1 // Copyright 2011 Google Inc. All Rights Reserved.
2 //
3 // Use of this source code is governed by a BSD-style license
4 // that can be found in the COPYING file in the root of the source
5 // tree. An additional intellectual property rights grant can be found
6 // in the file PATENTS. All contributing project authors may
7 // be found in the AUTHORS file in the root of the source tree.
8 // -----------------------------------------------------------------------------
9 //
10 // Internal objects and utils for mux.
11 //
12 // Authors: Urvang (urvang@google.com)
13 //          Vikas (vikasa@google.com)
14 
15 #include <assert.h>
16 #include "./muxi.h"
17 #include "../utils/utils.h"
18 
19 #if defined(__cplusplus) || defined(c_plusplus)
20 extern "C" {
21 #endif
22 
23 #define UNDEFINED_CHUNK_SIZE (-1)
24 
25 const ChunkInfo kChunks[] = {
26   { MKFOURCC('V', 'P', '8', 'X'),  WEBP_CHUNK_VP8X,    VP8X_CHUNK_SIZE },
27   { MKFOURCC('I', 'C', 'C', 'P'),  WEBP_CHUNK_ICCP,    UNDEFINED_CHUNK_SIZE },
28   { MKFOURCC('A', 'N', 'I', 'M'),  WEBP_CHUNK_ANIM,    ANIM_CHUNK_SIZE },
29   { MKFOURCC('A', 'N', 'M', 'F'),  WEBP_CHUNK_ANMF,    ANMF_CHUNK_SIZE },
30   { MKFOURCC('F', 'R', 'G', 'M'),  WEBP_CHUNK_FRGM,    FRGM_CHUNK_SIZE },
31   { MKFOURCC('A', 'L', 'P', 'H'),  WEBP_CHUNK_ALPHA,   UNDEFINED_CHUNK_SIZE },
32   { MKFOURCC('V', 'P', '8', ' '),  WEBP_CHUNK_IMAGE,   UNDEFINED_CHUNK_SIZE },
33   { MKFOURCC('V', 'P', '8', 'L'),  WEBP_CHUNK_IMAGE,   UNDEFINED_CHUNK_SIZE },
34   { MKFOURCC('E', 'X', 'I', 'F'),  WEBP_CHUNK_EXIF,    UNDEFINED_CHUNK_SIZE },
35   { MKFOURCC('X', 'M', 'P', ' '),  WEBP_CHUNK_XMP,     UNDEFINED_CHUNK_SIZE },
36   { MKFOURCC('U', 'N', 'K', 'N'),  WEBP_CHUNK_UNKNOWN, UNDEFINED_CHUNK_SIZE },
37 
38   { NIL_TAG,                       WEBP_CHUNK_NIL,     UNDEFINED_CHUNK_SIZE }
39 };
40 
41 //------------------------------------------------------------------------------
42 
WebPGetMuxVersion(void)43 int WebPGetMuxVersion(void) {
44   return (MUX_MAJ_VERSION << 16) | (MUX_MIN_VERSION << 8) | MUX_REV_VERSION;
45 }
46 
47 //------------------------------------------------------------------------------
48 // Life of a chunk object.
49 
ChunkInit(WebPChunk * const chunk)50 void ChunkInit(WebPChunk* const chunk) {
51   assert(chunk);
52   memset(chunk, 0, sizeof(*chunk));
53   chunk->tag_ = NIL_TAG;
54 }
55 
ChunkRelease(WebPChunk * const chunk)56 WebPChunk* ChunkRelease(WebPChunk* const chunk) {
57   WebPChunk* next;
58   if (chunk == NULL) return NULL;
59   if (chunk->owner_) {
60     WebPDataClear(&chunk->data_);
61   }
62   next = chunk->next_;
63   ChunkInit(chunk);
64   return next;
65 }
66 
67 //------------------------------------------------------------------------------
68 // Chunk misc methods.
