diff options
Diffstat (limited to 'thirdparty/libwebp/src/dec/vp8_dec.c')
| -rw-r--r-- | thirdparty/libwebp/src/dec/vp8_dec.c | 721 |
1 files changed, 721 insertions, 0 deletions
diff --git a/thirdparty/libwebp/src/dec/vp8_dec.c b/thirdparty/libwebp/src/dec/vp8_dec.c new file mode 100644 index 0000000000..6212efd179 --- /dev/null +++ b/thirdparty/libwebp/src/dec/vp8_dec.c @@ -0,0 +1,721 @@ +// Copyright 2010 Google Inc. All Rights Reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the COPYING file in the root of the source +// tree. An additional intellectual property rights grant can be found +// in the file PATENTS. All contributing project authors may +// be found in the AUTHORS file in the root of the source tree. +// ----------------------------------------------------------------------------- +// +// main entry for the decoder +// +// Author: Skal (pascal.massimino@gmail.com) + +#include <stdlib.h> + +#include "src/dec/alphai_dec.h" +#include "src/dec/vp8i_dec.h" +#include "src/dec/vp8li_dec.h" +#include "src/dec/webpi_dec.h" +#include "src/utils/bit_reader_inl_utils.h" +#include "src/utils/utils.h" + +//------------------------------------------------------------------------------ + +int WebPGetDecoderVersion(void) { + return (DEC_MAJ_VERSION << 16) | (DEC_MIN_VERSION << 8) | DEC_REV_VERSION; +} + +//------------------------------------------------------------------------------ +// Signature and pointer-to-function for GetCoeffs() variants below. + +typedef int (*GetCoeffsFunc)(VP8BitReader* const br, + const VP8BandProbas* const prob[], + int ctx, const quant_t dq, int n, int16_t* out); +static volatile GetCoeffsFunc GetCoeffs = NULL; + +static void InitGetCoeffs(void); + +//------------------------------------------------------------------------------ +// VP8Decoder + +static void SetOk(VP8Decoder* const dec) { + dec->status_ = VP8_STATUS_OK; + dec->error_msg_ = "OK"; +} + +int VP8InitIoInternal(VP8Io* const io, int version) { + if (WEBP_ABI_IS_INCOMPATIBLE(version, WEBP_DECODER_ABI_VERSION)) { + return 0; // mismatch error + } + if (io != NULL) { + memset(io, 0, sizeof(*io)); + } + return 1; +} + +VP8Decoder* VP8New(void) { + VP8Decoder* const dec = (VP8Decoder*)WebPSafeCalloc(1ULL, sizeof(*dec)); + if (dec != NULL) { + SetOk(dec); + WebPGetWorkerInterface()->Init(&dec->worker_); + dec->ready_ = 0; + dec->num_parts_minus_one_ = 0; + InitGetCoeffs(); + } + return dec; +} + +VP8StatusCode VP8Status(VP8Decoder* const dec) { + if (!dec) return VP8_STATUS_INVALID_PARAM; + return dec->status_; +} + +const char* VP8StatusMessage(VP8Decoder* const dec) { + if (dec == NULL) return "no object"; + if (!dec->error_msg_) return "OK"; + return dec->error_msg_; +} + +void VP8Delete(VP8Decoder* const dec) { + if (dec != NULL) { + VP8Clear(dec); + WebPSafeFree(dec); + } +} + +int VP8SetError(VP8Decoder* const dec, + VP8StatusCode error, const char* const msg) { + // The oldest error reported takes precedence over the new one. + if (dec->status_ == VP8_STATUS_OK) { + dec->status_ = error; + dec->error_msg_ = msg; + dec->ready_ = 0; + } + return 0; +} + +//------------------------------------------------------------------------------ + +int VP8CheckSignature(const uint8_t* const data, size_t data_size) { + return (data_size >= 3 && + data[0] == 0x9d && data[1] == 0x01 && data[2] == 0x2a); +} + +int VP8GetInfo(const uint8_t* data, size_t data_size, size_t chunk_size, + int* const width, int* const height) { + if (data == NULL || data_size < VP8_FRAME_HEADER_SIZE) { + return 0; // not enough data + } + // check signature + if (!VP8CheckSignature(data + 3, data_size - 3)) { + return 0; // Wrong signature. + } else { + const uint32_t bits = data[0] | (data[1] << 8) | (data[2] << 16); + const int key_frame = !