libs/protoutil/src/EncodedBuffer.cpp

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#define LOG_TAG "libprotoutil"

#include <stdlib.h>
#include <sys/mman.h>
#include <unistd.h>

#include <android/util/EncodedBuffer.h>
#include <android/util/protobuf.h>
#include <cutils/log.h>

namespace android {
namespace util {

constexpr size_t BUFFER_SIZE = 8 * 1024; // 8 KB
const size_t kPageSize = getpagesize();

EncodedBuffer::Pointer::Pointer() : Pointer(BUFFER_SIZE)
{
}

EncodedBuffer::Pointer::Pointer(size_t chunkSize)
        :mIndex(0),
         mOffset(0)
{
    mChunkSize = chunkSize == 0 ? BUFFER_SIZE : chunkSize;
}

size_t
EncodedBuffer::Pointer::pos() const
{
    return mIndex * mChunkSize + mOffset;
}

size_t
EncodedBuffer::Pointer::index() const
{
    return mIndex;
}

size_t
EncodedBuffer::Pointer::offset() const
{
    return mOffset;
}

EncodedBuffer::Pointer*
EncodedBuffer::Pointer::move(size_t amt)
{
    size_t newOffset = mOffset + amt;
    mIndex += newOffset / mChunkSize;
    mOffset = newOffset % mChunkSize;
    return this;
}

EncodedBuffer::Pointer*
EncodedBuffer::Pointer::rewind()
{
    mIndex = 0;
    mOffset = 0;
    return this;
}

EncodedBuffer::Pointer
EncodedBuffer::Pointer::copy() const
{
    Pointer p = Pointer(mChunkSize);
    p.mIndex = mIndex;
    p.mOffset = mOffset;
    return p;
}

// ===========================================================
EncodedBuffer::EncodedBuffer() : EncodedBuffer(BUFFER_SIZE)
{
}

EncodedBuffer::EncodedBuffer(size_t chunkSize)
        :mBuffers()
{
    // Align chunkSize to memory page size
    chunkSize = chunkSize == 0 ? BUFFER_SIZE : chunkSize;
    mChunkSize = (chunkSize + (kPageSize - 1)) & ~(kPageSize - 1);
    mWp = Pointer(mChunkSize);
    mEp = Pointer(mChunkSize);
}

EncodedBuffer::~EncodedBuffer()
{
    for (size_t i=0; i<mBuffers.size(); i++) {
        uint8_t* buf = mBuffers[i];
        munmap(buf, mChunkSize);
    }
}

inline uint8_t*
EncodedBuffer::at(const Pointer& p) const
{
    return mBuffers[p.index()] + p.offset();
}

void
EncodedBuffer::clear()
{
    mWp.rewind();
    mEp.rewind();
}

/******************************** Write APIs ************************************************/
size_t
EncodedBuffer::size() const
{
    return mWp.pos();
}

EncodedBuffer::Pointer*
EncodedBuffer::wp()
{
    return &mWp;
}

uint8_t*
EncodedBuffer::writeBuffer()
{
    // This prevents write pointer move too fast than allocating the buffer.
    if (mWp.index() > mBuffers.size()) return NULL;
    uint8_t* buf = NULL;
    if (mWp.index() == mBuffers.size()) {
        // Use mmap instead of malloc to ensure memory alignment i.e. no fragmentation so that
        // the mem region can be immediately reused by the allocator after calling munmap()
        buf = (uint8_t*)mmap(NULL, mChunkSize, PROT_READ | PROT_WRITE,
                MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);

        if (buf == NULL) return NULL; // This indicates NO_MEMORY

        mBuffers.push_back(buf);
    }
    return at(mWp);
}

size_t
EncodedBuffer::currentToWrite()
{
    return mChunkSize - mWp.offset();
}

void
EncodedBuffer::writeRawByte(uint8_t val)
{
    *writeBuffer() = val;
    mWp.move();
}

size_t
EncodedBuffer::writeRawVarint64(uint64_t val)
{
    size_t size = 0;
    while (true) {
        size++;
        if ((val & ~0x7F) == 0) {
            writeRawByte((uint8_t) val);
            return size;
        } else {
            writeRawByte((uint8_t)((val & 0x7F) | 0x80));
            val >>= 7;
        }
    }
}

size_t
EncodedBuffer::writeRawVarint32(uint32_t val)
{
    uint64_t v =(uint64_t)val;
    return writeRawVarint64(v);
}

void
EncodedBuffer::writeRawFixed32(uint32_t val)
{
    writeRawByte((uint8_t) val);
    writeRawByte((uint8_t) (val>>8));
    writeRawByte((uint8_t) (val>>16));
    writeRawByte((uint8_t) (val>>24));
}

void
EncodedBuffer::writeRawFixed64(uint64_t val)
{
    writeRawByte((uint8_t) val);
    writeRawByte((uint8_t) (val>>8));
    writeRawByte((uint8_t) (val>>16));
    writeRawByte((uint8_t) (val>>24));
    writeRawByte((uint8_t) (val>>32));
    writeRawByte((uint8_t) (val>>40));
    writeRawByte((uint8_t) (val>>48));
    writeRawByte((uint8_t) (val>>56));
}

