1 files changed, 63 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/base/padded_bytes.cc b/third_party/jpeg-xl/lib/jxl/base/padded_bytes.cc
new file mode 100644
index 0000000000..11e4bff6fe
--- /dev/null
+++ b/third_party/jpeg-xl/lib/jxl/base/padded_bytes.cc
@@ -0,0 +1,63 @@
+// Copyright (c) the JPEG XL Project Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "lib/jxl/base/padded_bytes.h"
+
+namespace jxl {
+
+void PaddedBytes::IncreaseCapacityTo(size_t capacity) {
+  JXL_ASSERT(capacity > capacity_);
+
+  size_t new_capacity = std::max(capacity, 3 * capacity_ / 2);
+  new_capacity = std::max<size_t>(64, new_capacity);
+
+  // BitWriter writes up to 7 bytes past the end.
+  CacheAlignedUniquePtr new_data = AllocateArray(new_capacity + 8);
+  if (new_data == nullptr) {
+    // Allocation failed, discard all data to ensure this is noticed.
+    size_ = capacity_ = 0;
+    return;
+  }
+
+  if (data_ == nullptr) {
+    // First allocation: ensure first byte is initialized (won't be copied).
+    new_data[0] = 0;
+  } else {
+    // Subsequent resize: copy existing data to new location.
+    memcpy(new_data.get(), data_.get(), size_);
+    // Ensure that the first new byte is initialized, to allow write_bits to
+    // safely append to the newly-resized PaddedBytes.
+    new_data[size_] = 0;
+  }
+
+  capacity_ = new_capacity;
+  std::swap(new_data, data_);
+}
+
+void PaddedBytes::assign(const uint8_t* new_begin, const uint8_t* new_end) {
+  JXL_DASSERT(new_begin <= new_end);
+  const size_t new_size = static_cast<size_t>(new_end - new_begin);
+
+  // memcpy requires non-overlapping ranges, and resizing might invalidate the
+  // new range. Neither happens if the new range is completely to the left or
+  // right of the _allocated_ range (irrespective of size_).
+  const uint8_t* allocated_end = begin() + capacity_;
+  const bool outside = new_end <= begin() || new_begin >= allocated_end;
+  if (outside) {
+    resize(new_size);  // grow or shrink
+    memcpy(data(), new_begin, new_size);
+    return;
+  }
+
+  // There is overlap. The new size cannot be larger because we own the memory
+  // and the new range cannot include anything outside the allocated range.
+  JXL_ASSERT(new_size <= capacity_);
+
+  // memmove allows overlap and capacity_ is sufficient.
+  memmove(data(), new_begin, new_size);
+  size_ = new_size;  // shrink
+}
+
+}  // namespace jxl