/*
* Uncompress an entry, in its entirety, to an open file descriptor.
*
* TODO: this doesn't verify the data's CRC, but probably should (especially
* for uncompressed data).
*/
bool dexZipExtractEntryToFile(const ZipArchive* pArchive,
const ZipEntry entry, int fd)
{
bool result = false;
int ent = entryToIndex(pArchive, entry);
if (ent < 0)
return -1;
const unsigned char* basePtr = (const unsigned char*)pArchive->mMap.addr;
int method;
long uncompLen, compLen;
off_t offset;
if (!dexZipGetEntryInfo(pArchive, entry, &method, &uncompLen, &compLen,
&offset, NULL, NULL))
{
goto bail;
}
if (method == kCompressStored) {
ssize_t actual;
actual = write(fd, basePtr + offset, uncompLen);
if (actual < 0) {
LOGE("Write failed: %s\n", strerror(errno));
goto bail;
} else if (actual != uncompLen) {
LOGE("Partial write during uncompress (%d of %ld)\n",
(int) actual, uncompLen);
goto bail;
} else {
LOGI("+++ successful write\n");
}
} else {
if (!inflateToFile(fd, basePtr+offset, uncompLen, compLen))
goto bail;
}
result = true;
bail:
return result;
}
/*
* Uncompress an entry, in its entirety, to an open file descriptor.
*
* TODO: this doesn't verify the data's CRC, but probably should (especially
* for uncompressed data).
*/
int dexZipExtractEntryToFile(const ZipArchive* pArchive,
const ZipEntry entry, int fd)
{
int result = -1;
int ent = entryToIndex(pArchive, entry);
if (ent < 0) {
LOGW("Zip: extract can't find entry %p\n", entry);
goto bail;
}
int method;
size_t uncompLen, compLen;
off_t dataOffset;
if (dexZipGetEntryInfo(pArchive, entry, &method, &uncompLen, &compLen,
&dataOffset, NULL, NULL) != 0)
{
goto bail;
}
if (lseek(pArchive->mFd, dataOffset, SEEK_SET) != dataOffset) {
LOGW("Zip: lseek to data at %ld failed\n", (long) dataOffset);
goto bail;
}
if (method == kCompressStored) {
if (copyFileToFile(pArchive->mFd, fd, uncompLen) != 0)
goto bail;
} else {
if (inflateToFile(pArchive->mFd, fd, uncompLen, compLen) != 0)
goto bail;
}
result = 0;
bail:
return result;
}
/*
* Extract "classes.dex" from zipFd into "cacheFd", leaving a little space
* up front for the DEX optimization header.
*/
static int extractAndProcessZip(int zipFd, int cacheFd,
const char* debugFileName, bool isBootstrap, const char* bootClassPath,
const char* dexoptFlagStr)
{
ZipArchive zippy; // 用于描述ZIP压缩文件的数据结构
ZipEntry zipEntry; // 用于表示一个ZIP入口
size_t uncompLen;
long modWhen, crc32;
off_t dexOffset; // 用于表示在Odex文件中，原Dex文件的起始地址
int err;
int result = -1;
int dexoptFlags = 0; /* bit flags, from enum DexoptFlags */
// 设置默认的优化模式
DexClassVerifyMode verifyMode = VERIFY_MODE_ALL;
DexOptimizerMode dexOptMode = OPTIMIZE_MODE_VERIFIED;
memset(&zippy, 0, sizeof(zippy));
/* make sure we're still at the start of an empty file */
if (lseek(cacheFd, 0, SEEK_END) != 0) {
ALOGE("DexOptZ: new cache file '%s' is not empty", debugFileName);
goto bail;
}
/*
* Write a skeletal DEX optimization header. We want the classes.dex
* to come just after it.
*/
err = dexOptCreateEmptyHeader(cacheFd);
if (err != 0)
goto bail;
/* record the file position so we can get back here later */
// 取得Odex文件中原Dex文件的起始位置，实际就是一个Odex文件头部的长度
dexOffset = lseek(cacheFd, 0, SEEK_CUR);
if (dexOffset < 0)
goto bail;
/*
* Open the zip archive, find the DEX entry.
