android adb源码分析(1)

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ADB是Android debug bridge的缩写，它使用PC机可以通过USB或网络与android设备通讯。

adb的源码位于system/core/adb目录下，先来看下编译脚本Android.mk：

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# Copyright 2005 The Android Open Source Project

#

# Android.mk for adb

#

LOCAL_PATH:= $(call my-dir)

# adb host tool

# =========================================================

include $(CLEAR_VARS)

# Default to a virtual (sockets) usb interface

USB_SRCS :=

EXTRA_SRCS :=

ifeq ($(HOST_OS),linux)

USB_SRCS := usb_linux.c

EXTRA_SRCS := get_my_path_linux.c

LOCAL_LDLIBS += -lrt -ldl -lpthread

LOCAL_CFLAGS += -DWORKAROUND_BUG6558362

endif

ifeq ($(HOST_OS),darwin)

USB_SRCS := usb_osx.c

EXTRA_SRCS := get_my_path_darwin.c

LOCAL_LDLIBS += -lpthread -framework CoreFoundation -framework IOKit -framework Carbon

endif

ifeq ($(HOST_OS),freebsd)

USB_SRCS := usb_libusb.c

EXTRA_SRCS := get_my_path_freebsd.c

LOCAL_LDLIBS += -lpthread -lusb

endif

ifeq ($(HOST_OS),windows)

USB_SRCS := usb_windows.c

EXTRA_SRCS := get_my_path_windows.c ../libcutils/list.c

EXTRA_STATIC_LIBS := AdbWinApi

ifneq ($(strip $(USE_CYGWIN)),)

# Pure cygwin case

LOCAL_LDLIBS += -lpthread -lgdi32

LOCAL_C_INCLUDES += /usr/include/w32api/ddk

endif

ifneq ($(strip $(USE_MINGW)),)

# MinGW under Linux case

LOCAL_LDLIBS += -lws2_32 -lgdi32

USE_SYSDEPS_WIN32 := 1

LOCAL_C_INCLUDES += /usr/i586-mingw32msvc/include/ddk

endif

LOCAL_C_INCLUDES += development/host/windows/usb/api/

endif

LOCAL_SRC_FILES := \

adb.c \

console.c \

transport.c \

transport_local.c \

transport_usb.c \

commandline.c \

adb_client.c \

adb_auth_host.c \

sockets.c \

services.c \

file_sync_client.c \

$(EXTRA_SRCS) \

$(USB_SRCS) \

usb_vendors.c

LOCAL_C_INCLUDES += external/openssl/include

ifneq ($(USE_SYSDEPS_WIN32),)

LOCAL_SRC_FILES += sysdeps_win32.c

else

LOCAL_SRC_FILES += fdevent.c

endif

LOCAL_CFLAGS += -O2 -g -DADB_HOST=1 -Wall -Wno-unused-parameter

LOCAL_CFLAGS += -D_XOPEN_SOURCE -D_GNU_SOURCE

LOCAL_MODULE := adb

LOCAL_MODULE_TAGS := debug

LOCAL_STATIC_LIBRARIES := libzipfile libunz libcrypto_static $(EXTRA_STATIC_LIBS)

ifeq ($(USE_SYSDEPS_WIN32),)

LOCAL_STATIC_LIBRARIES += libcutils

endif

include $(BUILD_HOST_EXECUTABLE)

$(call dist-for-goals,dist_files sdk,$(LOCAL_BUILT_MODULE))

ifeq ($(HOST_OS),windows)

$(LOCAL_INSTALLED_MODULE): \

$(HOST_OUT_EXECUTABLES)/AdbWinApi.dll \

$(HOST_OUT_EXECUTABLES)/AdbWinUsbApi.dll

endif

# adbd device daemon

# =========================================================

include $(CLEAR_VARS)

LOCAL_SRC_FILES := \

adb.c \

backup_service.c \

fdevent.c \

transport.c \

transport_local.c \

transport_usb.c \

adb_auth_client.c \

sockets.c \

services.c \

file_sync_service.c \

jdwp_service.c \

framebuffer_service.c \

remount_service.c \

usb_linux_client.c \

log_service.c

LOCAL_CFLAGS := -O2 -g -DADB_HOST=0 -Wall -Wno-unused-parameter

LOCAL_CFLAGS += -D_XOPEN_SOURCE -D_GNU_SOURCE

ifneq (,$(filter userdebug eng,$(TARGET_BUILD_VARIANT)))

