mirror of
https://github.com/dart-lang/sdk
synced 2024-09-19 20:41:45 +00:00
a5ff656da1
This reverts commit 80102c981b
.
Reason for revert: b/186359854
Original change's description:
> [vm] Switch datastream Write/WriteUnsigned to (S)LEB128.
>
> This reduces the number of variable-length integer encodings in our
> database from 2 to 1, and chooses the more standard one.
>
> TEST=Existing tests, in particular any that involve snapshots.
>
> Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-asan-linux-release-x64-try,vm-kernel-precomp-dwarf-linux-product-x64-try,vm-kernel-precomp-msan-linux-release-x64-try,vm-kernel-precomp-ubsan-linux-release-x64-try,vm-kernel-precomp-tsan-linux-release-x64-try,vm-kernel-precomp-nnbd-linux-debug-x64-try,vm-kernel-precomp-nnbd-linux-debug-simarm_x64-try,vm-kernel-precomp-linux-debug-simarm64c-try,vm-kernel-precomp-linux-debug-simarm_x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-kernel-precomp-linux-debug-x64c-try,vm-kernel-precomp-linux-product-x64-try,vm-kernel-precomp-linux-release-x64-try
> Change-Id: Ia700158ac873ad32ac28c1027a669895961bc715
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/196321
> Commit-Queue: Tess Strickland <sstrickl@google.com>
> Reviewed-by: Ryan Macnak <rmacnak@google.com>
> Reviewed-by: Martin Kustermann <kustermann@google.com>
# Not skipping CQ checks because original CL landed > 1 day ago.
Change-Id: Idf32bdd879cf8bb7407f6dae764312140ad6eeb2
Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-asan-linux-release-x64-try,vm-kernel-precomp-dwarf-linux-product-x64-try,vm-kernel-precomp-msan-linux-release-x64-try,vm-kernel-precomp-ubsan-linux-release-x64-try,vm-kernel-precomp-tsan-linux-release-x64-try,vm-kernel-precomp-nnbd-linux-debug-x64-try,vm-kernel-precomp-nnbd-linux-debug-simarm_x64-try,vm-kernel-precomp-linux-debug-simarm64c-try,vm-kernel-precomp-linux-debug-simarm_x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-kernel-precomp-linux-debug-x64c-try,vm-kernel-precomp-linux-product-x64-try,vm-kernel-precomp-linux-release-x64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/196920
Reviewed-by: Ivan Inozemtsev <iinozemtsev@google.com>
Commit-Queue: Ivan Inozemtsev <iinozemtsev@google.com>
659 lines
21 KiB
C++
659 lines
21 KiB
C++
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#ifndef RUNTIME_VM_DATASTREAM_H_
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#define RUNTIME_VM_DATASTREAM_H_
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#include "platform/assert.h"
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#include "platform/utils.h"
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#include "vm/allocation.h"
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#include "vm/exceptions.h"
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#include "vm/globals.h"
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#include "vm/os.h"
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#include "vm/zone.h"
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namespace dart {
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static const int8_t kDataBitsPerByte = 7;
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static const int8_t kByteMask = (1 << kDataBitsPerByte) - 1;
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static const int8_t kMaxUnsignedDataPerByte = kByteMask;
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static const int8_t kMinDataPerByte = -(1 << (kDataBitsPerByte - 1));
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static const int8_t kMaxDataPerByte = (~kMinDataPerByte & kByteMask); // NOLINT
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static const uint8_t kEndByteMarker = (255 - kMaxDataPerByte);
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static const uint8_t kEndUnsignedByteMarker = (255 - kMaxUnsignedDataPerByte);
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struct LEB128Constants : AllStatic {
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// Convenience template for ensuring non-signed types trigger SFINAE.
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template <typename T, typename S>
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using only_if_signed =
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typename std::enable_if<std::is_signed<T>::value, S>::type;
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// Convenience template for ensuring signed types trigger SFINAE.
