commit b100cbf178e91d6652ebbad3ed36684cacb9d10e
author Christopher Tate <ctate@google.com> Mon Jul 26 11:24:18 2010 -0700
committer Christopher Tate <ctate@google.com> Wed Jul 28 15:33:28 2010 -0700
tree acb386c8adee2d0390193fc631f841f8d76ea5d7
parent 0c39b6c65bcb96ed6438c7d792a67708409d8f0f

Support streaming of compressed assets > 1 megabyte

Compressed assets larger than one megabyte are now decompressed on demand
rather than being decompressed in their entirety and held in memory.  Reading
the data in order is relatively efficient, as is seeking forward in the stream.
Seeking backwards is supported, but requires reprocessing the compressed data
from the beginning, so is very inefficient.

In addition, the size limit on compressed assets has been eliminated.

Change-Id: I6e68247957e6c53e7e8ba70d12764695f1723bad

libs/utils/Asset.cpp

diff --git a/libs/utils/Asset.cpp b/libs/utils/Asset.cpp
index 4295123..cef7db4 100644
--- a/libs/utils/Asset.cpp
+++ b/libs/utils/Asset.cpp
@@ -24,6 +24,7 @@
 #include <utils/Asset.h>
 #include <utils/Atomic.h>
 #include <utils/FileMap.h>
+#include <utils/StreamingZipInflater.h>
 #include <utils/ZipUtils.h>
 #include <utils/ZipFileRO.h>
 #include <utils/Log.h>
@@ -659,7 +660,7 @@
  */
 _CompressedAsset::_CompressedAsset(void)
     : mStart(0), mCompressedLen(0), mUncompressedLen(0), mOffset(0),
-      mMap(NULL), mFd(-1), mBuf(NULL)
+      mMap(NULL), mFd(-1), mZipInflater(NULL), mBuf(NULL)
 {
 }
 
@@ -698,6 +699,10 @@
     mFd = fd;
     assert(mBuf == NULL);
 
+    if (uncompressedLen > StreamingZipInflater::OUTPUT_CHUNK_SIZE) {
+        mZipInflater = new StreamingZipInflater(mFd, offset, uncompressedLen, compressedLen);
+    }
+
     return NO_ERROR;
 }
 
@@ -724,6 +729,9 @@
     mUncompressedLen = uncompressedLen;
     assert(mOffset == 0);
 
+    if (uncompressedLen > StreamingZipInflater::OUTPUT_CHUNK_SIZE) {
+        mZipInflater = new StreamingZipInflater(dataMap, uncompressedLen);
+    }
     return NO_ERROR;
 }
 
@@ -739,26 +747,29 @@
 
     assert(mOffset >= 0 && mOffset <= mUncompressedLen);
 
-    // TODO: if mAccessMode == ACCESS_STREAMING, use zlib more cleverly
+    /* If we're relying on a streaming inflater, go through that */
+    if (mZipInflater) {
+        actual = mZipInflater->read(buf, count);
+    } else {
+        if (mBuf == NULL) {
+            if (getBuffer(false) == NULL)
+                return -1;
+        }
+        assert(mBuf != NULL);
 
-    if (mBuf == NULL) {
-        if (getBuffer(false) == NULL)
-            return -1;
+        /* adjust count if we're near EOF */
+        maxLen = mUncompressedLen - mOffset;
+        if (count > maxLen)
+            count = maxLen;
+
+        if (!count)
+            return 0;
+
+        /* copy from buffer */
+        //printf("comp buf read\n");
+        memcpy(buf, (char*)mBuf + mOffset, count);
+        actual = count;
     }
-    assert(mBuf != NULL);
-
-    /* adjust count if we're near EOF */
-    maxLen = mUncompressedLen - mOffset;
-    if (count > maxLen)
-        count = maxLen;
-
-    if (!count)
-        return 0;
-
-    /* copy from buffer */
-    //printf("comp buf read\n");
-    memcpy(buf, (char*)mBuf + mOffset, count);
-    actual = count;
 
     mOffset += actual;
     return actual;
@@ -780,6 +791,9 @@
     if (newPosn == (off_t) -1)
         return newPosn;
 
+    if (mZipInflater) {
+        mZipInflater->seekAbsolute(newPosn);
+    }
     mOffset = newPosn;
     return mOffset;
 }
@@ -793,10 +807,12 @@
         mMap->release();
         mMap = NULL;
     }
-    if (mBuf != NULL) {
-        delete[] mBuf;
-        mBuf = NULL;
-    }
+
+    delete[] mBuf;
+    mBuf = NULL;
+
+    delete mZipInflater;
+    mZipInflater = NULL;
 
     if (mFd > 0) {
         ::close(mFd);
@@ -817,12 +833,6 @@
     if (mBuf != NULL)
         return mBuf;
 
-    if (mUncompressedLen > UNCOMPRESS_DATA_MAX) {
-        LOGD("Data exceeds UNCOMPRESS_DATA_MAX (%ld vs %d)\n",
-            (long) mUncompressedLen, UNCOMPRESS_DATA_MAX);
-        goto bail;
-    }
-
     /*
      * Allocate a buffer and read the file into it.
      */
@@ -853,7 +863,13 @@
             goto bail;
     }
 
-    /* success! */
+    /*
+     * Success - now that we have the full asset in RAM we
+     * no longer need the streaming inflater
+     */
+    delete mZipInflater;
+    mZipInflater = NULL;
+
     mBuf = buf;
     buf = NULL;