LOCAL_CFLAGS += -DALLOW_ADBD_ROOT=1

endif

LOCAL_MODULE := adbd

LOCAL_FORCE_STATIC_EXECUTABLE := true

LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT_SBIN)

LOCAL_UNSTRIPPED_PATH := $(TARGET_ROOT_OUT_SBIN_UNSTRIPPED)

LOCAL_STATIC_LIBRARIES := liblog libcutils libc libmincrypt

include $(BUILD_EXECUTABLE)

# adb host tool for device-as-host

# =========================================================

ifneq ($(SDK_ONLY),true)

include $(CLEAR_VARS)

LOCAL_LDLIBS := -lrt -ldl -lpthread

LOCAL_SRC_FILES := \

adb.c \

console.c \

transport.c \

transport_local.c \

transport_usb.c \

commandline.c \

adb_client.c \

adb_auth_host.c \

sockets.c \

services.c \

file_sync_client.c \

get_my_path_linux.c \

usb_linux.c \

usb_vendors.c \

fdevent.c

LOCAL_CFLAGS := \

-O2 \

-g \

-DADB_HOST=1 \

-DADB_HOST_ON_TARGET=1 \

-Wall \

-Wno-unused-parameter \

-D_XOPEN_SOURCE \

-D_GNU_SOURCE

LOCAL_C_INCLUDES += external/openssl/include

LOCAL_MODULE := adb

LOCAL_STATIC_LIBRARIES := libzipfile libunz libcutils

LOCAL_SHARED_LIBRARIES := libcrypto

include $(BUILD_EXECUTABLE)

endif

可以看到，最终会有3个执行文件被生成，adbd和两个adb程序。adbd是手机终的守护进程；adb一个是windows、linux、darwin或freebsd运行的程序，另一个是目标机上运行的程序。

宏ADB_HOST用于区分是PC端程序还是目标机端的程序。宏ADB_HOST_ON_TARGET用于区分adb程序是否是在目标机上运行。这3个程序使用的是同一份源码，在内部，使用这些宏来区别不同的程序。

程序的入口在adb.c的main()函数：

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int main(int argc, char **argv)

{

#if ADB_HOST

adb_sysdeps_init();

adb_trace_init();

D("Handling commandline()\n");

return adb_commandline(argc - 1, argv + 1);

#else

/* If adbd runs inside the emulator this will enable adb tracing via

* adb-debug qemud service in the emulator. */

adb_qemu_trace_init();

if((argc > 1) && (!strcmp(argv[1],"recovery"))) {

adb_device_banner = "recovery";

recovery_mode = 1;

}

start_device_log();

D("Handling main()\n");

return adb_main(0, DEFAULT_ADB_PORT);

#endif

}

先来看adbd程序，此时宏的设置是ADB_HOST=0。上面代码中start_device_log()是log的初始化操作，可以重定向输出的log信息，接着进入adb_main()函数。先来看下它的参数DEFAULT_ADB_PORT：

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#if ADB_HOST_ON_TARGET

/* adb and adbd are coexisting on the target, so use 5038 for adb

* to avoid conflicting with adbd's usage of 5037

*/

# define DEFAULT_ADB_PORT 5038

#else

# define DEFAULT_ADB_PORT 5037

#endif

如果是目标机程序，它的值是5038，否则它的值是5037。这里没有定义ADB_HOST_ON_TARGET， 所以它是5037。

adb_main()的源代码如下：

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int adb_main(int is_daemon, int server_port)

{

#if !ADB_HOST

int port;

char value[PROPERTY_VALUE_MAX];

umask(000);

#endif

atexit(adb_cleanup);

#ifdef HAVE_WIN32_PROC

SetConsoleCtrlHandler( ctrlc_handler, TRUE );

#elif defined(HAVE_FORKEXEC)

// No SIGCHLD. Let the service subproc handle its children.

signal(SIGPIPE, SIG_IGN);

#endif

init_transport_registration();

#if ADB_HOST

HOST = 1;

usb_vendors_init();

usb_init();

local_init(DEFAULT_ADB_LOCAL_TRANSPORT_PORT);

adb_auth_init();

char local_name[30];

build_local_name(local_name, sizeof(local_name), server_port);

if(install_listener(local_name, "*smartsocket*", NULL)) {

exit(1);

}

#else

property_get("ro.adb.secure", value, "0");

auth_enabled = !strcmp(value, "1");

if (auth_enabled)

adb_auth_init();