69 
ChunkGetIndexFromTag(uint32_t tag)70 CHUNK_INDEX ChunkGetIndexFromTag(uint32_t tag) {
71   int i;
72   for (i = 0; kChunks[i].tag != NIL_TAG; ++i) {
73     if (tag == kChunks[i].tag) return i;
74   }
75   return IDX_NIL;
76 }
77 
ChunkGetIdFromTag(uint32_t tag)78 WebPChunkId ChunkGetIdFromTag(uint32_t tag) {
79   int i;
80   for (i = 0; kChunks[i].tag != NIL_TAG; ++i) {
81     if (tag == kChunks[i].tag) return kChunks[i].id;
82   }
83   return WEBP_CHUNK_NIL;
84 }
85 
ChunkGetTagFromFourCC(const char fourcc[4])86 uint32_t ChunkGetTagFromFourCC(const char fourcc[4]) {
87   return MKFOURCC(fourcc[0], fourcc[1], fourcc[2], fourcc[3]);
88 }
89 
ChunkGetIndexFromFourCC(const char fourcc[4])90 CHUNK_INDEX ChunkGetIndexFromFourCC(const char fourcc[4]) {
91   const uint32_t tag = ChunkGetTagFromFourCC(fourcc);
92   const CHUNK_INDEX idx = ChunkGetIndexFromTag(tag);
93   return (idx == IDX_NIL) ? IDX_UNKNOWN : idx;
94 }
95 
96 //------------------------------------------------------------------------------
97 // Chunk search methods.
98 
99 // Returns next chunk in the chunk list with the given tag.
ChunkSearchNextInList(WebPChunk * chunk,uint32_t tag)100 static WebPChunk* ChunkSearchNextInList(WebPChunk* chunk, uint32_t tag) {
101   while (chunk != NULL && chunk->tag_ != tag) {
102     chunk = chunk->next_;
103   }
104   return chunk;
105 }
106 
ChunkSearchList(WebPChunk * first,uint32_t nth,uint32_t tag)107 WebPChunk* ChunkSearchList(WebPChunk* first, uint32_t nth, uint32_t tag) {
108   uint32_t iter = nth;
109   first = ChunkSearchNextInList(first, tag);
110   if (first == NULL) return NULL;
111 
112   while (--iter != 0) {
113     WebPChunk* next_chunk = ChunkSearchNextInList(first->next_, tag);
114     if (next_chunk == NULL) break;
115     first = next_chunk;
116   }
117   return ((nth > 0) && (iter > 0)) ? NULL : first;
118 }
119 
120 // Outputs a pointer to 'prev_chunk->next_',
121 //   where 'prev_chunk' is the pointer to the chunk at position (nth - 1).
122 // Returns true if nth chunk was found.
ChunkSearchListToSet(WebPChunk ** chunk_list,uint32_t nth,WebPChunk *** const location)123 static int ChunkSearchListToSet(WebPChunk** chunk_list, uint32_t nth,
124                                 WebPChunk*** const location) {
125   uint32_t count = 0;
126   assert(chunk_list != NULL);
127   *location = chunk_list;
128 
129   while (*chunk_list != NULL) {
130     WebPChunk* const cur_chunk = *chunk_list;
131     ++count;
132     if (count == nth) return 1;  // Found.
133     chunk_list = &cur_chunk->next_;
134     *location = chunk_list;
135   }
136 
137   // *chunk_list is ok to be NULL if adding at last location.
138   return (nth == 0 || (count == nth - 1)) ? 1 : 0;
139 }
140 
141 //------------------------------------------------------------------------------
142 // Chunk writer methods.
143 
ChunkAssignData(WebPChunk * chunk,const WebPData * const data,int copy_data,uint32_t tag)144 WebPMuxError ChunkAssignData(WebPChunk* chunk, const WebPData* const data,
145                              int copy_data, uint32_t tag) {
146   // For internally allocated chunks, always copy data & make it owner of data.
147   if (tag == kChunks[IDX_VP8X].tag || tag == kChunks[IDX_ANIM].tag) {
148     copy_data = 1;
149   }
150 
151   ChunkRelease(chunk);
152 
153   if (data != NULL) {
154     if (copy_data) {        // Copy data.
155       if (!WebPDataCopy(data, &chunk->data_)) return WEBP_MUX_MEMORY_ERROR;
156       chunk->owner_ = 1;    // Chunk is owner of data.