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template <typename T, typename S>
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using only_if_unsigned =
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typename std::enable_if<std::is_unsigned<T>::value, S>::type;
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// (S)LEB128 encodes 7 bits of data per byte (hence 128).
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static constexpr uint8_t kDataBitsPerByte = 7;
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static constexpr uint8_t kDataByteMask = (1 << kDataBitsPerByte) - 1;
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// If more data follows a given data byte, the high bit is set.
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static constexpr uint8_t kMoreDataMask = (1 << kDataBitsPerByte);
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// For SLEB128, the high bit in the data of the last byte is the sign bit.
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static constexpr uint8_t kSignMask = (1 << (kDataBitsPerByte - 1));
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};
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class NonStreamingWriteStream;
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// Stream for reading various types from a buffer.
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class ReadStream : public ValueObject {
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public:
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ReadStream(const uint8_t* buffer, intptr_t size)
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: buffer_(buffer), current_(buffer), end_(buffer + size) {}
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// Creates a ReadStream that starts at a given position in the buffer.
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ReadStream(const uint8_t* buffer, intptr_t size, intptr_t pos)
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: ReadStream(buffer, size) {
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SetPosition(pos);
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}
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template <int N, typename T>
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class Raw {};
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template <typename T>
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class Raw<1, T> {
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public:
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static T Read(ReadStream* st) { return bit_cast<T>(st->ReadByte()); }
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};
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template <typename T>
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class Raw<2, T> {
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public:
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static T Read(ReadStream* st) { return bit_cast<T>(st->Read16()); }
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};
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template <typename T>
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class Raw<4, T> {
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public:
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static T Read(ReadStream* st) { return bit_cast<T>(st->Read32()); }
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};
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template <typename T>
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class Raw<8, T> {
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public:
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static T Read(ReadStream* st) { return bit_cast<T>(st->Read64()); }
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};
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// Reads 'len' bytes from the stream.
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void ReadBytes(uint8_t* addr, intptr_t len) {
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ASSERT((end_ - current_) >= len);
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if (len != 0) {
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memmove(addr, current_, len);
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}
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current_ += len;
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}
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template <typename T = intptr_t>
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T ReadUnsigned() {
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return Read<T>(kEndUnsignedByteMarker);
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}
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intptr_t Position() const { return current_ - buffer_; }
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void SetPosition(intptr_t value) {
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ASSERT((end_ - buffer_) >= value);
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current_ = buffer_ + value;
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}
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void Align(intptr_t alignment) {
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intptr_t position_before = Position();
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intptr_t position_after = Utils::RoundUp(position_before, alignment);
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Advance(position_after - position_before);
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}
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const uint8_t* AddressOfCurrentPosition() const { return current_; }
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void Advance(intptr_t value) {
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ASSERT((end_ - current_) >= value);
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current_ = current_ + value;
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}
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intptr_t PendingBytes() const {
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ASSERT(end_ >= current_);
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return (end_ - current_);
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}
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template <typename T>
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T Read() {
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return Read<T>(kEndByteMarker);
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}
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uword ReadWordWith32BitReads() {
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constexpr intptr_t kNumRead32PerWord = kBitsPerWord / kBitsPerInt32;
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uword value = 0;
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for (intptr_t j = 0; j < kNumRead32PerWord; j++) {
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const auto partial_value = Raw<kInt32Size, uint32_t>::Read(this);
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value |= (static_cast<uword>(partial_value) << (j * kBitsPerInt32));
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}
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return value;
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}
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private:
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using C = LEB128Constants;
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public:
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template <typename T = uintptr_t>
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C::only_if_unsigned<T, T> ReadLEB128() {
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constexpr intptr_t kBitsPerT = kBitsPerByte * sizeof(T);
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T r = 0;
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uint8_t s = 0;
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uint8_t b;
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do {
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ASSERT(s < kBitsPerT);
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b = ReadByte();
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r |= static_cast<T>(b & C::kDataByteMask) << s;
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s += C::kDataBitsPerByte;
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} while ((b & C::kMoreDataMask) != 0);
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ASSERT(s < C::kDataBitsPerByte + kBitsPerT);
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return r;
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}
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template <typename T>
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C::only_if_signed<T, T> ReadLEB128() {
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return bit_cast<T>(ReadLEB128<typename std::make_unsigned<T>::type>());
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}
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template <typename T>
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C::only_if_unsigned<T, T> ReadSLEB128() {
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constexpr intptr_t kBitsPerT = kBitsPerByte * sizeof(T);
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T r = 0;
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uint8_t s = 0;
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uint8_t b;
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do {
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ASSERT(s < kBitsPerT);
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b = ReadByte();
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r |= static_cast<T>(b & C::kDataByteMask) << s;
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s += C::kDataBitsPerByte;
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} while ((b & C::kMoreDataMask) != 0);
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ASSERT(s < C::kDataBitsPerByte + kBitsPerT);
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// At this point, [s] contains how many data bits have made it into the
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// value. If the value is negative and the count of data bits is less than
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// the size of the value, then we need to extend the sign by setting the
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// remaining (unset) most significant bits (MSBs).