(bits & 1); + const int w = ((data[7] << 8) | data[6]) & 0x3fff; + const int h = ((data[9] << 8) | data[8]) & 0x3fff; + + if (!key_frame) { // Not a keyframe. + return 0; + } + + if (((bits >> 1) & 7) > 3) { + return 0; // unknown profile + } + if (!((bits >> 4) & 1)) { + return 0; // first frame is invisible! + } + if (((bits >> 5)) >= chunk_size) { // partition_length + return 0; // inconsistent size information. + } + if (w == 0 || h == 0) { + return 0; // We don't support both width and height to be zero. + } + + if (width) { + *width = w; + } + if (height) { + *height = h; + } + + return 1; + } +} + +//------------------------------------------------------------------------------ +// Header parsing + +static void ResetSegmentHeader(VP8SegmentHeader* const hdr) { + assert(hdr != NULL); + hdr->use_segment_ = 0; + hdr->update_map_ = 0; + hdr->absolute_delta_ = 1; + memset(hdr->quantizer_, 0, sizeof(hdr->quantizer_)); + memset(hdr->filter_strength_, 0, sizeof(hdr->filter_strength_)); +} + +// Paragraph 9.3 +static int ParseSegmentHeader(VP8BitReader* br, + VP8SegmentHeader* hdr, VP8Proba* proba) { + assert(br != NULL); + assert(hdr != NULL); + hdr->use_segment_ = VP8Get(br); + if (hdr->use_segment_) { + hdr->update_map_ = VP8Get(br); + if (VP8Get(br)) { // update data + int s; + hdr->absolute_delta_ = VP8Get(br); + for (s = 0; s < NUM_MB_SEGMENTS; ++s) { + hdr->quantizer_[s] = VP8Get(br) ? VP8GetSignedValue(br, 7) : 0; + } + for (s = 0; s < NUM_MB_SEGMENTS; ++s) { + hdr->filter_strength_[s] = VP8Get(br) ? VP8GetSignedValue(br, 6) : 0; + } + } + if (hdr->update_map_) { + int s; + for (s = 0; s < MB_FEATURE_TREE_PROBS; ++s) { + proba->segments_[s] = VP8Get(br) ? VP8GetValue(br, 8) : 255u; + } + } + } else { + hdr->update_map_ = 0; + } + return !br->eof_; +} + +// Paragraph 9.5 +// This function returns VP8_STATUS_SUSPENDED if we don't have all the +// necessary data in 'buf'. +// This case is not necessarily an error (for incremental decoding). +// Still, no bitreader is ever initialized to make it possible to read +// unavailable memory. +// If we don't even have the partitions' sizes, than VP8_STATUS_NOT_ENOUGH_DATA +// is returned, and this is an unrecoverable error. +// If the partitions were positioned ok, VP8_STATUS_OK is returned. +static VP8StatusCode ParsePartitions(VP8Decoder* const dec, + const uint8_t* buf, size_t size) { + VP8BitReader* const br = &dec->br_; + const uint8_t* sz = buf; + const uint8_t* buf_end = buf + size; + const uint8_t* part_start; + size_t size_left = size; + size_t last_part; + size_t p; + + dec->num_parts_minus_one_ = (1 << VP8GetValue(br, 2)) - 1; + last_part = dec->num_parts_minus_one_; + if (size < 3 * last_part) { + // we can't even read the sizes with sz[]! That's a failure. + return VP8_STATUS_NOT_ENOUGH_DATA; + } + part_start = buf + last_part * 3; + size_left -= last_part * 3; + for (p = 0; p < last_part; ++p) { + size_t psize = sz[0] | (sz[1] << 8) | (sz[2] << 16); + if (psize > size_left) psize = size_left; + VP8InitBitReader(dec->parts_ + p, part_start, psize); + part_start += psize; + size_left -= psize; + sz += 3; + } + VP8InitBitReader(dec->parts_ + last_part, part_start, size_left); + return (part_start < buf_end) ? VP8_STATUS_OK : + VP8_STATUS_SUSPENDED; // Init is ok, but there's not enough data +} + +// Paragraph 9.4 +static int ParseFilterHeader(VP8BitReader* br, VP8Decoder* const dec) { + VP8FilterHeader* const hdr = &dec->filter_hdr_; + hdr->simple_ = VP8Get(br); + hdr->level_ = VP8GetValue(br, 6); + hdr->sharpness_ = VP8GetValue(br, 3); + hdr->use_lf_delta_ = VP8Get(br); + if (hdr->use_lf_delta_) { + if (VP8Get(br)) { // update lf-delta? + int i; + for (i = 0; i < NUM_REF_LF_DELTAS; ++i) { + if (VP8Get(br)) { + hdr->ref_lf_delta_[i] = VP8GetSignedValue(br, 6); + } + } + for (i = 0; i < NUM_MODE_LF_DELTAS; ++i) { + if (VP8Get(br)) { + hdr->mode_lf_delta_[i] = VP8GetSignedValue(br, 6); + } + } + } + } + dec->filter_type_ = (hdr->level_ == 0) ? 0 : hdr->simple_ ? 1 : 2; + return !br->eof_; +} + +// Topmost call +int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io) { + const uint8_t* buf; + size_t buf_size; + VP8FrameHeader* frm_hdr; + VP8PictureHeader* pic_hdr; + VP8BitReader* br; + VP8StatusCode status; + + if (dec == NULL) { + return 0; + } + SetOk(dec); + if (io == NULL) { + return VP8SetError(dec, VP8_STATUS_INVALID_PARAM, + "null VP8Io passed to VP8GetHeaders()"); + } + buf = io->data; + buf_size = io->data_size; + if (buf_size < 4) { + return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA, + "Truncated header."); + } + + // Paragraph 9.1 + { + const uint32_t bits = buf[0] | (buf[1] << 8) | (buf[2] << 16); + frm_hdr = &dec->frm_hdr_; + frm_hdr->key_frame_ = !(bits & 1); + frm_hdr->profile_ = (bits >> 1) & 7; + frm_hdr->show_ = (bits >> 4) & 1; + frm_hdr->partition_length_ = (bits >> 5); + if (frm_hdr->profile_ > 3) { + return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR, + "Incorrect keyframe parameters."); + } + if (!frm_hdr->show_) { + return VP8SetError(dec, VP8_STATUS_UNSUPPORTED_FEATURE, + "Frame not displayable."); + } + buf += 3; + buf_size -= 3; + } + + pic_hdr = &dec->pic_hdr_; + if (frm_hdr->key_frame_) { + // Paragraph 9.2 + if (buf_size < 7) { + return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA, + "cannot parse picture header"); + } + if (!VP8CheckSignature(buf, buf_size)) { + return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR, + "Bad code word"); + } + pic_hdr->width_ = ((buf[4] << 8) | buf[3]) & 0x3fff; + pic_hdr->xscale_ = buf[4] >> 6; // ratio: 1, 5/4 5/3 or 2 + pic_hdr->height_ = ((buf[6] << 8) | buf[5]) & 0x3fff; + pic_hdr->yscale_ = buf[6] >> 6; + buf += 7; + buf_size -= 7; + + dec->mb_w_ = (pic_hdr->width_ + 15) >> 4; + dec->mb_h_ = (pic_hdr->height_ + 15) >> 4; + + // Setup default output area (can be later modified during io->setup()) + io->width = pic_hdr->width_; + io->height = pic_hdr->height_; + // IMPORTANT! use some sane dimensions in crop_* and scaled_* fields. + // So they can be used interchangeably without always testing for + // 'use_cropping'. + io->use_cropping = 0; + io->crop_top = 0; + io->crop_left = 0; + io->crop_right = io->width; + io->crop_bottom = io->height; + io->use_scaling = 0; + io->scaled_width = io->width; + io->scaled_height = io->height; + + io->mb_w = io->width; // sanity check + io->mb_h = io->height; // ditto + + VP8ResetProba(&dec->proba_); + ResetSegmentHeader(&dec->segment_hdr_); + } + + // Check if we have all the partition #0 available, and initialize dec->br_ + // to read this partition (and this partition only). + if (frm_hdr->partition_length_ > buf_size) { + return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA, + "bad partition length"); + } + + br = &dec->br_; + VP8InitBitReader(br, buf, frm_hdr->partition_length_); + buf += frm_hdr->partition_length_; + buf_size -= frm_hdr->partition_length_; + + if (frm_hdr->key_frame_) { + pic_hdr->colorspace_ = VP8Get(br); + pic_hdr->clamp_type_ = VP8Get(br); + } + if (!ParseSegmentHeader(br, &dec->segment_hdr_, &dec->proba_)) { + return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR, + "cannot parse segment header"); + } + // Filter specs + if (!ParseFilterHeader(br, dec)) { + return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR, + "cannot parse filter header"); + } + status = ParsePartitions(dec, buf, buf_size); + if (status != VP8_STATUS_OK) { + return VP8SetError(dec, status, "cannot parse partitions"); + } + + // quantizer change + VP8ParseQuant(dec); + + // Frame buffer marking + if (!frm_hdr->key_frame_) { + return VP8SetError(dec, VP8_STATUS_UNSUPPORTED_FEATURE, + "Not a key frame."); + } + + VP8Get(br); // ignore the value of update_proba_ + + VP8ParseProba(br, dec); + + // sanitized state + dec->ready_ = 1; + return 1; +} + +//------------------------------------------------------------------------------ +// Residual decoding (Paragraph 13.2 / 13.3) + +static const uint8_t kCat3[] = { 173, 148, 140, 0 }; +static const uint8_t kCat4[] = { 176, 155, 140, 135, 0 }; +static const uint8_t kCat5[] = { 180, 157, 141, 134, 130, 0 }; +static const uint8_t kCat6[] = + { 254, 254, 243, 230, 196, 177, 153, 140, 133, 130, 129, 0 }; +static const uint8_t* const kCat3456[] = { kCat3, kCat4, kCat5, kCat6 }; +static const uint8_t kZigzag[16] = { + 0, 1, 4, 8, 5, 2, 3, 6, 9, 12, 13, 10, 7, 11, 14, 15 +}; + +// See section 13-2: http://tools.ietf.org/html/rfc6386#section-13.2 +static int GetLargeValue(VP8BitReader* const br, const uint8_t* const p) { + int v; + if (!VP8GetBit(br, p[3])) { + if (!VP8GetBit(br, p[4])) { + v = 2; + } else { + v = 3 + VP8GetBit(br, p[5]); + } + } else { + if (!VP8GetBit(br, p[6])) { + if (!VP8GetBit(br, p[7])) { + v = 5 + VP8GetBit(br, 159); + } else { + v = 7 + 2 * VP8GetBit(br, 165); + v += VP8GetBit(br, 145); + } + } else { + const uint8_t* tab; + const int bit1 = VP8GetBit(br, p[8]); + const int bit0 = VP8GetBit(br, p[9 + bit1]); + const int cat = 2 * bit1 + bit0; + v = 0; + for (tab = kCat3456[cat]; *tab; ++tab) { + v += v + VP8GetBit(br, *tab); + } + v += 3 + (8 << cat); + } + } + return v; +} + +// Returns the position of the last non-zero coeff plus one +static int GetCoeffsFast(VP8BitReader* const br, + const VP8BandProbas* const prob[], + int ctx, const quant_t dq, int n, int16_t* out) { + const uint8_t* p = prob[n]->probas_[ctx]; + for (; n < 16; ++n) { + if (!VP8GetBit(br, p[0])) { + return n; // previous coeff was last non-zero coeff + } + while (!VP8GetBit(br, p[1])) { // sequence of zero coeffs + p = prob[++n]->probas_[0]; + if (n == 16) return 16; + } + { // non zero coeff + const VP8ProbaArray* const p_ctx = &prob[n + 1]->probas_[0]; + int v; + if (!VP8GetBit(br, p[2])) { + v = 1; + p = p_ctx[1]; + } else { + v = GetLargeValue(br, p); + p = p_ctx[2]; + } + out[kZigzag[n]] = VP8GetSigned(br, v) * dq[n > 0]; + } + } + return 16; +} + +// This version of GetCoeffs() uses VP8GetBitAlt() which is an alternate version +// of VP8GetBitAlt() targeting specific platforms. +static int GetCoeffsAlt(VP8BitReader* const br, + const VP8BandProbas* const prob[], + int ctx, const