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/*
* Copyright (C) 2009 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.
*/
#include <utils/backup_helpers.h>
#include <utils/ByteOrder.h>
#include <stdio.h>
#include <unistd.h>
namespace android {
/*
* File Format (v1):
*
* All ints are stored little-endian.
*
* - An app_header_v1 struct.
* - The name of the package, utf-8, null terminated, padded to 4-byte boundary.
* - A sequence of zero or more key/value paires (entities), each with
* - A entity_header_v1 struct
* - The key, utf-8, null terminated, padded to 4-byte boundary.
* - The value, padded to 4 byte boundary
*/
#define APP_MAGIC_V1 0x31707041 // App1 (little endian)
#define ENTITY_MAGIC_V1 0x61746144 // Data (little endian)
#define FOOTER_MAGIC_V1 0x746f6f46 // Foot (little endian)
typedef struct {
int type; // == APP_MAGIC_V1
int packageLen; // length of the name of the package that follows, not including the null.
} app_header_v1;
typedef struct {
int type; // ENTITY_MAGIC_V1
int keyLen; // length of the key name, not including the null terminator
int dataSize; // size of the data, not including the padding
} entity_header_v1;
typedef struct {
int type; // FOOTER_MAGIC_V1
int entityCount; // the number of entities that were written
} app_footer_v1;
const static int ROUND_UP[4] = { 0, 3, 2, 1 };
static inline size_t
round_up(size_t n)
{
return n + ROUND_UP[n % 4];
}
static inline size_t
padding_extra(size_t n)
{
return ROUND_UP[n % 4];
}
BackupDataWriter::BackupDataWriter(int fd)
:m_fd(fd),
m_status(NO_ERROR),
m_pos(0),
m_entityCount(0)
{
}
BackupDataWriter::~BackupDataWriter()
{
}
// Pad out anything they've previously written to the next 4 byte boundary.
status_t
BackupDataWriter::write_padding_for(int n)
{
ssize_t amt;
ssize_t paddingSize;
paddingSize = padding_extra(n);
if (paddingSize > 0) {
uint32_t padding = 0xbcbcbcbc;
amt = write(m_fd, &padding, paddingSize);
if (amt != paddingSize) {
m_status = errno;
return m_status;
}
m_pos += amt;
}
return NO_ERROR;
}
status_t
BackupDataWriter::WriteAppHeader(const String8& packageName)
{
if (m_status != NO_ERROR) {
return m_status;
}
ssize_t amt;
amt = write_padding_for(m_pos);
if (amt != 0) {
return amt;
}
app_header_v1 header;
ssize_t nameLen;
nameLen = packageName.length();
header.type = tolel(APP_MAGIC_V1);
header.packageLen = tolel(nameLen);
amt = write(m_fd, &header, sizeof(app_header_v1));
if (amt != sizeof(app_header_v1)) {
m_status = errno;
return m_status;
}
m_pos += amt;
amt = write(m_fd, packageName.string(), nameLen+1);
if (amt != nameLen+1) {
m_status = errno;
return m_status;
}
m_pos += amt;
return NO_ERROR;
}
status_t
BackupDataWriter::WriteEntityHeader(const String8& key, size_t dataSize)
{
if (m_status != NO_ERROR) {
return m_status;
}
ssize_t amt;
amt = write_padding_for(m_pos);
if (amt != 0) {
return amt;
}
entity_header_v1 header;
ssize_t keyLen;
keyLen = key.length();
header.type = tolel(ENTITY_MAGIC_V1);
header.keyLen = tolel(keyLen);
header.dataSize = tolel(dataSize);
amt = write(m_fd, &header, sizeof(entity_header_v1));
if (amt != sizeof(entity_header_v1)) {
m_status = errno;
return m_status;
}
m_pos += amt;
amt = write(m_fd, key.string(), keyLen+1);
if (amt != keyLen+1) {
m_status = errno;
return m_status;
}
m_pos += amt;
amt = write_padding_for(keyLen+1);
m_entityCount++;
return amt;
}
status_t
BackupDataWriter::WriteEntityData(const void* data, size_t size)
{
if (m_status != NO_ERROR) {
return m_status;
}
// We don't write padding here, because they're allowed to call this several
// times with smaller buffers. We write it at the end of WriteEntityHeader
// instead.
ssize_t amt = write(m_fd, data, size);
if (amt != (ssize_t)size) {
m_status = errno;
return m_status;
}
m_pos += amt;
return NO_ERROR;
}
status_t
BackupDataWriter::WriteAppFooter()
{
if (m_status != NO_ERROR) {
return m_status;
}
ssize_t amt;
amt = write_padding_for(m_pos);
if (amt != 0) {
return amt;
}
app_footer_v1 footer;
ssize_t nameLen;
footer.type = tolel(FOOTER_MAGIC_V1);
footer.entityCount = tolel(m_entityCount);
amt = write(m_fd, &footer, sizeof(app_footer_v1));
if (amt != sizeof(app_footer_v1)) {
m_status = errno;
return m_status;
}
m_pos += amt;
return NO_ERROR;
}
} // namespace android
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