// Our external storage path may be different than apps, since

// we aren't able to bind mount after dropping root.

const char* adb_external_storage = getenv("ADB_EXTERNAL_STORAGE");

if (NULL != adb_external_storage) {

setenv("EXTERNAL_STORAGE", adb_external_storage, 1);

} else {

D("Warning: ADB_EXTERNAL_STORAGE is not set. Leaving EXTERNAL_STORAGE"

" unchanged.\n");

}

/* don't listen on a port (default 5037) if running in secure mode */

/* don't run as root if we are running in secure mode */

if (should_drop_privileges()) {

struct __user_cap_header_struct header;

struct __user_cap_data_struct cap;

if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) != 0) {

exit(1);

}

/* add extra groups:

** AID_ADB to access the USB driver

** AID_LOG to read system logs (adb logcat)

** AID_INPUT to diagnose input issues (getevent)

** AID_INET to diagnose network issues (netcfg, ping)

** AID_GRAPHICS to access the frame buffer

** AID_NET_BT and AID_NET_BT_ADMIN to diagnose bluetooth (hcidump)

** AID_SDCARD_R to allow reading from the SD card

** AID_SDCARD_RW to allow writing to the SD card

** AID_MOUNT to allow unmounting the SD card before rebooting

** AID_NET_BW_STATS to read out qtaguid statistics

*/

gid_t groups[] = { AID_ADB, AID_LOG, AID_INPUT, AID_INET, AID_GRAPHICS,

AID_NET_BT, AID_NET_BT_ADMIN, AID_SDCARD_R, AID_SDCARD_RW,

AID_MOUNT, AID_NET_BW_STATS };

if (setgroups(sizeof(groups)/sizeof(groups[0]), groups) != 0) {

exit(1);

}

/* then switch user and group to "shell" */

if (setgid(AID_SHELL) != 0) {

exit(1);

}

if (setuid(AID_SHELL) != 0) {

exit(1);

}

/* set CAP_SYS_BOOT capability, so "adb reboot" will succeed */

header.version = _LINUX_CAPABILITY_VERSION;

header.pid = 0;

cap.effective = cap.permitted = (1 << CAP_SYS_BOOT);

cap.inheritable = 0;

capset(&header, &cap);

D("Local port disabled\n");

} else {

char local_name[30];

build_local_name(local_name, sizeof(local_name), server_port);

if(install_listener(local_name, "*smartsocket*", NULL)) {

exit(1);

}

}

int usb = 0;

if (access(USB_ADB_PATH, F_OK) == 0 || access(USB_FFS_ADB_EP0, F_OK) == 0) {

// listen on USB

usb_init();

usb = 1;

}

// If one of these properties is set, also listen on that port

// If one of the properties isn't set and we couldn't listen on usb,

// listen on the default port.

property_get("service.adb.tcp.port", value, "");

if (!value[0]) {

property_get("persist.adb.tcp.port", value, "");

}

if (sscanf(value, "%d", &port) == 1 && port > 0) {

printf("using port=%d\n", port);

// listen on TCP port specified by service.adb.tcp.port property

local_init(port);

} else if (!usb) {

// listen on default port

local_init(DEFAULT_ADB_LOCAL_TRANSPORT_PORT);

}

D("adb_main(): pre init_jdwp()\n");

init_jdwp();

D("adb_main(): post init_jdwp()\n");

#endif

if (is_daemon)

{

// inform our parent that we are up and running.

#ifdef HAVE_WIN32_PROC

DWORD count;

WriteFile( GetStdHandle( STD_OUTPUT_HANDLE ), "OK\n", 3, &count, NULL );

#elif defined(HAVE_FORKEXEC)

fprintf(stderr, "OK\n");

#endif

start_logging();

}

D("Event loop starting\n");

fdevent_loop();

usb_cleanup();

return 0;

}

(1) init_transport_registration()初始化fevent transport_registration_fde；

(2) 判断系统属性ro.adb.secure，目标板没有设置这个宏；

(3) 没有定义环境变量adb_external_storage；

(4) should_drop_privileges()根据android编译环境should_drop_privileges返回不同的值，如果它的值是userdebug或eng，宏ALLOW_ADBD_ROOT的值被定义为1，执行install_listener()，否则不会定义，这种情况下，由于adbd运行在root下，为保证它的安全性，它需要降级运行；