quant_t dq, int n, int16_t* out) { + const uint8_t* p = prob[n]->probas_[ctx]; + for (; n < 16; ++n) { + if (!VP8GetBitAlt(br, p[0])) { + return n; // previous coeff was last non-zero coeff + } + while (!VP8GetBitAlt(br, p[1])) { // sequence of zero coeffs + p = prob[++n]->probas_[0]; + if (n == 16) return 16; + } + { // non zero coeff + const VP8ProbaArray* const p_ctx = &prob[n + 1]->probas_[0]; + int v; + if (!VP8GetBitAlt(br, p[2])) { + v = 1; + p = p_ctx[1]; + } else { + v = GetLargeValue(br, p); + p = p_ctx[2]; + } + out[kZigzag[n]] = VP8GetSigned(br, v) * dq[n > 0]; + } + } + return 16; +} + +WEBP_TSAN_IGNORE_FUNCTION static void InitGetCoeffs(void) { + if (GetCoeffs == NULL) { + if (VP8GetCPUInfo != NULL && VP8GetCPUInfo(kSlowSSSE3)) { + GetCoeffs = GetCoeffsAlt; + } else { + GetCoeffs = GetCoeffsFast; + } + } +} + +static WEBP_INLINE uint32_t NzCodeBits(uint32_t nz_coeffs, int nz, int dc_nz) { + nz_coeffs <<= 2; + nz_coeffs |= (nz > 3) ? 3 : (nz > 1) ? 2 : dc_nz; + return nz_coeffs; +} + +static int ParseResiduals(VP8Decoder* const dec, + VP8MB* const mb, VP8BitReader* const token_br) { + const VP8BandProbas* (* const bands)[16 + 1] = dec->proba_.bands_ptr_; + const VP8BandProbas* const * ac_proba; + VP8MBData* const block = dec->mb_data_ + dec->mb_x_; + const VP8QuantMatrix* const q = &dec->dqm_[block->segment_]; + int16_t* dst = block->coeffs_; + VP8MB* const left_mb = dec->mb_info_ - 1; + uint8_t tnz, lnz; + uint32_t non_zero_y = 0; + uint32_t non_zero_uv = 0; + int x, y, ch; + uint32_t out_t_nz, out_l_nz; + int first; + + memset(dst, 0, 384 * sizeof(*dst)); + if (!block->is_i4x4_) { // parse DC + int16_t dc[16] = { 0 }; + const int ctx = mb->nz_dc_ + left_mb->nz_dc_; + const int nz = GetCoeffs(token_br, bands[1], ctx, q->y2_mat_, 0, dc); + mb->nz_dc_ = left_mb->nz_dc_ = (nz > 0); + if (nz > 1) { // more than just the DC -> perform the full transform + VP8TransformWHT(dc, dst); + } else { // only DC is non-zero -> inlined simplified transform + int i; + const int dc0 = (dc[0] + 3) >> 3; + for (i = 0; i < 16 * 16; i += 16) dst[i] = dc0; + } + first = 1; + ac_proba = bands[0]; + } else { + first = 0; + ac_proba = bands[3]; + } + + tnz = mb->nz_ & 0x0f; + lnz = left_mb->nz_ & 0x0f; + for (y = 0; y < 4; ++y) { + int l = lnz & 1; + uint32_t nz_coeffs = 0; + for (x = 0; x < 4; ++x) { + const int ctx = l + (tnz & 1); + const int nz = GetCoeffs(token_br, ac_proba, ctx, q->y1_mat_, first, dst); + l = (nz > first); + tnz = (tnz >> 1) | (l << 7); + nz_coeffs = NzCodeBits(nz_coeffs, nz, dst[0] != 0); + dst += 16; + } + tnz >>= 4; + lnz = (lnz >> 1) | (l << 7); + non_zero_y = (non_zero_y << 8) | nz_coeffs; + } + out_t_nz = tnz; + out_l_nz = lnz >> 4; + + for (ch = 0; ch < 4; ch += 2) { + uint32_t nz_coeffs = 0; + tnz = mb->nz_ >> (4 + ch); + lnz = left_mb->nz_ >> (4 + ch); + for (y = 0; y < 2; ++y) { + int l = lnz & 1; + for (x = 0; x < 2; ++x) { + const int ctx = l + (tnz & 1); + const int nz = GetCoeffs(token_br, bands[2], ctx, q->uv_mat_, 0, dst); + l = (nz > 0); + tnz = (tnz >> 1) | (l << 3); + nz_coeffs = NzCodeBits(nz_coeffs, nz, dst[0] != 0); + dst += 16; + } + tnz >>= 2; + lnz = (lnz >> 1) | (l << 5); + } + // Note: we don't really need the per-4x4 details for U/V blocks. + non_zero_uv |= nz_coeffs << (4 * ch); + out_t_nz |= (tnz << 4) << ch; + out_l_nz |= (lnz & 0xf0) << ch; + } + mb->nz_ = out_t_nz; + left_mb->nz_ = out_l_nz; + + block->non_zero_y_ = non_zero_y; + block->non_zero_uv_ = non_zero_uv; + + // We look at the mode-code of each block and check if some blocks have less + // than three non-zero coeffs (code < 2). This is to avoid dithering flat and + // empty blocks. + block->dither_ = (non_zero_uv & 0xaaaa) ? 