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T sign_bits = 0;
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if ((b & C::kSignMask) != 0 && s < kBitsPerT) {
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// Create a bitmask for the current data bits and invert it.
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sign_bits = ~((static_cast<T>(1) << s) - 1);
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}
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return r | sign_bits;
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}
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template <typename T = intptr_t>
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C::only_if_signed<T, T> ReadSLEB128() {
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return bit_cast<T>(ReadSLEB128<typename std::make_unsigned<T>::type>());
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}
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private:
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uint16_t Read16() { return Read16(kEndByteMarker); }
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uint32_t Read32() { return Read32(kEndByteMarker); }
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uint64_t Read64() { return Read64(kEndByteMarker); }
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template <typename T>
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T Read(uint8_t end_byte_marker) {
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using Unsigned = typename std::make_unsigned<T>::type;
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Unsigned b = ReadByte();
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if (b > kMaxUnsignedDataPerByte) {
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return b - end_byte_marker;
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}
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T r = 0;
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uint8_t s = 0;
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do {
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r |= static_cast<Unsigned>(b) << s;
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s += kDataBitsPerByte;
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b = ReadByte();
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} while (b <= kMaxUnsignedDataPerByte);
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return r | (static_cast<Unsigned>(b - end_byte_marker) << s);
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}
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// Setting up needed variables for the unrolled loop sections below.
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#define UNROLLED_INIT() \
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using Unsigned = typename std::make_unsigned<T>::type; \
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Unsigned b = ReadByte(); \
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if (b > kMaxUnsignedDataPerByte) { \
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return b - end_byte_marker; \
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} \
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T r = b;
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// Part of the unrolled loop where the loop may stop, having read the last part,
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// or continue reading.
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#define UNROLLED_BODY(bit_start) \
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static_assert(bit_start % kDataBitsPerByte == 0, \
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"Bit start must be a multiple of the data bits per byte"); \
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static_assert(bit_start >= 0 && bit_start < kBitsPerByte * sizeof(T), \
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"Starting unrolled body at invalid bit position"); \
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static_assert(bit_start + kDataBitsPerByte < kBitsPerByte * sizeof(T), \
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"Unrolled body should not contain final bits in value"); \
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b = ReadByte(); \
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if (b > kMaxUnsignedDataPerByte) { \
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return r | (static_cast<T>(b - end_byte_marker) << bit_start); \
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} \
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r |= b << bit_start;
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// The end of the unrolled loop.