(5) 判断是否存在设备文件USB_ADB_PATH或USB_FFS_ADB_EP0，存在则执行usb_init()；

(6) 读取属性service.adb.tcp.port或persist.adb.tcp.port（目标板均未定义），执行local_init()，它内部会创建adb thread；

(7) 执行init_jdwp()，jdwp是Java调试体系中的一种，具体可百度；

(8) 调用fdevent_loop()监听fdevent并处理；

(9) 程序结束。

再来看adb程序的执行：

在main()中调用return adb_commandline(argc - 1, argv + 1)：

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int adb_commandline(int argc, char **argv)

{

char buf[4096];

int no_daemon = 0;

int is_daemon = 0;

int is_server = 0;

int persist = 0;

int r;

int quote;

transport_type ttype = kTransportAny;

char* serial = NULL;

char* server_port_str = NULL;

/* If defined, this should be an absolute path to

* the directory containing all of the various system images

* for a particular product. If not defined, and the adb

* command requires this information, then the user must

* specify the path using "-p".

*/

gProductOutPath = getenv("ANDROID_PRODUCT_OUT");

if (gProductOutPath == NULL || gProductOutPath[0] == '\0') {

gProductOutPath = NULL;

}

// TODO: also try TARGET_PRODUCT/TARGET_DEVICE as a hint

serial = getenv("ANDROID_SERIAL");

/* Validate and assign the server port */

server_port_str = getenv("ANDROID_ADB_SERVER_PORT");

int server_port = DEFAULT_ADB_PORT;

if (server_port_str && strlen(server_port_str) > 0) {

server_port = (int) strtol(server_port_str, NULL, 0);

if (server_port <= 0) {

fprintf(stderr,

"adb: Env var ANDROID_ADB_SERVER_PORT must be a positive number. Got \"%s\"\n",

server_port_str);

return usage();

}

}

/* modifiers and flags */

while(argc > 0) {

if(!strcmp(argv[0],"server")) {

is_server = 1;

} else if(!strcmp(argv[0],"nodaemon")) {

no_daemon = 1;

} else if (!strcmp(argv[0], "fork-server")) {

/* this is a special flag used only when the ADB client launches the ADB Server */

is_daemon = 1;

} else if(!strcmp(argv[0],"persist")) {

persist = 1;

} else if(!strncmp(argv[0], "-p", 2)) {

const char *product = NULL;

if (argv[0][2] == '\0') {

if (argc < 2) return usage();

product = argv[1];

argc--;

argv++;

} else {

product = argv[0] + 2;

}

gProductOutPath = find_product_out_path(product);

if (gProductOutPath == NULL) {

fprintf(stderr, "adb: could not resolve \"-p %s\"\n",

product);

return usage();

}

} else if (argv[0][0]=='-' && argv[0][1]=='s') {

if (isdigit(argv[0][2])) {

serial = argv[0] + 2;

} else {

if(argc < 2 || argv[0][2] != '\0') return usage();

serial = argv[1];

argc--;

argv++;

}

} else if (!strcmp(argv[0],"-d")) {

ttype = kTransportUsb;

} else if (!strcmp(argv[0],"-e")) {

ttype = kTransportLocal;

} else {

/* out of recognized modifiers and flags */

break;

}

argc--;

argv++;

}

adb_set_transport(ttype, serial);

adb_set_tcp_specifics(server_port);

if (is_server) {

if (no_daemon || is_daemon) {

r = adb_main(is_daemon, server_port);

} else {

r = launch_server(server_port);

}

if(r) {

fprintf(stderr,"* could not start server *\n");

}

return r;

}

top:

if(argc == 0) {

return usage();

}

/* adb_connect() commands */

if(!strcmp(argv[0], "devices")) {

char *tmp;

char *listopt;

if (argc < 2)

listopt = "";

else if (argc == 2 && !strcmp(argv[1], "-l"))

listopt = argv[1];

else {

fprintf(stderr, "Usage: adb devices [-l]\n");

return 1;

}

snprintf(buf, sizeof buf, "host:%s%s", argv[0], listopt);

tmp = adb_query(buf);

if(tmp) {

printf("List of devices attached \n");

printf("%s\n", tmp);

return 0;

} else {

return 1;

}

}

if(!strcmp(argv[0], "connect")) {

char *tmp;

if (argc != 2) {

fprintf(stderr, "Usage: adb connect <host>[:<port>]\n");

return 1;

}

snprintf(buf, sizeof buf, "host:connect:%s", argv[1]);

tmp = adb_query(buf);

if(tmp) {

printf("%s\n", tmp);

return 0;

