From 293fa3120bbf1353fb7ea3674a32ec141f8ec12b Mon Sep 17 00:00:00 2001
From: Vincent Rabaud <vrabaud@google.com>
Date: Mon, 18 Sep 2023 16:39:46 +0200
Subject: [PATCH] [libwebp] Never send VP8_STATUS_SUSPENDED back in
 non-incremental.

Add the incremental_ member to the internal VP8Decoder,
to mimic VP8LDecoder

Change-Id: I34842e473bb566f51c18fe42afda63e66c0185b6
---
 media/libwebp/dec/idec_dec.c |  1 +
 media/libwebp/dec/vp8_dec.c  | 20 ++++++++++++--------
 media/libwebp/dec/vp8i_dec.h |  1 +
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/media/libwebp/dec/idec_dec.c b/media/libwebp/dec/idec_dec.c
index 3a592d59ed..2ae4f0a50c 100644
--- a/media/libwebp/dec/idec_dec.c
+++ b/media/libwebp/dec/idec_dec.c
@@ -326,6 +326,7 @@ static VP8StatusCode DecodeWebPHeaders(WebPIDecoder* const idec) {
   idec->is_lossless_ = headers.is_lossless;
   if (!idec->is_lossless_) {
     VP8Decoder* const dec = VP8New();
+    dec->incremental_ = 1;
     if (dec == NULL) {
       return VP8_STATUS_OUT_OF_MEMORY;
     }
diff --git a/media/libwebp/dec/vp8_dec.c b/media/libwebp/dec/vp8_dec.c
index 5f51363e53..477874f604 100644
--- a/media/libwebp/dec/vp8_dec.c
+++ b/media/libwebp/dec/vp8_dec.c
@@ -86,6 +86,8 @@ void VP8Delete(VP8Decoder* const dec) {
 
 int VP8SetError(VP8Decoder* const dec,
                 VP8StatusCode error, const char* const msg) {
+  // VP8_STATUS_SUSPENDED is only meaningful in incremental decoding.
+  assert(dec->incremental_ || error != VP8_STATUS_SUSPENDED);
   // The oldest error reported takes precedence over the new one.
   if (dec->status_ == VP8_STATUS_OK) {
     dec->status_ = error;
@@ -190,12 +192,12 @@ static int ParseSegmentHeader(VP8BitReader* br,
 }
 
 // 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
+// If we don't have all the necessary data in 'buf', this function returns
+// VP8_STATUS_SUSPENDED in incremental decoding, VP8_STATUS_NOT_ENOUGH_DATA
+// otherwise.
+// In incremental decoding, this case is not necessarily an error. Still, no
+// bitreader is ever initialized to make it possible to read unavailable memory.
+// If we don't even have the partitions' sizes, then 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,
@@ -225,8 +227,10 @@ static VP8StatusCode ParsePartitions(VP8Decoder* const dec,
     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
+  if (part_start < buf_end) return VP8_STATUS_OK;
+  return dec->incremental_
+             ? VP8_STATUS_SUSPENDED  // Init is ok, but there's not enough data
+             : VP8_STATUS_NOT_ENOUGH_DATA;
 }
 
 // Paragraph 9.4
diff --git a/media/libwebp/dec/vp8i_dec.h b/media/libwebp/dec/vp8i_dec.h
index 31d9080ca1..364896318c 100644
--- a/media/libwebp/dec/vp8i_dec.h
+++ b/media/libwebp/dec/vp8i_dec.h
@@ -186,6 +186,7 @@ struct VP8Decoder {
 
   // Main data source
   VP8BitReader br_;
+  int incremental_;  // if true, incremental decoding is expected
 
   // headers
   VP8FrameHeader   frm_hdr_;