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#define UNROLLED_END(bit_start) \
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static_assert(bit_start % kDataBitsPerByte == 0, \
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"Bit start must be a multiple of the data bits per byte"); \
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static_assert(bit_start >= 0 && bit_start < kBitsPerByte * sizeof(T), \
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"Starting unrolled end at invalid bit position"); \
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static_assert(bit_start + kDataBitsPerByte >= kBitsPerByte * sizeof(T), \
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"Unrolled end does not contain final bits in value"); \
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b = ReadByte(); \
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ASSERT(b > kMaxUnsignedDataPerByte); \
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return r | (static_cast<T>(b - end_byte_marker) << bit_start);
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uint16_t Read16(uint8_t end_byte_marker) {
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using T = uint16_t;
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UNROLLED_INIT();
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UNROLLED_BODY(7);
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UNROLLED_END(14);
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}
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uint32_t Read32(uint8_t end_byte_marker) {
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using T = uint32_t;
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UNROLLED_INIT();
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UNROLLED_BODY(7);
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UNROLLED_BODY(14);
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UNROLLED_BODY(21);
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UNROLLED_END(28);
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}
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uint64_t Read64(uint8_t end_byte_marker) {
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using T = uint64_t;
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UNROLLED_INIT();
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UNROLLED_BODY(7);
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UNROLLED_BODY(14);
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UNROLLED_BODY(21);
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UNROLLED_BODY(28);
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UNROLLED_BODY(35);
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UNROLLED_BODY(42);
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UNROLLED_BODY(49);
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UNROLLED_BODY(56);
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UNROLLED_END(63);
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}
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DART_FORCE_INLINE uint8_t ReadByte() {
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ASSERT(current_ < end_);
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return *current_++;
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}
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private:
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const uint8_t* buffer_;
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const uint8_t* current_;
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const uint8_t* end_;
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DISALLOW_COPY_AND_ASSIGN(ReadStream);
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};
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// Base class for streams that writing various types into a buffer, possibly
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// flushing data out periodically to a more permanent store.
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class BaseWriteStream : public ValueObject {
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public:
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explicit BaseWriteStream(intptr_t initial_size)
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: initial_size_(Utils::RoundUpToPowerOfTwo(initial_size)) {}
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virtual ~BaseWriteStream() {}
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DART_FORCE_INLINE intptr_t bytes_written() const { return Position(); }
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virtual intptr_t Position() const { return current_ - buffer_; }
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intptr_t Align(intptr_t alignment) {
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const intptr_t position_before = Position();
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const intptr_t position_after = Utils::RoundUp(position_before, alignment);
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const intptr_t length = position_after - position_before;
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if (length != 0) {
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EnsureSpace(length);
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memset(current_, 0, length);
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SetPosition(position_after);
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}
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return length;
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}
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template <int N, typename T>
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class Raw {};
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template <typename T>
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class Raw<1, T> {
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public:
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static void Write(BaseWriteStream* st, T value) {
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st->WriteByte(bit_cast<uint8_t>(value));
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}
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};
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template <typename T>
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class Raw<2, T> {
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public:
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static void Write(BaseWriteStream* st, T value) {
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st->Write<int16_t>(bit_cast<int16_t>(value));
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}
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};
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template <typename T>
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class Raw<4, T> {
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public:
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static void Write(BaseWriteStream* st, T value) {
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st->Write<int32_t>(bit_cast<int32_t>(value));
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}
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};
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template <typename T>
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class Raw<8, T> {
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public:
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static void Write(BaseWriteStream* st, T value) {
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st->Write<int64_t>(bit_cast<int64_t>(value));
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}
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};
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void WriteWordWith32BitWrites(uword value) {
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constexpr intptr_t kNumWrite32PerWord = kBitsPerWord / kBitsPerInt32;
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const uint32_t mask = Utils::NBitMask(kBitsPerInt32);
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for (intptr_t j = 0; j < kNumWrite32PerWord; j++) {
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const uint32_t shifted_value = (value >> (j * kBitsPerInt32));
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Raw<kInt32Size, uint32_t>::Write(this, shifted_value & mask);
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}
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}
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template <typename T>
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void WriteUnsigned(T value) {
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ASSERT(value >= 0);
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while (value > kMaxUnsignedDataPerByte) {
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WriteByte(static_cast<uint8_t>(value & kByteMask));
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value = value >> kDataBitsPerByte;
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}
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WriteByte(static_cast<uint8_t>(value + kEndUnsignedByteMarker));
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}
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void WriteBytes(const void* addr, intptr_t len) {
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if (len != 0) {
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EnsureSpace(len);
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memmove(current_, addr, len);
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current_ += len;
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}
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}
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void WriteWord(uword value) { WriteFixed(value); }
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void WriteTargetWord(word value);
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void Printf(const char* format, ...) PRINTF_ATTRIBUTE(2, 3) {
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va_list args;
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va_start(args, format);
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VPrintf(format, args);
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va_end(args);
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}
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void VPrintf(const char* format, va_list args) {
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// Measure.
