lua源码阅读(5)-lua_State

在C语言中编写的脚本解释器运行lua是，首先是要创建lua_Stat结构体。lua_State中管理了一个数组，可以视为lua虚拟机的"寄存器"。在Lstat.h中

struct lua_State {  CommonHeader;  lu_byte status;  //线程栈的栈顶指针  StkId top;  /* first free slot in the stack */    StkId base;  /* base of current function */    global_State *l_G;  //当前运行的函数调用信息  CallInfo *ci;  /* call info for current function */  //函数调用前，记录上一个函数的pc位置  const Instruction *savedpc;  /* `savedpc' of current function */  //栈的实际最后一个位置（栈的长度是动态增长的）  StkId stack_last;  /* last free slot in the stack */  //栈的数组的指针  StkId stack;  /* stack base */  CallInfo *end_ci;  /* points after end of ci array*/  CallInfo *base_ci;  /* array of CallInfo's */  int stacksize;    int size_ci;  /* size of array `base_ci' */    unsigned short nCcalls;  /* number of nested C calls */  unsigned short baseCcalls;  /* nested C calls when resuming coroutine */  lu_byte hookmask;  lu_byte allowhook;  int basehookcount;  int hookcount;  lua_Hook hook;  TValue l_gt;  /* table of globals */  TValue env;  /* temporary place for environments */  GCObject *openupval;  /* list of open upvalues in this stack */  GCObject *gclist;  struct lua_longjmp *errorJmp;  /* current error recover point */  ptrdiff_t errfunc;  /* current error handling function (stack index) */};

typedef struct CallInfo {  StkId base;  /* base for this function */  StkId func;  /* function index in the stack */  StkIdtop;  /* top for this function */  const Instruction *savedpc;  int nresults;  /* expected number of results from this function */  int tailcalls;  /* number of tail calls lost under this entry */} CallInfo;

CallInfo描述了一个函数调用时使用寄存器的信息。因为许多函数调用都是共用同一个lua_State的，需要对位置进行记录。lua_State中，指针stack指向一个数组，就是所谓的寄存器。整个lua_State结构大概如下:

调用一个函数的时候，函数也是一个变量，存放在func位置，之后是参数，这些信息由一个调callinfo记录。在Lstate.h中，还有一个global_state的结构体

typedef struct global_State {//字符串hash表  stringtable strt;  /* hash table for strings *///内存分配函数  lua_Alloc frealloc;  /* function to reallocate memory */  void *ud;         /* auxiliary data to `frealloc' */    lu_byte currentwhite;  lu_byte gcstate;  /* state of garbage collector */  int sweepstrgc;  /* position of sweep in `strt' */  GCObject *rootgc;  /* list of all collectable objects */  GCObject **sweepgc;  /* position of sweep in `rootgc' */  GCObject *gray;  /* list of gray objects */  GCObject *grayagain;  /* list of objects to be traversed atomically */  GCObject *weak;  /* list of weak tables (to be cleared) */  GCObject *tmudata;  /* last element of list of userdata to be GC */  Mbuffer buff;  /* temporary buffer for string concatentation */  lu_mem GCthreshold;  lu_mem totalbytes;  /* number of bytes currently allocated */  lu_mem estimate;  /* an estimate of number of bytes actually in use */  lu_mem gcdept;  /* how much GC is `behind schedule' */  int gcpause;  /* size of pause between successive GCs */  int gcstepmul;  /* GC `granularity' */  lua_CFunction panic;  /* to be called in unprotected errors */  TValue l_registry;  struct lua_State *mainthread;  UpVal uvhead;  /* head of double-linked list of all open upvalues */  struct Table *mt[NUM_TAGS];  /* metatables for basic types */  TString *tmname[TM_N];  /* array with tag-method names */} global_State;

该结构体中有字符串hash表，内存分配函数，还有许多与gc有关的部分，暂不研究。每一个lua_State中都有一个指向blobal_State的指针。在创建lua_State的时候，也会创建global_State,在创建协程的时候，只会创建lua_State,所以，如果加入协程的话，lua_State的结构如下

lua_State提供了执行lua代码的环境，global_State管理内存。