157     } else {                // Don't copy data.
158       chunk->data_ = *data;
159     }
160   }
161   chunk->tag_ = tag;
162   return WEBP_MUX_OK;
163 }
164 
ChunkSetNth(WebPChunk * chunk,WebPChunk ** chunk_list,uint32_t nth)165 WebPMuxError ChunkSetNth(WebPChunk* chunk, WebPChunk** chunk_list,
166                          uint32_t nth) {
167   WebPChunk* new_chunk;
168 
169   if (!ChunkSearchListToSet(chunk_list, nth, &chunk_list)) {
170     return WEBP_MUX_NOT_FOUND;
171   }
172 
173   new_chunk = (WebPChunk*)malloc(sizeof(*new_chunk));
174   if (new_chunk == NULL) return WEBP_MUX_MEMORY_ERROR;
175   *new_chunk = *chunk;
176   chunk->owner_ = 0;
177   new_chunk->next_ = *chunk_list;
178   *chunk_list = new_chunk;
179   return WEBP_MUX_OK;
180 }
181 
182 //------------------------------------------------------------------------------
183 // Chunk deletion method(s).
184 
ChunkDelete(WebPChunk * const chunk)185 WebPChunk* ChunkDelete(WebPChunk* const chunk) {
186   WebPChunk* const next = ChunkRelease(chunk);
187   free(chunk);
188   return next;
189 }
190 
191 //------------------------------------------------------------------------------
192 // Chunk serialization methods.
193 
ChunksListDiskSize(const WebPChunk * chunk_list)194 size_t ChunksListDiskSize(const WebPChunk* chunk_list) {
195   size_t size = 0;
196   while (chunk_list != NULL) {
197     size += ChunkDiskSize(chunk_list);
198     chunk_list = chunk_list->next_;
199   }
200   return size;
201 }
202 
ChunkEmit(const WebPChunk * const chunk,uint8_t * dst)203 static uint8_t* ChunkEmit(const WebPChunk* const chunk, uint8_t* dst) {
204   const size_t chunk_size = chunk->data_.size;
205   assert(chunk);
206   assert(chunk->tag_ != NIL_TAG);
207   PutLE32(dst + 0, chunk->tag_);
208   PutLE32(dst + TAG_SIZE, (uint32_t)chunk_size);
209   assert(chunk_size == (uint32_t)chunk_size);
210   memcpy(dst + CHUNK_HEADER_SIZE, chunk->data_.bytes, chunk_size);
211   if (chunk_size & 1)
212     dst[CHUNK_HEADER_SIZE + chunk_size] = 0;  // Add padding.
213   return dst + ChunkDiskSize(chunk);
214 }
215 
ChunkListEmit(const WebPChunk * chunk_list,uint8_t * dst)216 uint8_t* ChunkListEmit(const WebPChunk* chunk_list, uint8_t* dst) {
217   while (chunk_list != NULL) {
218     dst = ChunkEmit(chunk_list, dst);
219     chunk_list = chunk_list->next_;
220   }
221   return dst;
222 }
223 
224 //------------------------------------------------------------------------------
225 // Life of a MuxImage object.
226 
MuxImageInit(WebPMuxImage * const wpi)227 void MuxImageInit(WebPMuxImage* const wpi) {
228   assert(wpi);
229   memset(wpi, 0, sizeof(*wpi));
230 }
231 
MuxImageRelease(WebPMuxImage * const wpi)232 WebPMuxImage* MuxImageRelease(WebPMuxImage* const wpi) {
233   WebPMuxImage* next;
234   if (wpi == NULL) return NULL;
235   ChunkDelete(wpi->header_);
236   ChunkDelete(wpi->alpha_);
237   ChunkDelete(wpi->img_);
238 
239   next = wpi->next_;
240   MuxImageInit(wpi);
241   return next;
242 }
243 
244 //------------------------------------------------------------------------------
245 // MuxImage search methods.
246 
MuxImageCount(const WebPMuxImage * wpi_list,WebPChunkId id)247 int MuxImageCount(const WebPMuxImage* wpi_list, WebPChunkId id) {
248   int count = 0;
249   const WebPMuxImage* current;
250   for (current = wpi_list; current != NULL; current = current->next_) {
251     if (id == WEBP_CHUNK_NIL) {
252       ++count;  // Special case: count all images.