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va_list measure_args;
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va_copy(measure_args, args);
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intptr_t len = Utils::VSNPrint(nullptr, 0, format, measure_args);
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va_end(measure_args);
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// Alloc.
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EnsureSpace(len + 1);
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// Print.
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va_list print_args;
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va_copy(print_args, args);
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Utils::VSNPrint(reinterpret_cast<char*>(current_), len + 1, format,
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print_args);
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va_end(print_args);
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current_ += len; // Not len + 1 to swallow the terminating NUL.
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}
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template <typename T>
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void Write(T value) {
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T v = value;
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while (v < kMinDataPerByte || v > kMaxDataPerByte) {
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WriteByte(static_cast<uint8_t>(v & kByteMask));
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v = v >> kDataBitsPerByte;
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}
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WriteByte(static_cast<uint8_t>(v + kEndByteMarker));
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}
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template <typename T>
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void WriteFixed(T value) {
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WriteBytes(&value, sizeof(value));
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}
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DART_FORCE_INLINE void WriteByte(uint8_t value) {
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EnsureSpace(1);
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*current_++ = value;
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}
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void WriteString(const char* cstr) { WriteBytes(cstr, strlen(cstr)); }
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private:
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using C = LEB128Constants;
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public:
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template <typename T>
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C::only_if_unsigned<T, void> WriteLEB128(T value) {
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T remainder = value;
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bool is_last_part;
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do {
|
|
uint8_t part = static_cast<uint8_t>(remainder & C::kDataByteMask);
|
|
remainder >>= C::kDataBitsPerByte;
|
|
// For unsigned types, we're done when the remainder has no bits set.
|
|
is_last_part = remainder == static_cast<T>(0);
|
|
if (!is_last_part) {
|
|
// Mark this part as a non-final part for this value.
|
|
part |= C::kMoreDataMask;
|
|
}
|
|
WriteByte(part);
|
|
} while (!is_last_part);
|
|
}
|
|
|
|
template <typename T>
|
|
C::only_if_signed<T, void> WriteLEB128(T value) {
|
|
// If we're trying to LEB128 encode a negative value, chances are we should
|
|
// be using SLEB128 instead.
|
|
ASSERT(value >= 0);
|
|
return WriteLEB128(bit_cast<typename std::make_unsigned<T>::type>(value));
|
|
}
|
|
|
|
template <typename T>
|
|
C::only_if_signed<T, void> WriteSLEB128(T value) {
|
|
constexpr intptr_t kBitsPerT = kBitsPerByte * sizeof(T);
|
|
using Unsigned = typename std::make_unsigned<T>::type;
|
|
// Record whether the original value was negative.
|
|
const bool is_negative = value < 0;
|
|
T remainder = value;
|
|
bool is_last_part;
|
|
do {
|
|
uint8_t part = static_cast<uint8_t>(remainder & C::kDataByteMask);
|
|
remainder >>= C::kDataBitsPerByte;
|
|
// For signed types, we're done when either:
|
|
// - the remainder has all bits set and the part's sign bit is set
|
|
// for negative values, or
|
|
// - the remainder has no bits set and the part's sign bit is unset for
|
|
// non-negative values.
|
|
// If the remainder matches but the sign bit does not, we need one more
|
|
// part to set the sign bit correctly when decoding.