} else {

return 1;

}

}

if(!strcmp(argv[0], "disconnect")) {

char *tmp;

if (argc > 2) {

fprintf(stderr, "Usage: adb disconnect [<host>[:<port>]]\n");

return 1;

}

if (argc == 2) {

snprintf(buf, sizeof buf, "host:disconnect:%s", argv[1]);

} else {

snprintf(buf, sizeof buf, "host:disconnect:");

}

tmp = adb_query(buf);

if(tmp) {

printf("%s\n", tmp);

return 0;

} else {

return 1;

}

}

if (!strcmp(argv[0], "emu")) {

return adb_send_emulator_command(argc, argv);

}

if(!strcmp(argv[0], "shell") || !strcmp(argv[0], "hell")) {

int r;

int fd;

char h = (argv[0][0] == 'h');

if (h) {

printf("\x1b[41;33m");

fflush(stdout);

}

if(argc < 2) {

D("starting interactive shell\n");

r = interactive_shell();

if (h) {

printf("\x1b[0m");

fflush(stdout);

}

return r;

}

snprintf(buf, sizeof buf, "shell:%s", argv[1]);

argc -= 2;

argv += 2;

while(argc-- > 0) {

strcat(buf, " ");

/* quote empty strings and strings with spaces */

quote = (**argv == 0 || strchr(*argv, ' '));

if (quote)

strcat(buf, "\"");

strcat(buf, *argv++);

if (quote)

strcat(buf, "\"");

}

for(;;) {

D("interactive shell loop. buff=%s\n", buf);

fd = adb_connect(buf);

if(fd >= 0) {

D("about to read_and_dump(fd=%d)\n", fd);

read_and_dump(fd);

D("read_and_dump() done.\n");

adb_close(fd);

r = 0;

} else {

fprintf(stderr,"error: %s\n", adb_error());

r = -1;

}

if(persist) {

fprintf(stderr,"\n- waiting for device -\n");

adb_sleep_ms(1000);

do_cmd(ttype, serial, "wait-for-device", 0);

} else {

if (h) {

printf("\x1b[0m");

fflush(stdout);

}

D("interactive shell loop. return r=%d\n", r);

return r;

}

}

}

if(!strcmp(argv[0], "kill-server")) {

int fd;

fd = _adb_connect("host:kill");

if(fd == -1) {

fprintf(stderr,"* server not running *\n");

return 1;

}

return 0;

}

if(!strcmp(argv[0], "sideload")) {

if(argc != 2) return usage();

if(adb_download("sideload", argv[1], 1)) {

return 1;

} else {

return 0;

}

}

if(!strcmp(argv[0], "remount") || !strcmp(argv[0], "reboot")

|| !strcmp(argv[0], "reboot-bootloader")

|| !strcmp(argv[0], "tcpip") || !strcmp(argv[0], "usb")

|| !strcmp(argv[0], "root")) {

char command[100];

if (!strcmp(argv[0], "reboot-bootloader"))

snprintf(command, sizeof(command), "reboot:bootloader");

else if (argc > 1)

snprintf(command, sizeof(command), "%s:%s", argv[0], argv[1]);

else

snprintf(command, sizeof(command), "%s:", argv[0]);

int fd = adb_connect(command);

if(fd >= 0) {

read_and_dump(fd);

adb_close(fd);

return 0;

}

fprintf(stderr,"error: %s\n", adb_error());

return 1;

}

if(!strcmp(argv[0], "bugreport")) {

if (argc != 1) return usage();

do_cmd(ttype, serial, "shell", "bugreport", 0);

return 0;

}

/* adb_command() wrapper commands */

if(!strncmp(argv[0], "wait-for-", strlen("wait-for-"))) {

char* service = argv[0];

if (!strncmp(service, "wait-for-device", strlen("wait-for-device"))) {

if (ttype == kTransportUsb) {

service = "wait-for-usb";

} else if (ttype == kTransportLocal) {

service = "wait-for-local";

} else {

service = "wait-for-any";

}

}

format_host_command(buf, sizeof buf, service, ttype, serial);

if (adb_command(buf)) {

D("failure: %s *\n",adb_error());

fprintf(stderr,"error: %s\n", adb_error());

return 1;

}

/* Allow a command to be run after wait-for-device,

* e.g. 'adb wait-for-device shell'.