253     } else {
254       const WebPChunk* const wpi_chunk = *MuxImageGetListFromId(current, id);
255       if (wpi_chunk != NULL) {
256         const WebPChunkId wpi_chunk_id = ChunkGetIdFromTag(wpi_chunk->tag_);
257         if (wpi_chunk_id == id) ++count;  // Count images with a matching 'id'.
258       }
259     }
260   }
261   return count;
262 }
263 
264 // Outputs a pointer to 'prev_wpi->next_',
265 //   where 'prev_wpi' is the pointer to the image at position (nth - 1).
266 // Returns true if nth image was found.
SearchImageToGetOrDelete(WebPMuxImage ** wpi_list,uint32_t nth,WebPMuxImage *** const location)267 static int SearchImageToGetOrDelete(WebPMuxImage** wpi_list, uint32_t nth,
268                                     WebPMuxImage*** const location) {
269   uint32_t count = 0;
270   assert(wpi_list);
271   *location = wpi_list;
272 
273   if (nth == 0) {
274     nth = MuxImageCount(*wpi_list, WEBP_CHUNK_NIL);
275     if (nth == 0) return 0;  // Not found.
276   }
277 
278   while (*wpi_list != NULL) {
279     WebPMuxImage* const cur_wpi = *wpi_list;
280     ++count;
281     if (count == nth) return 1;  // Found.
282     wpi_list = &cur_wpi->next_;
283     *location = wpi_list;
284   }
285   return 0;  // Not found.
286 }
287 
288 //------------------------------------------------------------------------------
289 // MuxImage writer methods.
290 
MuxImagePush(const WebPMuxImage * wpi,WebPMuxImage ** wpi_list)291 WebPMuxError MuxImagePush(const WebPMuxImage* wpi, WebPMuxImage** wpi_list) {
292   WebPMuxImage* new_wpi;
293 
294   while (*wpi_list != NULL) {
295     WebPMuxImage* const cur_wpi = *wpi_list;
296     if (cur_wpi->next_ == NULL) break;
297     wpi_list = &cur_wpi->next_;
298   }
299 
300   new_wpi = (WebPMuxImage*)malloc(sizeof(*new_wpi));
301   if (new_wpi == NULL) return WEBP_MUX_MEMORY_ERROR;
302   *new_wpi = *wpi;
303   new_wpi->next_ = NULL;
304 
305   if (*wpi_list != NULL) {
306     (*wpi_list)->next_ = new_wpi;
307   } else {
308     *wpi_list = new_wpi;
309   }
310   return WEBP_MUX_OK;
311 }
312 
313 //------------------------------------------------------------------------------
314 // MuxImage deletion methods.
315 
MuxImageDelete(WebPMuxImage * const wpi)316 WebPMuxImage* MuxImageDelete(WebPMuxImage* const wpi) {
317   // Delete the components of wpi. If wpi is NULL this is a noop.
318   WebPMuxImage* const next = MuxImageRelease(wpi);
319   free(wpi);
320   return next;
321 }
322 
MuxImageDeleteAll(WebPMuxImage ** const wpi_list)323 void MuxImageDeleteAll(WebPMuxImage** const wpi_list) {
324   while (*wpi_list != NULL) {
325     *wpi_list = MuxImageDelete(*wpi_list);
326   }
327 }
328 
MuxImageDeleteNth(WebPMuxImage ** wpi_list,uint32_t nth)329 WebPMuxError MuxImageDeleteNth(WebPMuxImage** wpi_list, uint32_t nth) {
330   assert(wpi_list);
331   if (!SearchImageToGetOrDelete(wpi_list, nth, &wpi_list)) {
332     return WEBP_MUX_NOT_FOUND;
333   }
334   *wpi_list = MuxImageDelete(*wpi_list);
335   return WEBP_MUX_OK;
336 }
337 
338 //------------------------------------------------------------------------------
339 // MuxImage reader methods.
