Fix one-off in dcheck.

How to prove correctness:
1) when `position` is `0`, `max_length` is allowed to be `ringbuffer_size`
2) in other words: `position + max_length <= ringbuffer_size`
3) `ringbuffer_mask == ringbuffer_size - 1`
4) thus `position + max_length <= ringbuffer_size + 1`

PiperOrigin-RevId: 836145553

Author: eustas

c/enc/backward_references_hq.c

@@ -433,7 +433,7 @@ static size_t UpdateNodes(
   const CompoundDictionary* addon = &params->dictionary.compound;
   size_t gap = addon->total_size;
 
-  BROTLI_DCHECK(cur_ix_masked + max_len <= ringbuffer_mask);
+  BROTLI_DCHECK(cur_ix_masked + max_len <= ringbuffer_mask + 1);
 
   EvaluateNode(block_start + stream_offset, pos, max_backward_limit, gap,
       starting_dist_cache, model, queue, nodes);

c/enc/hash.h

@@ -545,7 +545,7 @@ static BROTLI_INLINE void FindCompoundDictionaryMatch(
     source = (const uint8_t*)BROTLI_UNALIGNED_LOAD_PTR((const uint8_t**)tail);
   }
 
-  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask + 1);
 
   for (i = 0; i < 4; ++i) {
     const size_t distance = (size_t)distance_cache[i];
@@ -656,7 +656,7 @@ static BROTLI_INLINE size_t FindAllCompoundDictionaryMatches(
     source = (const uint8_t*)BROTLI_UNALIGNED_LOAD_PTR((const uint8_t**)tail);
   }
 
-  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask + 1);
 
   while (item == 0) {
     size_t offset;

c/enc/hash_forgetful_chain_inc.h

@@ -213,7 +213,7 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   out->len = 0;
   out->len_code_delta = 0;
 
-  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask + 1);
 
   /* Try last distance first. */
   for (i = 0; i < NUM_LAST_DISTANCES_TO_CHECK; ++i) {

c/enc/hash_longest_match64_inc.h

@@ -178,7 +178,7 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   out->len = 0;
   out->len_code_delta = 0;
 
-  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask + 1);
 
   /* Try last distance first. */
   for (i = 0; i < (size_t)self->num_last_distances_to_check_; ++i) {

c/enc/hash_longest_match64_simd_inc.h

@@ -195,7 +195,7 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   out->len = 0;
   out->len_code_delta = 0;
 
-  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask + 1);
 
   /* Try last distance first. */
   for (i = 0; i < (size_t)self->num_last_distances_to_check_; ++i) {

c/enc/hash_longest_match_inc.h

@@ -178,7 +178,7 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   out->len = 0;
   out->len_code_delta = 0;
 
-  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask + 1);
 
   /* Try last distance first. */
   for (i = 0; i < (size_t)self->num_last_distances_to_check_; ++i) {

c/enc/hash_longest_match_quickly_inc.h

@@ -165,7 +165,7 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   size_t cached_backward = (size_t)distance_cache[0];
   size_t prev_ix = cur_ix - cached_backward;
 
-  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask + 1);
 
   out->len_code_delta = 0;
   if (prev_ix < cur_ix) {

c/enc/hash_longest_match_simd_inc.h

@@ -170,7 +170,7 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   out->len = 0;
   out->len_code_delta = 0;
 
-  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask + 1);
 
   /* Try last distance first. */
   for (i = 0; i < (size_t)self->num_last_distances_to_check_; ++i) {