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Diffstat (limited to 'libs/utils/StreamingZipInflater.cpp')
| -rw-r--r-- | libs/utils/StreamingZipInflater.cpp | 225 |
1 files changed, 225 insertions, 0 deletions
diff --git a/libs/utils/StreamingZipInflater.cpp b/libs/utils/StreamingZipInflater.cpp new file mode 100644 index 000000000000..7ebde78cd85b --- /dev/null +++ b/libs/utils/StreamingZipInflater.cpp @@ -0,0 +1,225 @@ +/* + * Copyright (C) 2010 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 "szipinf" +#include <utils/Log.h> + +#include <utils/FileMap.h> +#include <utils/StreamingZipInflater.h> +#include <string.h> +#include <stddef.h> +#include <assert.h> + +static inline size_t min_of(size_t a, size_t b) { return (a < b) ? a : b; } + +using namespace android; + +/* + * Streaming access to compressed asset data in an open fd + */ +StreamingZipInflater::StreamingZipInflater(int fd, off_t compDataStart, + size_t uncompSize, size_t compSize) { + mFd = fd; + mDataMap = NULL; + mInFileStart = compDataStart; + mOutTotalSize = uncompSize; + mInTotalSize = compSize; + + mInBufSize = StreamingZipInflater::INPUT_CHUNK_SIZE; + mInBuf = new uint8_t[mInBufSize]; + + mOutBufSize = StreamingZipInflater::OUTPUT_CHUNK_SIZE; + mOutBuf = new uint8_t[mOutBufSize]; + + initInflateState(); +} + +/* + * Streaming access to compressed data held in an mmapped region of memory + */ +StreamingZipInflater::StreamingZipInflater(FileMap* dataMap, size_t uncompSize) { + mFd = -1; + mDataMap = dataMap; + mOutTotalSize = uncompSize; + mInTotalSize = dataMap->getDataLength(); + + mInBuf = (uint8_t*) dataMap->getDataPtr(); + mInBufSize = mInTotalSize; + + mOutBufSize = StreamingZipInflater::OUTPUT_CHUNK_SIZE; + mOutBuf = new uint8_t[mOutBufSize]; + + initInflateState(); +} + +StreamingZipInflater::~StreamingZipInflater() { + // tear down the in-flight zip state just in case + ::inflateEnd(&mInflateState); + + if (mDataMap == NULL) { + delete [] mInBuf; + } + delete [] mOutBuf; +} + +void StreamingZipInflater::initInflateState() { + LOGD("Initializing inflate state"); + + memset(&mInflateState, 0, sizeof(mInflateState)); + mInflateState.zalloc = Z_NULL; + mInflateState.zfree = Z_NULL; + mInflateState.opaque = Z_NULL; + mInflateState.next_in = (Bytef*)mInBuf; + mInflateState.next_out = (Bytef*) mOutBuf; + mInflateState.avail_out = mOutBufSize; + mInflateState.data_type = Z_UNKNOWN; + + mOutLastDecoded = mOutDeliverable = mOutCurPosition = 0; + mInNextChunkOffset = 0; + mStreamNeedsInit = true; + + if (mDataMap == NULL) { + ::lseek(mFd, mInFileStart, SEEK_SET); + mInflateState.avail_in = 0; // set when a chunk is read in + } else { + mInflateState.avail_in = mInBufSize; + } +} + +/* + * Basic approach: + * + * 1. If we have undelivered uncompressed data, send it. At this point + * either we've satisfied the request, or we've exhausted the available + * output data in mOutBuf. + * + * 2. While we haven't sent enough data to satisfy the request: + * 0. if the request is for more data than exists, bail. + * a. if there is no input data to decode, read some into the input buffer + * and readjust the z_stream input pointers + * b. point the output to the start of the output buffer and decode what we can + * c. deliver whatever output data we can + */ +ssize_t StreamingZipInflater::read(void* outBuf, size_t count) { + uint8_t* dest = (uint8_t*) outBuf; + size_t bytesRead = 0; + size_t toRead = min_of(count, size_t(mOutTotalSize - mOutCurPosition)); + while (toRead > 0) { + // First, write from whatever we already have decoded and ready to go + size_t deliverable = min_of(toRead, mOutLastDecoded - mOutDeliverable); + if (deliverable > 0) { + if (outBuf != NULL) memcpy(dest, mOutBuf + mOutDeliverable, deliverable); + mOutDeliverable += deliverable; + mOutCurPosition += deliverable; + dest += deliverable; + bytesRead += deliverable; + toRead -= deliverable; + } + + // need more data? time to decode some. + if (toRead > 0) { + // if we don't have any data to decode, read some in. If we're working + // from mmapped data this won't happen, because the clipping to total size + // will prevent reading off the end of the mapped input chunk. + if (mInflateState.avail_in == 0) { + int err = readNextChunk(); + if (err < 0) { + LOGE("Unable to access asset data: %d", err); + if (!mStreamNeedsInit) { + ::inflateEnd(&mInflateState); + initInflateState(); + } + return -1; + } + } + // we know we've drained whatever is in the out buffer now, so just + // start from scratch there, reading all the input we have at present. + mInflateState.next_out = (Bytef*) mOutBuf; + mInflateState.avail_out = mOutBufSize; + + /* + LOGD("Inflating to outbuf: avail_in=%u avail_out=%u next_in=%p next_out=%p", + mInflateState.avail_in, mInflateState.avail_out, + mInflateState.next_in, mInflateState.next_out); + */ + int result = Z_OK; + if (mStreamNeedsInit) { + LOGI("Initializing zlib to inflate"); + result = inflateInit2(&mInflateState, -MAX_WBITS); + mStreamNeedsInit = false; + } + if (result == Z_OK) result = ::inflate(&mInflateState, Z_SYNC_FLUSH); + if (result < 0) { + // Whoops, inflation failed + LOGE("Error inflating asset: %d", result); + ::inflateEnd(&mInflateState); + initInflateState(); + return -1; + } else { + if (result == Z_STREAM_END) { + // we know we have to have reached the target size here and will + // not try to read any further, so just wind things up. + ::inflateEnd(&mInflateState); + } + + // Note how much data we got, and off we go + mOutDeliverable = 0; + mOutLastDecoded = mOutBufSize - mInflateState.avail_out; + } + } + } + return bytesRead; +} + +int StreamingZipInflater::readNextChunk() { + assert(mDataMap == NULL); + + if (mInNextChunkOffset < mInTotalSize) { + size_t toRead = min_of(mInBufSize, mInTotalSize - mInNextChunkOffset); + if (toRead > 0) { + ssize_t didRead = ::read(mFd, mInBuf, toRead); + //LOGD("Reading input chunk, size %08x didread %08x", toRead, didRead); + if (didRead < 0) { + // TODO: error + LOGE("Error reading asset data"); + return didRead; + } else { + mInNextChunkOffset += didRead; + mInflateState.next_in = (Bytef*) mInBuf; + mInflateState.avail_in = didRead; + } + } + } + return 0; +} + +// seeking backwards requires uncompressing fom the beginning, so is very +// expensive. seeking forwards only requires uncompressing from the current +// position to the destination. +off_t StreamingZipInflater::seekAbsolute(off_t absoluteInputPosition) { + if (absoluteInputPosition < mOutCurPosition) { + // rewind and reprocess the data from the beginning + if (!mStreamNeedsInit) { + ::inflateEnd(&mInflateState); + } + initInflateState(); + read(NULL, absoluteInputPosition); + } else if (absoluteInputPosition > mOutCurPosition) { + read(NULL, absoluteInputPosition - mOutCurPosition); + } + // else if the target position *is* our current position, do nothing + return absoluteInputPosition; +} |