*/
if (dexZipPrepArchive(zipFd, debugFileName, &zippy) != 0) {
ALOGW("DexOptZ: unable to open zip archive '%s'", debugFileName);
goto bail;
}
// 获取目标Dex文件的解压入口
zipEntry = dexZipFindEntry(&zippy, kClassesDex);
if (zipEntry == NULL) {
ALOGW("DexOptZ: zip archive '%s' does not include %s",
debugFileName, kClassesDex);
goto bail;
}
/*
* Extract some info about the zip entry.
*/
if (dexZipGetEntryInfo(&zippy, zipEntry, NULL, &uncompLen, NULL, NULL,
&modWhen, &crc32) != 0)
{
ALOGW("DexOptZ: zip archive GetEntryInfo failed on %s", debugFileName);
goto bail;
}
uncompLen = uncompLen;
modWhen = modWhen;
crc32 = crc32;
/*
* Extract the DEX data into the cache file at the current offset.
* 从ZIP文件将目标Dex文件解压出来，并写入cacheFd所指文件，此时cacheFd所指文件非空，
* 包括一个Odex文件头部加上一个原始的Dex文件
*/
if (dexZipExtractEntryToFile(&zippy, zipEntry, cacheFd) != 0) {
ALOGW("DexOptZ: extraction of %s from %s failed",
kClassesDex, debugFileName);
goto bail;
}
/* Parse the options. */
/*
* 入口参数dexoptFlagStr，对验证优化需求进行分析，dexoptFlagStr实际上是一个字符串，
* 记录了验证优化选项
*/
if (dexoptFlagStr[0] != '\0') {
const char* opc;
const char* val;
// 设置验证模式
opc = strstr(dexoptFlagStr, "v="); /* verification */
if (opc != NULL) {
switch (*(opc+2)) {
case 'n': verifyMode = VERIFY_MODE_NONE; break;
case 'r': verifyMode = VERIFY_MODE_REMOTE; break;
case 'a': verifyMode = VERIFY_MODE_ALL; break;
default: break;
}
}
// 设置优化模式
opc = strstr(dexoptFlagStr, "o="); /* optimization */
if (opc != NULL) {
switch (*(opc+2)) {
case 'n': dexOptMode = OPTIMIZE_MODE_NONE; break;
case 'v': dexOptMode = OPTIMIZE_MODE_VERIFIED; break;
case 'a': dexOptMode = OPTIMIZE_MODE_ALL; break;
case 'f': dexOptMode = OPTIMIZE_MODE_FULL; break;
default: break;
}
}
opc = strstr(dexoptFlagStr, "m=y"); /* register map */
if (opc != NULL) {
dexoptFlags |= DEXOPT_GEN_REGISTER_MAPS;
}
opc = strstr(dexoptFlagStr, "u="); /* uniprocessor target */
if (opc != NULL) {
switch (*(opc+2)) {
case 'y': dexoptFlags |= DEXOPT_UNIPROCESSOR; break;
case 'n': dexoptFlags |= DEXOPT_SMP; break;
default: break;
}
}
}
/*
* Prep the VM and perform the optimization.
* 完成了原Dex文件的提取以及验证优化选项的设置，即可以开始真正的优化工作，需要
* 初始化一个虚拟机专门用于验证优化工作
*/
if (dvmPrepForDexOpt(bootClassPath, dexOptMode, verifyMode,
dexoptFlags) != 0)
{
ALOGE("DexOptZ: VM init failed");
goto bail;
}
//vmStarted = 1;
/* do the optimization */
if (!dvmContinueOptimization(cacheFd, dexOffset, uncompLen, debugFileName,
modWhen, crc32, isBootstrap))
{
ALOGE("Optimization failed");
goto bail;
}
/* we don't shut the VM down -- process is about to exit */
result = 0;
bail:
dexZipCloseArchive(&zippy);
return result;
}