|
|
if (is_negative) {
|
|
// Right shifts of negative values in C are not guaranteed to be
|
|
// arithmetic. For negative values, set the [kDataBitsPerByte] most
|
|
// significant bits after shifting to ensure the value stays negative.
|
|
constexpr intptr_t preserved_bits = kBitsPerT - C::kDataBitsPerByte;
|
|
// The sign extension mask is the inverse of the preserved bits mask.
|
|
constexpr T sign_extend =
|
|
~static_cast<T>((static_cast<Unsigned>(1) << preserved_bits) - 1);
|
|
// Sign extend for negative values just in case a non-arithmetic right
|
|
// shift is used by the compiler.
|
|
remainder |= sign_extend;
|
|
ASSERT(remainder < 0); // Remainder should still be negative.
|
|
is_last_part =
|
|
remainder == ~static_cast<T>(0) && (part & C::kSignMask) != 0;
|
|
} else {
|
|
ASSERT(remainder >= 0); // Remainder should still be non-negative.
|
|
is_last_part =
|
|
(remainder == static_cast<T>(0) && (part & C::kSignMask) == 0);
|
|
}
|
|
if (!is_last_part) {
|
|
// Mark this part as a non-final part for this value.
|
|
part |= C::kMoreDataMask;
|
|
}
|
|
WriteByte(part);
|
|
} while (!is_last_part);
|
|
}
|
|
|
|
template <typename T>
|
|
C::only_if_unsigned<T, void> WriteSLEB128(T value) {
|
|
return WriteSLEB128(bit_cast<typename std::make_signed<T>::type>(value));
|
|
}
|
|
|
|
protected:
|
|
void EnsureSpace(intptr_t size_needed) {
|
|
if (Remaining() >= size_needed) return;
|
|
intptr_t increment_size = capacity_;
|
|
if (size_needed > increment_size) {
|
|
increment_size = Utils::RoundUp(size_needed, initial_size_);
|
|
}
|
|
intptr_t new_size = capacity_ + increment_size;
|
|
ASSERT(new_size > capacity_);
|
|
Realloc(new_size);
|
|
if (buffer_ == nullptr) {
|
|
Exceptions::ThrowOOM();
|
|
}
|
|
ASSERT(Remaining() >= size_needed);
|
|
}
|
|
|
|
virtual void SetPosition(intptr_t value) {
|
|
EnsureSpace(value - BaseWriteStream::Position());
|
|
current_ = buffer_ + value;
|
|
}
|
|
|
|
DART_FORCE_INLINE intptr_t Remaining() const {
|
|
return capacity_ - BaseWriteStream::Position();
|
|
}
|
|
|
|
// Resizes the internal buffer to the requested new capacity. Should set
|
|
// buffer_, capacity_, and current_ appropriately.
|
|
//
|
|
// Instead of templating over an Allocator (which would then cause users
|
|
// of the templated class to need to be templated, etc.), we just add an
|
|
// Realloc method to override appropriately in subclasses. Less flexible,
|
|
// but requires less changes throughout the codebase.
|
|
virtual void Realloc(intptr_t new_capacity) = 0;
|
|
|
|
const intptr_t initial_size_;
|
|
uint8_t* buffer_ = nullptr;
|
|
uint8_t* current_ = nullptr;
|
|
intptr_t capacity_ = 0;
|
|
|
|
DISALLOW_COPY_AND_ASSIGN(BaseWriteStream);
|
|
};
|
|
|
|
// A base class for non-streaming write streams. Since these streams are
|
|
// not flushed periodically, the internal buffer contains all written data
|
|
// and can be retrieved via buffer(). NonStreamingWriteStream also provides
|
|
// SetPosition as part of its public API for non-sequential writing.
