[FFmpeg-devel] [PATCH] avcodec/exr: simplify piz decompression
Paul B Mahol
onemda at gmail.com
Sun Feb 21 01:46:06 EET 2021
On Sat, Feb 20, 2021 at 11:11 PM Andreas Rheinhardt <
andreas.rheinhardt at gmail.com> wrote:
> Paul B Mahol:
> > Signed-off-by: Paul B Mahol <onemda at gmail.com>
> > ---
> > libavcodec/exr.c | 212 +++++++++++++++--------------------------------
> > 1 file changed, 65 insertions(+), 147 deletions(-)
> >
> > diff --git a/libavcodec/exr.c b/libavcodec/exr.c
> > index cacdff5774..625ee4680c 100644
> > --- a/libavcodec/exr.c
> > +++ b/libavcodec/exr.c
> > @@ -91,6 +91,12 @@ enum ExrTileLevelRound {
> > EXR_TILE_ROUND_UNKNOWN,
> > };
> >
> > +typedef struct HuffEntry {
> > + uint8_t len;
> > + uint16_t sym;
> > + uint16_t code;
>
> The old code allowed codes with a length of <= 58. This is more than our
> VLC-API allows and even more than fits into a 16-bit code. You seem to
> believe that all codes have a length <= 16 just because HUF_ENCBITS is
> 16. But this is wrong: It just means that there are at most 1<<16
> ordinary symbols and one special symbol for runs. It also means that we
> can't even distinguish all possible symbols because VLC_TYPE is 16 bits.
>
Fixed to use 32bits code, also added messages to ask for sample if more is
needed.
> > +} HuffEntry;
> > +
> > typedef struct EXRChannel {
> > int xsub, ysub;
> > enum ExrPixelType pixel_type;
> > @@ -116,6 +122,11 @@ typedef struct EXRThreadData {
> > int ysize, xsize;
> >
> > int channel_line_size;
> > +
> > + uint16_t run_sym;
> > + HuffEntry *he;
> > + uint64_t *freq;
> > + VLC vlc;
> > } EXRThreadData;
> >
> > typedef struct EXRContext {
> > @@ -319,11 +330,8 @@ static void apply_lut(const uint16_t *lut, uint16_t
> *dst, int dsize)
> > }
> >
> > #define HUF_ENCBITS 16 // literal (value) bit length
> > -#define HUF_DECBITS 14 // decoding bit size (>= 8)
> >
> > #define HUF_ENCSIZE ((1 << HUF_ENCBITS) + 1) // encoding table size
> > -#define HUF_DECSIZE (1 << HUF_DECBITS) // decoding table size
> > -#define HUF_DECMASK (HUF_DECSIZE - 1)
> >
> > typedef struct HufDec {
> > int len;
> > @@ -336,7 +344,7 @@ static void huf_canonical_code_table(uint64_t *hcode)
> > uint64_t c, n[59] = { 0 };
> > int i;
> >
> > - for (i = 0; i < HUF_ENCSIZE; ++i)
> > + for (i = 0; i < HUF_ENCSIZE; i++)
>
> Spurious change.
>
> > n[hcode[i]] += 1;
> >
> > c = 0;
> > @@ -399,149 +407,63 @@ static int huf_unpack_enc_table(GetByteContext
> *gb,
> > return 0;
> > }
> >
> > -static int huf_build_dec_table(const uint64_t *hcode, int im,
> > - int iM, HufDec *hdecod)
> > +static int huf_build_dec_table(EXRThreadData *td, int im, int iM)
> > {
> > - for (; im <= iM; im++) {
> > - uint64_t c = hcode[im] >> 6;
> > - int i, l = hcode[im] & 63;
> > -
> > - if (c >> l)
> > - return AVERROR_INVALIDDATA;
> > -
> > - if (l > HUF_DECBITS) {
> > - HufDec *pl = hdecod + (c >> (l - HUF_DECBITS));
> > - if (pl->len)
> > - return AVERROR_INVALIDDATA;
> > -
> > - pl->lit++;
> > -
> > - pl->p = av_realloc(pl->p, pl->lit * sizeof(int));
> > - if (!pl->p)
> > - return AVERROR(ENOMEM);
> > -
> > - pl->p[pl->lit - 1] = im;
