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qemu参数解析：struct QemuOpt {
   	char *name;	char *str;	const QemuOptDesc *desc;	union {
   		bool boolean;		uint64_t uint;	} value;	QemuOpts *opts;	QTAILQ_ENTRY(QemuOpt) next;};struct QemuOpts {
   	char *id;	QemuOptList *list;	Location loc;	QTAILQ_HEAD(, QemuOpt) head;	QTAILQ_ENTRY(QemuOpts) next;};struct QemuOptList {
   	const char *name;	const char *implied_opt_name;	bool merge_lists;	QTAILQ_HEAD(, QemuOpts) head;	QemuOptDesc desc[];};根据命令行格式:qemu-system-xxx [-options] [arg1, arg2, ...]以及上边的三个结构体，可知qemu对于参数的解析模式为：QemuOptList结构体将命令行参数中的optioins链接成链表形式，每个节点元素的类型为QemuOpts。每个option中可能会存在多个参数，QemuOpts将这些参数链接成链表形式，每个节点元素的类型为QemuOpt。因此，整体结构如下：QemuOptList(command line)	|	QemuOpts1------------------>QemuOpts2--->...(options)		|							|		arg1--->arg2--->...			arg1--->arg2--->...(arguments)关于QemuOptLists链表，主要分为两类，一类是vm_config；另一类是drive_config。因此，qemu提供了两种不同的接口：void qemu_add_opts(QemuOptsLists *list){
   	int entries, i;		entries = ARRAY_SIZE(vm_config_groups);	entries--;	for (i = 0; i < entries; i++) {
   		if (i = 0; i < entries; i++) {
   			vm_config_groups[i] = list;			return;		}	}	fprinitf(stderr, "ran out of space in vm_config_groups");	abort();}void qemu_add_drive_opts(QemuOptsLists *list){
   	int entries, i;	entries =  ARRAY_SIZE(drive_config_groups);	entries--;	for (i = 0; i < entries; i++) {
   		if (drive_config_groups[i] == NULL) {
   			drive_config_groups[i] = list;		}	}	fprintf(stderr, "ran out of space in drive_config_groups");	abort();}{
   	optind = 1;	while (optind < argc) {
   		if (argv[optind][0] != '-') {
   		//如果首字符不为“-”，则表示该argv不是option字符			optind++;		} else {
   			const QEMUOption *popt;			popt = lookup_opt(argc, argv, &optarg, &optind);			//获取与option相对应的QEMUOption结构体			switch(popt->index) {
   			case QEMU_OPTION_nouserconfig:				userconfig = false;				break;			}		}	}	//判断命令行中的option是否需要用户配置	if (userconfig) {
   		if (qemu_read_default_config_file() < 0) {
   			exit(1);		}	}	//如果需要用户配置，则需要读取默认的配置文件	optind = 1;	for (;;) {
   		if (optind >= argc)			break;		if (argv[optind][0] != '-') {
   			loc_set_cmdline(argv, optind, 1)			drive_add(IF_DEFAULT, 0, argv[optind++], HD_OPTS);		} else {
   			const QEMUOption *popt;			popt = lookup_opt(argc, argv, &optarg, &optind);			if (!(popt->arch_mask &arch_type)) {
   				}			switch(popt->index) {
   			case QEMU_OPTION_cpu:				cpu_option = optarg;				break;			case QEMU_OPTION_kernel:				qemu_opt_set(qemu_find_opts("machine"), NULL, "kernel", optarg, &error_abort);				break;			...			}		}	}}static const QEMUOption *lookup_opt(int argc, char **argv, const char **poptarg, int *poptind){
   	const QEMUOption *popt;	int optind = *poptind;	char *r = argv[optind];	const char *optarg;	loc_set_cmdline(argv, optind, 1);	optind++;		if (r[1] == '-')		r++;	//如果option为“--x”，则将其处理为“-x”	popt = qemu_options;	//qemu_options变量是一个特殊的全局变量，其中存放qemu所有的options信息		for(;;) {
   		if (!popt->name) {
   			error_report("invalid option");			exit(1);		}		if (!strcmp(popt->name, r + 1))			break;		popt++;	}	//判断命令行中的options是否存在。如果存在，则将该option相关的QEMUOption结构体返回	if (popt->flags & HAS_ARG) {
   		if (optind >= argc) {
   			error_report("requires an argument");			exit(1);		}		optarg = argv[optind++];		loc_set_cmdline(argv, optind - 2, 2);	} else {
   		optarg = NULL;	}	//判断该option是否允许带有参数，如果允许，则读取该参数	*poptarg = optarg;	*poptind = optind;	return popt;}在代码中，变量qemu_options需要进一步解释。qemu_options变量原型为：static const QEMUOption qemu_options[] = {
   	{
    "h", 0, QEMU_OPTION_h, QEMU_ARCH_ALL },#define QEMU_OPTIONS_GENERATE_OPTIONS#include "qemu-options-wrapper.h"	{
    NULL },};qemu-optinons-wrapper.h {
   #include "qemu-options.def" }qemu-options.def {
   DEFHEADING(Standard options:)DEF("help", 0, QEMU_OPTION_h, "-h or -help display this help and exit\n", QEMU_ARCH_ALL)...}#elif define (QEMU_OPTIONS_GENERATE_OPTIONS)#define DEF(option, opt_arg, opt_enum, opt_help, arch_mask) { option, opt_arg, opt_enum, arch_mask },#define DEFHEADING(text)通过上边的代码可知，qemu所有的options变量存放在qemu_options全局数组当中。vm_config_groups数组存储不同类型的参数链表表头，因此结构为十字链表结构。drive_config_groups与其结构类似。如果解析的变量不是option，则调用drive_add接口来处理。QemuOpts *drive_add(BlockInterfaceType type, int index, const char *file, const char *optstr){
