUBCODE && !defined(CHDR_SYSTEM_ZLIB)
static chd_error cd_lend_subcode_inflater(chd_file *chd, uint32_t tag, void *codec);
#endif
static chd_error hunk_read_into_memory(chd_file *chd, uint32_t hunknum, uint8_t *dest);

/*-------------------------------------------------
Expand Down Expand Up @@ -1877,6 +1891,14 @@ static chd_error ensure_codec_ready(chd_file *chd, size_t slot, void *codec)
}
}

#if WANT_SUBCODE && !defined(CHDR_SYSTEM_ZLIB)
{
chd_error lerr = cd_lend_subcode_inflater(chd, chd->codecintf[slot]->compression, codec);
if (lerr != CHDERR_NONE)
return lerr;
}
#endif

if (chd->codecintf[slot]->init != NULL)
{
chd_error err = chd->codecintf[slot]->init(codec, chd->header.hunkbytes);
Expand Down Expand Up @@ -2163,6 +2185,13 @@ CHD_EXPORT chd_error chd_open_core_file_callbacks(const core_file_callbacks *cal
if (codec == NULL)
EARLY_EXIT(err = CHDERR_UNSUPPORTED_FORMAT);

#if WANT_SUBCODE && !defined(CHDR_SYSTEM_ZLIB)
err = cd_lend_subcode_inflater(newchd,
newchd->header.compression[decompnum], codec);
if (err != CHDERR_NONE)
EARLY_EXIT(err);
#endif

err = newchd->codecintf[decompnum]->init(codec, newchd->header.hunkbytes);
if (err != CHDERR_NONE)
EARLY_EXIT(err);
Expand Down Expand Up @@ -2318,6 +2347,12 @@ CHD_EXPORT void chd_close(chd_file *chd)
if (chd == NULL || chd->cookie != COOKIE_VALUE)
return;

#if WANT_SUBCODE && !defined(CHDR_SYSTEM_ZLIB)
/* The CD codecs only borrowed this one; free it here, once, after they
* have all dropped their pointers to it. */
zlib_codec_free(&chd->subcode_shared);
#endif

/* deinit the codec */
if (chd->header.version < 5)
{
Expand Down Expand Up @@ -3079,6 +3114,40 @@ static chd_error hunk_read_uncompressed(chd_file *chd, uint64_t offset, size_t s
return CHDERR_NONE;
}

#if WANT_SUBCODE && !defined(CHDR_SYSTEM_ZLIB)
/*-------------------------------------------------
cd_lend_subcode_inflater - seed a CD codec's
subcode inflater from the shared one
-------------------------------------------------*/

/* Seeds before the codec's own init runs: zlib_codec_init() keeps an inflater
* that is already marked borrowed, so nothing is allocated and then thrown
* away. Ordering-proof, which matters because LOWRAM_TARGET readies codecs
* lazily and in whatever order the hunks ask for them. */
static chd_error cd_lend_subcode_inflater(chd_file *chd, uint32_t tag, void *codec)
{
void *sub;

switch (tag)
{
case CHD_CODEC_CD_ZLIB: sub = &((cdzl_codec_data *)codec)->subcode_decompressor; break;
case CHD_CODEC_CD_LZMA: sub = &((cdlz_codec_data *)codec)->subcode_decompressor; break;
case CHD_CODEC_CD_FLAC: sub = &((cdfl_codec_data *)codec)->subcode_decompressor; break;
default: return CHDERR_NONE;
}

if (chd->subcode_shared.inflater == NULL)
{
chd_error err = zlib_codec_init(&chd->subcode_shared, 0);
if (err != CHDERR_NONE)
return err;
}

zlib_codec_lend(sub, &chd->subcode_shared);
return CHDERR_NONE;
}
#endif

/*-------------------------------------------------
hunk_read_into_memory - read a hunk into
memory at the given location
Expand Down
28 changes: 27 additions & 1 deletion src/libchdr_codec_zlib.c
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Original file line number Diff line number Diff line change
Expand Up @@ -18,13 +18,37 @@ static void zlib_allocator_free(voidpf opaque);

/* ---- bundled miniz: drive tinfl directly, no 32KB dictionary ---- */

/*-------------------------------------------------
zlib_codec_lend - point this codec's inflater
at one owned elsewhere
-------------------------------------------------*/

void zlib_codec_lend(void *codec, void *owner)
{
zlib_codec_data *data = (zlib_codec_data *)codec;
zlib_codec_data *src = (zlib_codec_data *)owner;

data->inflater = src->inflater;
data->borrowed = 1;
}

chd_error zlib_codec_init(void *codec, uint32_t hunkbytes)
{
zlib_codec_data *data = (zlib_codec_data *)codec;

(void)hunkbytes;

/* A borrowed inflater is seeded before init runs; keep it across the
* wipe rather than allocating a second one. */
tinfl_decompressor *lent = data->borrowed ? data->inflater : NULL;

memset(data, 0, sizeof(zlib_codec_data));
if (lent != NULL)
{
data->inflater = lent;
data->borrowed = 1;
return CHDERR_NONE;
}
data->inflater = (tinfl_decompressor *)malloc(sizeof(tinfl_decompressor));
if (data->inflater == NULL)
return CHDERR_OUT_OF_MEMORY;
Expand All @@ -38,8 +62,10 @@ void zlib_codec_free(void *codec)

if (data != NULL && data->inflater != NULL)
{
free(data->inflater);
if (!data->borrowed)
free(data->inflater);
data->inflater = NULL;
data->borrowed = 0;
}
}

Expand Down
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