--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/brotli/c/enc/ringbuffer.h	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,168 @@
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Sliding window over the input data. */
+
+#ifndef BROTLI_ENC_RINGBUFFER_H_
+#define BROTLI_ENC_RINGBUFFER_H_
+
+#include <string.h>  /* memcpy */
+
+#include <brotli/types.h>
+
+#include "../common/platform.h"
+#include "memory.h"
+#include "quality.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+/* A RingBuffer(window_bits, tail_bits) contains `1 << window_bits' bytes of
+   data in a circular manner: writing a byte writes it to:
+     `position() % (1 << window_bits)'.
+   For convenience, the RingBuffer array contains another copy of the
+   first `1 << tail_bits' bytes:
+     buffer_[i] == buffer_[i + (1 << window_bits)], if i < (1 << tail_bits),
+   and another copy of the last two bytes:
+     buffer_[-1] == buffer_[(1 << window_bits) - 1] and
+     buffer_[-2] == buffer_[(1 << window_bits) - 2]. */
+typedef struct RingBuffer {
+  /* Size of the ring-buffer is (1 << window_bits) + tail_size_. */
+  const uint32_t size_;
+  const uint32_t mask_;
+  const uint32_t tail_size_;
+  const uint32_t total_size_;
+
+  uint32_t cur_size_;
+  /* Position to write in the ring buffer. */
+  uint32_t pos_;
+  /* The actual ring buffer containing the copy of the last two bytes, the data,
+     and the copy of the beginning as a tail. */
+  uint8_t* data_;
+  /* The start of the ring-buffer. */
+  uint8_t* buffer_;
+} RingBuffer;
+
+static BROTLI_INLINE void RingBufferInit(RingBuffer* rb) {
+  rb->cur_size_ = 0;
+  rb->pos_ = 0;
+  rb->data_ = 0;
+  rb->buffer_ = 0;
+}
+
+static BROTLI_INLINE void RingBufferSetup(
+    const BrotliEncoderParams* params, RingBuffer* rb) {
+  int window_bits = ComputeRbBits(params);
+  int tail_bits = params->lgblock;
+  *(uint32_t*)&rb->size_ = 1u << window_bits;
+  *(uint32_t*)&rb->mask_ = (1u << window_bits) - 1;
+  *(uint32_t*)&rb->tail_size_ = 1u << tail_bits;
+  *(uint32_t*)&rb->total_size_ = rb->size_ + rb->tail_size_;
+}
+
+static BROTLI_INLINE void RingBufferFree(MemoryManager* m, RingBuffer* rb) {
+  BROTLI_FREE(m, rb->data_);
+}
+
+/* Allocates or re-allocates data_ to the given length + plus some slack
+   region before and after. Fills the slack regions with zeros. */
+static BROTLI_INLINE void RingBufferInitBuffer(
+    MemoryManager* m, const uint32_t buflen, RingBuffer* rb) {
+  static const size_t kSlackForEightByteHashingEverywhere = 7;
+  uint8_t* new_data = BROTLI_ALLOC(
+      m, uint8_t, 2 + buflen + kSlackForEightByteHashingEverywhere);
+  size_t i;
+  if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(new_data)) return;
+  if (rb->data_) {
+    memcpy(new_data, rb->data_,
+        2 + rb->cur_size_ + kSlackForEightByteHashingEverywhere);
+    BROTLI_FREE(m, rb->data_);
+  }
+  rb->data_ = new_data;
+  rb->cur_size_ = buflen;
+  rb->buffer_ = rb->data_ + 2;
+  rb->buffer_[-2] = rb->buffer_[-1] = 0;
+  for (i = 0; i < kSlackForEightByteHashingEverywhere; ++i) {
+    rb->buffer_[rb->cur_size_ + i] = 0;
+  }
+}
+
+static BROTLI_INLINE void RingBufferWriteTail(
+    const uint8_t* bytes, size_t n, RingBuffer* rb) {
+  const size_t masked_pos = rb->pos_ & rb->mask_;
+  if (BROTLI_PREDICT_FALSE(masked_pos < rb->tail_size_)) {
+    /* Just fill the tail buffer with the beginning data. */
+    const size_t p = rb->size_ + masked_pos;
+    memcpy(&rb->buffer_[p], bytes,
+        BROTLI_MIN(size_t, n, rb->tail_size_ - masked_pos));
+  }
+}
+
+/* Push bytes into the ring buffer. */
+static BROTLI_INLINE void RingBufferWrite(
+    MemoryManager* m, const uint8_t* bytes, size_t n, RingBuffer* rb) {
+  if (rb->pos_ == 0 && n < rb->tail_size_) {
+    /* Special case for the first write: to process the first block, we don't
+       need to allocate the whole ring-buffer and we don't need the tail
+       either. However, we do this memory usage optimization only if the
+       first write is less than the tail size, which is also the input block
+       size, otherwise it is likely that other blocks will follow and we
+       will need to reallocate to the full size anyway. */
+    rb->pos_ = (uint32_t)n;
+    RingBufferInitBuffer(m, rb->pos_, rb);
+    if (BROTLI_IS_OOM(m)) return;
+    memcpy(rb->buffer_, bytes, n);
+    return;
+  }
+  if (rb->cur_size_ < rb->total_size_) {
+    /* Lazily allocate the full buffer. */
+    RingBufferInitBuffer(m, rb->total_size_, rb);
+    if (BROTLI_IS_OOM(m)) return;
+    /* Initialize the last two bytes to zero, so that we don't have to worry
+       later when we copy the last two bytes to the first two positions. */
+    rb->buffer_[rb->size_ - 2] = 0;
+    rb->buffer_[rb->size_ - 1] = 0;
+    /* Initialize tail; might be touched by "best_len++" optimization when
+       ring buffer is "full". */
+    rb->buffer_[rb->size_] = 241;
+  }
+  {
+    const size_t masked_pos = rb->pos_ & rb->mask_;
+    /* The length of the writes is limited so that we do not need to worry
+       about a write */
+    RingBufferWriteTail(bytes, n, rb);
+    if (BROTLI_PREDICT_TRUE(masked_pos + n <= rb->size_)) {
+      /* A single write fits. */
+      memcpy(&rb->buffer_[masked_pos], bytes, n);
+    } else {
+      /* Split into two writes.
+         Copy into the end of the buffer, including the tail buffer. */
+      memcpy(&rb->buffer_[masked_pos], bytes,
+             BROTLI_MIN(size_t, n, rb->total_size_ - masked_pos));
+      /* Copy into the beginning of the buffer */
+      memcpy(&rb->buffer_[0], bytes + (rb->size_ - masked_pos),
+             n - (rb->size_ - masked_pos));
+    }
+  }
+  {
+    BROTLI_BOOL not_first_lap = (rb->pos_ & (1u << 31)) != 0;
+    uint32_t rb_pos_mask = (1u << 31) - 1;
+    rb->buffer_[-2] = rb->buffer_[rb->size_ - 2];
+    rb->buffer_[-1] = rb->buffer_[rb->size_ - 1];
+    rb->pos_ = (rb->pos_ & rb_pos_mask) + (uint32_t)(n & rb_pos_mask);
+    if (not_first_lap) {
+      /* Wrap, but preserve not-a-first-lap feature. */
+      rb->pos_ |= 1u << 31;
+    }
+  }
+}
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}  /* extern "C" */
+#endif
+
+#endif  /* BROTLI_ENC_RINGBUFFER_H_ */