340 
MuxImageGetNth(const WebPMuxImage ** wpi_list,uint32_t nth,WebPMuxImage ** wpi)341 WebPMuxError MuxImageGetNth(const WebPMuxImage** wpi_list, uint32_t nth,
342                             WebPMuxImage** wpi) {
343   assert(wpi_list);
344   assert(wpi);
345   if (!SearchImageToGetOrDelete((WebPMuxImage**)wpi_list, nth,
346                                 (WebPMuxImage***)&wpi_list)) {
347     return WEBP_MUX_NOT_FOUND;
348   }
349   *wpi = (WebPMuxImage*)*wpi_list;
350   return WEBP_MUX_OK;
351 }
352 
353 //------------------------------------------------------------------------------
354 // MuxImage serialization methods.
355 
356 // Size of an image.
MuxImageDiskSize(const WebPMuxImage * const wpi)357 size_t MuxImageDiskSize(const WebPMuxImage* const wpi) {
358   size_t size = 0;
359   if (wpi->header_ != NULL) size += ChunkDiskSize(wpi->header_);
360   if (wpi->alpha_ != NULL) size += ChunkDiskSize(wpi->alpha_);
361   if (wpi->img_ != NULL) size += ChunkDiskSize(wpi->img_);
362   return size;
363 }
364 
MuxImageListDiskSize(const WebPMuxImage * wpi_list)365 size_t MuxImageListDiskSize(const WebPMuxImage* wpi_list) {
366   size_t size = 0;
367   while (wpi_list != NULL) {
368     size += MuxImageDiskSize(wpi_list);
369     wpi_list = wpi_list->next_;
370   }
371   return size;
372 }
373 
374 // Special case as ANMF/FRGM chunk encapsulates other image chunks.
ChunkEmitSpecial(const WebPChunk * const header,size_t total_size,uint8_t * dst)375 static uint8_t* ChunkEmitSpecial(const WebPChunk* const header,
376                                  size_t total_size, uint8_t* dst) {
377   const size_t header_size = header->data_.size;
378   const size_t offset_to_next = total_size - CHUNK_HEADER_SIZE;
379   assert(header->tag_ == kChunks[IDX_ANMF].tag ||
380          header->tag_ == kChunks[IDX_FRGM].tag);
381   PutLE32(dst + 0, header->tag_);
382   PutLE32(dst + TAG_SIZE, (uint32_t)offset_to_next);
383   assert(header_size == (uint32_t)header_size);
384   memcpy(dst + CHUNK_HEADER_SIZE, header->data_.bytes, header_size);
385   if (header_size & 1) {
386     dst[CHUNK_HEADER_SIZE + header_size] = 0;  // Add padding.
387   }
388   return dst + ChunkDiskSize(header);
389 }
390 
MuxImageEmit(const WebPMuxImage * const wpi,uint8_t * dst)391 uint8_t* MuxImageEmit(const WebPMuxImage* const wpi, uint8_t* dst) {
392   // Ordering of chunks to be emitted is strictly as follows:
393   // 1. ANMF/FRGM chunk (if present).
394   // 2. ALPH chunk (if present).
395   // 3. VP8/VP8L chunk.
396   assert(wpi);
397   if (wpi->header_ != NULL) {
398     dst = ChunkEmitSpecial(wpi->header_, MuxImageDiskSize(wpi), dst);
399   }
400   if (wpi->alpha_ != NULL) dst = ChunkEmit(wpi->alpha_, dst);
401   if (wpi->img_ != NULL) dst = ChunkEmit(wpi->img_, dst);
402   return dst;
403 }
404 
MuxImageListEmit(const WebPMuxImage * wpi_list,uint8_t * dst)405 uint8_t* MuxImageListEmit(const WebPMuxImage* wpi_list, uint8_t* dst) {
406   while (wpi_list != NULL) {
407     dst = MuxImageEmit(wpi_list, dst);
408     wpi_list = wpi_list->next_;
409   }
410   return dst;
411 }
412 
413 //------------------------------------------------------------------------------
414 // Helper methods for mux.