> > - } else if (l) {
> > - HufDec *pl = hdecod + (c << (HUF_DECBITS - l));
> > -
> > - for (i = 1 << (HUF_DECBITS - l); i > 0; i--, pl++) {
> > - if (pl->len || pl->p)
> > - return AVERROR_INVALIDDATA;
> > - pl->len = l;
> > - pl->lit = im;
> > - }
> > - }
> > + int j = 0;
> > +
> > + for (int i = im; i < iM; i++) {
> > + td->he[j].sym = i;
> > + td->he[j].len = td->freq[i] & 63;
> > + td->he[j].code = td->freq[i] >> 6;> + if (td->he[j].len
> > 0)
> > + j++;
> > + else
> > + td->run_sym = i;
> > }
> >
> > - return 0;
> > -}
> > -
> > -#define get_char(c, lc, gb)
> \
> > -{
> \
> > - c = (c << 8) | bytestream2_get_byte(gb);
> \
> > - lc += 8;
> \
> > -}
> > + td->he[j].sym = td->run_sym;
> > + td->he[j].len = td->freq[iM] & 63;
> > + td->he[j].code = td->freq[iM] >> 6;
> > + j++;
> >
> > -#define get_code(po, rlc, c, lc, gb, out, oe, outb)
> \
> > -{
> \
> > - if (po == rlc) {
> \
> > - if (lc < 8)
> \
> > - get_char(c, lc, gb);
> \
> > - lc -= 8;
> \
> > -
> \
> > - cs = c >> lc;
> \
> > -
> \
> > - if (out + cs > oe || out == outb)
> \
> > - return AVERROR_INVALIDDATA;
> \
> > -
> \
> > - s = out[-1];
> \
> > -
> \
> > - while (cs-- > 0)
> \
> > - *out++ = s;
> \
> > - } else if (out < oe) {
> \
> > - *out++ = po;
> \
> > - } else {
> \
> > - return AVERROR_INVALIDDATA;
> \
> > - }
> \
> > + ff_free_vlc(&td->vlc);
> > + return ff_init_vlc_sparse(&td->vlc, 12, j,
> > + &td->he[0].len, sizeof(td->he[0]),
> sizeof(td->he[0].len),
> > + &td->he[0].code, sizeof(td->he[0]),
> sizeof(td->he[0].code),
> > + &td->he[0].sym, sizeof(td->he[0]),
> sizeof(td->he[0].sym), 0);
> > }
> >
> > -static int huf_decode(const uint64_t *hcode, const HufDec *hdecod,
> > - GetByteContext *gb, int nbits,
> > - int rlc, int no, uint16_t *out)
> > +static int huf_decode(VLC *vlc, GetByteContext *gb, int nbits, int
> run_sym,
> > + int no, uint16_t *out)
> > {
> > - uint64_t c = 0;
> > - uint16_t *outb = out;
> > - uint16_t *oe = out + no;
> > - const uint8_t *ie = gb->buffer + (nbits + 7) / 8; // input byte size
> > - uint8_t cs;
> > - uint16_t s;
> > - int i, lc = 0;
> > -
> > - while (gb->buffer < ie) {
> > - get_char(c, lc, gb);
> > -
> > - while (lc >= HUF_DECBITS) {
> > - const HufDec pl = hdecod[(c >> (lc - HUF_DECBITS)) &
> HUF_DECMASK];
> > -
> > - if (pl.len) {
> > - lc -= pl.len;
> > - get_code(pl.lit, rlc, c, lc, gb, out, oe, outb);
> > - } else {
> > - int j;
> > -
> > - if (!pl.p)
> > - return AVERROR_INVALIDDATA;
> > -
> > - for (j = 0; j < pl.lit; j++) {
> > - int l = hcode[pl.p[j]] & 63;
> > -
> > - while (lc < l && bytestream2_get_bytes_left(gb) > 0)
> > - get_char(c, lc, gb);
> > -
> > - if (lc >= l) {
> > - if ((hcode[pl.p[j]] >> 6) ==
> > - ((c >> (lc - l)) & ((1LL << l) - 1))) {
> > - lc -= l;
> > - get_code(pl.p[j], rlc, c, lc, gb, out, oe,
> outb);
> > - break;
> > - }
> > - }
> > - }
> > -
> > - if (j == pl.lit)
> > - return AVERROR_INVALIDDATA;
> > - }
> > - }
> > - }
> > + GetBitContext gbit;
> > + int oe = 0;
> >
> > - i = (8 - nbits) & 7;
> > - c >>= i;
> > - lc -= i;
> > + init_get_bits(&gbit, gb->buffer, nbits);
