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      1 /*	$NetBSD: lzio.c,v 1.9 2023/04/16 20:46:17 nikita Exp $	*/
      2 
      3 /*
      4 ** Id: lzio.c
      5 ** Buffered streams
      6 ** See Copyright Notice in lua.h
      7 */
      8 
      9 #define lzio_c
     10 #define LUA_CORE
     11 
     12 #include "lprefix.h"
     13 
     14 
     15 #ifndef _KERNEL
     16 #include <string.h>
     17 #endif /* _KERNEL */
     18 
     19 #include "lua.h"
     20 
     21 #include "llimits.h"
     22 #include "lmem.h"
     23 #include "lstate.h"
     24 #include "lzio.h"
     25 
     26 
     27 int luaZ_fill (ZIO *z) {
     28   size_t size;
     29   lua_State *L = z->L;
     30   const char *buff;
     31   lua_unlock(L);
     32   buff = z->reader(L, z->data, &size);
     33   lua_lock(L);
     34   if (buff == NULL || size == 0)
     35     return EOZ;
     36   z->n = size - 1;  /* discount char being returned */
     37   z->p = buff;
     38   return cast_uchar(*(z->p++));
     39 }
     40 
     41 
     42 void luaZ_init (lua_State *L, ZIO *z, lua_Reader reader, void *data) {
     43   z->L = L;
     44   z->reader = reader;
     45   z->data = data;
     46   z->n = 0;
     47   z->p = NULL;
     48 }
     49 
     50 
     51 /* --------------------------------------------------------------- read --- */
     52 size_t luaZ_read (ZIO *z, void *b, size_t n) {
     53   while (n) {
     54     size_t m;
     55     if (z->n == 0) {  /* no bytes in buffer? */
     56       if (luaZ_fill(z) == EOZ)  /* try to read more */
     57         return n;  /* no more input; return number of missing bytes */
     58       else {
     59         z->n++;  /* luaZ_fill consumed first byte; put it back */
     60         z->p--;
     61       }
     62     }
     63     m = (n <= z->n) ? n : z->n;  /* min. between n and z->n */
     64     memcpy(b, z->p, m);
     65     z->n -= m;
     66     z->p += m;
     67     b = (char *)b + m;
     68     n -= m;
     69   }
     70   return 0;
     71 }
     72 
     73