415 
MuxHasLosslessImages(const WebPMuxImage * images)416 int MuxHasLosslessImages(const WebPMuxImage* images) {
417   while (images != NULL) {
418     assert(images->img_ != NULL);
419     if (images->img_->tag_ == kChunks[IDX_VP8L].tag) {
420       return 1;
421     }
422     images = images->next_;
423   }
424   return 0;
425 }
426 
MuxEmitRiffHeader(uint8_t * const data,size_t size)427 uint8_t* MuxEmitRiffHeader(uint8_t* const data, size_t size) {
428   PutLE32(data + 0, MKFOURCC('R', 'I', 'F', 'F'));
429   PutLE32(data + TAG_SIZE, (uint32_t)size - CHUNK_HEADER_SIZE);
430   assert(size == (uint32_t)size);
431   PutLE32(data + TAG_SIZE + CHUNK_SIZE_BYTES, MKFOURCC('W', 'E', 'B', 'P'));
432   return data + RIFF_HEADER_SIZE;
433 }
434 
MuxGetChunkListFromId(const WebPMux * mux,WebPChunkId id)435 WebPChunk** MuxGetChunkListFromId(const WebPMux* mux, WebPChunkId id) {
436   assert(mux != NULL);
437   switch (id) {
438     case WEBP_CHUNK_VP8X:    return (WebPChunk**)&mux->vp8x_;
439     case WEBP_CHUNK_ICCP:    return (WebPChunk**)&mux->iccp_;
440     case WEBP_CHUNK_ANIM:    return (WebPChunk**)&mux->anim_;
441     case WEBP_CHUNK_EXIF:    return (WebPChunk**)&mux->exif_;
442     case WEBP_CHUNK_XMP:     return (WebPChunk**)&mux->xmp_;
443     case WEBP_CHUNK_UNKNOWN: return (WebPChunk**)&mux->unknown_;
444     default: return NULL;
445   }
446 }
447 
MuxValidateForImage(const WebPMux * const mux)448 WebPMuxError MuxValidateForImage(const WebPMux* const mux) {
449   const int num_images = MuxImageCount(mux->images_, WEBP_CHUNK_IMAGE);
450   const int num_frames = MuxImageCount(mux->images_, WEBP_CHUNK_ANMF);
451   const int num_fragments = MuxImageCount(mux->images_, WEBP_CHUNK_FRGM);
452 
453   if (num_images == 0) {
454     // No images in mux.
455     return WEBP_MUX_NOT_FOUND;
456   } else if (num_images == 1 && num_frames == 0 && num_fragments == 0) {
457     // Valid case (single image).
458     return WEBP_MUX_OK;
459   } else {
460     // Frame/Fragment case OR an invalid mux.
461     return WEBP_MUX_INVALID_ARGUMENT;
462   }
463 }
464 
IsNotCompatible(int feature,int num_items)465 static int IsNotCompatible(int feature, int num_items) {
466   return (feature != 0) != (num_items > 0);
467 }
468 
469 #define NO_FLAG 0
470 
471 // Test basic constraints:
472 // retrieval, maximum number of chunks by index (use -1 to skip)
473 // and feature incompatibility (use NO_FLAG to skip).
474 // On success returns WEBP_MUX_OK and stores the chunk count in *num.
ValidateChunk(const WebPMux * const mux,CHUNK_INDEX idx,WebPFeatureFlags feature,WebPFeatureFlags vp8x_flags,int max,int * num)475 static WebPMuxError ValidateChunk(const WebPMux* const mux, CHUNK_INDEX idx,
476                                   WebPFeatureFlags feature,
477                                   WebPFeatureFlags vp8x_flags,
478                                   int max, int* num) {
479   const WebPMuxError err =
480       WebPMuxNumChunks(mux, kChunks[idx].id, num);
481   if (err != WEBP_MUX_OK) return err;
482   if (max > -1 && *num > max) return WEBP_MUX_INVALID_ARGUMENT;
483   if (feature != NO_FLAG && IsNotCompatible(vp8x_flags & feature, *num)) {
484     return WEBP_MUX_INVALID_ARGUMENT;
485   }
486   return WEBP_MUX_OK;
487 }
488 
MuxValidate(const WebPMux * const mux)489 WebPMuxError MuxValidate(const WebPMux* const mux) {
490   int num_iccp;
491   int num_exif;
492   int num_xmp;
493   int num_anim;
494   int num_frames;
495   int num_fragments;
496   int num_vp8x;
497   int num_images;
498   int num_alpha;
499   uint32_t flags;
500   WebPMuxError err;
501 
502   // Verify mux is not NULL.
