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https://issues.apache.org/jira/browse/ARROW-2004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16330669#comment-16330669
]
ASF GitHub Bot commented on ARROW-2004:
---------------------------------------
wesm closed pull request #1486: ARROW-2004: [C++] Add shrink_to_fit parameter
to BufferBuilder::Resize, add Reserve method
URL: https://github.com/apache/arrow/pull/1486
This is a PR merged from a forked repository.
As GitHub hides the original diff on merge, it is displayed below for
the sake of provenance:
As this is a foreign pull request (from a fork), the diff is supplied
below (as it won't show otherwise due to GitHub magic):
diff --git a/cpp/src/arrow/buffer-test.cc b/cpp/src/arrow/buffer-test.cc
index 5fd2706f0..398cc0636 100644
--- a/cpp/src/arrow/buffer-test.cc
+++ b/cpp/src/arrow/buffer-test.cc
@@ -194,4 +194,29 @@ TEST(TestBuffer, SliceMutableBuffer) {
ASSERT_TRUE(slice->Equals(expected));
}
+TEST(TestBufferBuilder, ResizeReserve) {
+ const std::string data = "some data";
+ auto data_ptr = data.c_str();
+
+ BufferBuilder builder;
+
+ ASSERT_OK(builder.Append(data_ptr, 9));
+ ASSERT_EQ(9, builder.length());
+
+ ASSERT_OK(builder.Resize(128));
+ ASSERT_EQ(128, builder.capacity());
+
+ // Do not shrink to fit
+ ASSERT_OK(builder.Resize(64, false));
+ ASSERT_EQ(128, builder.capacity());
+
+ // Shrink to fit
+ ASSERT_OK(builder.Resize(64));
+ ASSERT_EQ(64, builder.capacity());
+
+ // Reserve elements
+ ASSERT_OK(builder.Reserve(60));
+ ASSERT_EQ(128, builder.capacity());
+}
+
} // namespace arrow
diff --git a/cpp/src/arrow/buffer.h b/cpp/src/arrow/buffer.h
index 450a4c78b..b50b1a1aa 100644
--- a/cpp/src/arrow/buffer.h
+++ b/cpp/src/arrow/buffer.h
@@ -25,6 +25,7 @@
#include <string>
#include <type_traits>
+#include "arrow/memory_pool.h"
#include "arrow/status.h"
#include "arrow/util/bit-util.h"
#include "arrow/util/macros.h"
@@ -32,13 +33,12 @@
namespace arrow {
-class MemoryPool;
-
// ----------------------------------------------------------------------
// Buffer classes
-/// Immutable API for a chunk of bytes which may or may not be owned by the
-/// class instance.
+/// \class Buffer
+/// \brief Object containing a pointer to a piece of contiguous memory with a
+/// particular size. Base class does not own its memory
///
/// Buffers have two related notions of length: size and capacity. Size is
/// the number of bytes that might have valid data. Capacity is the number
@@ -133,7 +133,8 @@ ARROW_EXPORT
std::shared_ptr<Buffer> SliceMutableBuffer(const std::shared_ptr<Buffer>&
buffer,
const int64_t offset, const int64_t
length);
-/// A Buffer whose contents can be mutated. May or may not own its data.
+/// \class MutableBuffer
+/// \brief A Buffer whose contents can be mutated. May or may not own its data.
class ARROW_EXPORT MutableBuffer : public Buffer {
public:
MutableBuffer(uint8_t* data, const int64_t size) : Buffer(data, size) {
@@ -148,6 +149,8 @@ class ARROW_EXPORT MutableBuffer : public Buffer {
MutableBuffer() : Buffer(NULLPTR, 0) {}
};
+/// \class ResizableBuffer
+/// \brief A mutable buffer that can be resized
class ARROW_EXPORT ResizableBuffer : public MutableBuffer {
public:
/// Change buffer reported size to indicated size, allocating memory if
@@ -190,13 +193,22 @@ class ARROW_EXPORT PoolBuffer : public ResizableBuffer {
MemoryPool* pool_;
};
+/// \class BufferBuilder
+/// \brief A class for incrementally building a contiguous chunk of in-memory
data
class ARROW_EXPORT BufferBuilder {
public:
- explicit BufferBuilder(MemoryPool* pool)
+ explicit BufferBuilder(MemoryPool* pool ARROW_MEMORY_POOL_DEFAULT)
: pool_(pool), data_(NULLPTR), capacity_(0), size_(0) {}
- /// Resizes the buffer to the nearest multiple of 64 bytes per Layout.md
- Status Resize(const int64_t elements) {
+ /// \brief Resizes the buffer to the nearest multiple of 64 bytes
+ ///
+ /// \param elements the new capacity of the of the builder. Will be rounded
+ /// up to a multiple of 64 bytes for padding
+ /// \param shrink_to_fit if new capacity smaller than existing size,
+ /// reallocate internal buffer. Set to false to avoid reallocations when
+ /// shrinking the builder
+ /// \return Status
+ Status Resize(const int64_t elements, bool shrink_to_fit = true) {
// Resize(0) is a no-op
if (elements == 0) {
return Status::OK();
@@ -205,7 +217,7 @@ class ARROW_EXPORT BufferBuilder {
buffer_ = std::make_shared<PoolBuffer>(pool_);
}
int64_t old_capacity = capacity_;
- RETURN_NOT_OK(buffer_->Resize(elements));
+ RETURN_NOT_OK(buffer_->Resize(elements, shrink_to_fit));
capacity_ = buffer_->capacity();
data_ = buffer_->mutable_data();
if (capacity_ > old_capacity) {
@@ -214,7 +226,14 @@ class ARROW_EXPORT BufferBuilder {
return Status::OK();
}
- Status Append(const uint8_t* data, int64_t length) {
+ /// \brief Ensure that builder can accommodate the additional number of bytes
+ /// without the need to perform allocations
+ ///
+ /// \param size number of additional bytes to make space for
+ /// \return Status
+ Status Reserve(const int64_t size) { return Resize(size_ + size, false); }
+
+ Status Append(const void* data, int64_t length) {
if (capacity_ < length + size_) {
int64_t new_capacity = BitUtil::NextPower2(length + size_);
RETURN_NOT_OK(Resize(new_capacity));
@@ -248,7 +267,7 @@ class ARROW_EXPORT BufferBuilder {
}
// Unsafe methods don't check existing size
- void UnsafeAppend(const uint8_t* data, int64_t length) {
+ void UnsafeAppend(const void* data, int64_t length) {
memcpy(data_ + size_, data, static_cast<size_t>(length));
size_ += length;
}
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> [C++] Add shrink_to_fit option in BufferBuilder::Resize
> -------------------------------------------------------
>
> Key: ARROW-2004
> URL: https://issues.apache.org/jira/browse/ARROW-2004
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Wes McKinney
> Assignee: Wes McKinney
> Priority: Major
> Labels: pull-request-available
> Fix For: 0.9.0
>
>
> See discussion in
> https://github.com/apache/arrow/pull/1481#discussion_r162157558
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