replicant-frameworks_native/include/utils/ZipFileRO.h
Kenny Root 61ef747e0e Use pread() in ZipFileRO for Linux
AssetManager instances are created by zygote and passed to all its
children so that they don't have to individually open
frameworks-res.apk. This creates a problem for determining the current
file offset when using lseek() on those files, because you can't
guarantee the cross-process locking of a mutex. Luckily, Linux
implements pread() to get around this suckiness.

The problem is that only Linux implements this, so we have to keep the
old locking for use on host builds with aapt and friends. aapt doesn't
have this same problem of sharing file descriptors across forked
processes, so we can keep the local AutoMutex to protect accesses of
those files.

Change-Id: Ibe9f11499a53fe345f50fbaea438815ec0fd363e
2010-10-04 15:17:19 -07:00

247 lines
7.8 KiB
C++

/*
* Copyright (C) 2007 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.
*/
/*
* Read-only access to Zip archives, with minimal heap allocation.
*
* This is similar to the more-complete ZipFile class, but no attempt
* has been made to make them interchangeable. This class operates under
* a very different set of assumptions and constraints.
*
* One such assumption is that if you're getting file descriptors for
* use with this class as a child of a fork() operation, you must be on
* a pread() to guarantee correct operation. This is because pread() can
* atomically read at a file offset without worrying about a lock around an
* lseek() + read() pair.
*/
#ifndef __LIBS_ZIPFILERO_H
#define __LIBS_ZIPFILERO_H
#include <utils/Errors.h>
#include <utils/FileMap.h>
#include <utils/threads.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
namespace android {
/*
* Trivial typedef to ensure that ZipEntryRO is not treated as a simple
* integer. We use NULL to indicate an invalid value.
*/
typedef void* ZipEntryRO;
/*
* Open a Zip archive for reading.
*
* We want "open" and "find entry by name" to be fast operations, and we
* want to use as little memory as possible. We memory-map the file,
* and load a hash table with pointers to the filenames (which aren't
* null-terminated). The other fields are at a fixed offset from the
* filename, so we don't need to extract those (but we do need to byte-read
* and endian-swap them every time we want them).
*
* To speed comparisons when doing a lookup by name, we could make the mapping
* "private" (copy-on-write) and null-terminate the filenames after verifying
* the record structure. However, this requires a private mapping of
* every page that the Central Directory touches. Easier to tuck a copy
* of the string length into the hash table entry.
*
* NOTE: If this is used on file descriptors inherited from a fork() operation,
* you must be on a platform that implements pread() to guarantee correctness
* on the shared file descriptors.
*/
class ZipFileRO {
public:
ZipFileRO()
: mFd(-1), mFileName(NULL), mFileLength(-1),
mDirectoryMap(NULL),
mNumEntries(-1), mDirectoryOffset(-1),
mHashTableSize(-1), mHashTable(NULL)
{}
~ZipFileRO();
/*
* Open an archive.
*/
status_t open(const char* zipFileName);
/*
* Find an entry, by name. Returns the entry identifier, or NULL if
* not found.
*
* If two entries have the same name, one will be chosen at semi-random.
*/
ZipEntryRO findEntryByName(const char* fileName) const;
/*
* Return the #of entries in the Zip archive.
*/
int getNumEntries(void) const {
return mNumEntries;
}
/*
* Return the Nth entry. Zip file entries are not stored in sorted
* order, and updated entries may appear at the end, so anyone walking
* the archive needs to avoid making ordering assumptions. We take
* that further by returning the Nth non-empty entry in the hash table
* rather than the Nth entry in the archive.
*
* Valid values are [0..numEntries).
*
* [This is currently O(n). If it needs to be fast we can allocate an
* additional data structure or provide an iterator interface.]
*/
ZipEntryRO findEntryByIndex(int idx) const;
/*
* Copy the filename into the supplied buffer. Returns 0 on success,
* -1 if "entry" is invalid, or the filename length if it didn't fit. The
* length, and the returned string, include the null-termination.
*/
int getEntryFileName(ZipEntryRO entry, char* buffer, int bufLen) const;
/*
* Get the vital stats for an entry. Pass in NULL pointers for anything
* you don't need.
*
* "*pOffset" holds the Zip file offset of the entry's data.
*
* Returns "false" if "entry" is bogus or if the data in the Zip file
* appears to be bad.
*/
bool getEntryInfo(ZipEntryRO entry, int* pMethod, size_t* pUncompLen,
size_t* pCompLen, off_t* pOffset, long* pModWhen, long* pCrc32) const;
/*
* Create a new FileMap object that maps a subset of the archive. For
* an uncompressed entry this effectively provides a pointer to the
* actual data, for a compressed entry this provides the input buffer
* for inflate().
*/
FileMap* createEntryFileMap(ZipEntryRO entry) const;
/*
* Uncompress the data into a buffer. Depending on the compression
* format, this is either an "inflate" operation or a memcpy.
*
* Use "uncompLen" from getEntryInfo() to determine the required
* buffer size.
*
* Returns "true" on success.
*/
bool uncompressEntry(ZipEntryRO entry, void* buffer) const;
/*
* Uncompress the data to an open file descriptor.
*/
bool uncompressEntry(ZipEntryRO entry, int fd) const;
/* Zip compression methods we support */
enum {
kCompressStored = 0, // no compression
kCompressDeflated = 8, // standard deflate
};
/*
* Utility function: uncompress deflated data, buffer to buffer.
*/
static bool inflateBuffer(void* outBuf, const void* inBuf,
size_t uncompLen, size_t compLen);
/*
* Utility function: uncompress deflated data, buffer to fd.
*/
static bool inflateBuffer(int fd, const void* inBuf,
size_t uncompLen, size_t compLen);
/*
* Some basic functions for raw data manipulation. "LE" means
* Little Endian.
*/
static inline unsigned short get2LE(const unsigned char* buf) {
return buf[0] | (buf[1] << 8);
}
static inline unsigned long get4LE(const unsigned char* buf) {
return buf[0] | (buf[1] << 8) | (buf[2] << 16) | (buf[3] << 24);
}
private:
/* these are private and not defined */
ZipFileRO(const ZipFileRO& src);
ZipFileRO& operator=(const ZipFileRO& src);
/* locate and parse the central directory */
bool mapCentralDirectory(void);
/* parse the archive, prepping internal structures */
bool parseZipArchive(void);
/* add a new entry to the hash table */
void addToHash(const char* str, int strLen, unsigned int hash);
/* compute string hash code */
static unsigned int computeHash(const char* str, int len);
/* convert a ZipEntryRO back to a hash table index */
int entryToIndex(const ZipEntryRO entry) const;
/*
* One entry in the hash table.
*/
typedef struct HashEntry {
const char* name;
unsigned short nameLen;
//unsigned int hash;
} HashEntry;
/* open Zip archive */
int mFd;
/* Lock for handling the file descriptor (seeks, etc) */
mutable Mutex mFdLock;
/* zip file name */
char* mFileName;
/* length of file */
size_t mFileLength;
/* mapped file */
FileMap* mDirectoryMap;
/* number of entries in the Zip archive */
int mNumEntries;
/* CD directory offset in the Zip archive */
off_t mDirectoryOffset;
/*
* We know how many entries are in the Zip archive, so we have a
* fixed-size hash table. We probe for an empty slot.
*/
int mHashTableSize;
HashEntry* mHashTable;
};
}; // namespace android
#endif /*__LIBS_ZIPFILERO_H*/