503   if (mux == NULL) return WEBP_MUX_INVALID_ARGUMENT;
504 
505   // Verify mux has at least one image.
506   if (mux->images_ == NULL) return WEBP_MUX_INVALID_ARGUMENT;
507 
508   err = WebPMuxGetFeatures(mux, &flags);
509   if (err != WEBP_MUX_OK) return err;
510 
511   // At most one color profile chunk.
512   err = ValidateChunk(mux, IDX_ICCP, ICCP_FLAG, flags, 1, &num_iccp);
513   if (err != WEBP_MUX_OK) return err;
514 
515   // At most one EXIF metadata.
516   err = ValidateChunk(mux, IDX_EXIF, EXIF_FLAG, flags, 1, &num_exif);
517   if (err != WEBP_MUX_OK) return err;
518 
519   // At most one XMP metadata.
520   err = ValidateChunk(mux, IDX_XMP, XMP_FLAG, flags, 1, &num_xmp);
521   if (err != WEBP_MUX_OK) return err;
522 
523   // Animation: ANIMATION_FLAG, ANIM chunk and ANMF chunk(s) are consistent.
524   // At most one ANIM chunk.
525   err = ValidateChunk(mux, IDX_ANIM, NO_FLAG, flags, 1, &num_anim);
526   if (err != WEBP_MUX_OK) return err;
527   err = ValidateChunk(mux, IDX_ANMF, NO_FLAG, flags, -1, &num_frames);
528   if (err != WEBP_MUX_OK) return err;
529 
530   {
531     const int has_animation = !!(flags & ANIMATION_FLAG);
532     if (has_animation && (num_anim == 0 || num_frames == 0)) {
533       return WEBP_MUX_INVALID_ARGUMENT;
534     }
535     if (!has_animation && (num_anim == 1 || num_frames > 0)) {
536       return WEBP_MUX_INVALID_ARGUMENT;
537     }
538   }
539 
540   // Fragmentation: FRAGMENTS_FLAG and FRGM chunk(s) are consistent.
541   err = ValidateChunk(mux, IDX_FRGM, FRAGMENTS_FLAG, flags, -1, &num_fragments);
542   if (err != WEBP_MUX_OK) return err;
543 
544   // Verify either VP8X chunk is present OR there is only one elem in
545   // mux->images_.
546   err = ValidateChunk(mux, IDX_VP8X, NO_FLAG, flags, 1, &num_vp8x);
547   if (err != WEBP_MUX_OK) return err;
548   err = ValidateChunk(mux, IDX_VP8, NO_FLAG, flags, -1, &num_images);
549   if (err != WEBP_MUX_OK) return err;
550   if (num_vp8x == 0 && num_images != 1) return WEBP_MUX_INVALID_ARGUMENT;
551 
552   // ALPHA_FLAG & alpha chunk(s) are consistent.
553   if (MuxHasLosslessImages(mux->images_)) {
554     if (num_vp8x > 0) {
555       // Special case: we have a VP8X chunk as well as some lossless images.
556       if (!(flags & ALPHA_FLAG)) return WEBP_MUX_INVALID_ARGUMENT;
557     }
558   } else {
559       err = ValidateChunk(mux, IDX_ALPHA, ALPHA_FLAG, flags, -1, &num_alpha);
560       if (err != WEBP_MUX_OK) return err;
561   }
562 
563   // num_fragments & num_images are consistent.
564   if (num_fragments > 0 && num_images != num_fragments) {
565     return WEBP_MUX_INVALID_ARGUMENT;
566   }
567 
568   return WEBP_MUX_OK;
569 }
570 
571 #undef NO_FLAG
572 
573 //------------------------------------------------------------------------------
574 
575 #if defined(__cplusplus) || defined(c_plusplus)
576 }    // extern "C"
577 #endif
578