*/

if(argc > 1) {

argc--;

argv++;

goto top;

}

return 0;

}

if(!strcmp(argv[0], "forward")) {

if(argc != 3) return usage();

if (serial) {

snprintf(buf, sizeof buf, "host-serial:%s:forward:%s;%s",serial, argv[1], argv[2]);

} else if (ttype == kTransportUsb) {

snprintf(buf, sizeof buf, "host-usb:forward:%s;%s", argv[1], argv[2]);

} else if (ttype == kTransportLocal) {

snprintf(buf, sizeof buf, "host-local:forward:%s;%s", argv[1], argv[2]);

} else {

snprintf(buf, sizeof buf, "host:forward:%s;%s", argv[1], argv[2]);

}

if(adb_command(buf)) {

fprintf(stderr,"error: %s\n", adb_error());

return 1;

}

return 0;

}

/* do_sync_*() commands */

if(!strcmp(argv[0], "ls")) {

if(argc != 2) return usage();

return do_sync_ls(argv[1]);

}

if(!strcmp(argv[0], "push")) {

if(argc != 3) return usage();

return do_sync_push(argv[1], argv[2], 0 /* no verify APK */);

}

if(!strcmp(argv[0], "pull")) {

if (argc == 2) {

return do_sync_pull(argv[1], ".");

} else if (argc == 3) {

return do_sync_pull(argv[1], argv[2]);

} else {

return usage();

}

}

if(!strcmp(argv[0], "install")) {

if (argc < 2) return usage();

return install_app(ttype, serial, argc, argv);

}

if(!strcmp(argv[0], "uninstall")) {

if (argc < 2) return usage();

return uninstall_app(ttype, serial, argc, argv);

}

if(!strcmp(argv[0], "sync")) {

char *srcarg, *android_srcpath, *data_srcpath;

int listonly = 0;

int ret;

if(argc < 2) {

/* No local path was specified. */

srcarg = NULL;

} else if (argc >= 2 && strcmp(argv[1], "-l") == 0) {

listonly = 1;

if (argc == 3) {

srcarg = argv[2];

} else {

srcarg = NULL;

}

} else if(argc == 2) {

/* A local path or "android"/"data" arg was specified. */

srcarg = argv[1];

} else {

return usage();

}

ret = find_sync_dirs(srcarg, &android_srcpath, &data_srcpath);

if(ret != 0) return usage();

if(android_srcpath != NULL)

ret = do_sync_sync(android_srcpath, "/system", listonly);

if(ret == 0 && data_srcpath != NULL)

ret = do_sync_sync(data_srcpath, "/data", listonly);

free(android_srcpath);

free(data_srcpath);

return ret;

}

/* passthrough commands */

if(!strcmp(argv[0],"get-state") ||

!strcmp(argv[0],"get-serialno") ||

!strcmp(argv[0],"get-devpath"))

{

char *tmp;

format_host_command(buf, sizeof buf, argv[0], ttype, serial);

tmp = adb_query(buf);

if(tmp) {

printf("%s\n", tmp);

return 0;

} else {

return 1;

}

}

/* other commands */

if(!strcmp(argv[0],"status-window")) {

status_window(ttype, serial);

return 0;

}

if(!strcmp(argv[0],"logcat") || !strcmp(argv[0],"lolcat") || !strcmp(argv[0],"longcat")) {

return logcat(ttype, serial, argc, argv);

}

if(!strcmp(argv[0],"ppp")) {

return ppp(argc, argv);

}

if (!strcmp(argv[0], "start-server")) {

return adb_connect("host:start-server");

}

if (!strcmp(argv[0], "backup")) {

return backup(argc, argv);

}

if (!strcmp(argv[0], "restore")) {

return restore(argc, argv);

}

if (!strcmp(argv[0], "jdwp")) {

int fd = adb_connect("jdwp");

if (fd >= 0) {

read_and_dump(fd);

adb_close(fd);

return 0;

} else {

fprintf(stderr, "error: %s\n", adb_error());

return -1;

}

}

/* "adb /?" is a common idiom under Windows */

if(!strcmp(argv[0], "help") || !strcmp(argv[0], "/?")) {

help();

return 0;

}

if(!strcmp(argv[0], "version")) {

version(stdout);

return 0;

}

usage();

return 1;

}

它的代码有点长，但可以很容易看明白它根据命令的参数执行不同的功能。adb程序可能以服务的方式或命令行客户端的方式运行。

－－－－－－－－－－

以上就是main()函数的执行过程，后续将分析其中的细节内容。