/*
* Open the specified file read-only. We memory-map the entire thing and
* parse the contents.
*
* This will be called on non-Zip files, especially during VM startup, so
* we don't want to be too noisy about certain types of failure. (Do
* we want a "quiet" flag?)
*
* On success, we fill out the contents of "pArchive" and return 0.
*/
int dexZipOpenArchive(const char* fileName, ZipArchive* pArchive)
{
int fd, err;
LOGV("Opening archive '%s' %p\n", fileName, pArchive);
fd = open(fileName, O_RDONLY, 0);
if (fd < 0) {
err = errno ? errno : -1;
LOGV("Unable to open '%s': %s\n", fileName, strerror(err));
return err;
}
return dexZipPrepArchive(fd, fileName, pArchive);
}
/*
* Open the specified file read-only. We examine the contents and verify
* that it appears to be a valid zip file.
*
* This will be called on non-Zip files, especially during VM startup, so
* we don't want to be too noisy about certain types of failure. (Do
* we want a "quiet" flag?)
*
* On success, we fill out the contents of "pArchive" and return 0. On
* failure we return the errno value.
*/
int dexZipOpenArchive(const char* fileName, ZipArchive* pArchive)
{
int fd, err;
LOGV("Opening as zip '%s' %p\n", fileName, pArchive);
memset(pArchive, 0, sizeof(ZipArchive));
fd = open(fileName, O_RDONLY /*| O_BINARY*/, 0);
if (fd < 0) {
err = errno ? errno : -1;
LOGV("Unable to open '%s': %s\n", fileName, strerror(err));
return err;
}
return dexZipPrepArchive(fd, fileName, pArchive);
}
/*
* 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;
}