> > + while (get_bits_left(&gbit) > 0 && oe < no) {
> > + uint16_t x = get_vlc2(&gbit, vlc->table, 12, 2);
> >
> > - while (lc > 0) {
> > - const HufDec pl = hdecod[(c << (HUF_DECBITS - lc)) &
> HUF_DECMASK];
> > + if (x == run_sym) {
> > + int run = get_bits(&gbit, 8);
> > + uint16_t fill = out[oe - 1];
> >
> > - if (pl.len && lc >= pl.len) {
> > - lc -= pl.len;
> > - get_code(pl.lit, rlc, c, lc, gb, out, oe, outb);
> > + while (run-- > 0)
> > + out[oe++] = fill;
> > } else {
> > - return AVERROR_INVALIDDATA;
> > + out[oe++] = x;
> > }
> > }
> >
> > - if (out - outb != no)
> > - return AVERROR_INVALIDDATA;
> > return 0;
> > }
> >
> > -static int huf_uncompress(GetByteContext *gb,
> > +static int huf_uncompress(EXRThreadData *td,
> > + GetByteContext *gb,
> > uint16_t *dst, int dst_size)
> > {
> > int32_t src_size, im, iM;
> > uint32_t nBits;
> > - uint64_t *freq;
> > - HufDec *hdec;
> > - int ret, i;
> > + int ret;
> >
> > src_size = bytestream2_get_le32(gb);
> > im = bytestream2_get_le32(gb);
> > @@ -555,34 +477,27 @@ static int huf_uncompress(GetByteContext *gb,
> >
> > bytestream2_skip(gb, 4);
> >
> > - freq = av_mallocz_array(HUF_ENCSIZE, sizeof(*freq));
> > - hdec = av_mallocz_array(HUF_DECSIZE, sizeof(*hdec));
> > - if (!freq || !hdec) {
> > + if (!td->freq)
> > + td->freq = av_malloc_array(HUF_ENCSIZE, sizeof(*td->freq));
> > + if (!td->he)
> > + td->he = av_calloc(HUF_ENCSIZE, sizeof(*td->he));
> > + if (!td->freq || !td->he) {
> > ret = AVERROR(ENOMEM);
> > - goto fail;
> > + return ret;
> > }
> >
> > - if ((ret = huf_unpack_enc_table(gb, im, iM, freq)) < 0)
> > - goto fail;
> > + memset(td->freq, 0, sizeof(*td->freq) * HUF_ENCSIZE);
> > + if ((ret = huf_unpack_enc_table(gb, im, iM, td->freq)) < 0)
> > + return ret;
> >
> > if (nBits > 8 * bytestream2_get_bytes_left(gb)) {
> > ret = AVERROR_INVALIDDATA;
> > - goto fail;
> > + return ret;
> > }
> >
> > - if ((ret = huf_build_dec_table(freq, im, iM, hdec)) < 0)
> > - goto fail;
> > - ret = huf_decode(freq, hdec, gb, nBits, iM, dst_size, dst);
> > -
> > -fail:
> > - for (i = 0; i < HUF_DECSIZE; i++)
> > - if (hdec)
> > - av_freep(&hdec[i].p);
> > -
> > - av_free(freq);
> > - av_free(hdec);
> > -
> > - return ret;
> > + if ((ret = huf_build_dec_table(td, im, iM)) < 0)
> > + return ret;
> > + return huf_decode(&td->vlc, gb, nBits, td->run_sym, dst_size, dst);
> > }
> >
> > static inline void wdec14(uint16_t l, uint16_t h, uint16_t *a, uint16_t
> *b)
> > @@ -730,7 +645,7 @@ static int piz_uncompress(EXRContext *s, const
> uint8_t *src, int ssize,
> >
> > maxval = reverse_lut(td->bitmap, td->lut);
> >
> > - ret = huf_uncompress(&gb, tmp, dsize / sizeof(uint16_t));
> > + ret = huf_uncompress(td, &gb, tmp, dsize / sizeof(uint16_t));
> > if (ret)
> > return ret;
> >
> > @@ -2045,6 +1960,9 @@ static av_cold int decode_end(AVCodecContext
> *avctx)
> > av_freep(&td->tmp);
> > av_freep(&td->bitmap);
> > av_freep(&td->lut);
> > + av_freep(&td->he);
> > + av_freep(&td->freq);
> > + ff_free_vlc(&td->vlc);
> > }
> >
> > av_freep(&s->thread_data);
> >
>
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