0 : q->dither_; + + return !(non_zero_y | non_zero_uv); // will be used for further optimization +} + +//------------------------------------------------------------------------------ +// Main loop + +int VP8DecodeMB(VP8Decoder* const dec, VP8BitReader* const token_br) { + VP8MB* const left = dec->mb_info_ - 1; + VP8MB* const mb = dec->mb_info_ + dec->mb_x_; + VP8MBData* const block = dec->mb_data_ + dec->mb_x_; + int skip = dec->use_skip_proba_ ? block->skip_ : 0; + + if (!skip) { + skip = ParseResiduals(dec, mb, token_br); + } else { + left->nz_ = mb->nz_ = 0; + if (!block->is_i4x4_) { + left->nz_dc_ = mb->nz_dc_ = 0; + } + block->non_zero_y_ = 0; + block->non_zero_uv_ = 0; + block->dither_ = 0; + } + + if (dec->filter_type_ > 0) { // store filter info + VP8FInfo* const finfo = dec->f_info_ + dec->mb_x_; + *finfo = dec->fstrengths_[block->segment_][block->is_i4x4_]; + finfo->f_inner_ |= !skip; + } + + return !token_br->eof_; +} + +void VP8InitScanline(VP8Decoder* const dec) { + VP8MB* const left = dec->mb_info_ - 1; + left->nz_ = 0; + left->nz_dc_ = 0; + memset(dec->intra_l_, B_DC_PRED, sizeof(dec->intra_l_)); + dec->mb_x_ = 0; +} + +static int ParseFrame(VP8Decoder* const dec, VP8Io* io) { + for (dec->mb_y_ = 0; dec->mb_y_ < dec->br_mb_y_; ++dec->mb_y_) { + // Parse bitstream for this row. + VP8BitReader* const token_br = + &dec->parts_[dec->mb_y_ & dec->num_parts_minus_one_]; + if (!VP8ParseIntraModeRow(&dec->br_, dec)) { + return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA, + "Premature end-of-partition0 encountered."); + } + for (; dec->mb_x_ < dec->mb_w_; ++dec->mb_x_) { + if (!VP8DecodeMB(dec, token_br)) { + return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA, + "Premature end-of-file encountered."); + } + } + VP8InitScanline(dec); // Prepare for next scanline + + // Reconstruct, filter and emit the row. + if (!VP8ProcessRow(dec, io)) { + return VP8SetError(dec, VP8_STATUS_USER_ABORT, "Output aborted."); + } + } + if (dec->mt_method_ > 0) { + if (!WebPGetWorkerInterface()->Sync(&dec->worker_)) return 0; + } + + return 1; +} + +// Main entry point +int VP8Decode(VP8Decoder* const dec, VP8Io* const io) { + int ok = 0; + if (dec == NULL) { + return 0; + } + if (io == NULL) { + return VP8SetError(dec, VP8_STATUS_INVALID_PARAM, + "NULL VP8Io parameter in VP8Decode()."); + } + + if (!dec->ready_) { + if (!VP8GetHeaders(dec, io)) { + return 0; + } + } + assert(dec->ready_); + + // Finish setting up the decoding parameter. Will call io->setup(). + ok = (VP8EnterCritical(dec, io) == VP8_STATUS_OK); + if (ok) { // good to go. + // Will allocate memory and prepare everything. + if (ok) ok = VP8InitFrame(dec, io); + + // Main decoding loop + if (ok) ok = ParseFrame(dec, io); + + // Exit. + ok &= VP8ExitCritical(dec, io); + } + + if (!ok) { + VP8Clear(dec); + return 0; + } + + dec->ready_ = 0; + return ok; +} + +void VP8Clear(VP8Decoder* const dec) { + if (dec == NULL) { + return; + } + WebPGetWorkerInterface()->End(&dec->worker_); + WebPDeallocateAlphaMemory(dec); + WebPSafeFree(dec->mem_); + dec->mem_ = NULL; + dec->mem_size_ = 0; + memset(&dec->br_, 0, sizeof(dec->br_)); + dec->ready_ = 0; +} + +//------------------------------------------------------------------------------ |