size_t
EncodedBuffer::writeHeader(uint32_t fieldId, uint8_t wireType)
{
    return writeRawVarint32((fieldId << FIELD_ID_SHIFT) | wireType);
}

status_t
EncodedBuffer::writeRaw(uint8_t const* buf, size_t size)
{
    while (size > 0) {
        uint8_t* target = writeBuffer();
        if (target == NULL) {
            return -ENOMEM;
        }
        size_t chunk = currentToWrite();
        if (chunk > size) {
            chunk = size;
        }
        memcpy(target, buf, chunk);
        size -= chunk;
        buf += chunk;
        mWp.move(chunk);
    }
    return NO_ERROR;
}

status_t
EncodedBuffer::writeRaw(const sp<ProtoReader>& reader)
{
    status_t err;
    uint8_t const* buf;
    while ((buf = reader->readBuffer()) != nullptr) {
        size_t amt = reader->currentToRead();
        err = writeRaw(buf, amt);
        reader->move(amt);
        if (err != NO_ERROR) {
            return err;
        }
    }
    return NO_ERROR;
}

status_t
EncodedBuffer::writeRaw(const sp<ProtoReader>& reader, size_t size)
{
    status_t err;
    uint8_t const* buf;
    while (size > 0 && (buf = reader->readBuffer()) != nullptr) {
        size_t amt = reader->currentToRead();
        if (size < amt) {
            amt = size;
        }
        err = writeRaw(buf, amt);
        reader->move(amt);
        size -= amt;
        if (err != NO_ERROR) {
            return err;
        }
    }
    return size == 0 ? NO_ERROR : NOT_ENOUGH_DATA;
}


/******************************** Edit APIs ************************************************/
EncodedBuffer::Pointer*
EncodedBuffer::ep()
{
    return &mEp;
}

uint8_t
EncodedBuffer::readRawByte()
{
    uint8_t val = *at(mEp);
    mEp.move();
    return val;
}

uint64_t
EncodedBuffer::readRawVarint()
{
    uint64_t val = 0, shift = 0;
    size_t start = mEp.pos();
    while (true) {
        uint8_t byte = readRawByte();
        val |= (UINT64_C(0x7F) & byte) << shift;
        if ((byte & 0x80) == 0) break;
        shift += 7;
    }
    return val;
}

uint32_t
EncodedBuffer::readRawFixed32()
{
    uint32_t val = 0;
    for (auto i=0; i<32; i+=8) {
        val += (uint32_t)readRawByte() << i;
    }
    return val;
}

uint64_t
EncodedBuffer::readRawFixed64()
{
    uint64_t val = 0;
    for (auto i=0; i<64; i+=8) {
        val += (uint64_t)readRawByte() << i;
    }
    return val;
}

void
EncodedBuffer::editRawFixed32(size_t pos, uint32_t val)
{
    size_t oldPos = mEp.pos();
    mEp.rewind()->move(pos);
    for (auto i=0; i<32; i+=8) {
        *at(mEp) = (uint8_t) (val >> i);
        mEp.move();
    }
    mEp.rewind()->move(oldPos);
}

void
EncodedBuffer::copy(size_t srcPos, size_t size)
{
    if (size == 0) return;
    Pointer cp(mChunkSize);
    cp.move(srcPos);

    while (cp.pos() < srcPos + size) {
        writeRawByte(*at(cp));
        cp.move();
    }
}

/********************************* Read APIs ************************************************/
sp<ProtoReader>
EncodedBuffer::read()
{
    return new EncodedBuffer::Reader(this);
}

EncodedBuffer::Reader::Reader(const sp<EncodedBuffer>& buffer)
        :mData(buffer),
         mRp(buffer->mChunkSize)
{
}

EncodedBuffer::Reader::~Reader() {
}

ssize_t
EncodedBuffer::Reader::size() const
{
    return (ssize_t)mData->size();
}

size_t
EncodedBuffer::Reader::bytesRead() const
{
    return mRp.pos();
}

uint8_t const*
EncodedBuffer::Reader::readBuffer()
{
    return hasNext() ? const_cast<uint8_t const*>(mData->at(mRp)) : NULL;
}

size_t
EncodedBuffer::Reader::currentToRead()
{
    return (mData->mWp.index() > mRp.index()) ?
            mData->mChunkSize - mRp.offset() :
            mData->mWp.offset() - mRp.offset();
}

bool
EncodedBuffer::Reader::hasNext()
{
    return mRp.pos() < mData->mWp.pos();
}

uint8_t
EncodedBuffer::Reader::next()
{
    uint8_t res = *(mData->at(mRp));
    mRp.move();
    return res;
}

uint64_t
EncodedBuffer::Reader::readRawVarint()
{
    uint64_t val = 0, shift = 0;
    while (true) {
        uint8_t byte = next();
        val |= (INT64_C(0x7F) & byte) << shift;
        if ((byte & 0x80) == 0) break;
        shift += 7;
    }
    return val;
}

void
EncodedBuffer::Reader::move(size_t amt)
{
    mRp.move(amt);
}

} // util
} // android