|
|
class NonStreamingWriteStream : public BaseWriteStream {
|
|
public:
|
|
explicit NonStreamingWriteStream(intptr_t initial_size)
|
|
: BaseWriteStream(initial_size) {}
|
|
|
|
public:
|
|
uint8_t* buffer() const { return buffer_; }
|
|
|
|
// Sets the position of the buffer
|
|
DART_FORCE_INLINE void SetPosition(intptr_t value) {
|
|
BaseWriteStream::SetPosition(value);
|
|
}
|
|
};
|
|
|
|
// A non-streaming write stream that uses realloc for reallocation, and frees
|
|
// the buffer when destructed unless ownership is transfered using Steal().
|
|
class MallocWriteStream : public NonStreamingWriteStream {
|
|
public:
|
|
explicit MallocWriteStream(intptr_t initial_size)
|
|
: NonStreamingWriteStream(initial_size) {}
|
|
~MallocWriteStream();
|
|
|
|
// Resets the stream and returns the original buffer, which is now considered
|
|
// owned by the caller. Sets [*length] to the length of the returned buffer.
|
|
uint8_t* Steal(intptr_t* length) {
|
|
ASSERT(length != nullptr);
|
|
*length = bytes_written();
|
|
uint8_t* const old_buffer = buffer_;
|
|
// We don't immediately reallocate a new space just in case this steal
|
|
// is the last use of this stream.
|
|
current_ = buffer_ = nullptr;
|
|
capacity_ = 0;
|
|
return old_buffer;
|
|
}
|
|
|
|
private:
|
|
virtual void Realloc(intptr_t new_size);
|
|
|
|
DISALLOW_COPY_AND_ASSIGN(MallocWriteStream);
|
|
};
|
|
|
|
// A non-streaming write stream that uses a zone for reallocation.
|
|
class ZoneWriteStream : public NonStreamingWriteStream {
|
|
public:
|
|
ZoneWriteStream(Zone* zone, intptr_t initial_size)
|
|
: NonStreamingWriteStream(initial_size), zone_(zone) {}
|
|
|
|
private:
|
|
virtual void Realloc(intptr_t new_size);
|
|
|
|
Zone* const zone_;
|
|
|
|
DISALLOW_COPY_AND_ASSIGN(ZoneWriteStream);
|
|
};
|
|
|
|
// A streaming write stream that uses the internal buffer only for non-flushed
|
|
// data. Like MallocWriteStream, uses realloc for reallocation, and flushes and
|
|
// frees the internal buffer when destructed. Since part or all of the written
|
|
// data may be flushed and no longer in the internal buffer, it does not provide
|
|
// a way to retrieve the written contents.
|
|
class StreamingWriteStream : public BaseWriteStream {
|
|
public:
|
|
explicit StreamingWriteStream(intptr_t initial_capacity,
|
|
Dart_StreamingWriteCallback callback,
|
|
void* callback_data)
|
|
: BaseWriteStream(initial_capacity),
|
|
callback_(callback),
|
|
callback_data_(callback_data) {}
|
|
~StreamingWriteStream();
|
|
|
|
private:
|
|
// Flushes any unflushed data to callback_data and resets the internal
|
|
// buffer. Changes current_ and flushed_size_ accordingly.
|
|
virtual void Flush();
|
|
|
|
virtual void Realloc(intptr_t new_size);
|
|
|
|
virtual intptr_t Position() const {
|
|
return flushed_size_ + BaseWriteStream::Position();
|
|
}
|
|
|
|
virtual void SetPosition(intptr_t value) {
|
|
// Make sure we're not trying to set the position to already-flushed data.
|
|
ASSERT(value >= flushed_size_);
|
|
BaseWriteStream::SetPosition(value - flushed_size_);
|
|
}
|
|
|
|
const Dart_StreamingWriteCallback callback_;
|
|
void* const callback_data_;
|
|
intptr_t flushed_size_ = 0;
|
|
|
|
DISALLOW_COPY_AND_ASSIGN(StreamingWriteStream);
|
|
};
|
|
|
|
} // namespace dart
|
|
|
|
#endif // RUNTIME_VM_DATASTREAM_H_
|