   	QemuOpts *opts;	opts = drive_def(optstr);	//根据optstr创建对应的QemuOpts结构体对象	if (!opts) {
   		return NULL;	}	if (type != IF_DEFAULT) {
   		qemu_opt_set(opts, "if", if_name[type], &error_abort);	}	if (index >= 0) {
   		qemu_opt_set_number(opts, "index", index, &error_abort);	}	if (file) 		qemu_opt_set(opts, "file", &error_abort);	return opts;}QemuOpts *drive_def(const char *optstr){
   	return qemu_opts_parse_noisily(qemu_find_opts("drive"), optstr, false);}QemuOptsList *qemu_find_opts(const char *group){
   	QemuOptList *ret;	Error *local_err = NULL;		ret = find_list(vm_config_groups, group, &local_err);	if (local_err) {
   		error_report_err(local_err);	}	return ret;	//返回所需的链表}static QemuOptsList *find_list(QemuOptsList **lists, const char *group, Error **errp){
   	int i;    for (i = 0; lists[i] != NULL; i++) {
           if (strcmp(lists[i]->name, group) == 0)		//从链表中查找名字与group相同的链表            break;    }    if (lists[i] == NULL) {
           error_setg(errp, "There is no option group '%s'", group);    }    return lists[i];	//返回QemuOptList链表对象}QemuOpts *qemu_opts_parse_noisily(QemuOptsList *list, const char *params,                                  bool permit_abbrev){
       Error *err = NULL;    QemuOpts *opts;    bool help_wanted = false;    opts = opts_parse(list, params, permit_abbrev, false, &help_wanted, &err);    if (err) {
           if (help_wanted) {
               qemu_opts_print_help(list, true);            error_free(err);        } else {
               error_report_err(err);        }    }    return opts;	//返回QemuOpts结构体对象}static QemuOpts *opts_parse(QemuOptsList *list, const char *params, bool permit_abbrev, bool defaults, bool *help_wanted, Error **errp){
       const char *firstname;    char *id = opts_parse_id(params);	//解析params参数，判断该参数中是否存在“id=xx或id xx”字符串信息	//这里的params参数是由qemu自定义的宏参    QemuOpts *opts;    assert(!permit_abbrev || list->implied_opt_name);    firstname = permit_abbrev ? list->implied_opt_name : NULL;    assert(!defaults || list->merge_lists);    opts = qemu_opts_create(list, id, !defaults, errp);	//创建QemuOpts结构体对象，并将QemuOpts与QemuOptList进行关联    g_free(id);    if (opts == NULL) {
           return NULL;    }    if (!opts_do_parse(opts, params, firstname, defaults, help_wanted,                       errp)) {
           qemu_opts_del(opts);        return NULL;    }    return opts;}bool qemu_opt_set(QemuOptList *list, const char *id, const char *name, const char *value, Error **errp){
   	QemuOpts *opts;	opts = qemu_opts_create(list, id, 1, errp);	if (!opts) {
   		return false;	}	return qemu_opt_set(opts, name, value, errp);}QemuOpts *qemu_opts_create(QemuOptList *list, const char *id, int fail_if_exists, Error **errp){
   //创建QemuOpt结构体对象，进行赋值，链表操作，并与QemuOptList进行关联	QemuOpts *opts = NULL;		if (id) {
   		...	} else if (list->merge_lists) {
   		...	}	opts = g_malloc0(sizeof(*opts));	opts->id = g_strdup(id);	opts->list = list;	loc_save(&opts->loc);	QTAILQ_INIT(&opts->head);	QTAILQ_INSERT_TAIL(&list->head, opts, next);	return opts;}bool qemu_opt_set(QemuOpts *opts, const char *name, const char *value, Error **errp){
   	QemuOpt *opt = opt_create(opts, name, g_strdup(value), false);	if (!opt_validate(opt, NULL, errp)) {
   		qemu_opt_del(opt);		return false;	}	return true;}static QemuOpt *opt_create(QemuOpts *opts, const char *name, char *value, bool prepend){
   //创建QemuOpt结构体对象，进行赋值，链表操作，并与QemuOpts进行关联	QemuOpt *opt = g_malloc0(sizeof(*opt));	opt->name = g_strdup(name);	opt->str = value;	opt->opts = opts;	if (prepend) {
   		QTAILQ_INSERT_HEAD(&opts->head, opt, next);	} else {
   		QTAILQ_INSERT_TAIL(&opts->head, opt, next);	}	return opt;}

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