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when reading large files, double buffer size at each iteration

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Roberto Ierusalimschy 2010-11-08 15:27:22 -02:00
parent f722ba6890
commit 700b003fb5
1 changed files with 10 additions and 4 deletions
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14
liolib.c
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@ -1,5 +1,5 @@
/* /*
** $Id: liolib.c,v 2.91 2010/07/28 15:51:59 roberto Exp roberto $ ** $Id: liolib.c,v 2.92 2010/10/25 19:01:37 roberto Exp roberto $
** Standard I/O (and system) library ** Standard I/O (and system) library
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -19,6 +19,9 @@
#include "lualib.h" #include "lualib.h"
#define MAX_SIZE_T (~(size_t)0)
/* /*
** lua_popen spawns a new process connected to the current one through ** lua_popen spawns a new process connected to the current one through
** the file streams. ** the file streams.
@ -377,10 +380,13 @@ static int read_chars (lua_State *L, FILE *f, size_t n) {
size_t nr; /* number of chars actually read in each cycle */ size_t nr; /* number of chars actually read in each cycle */
luaL_Buffer b; luaL_Buffer b;
luaL_buffinit(L, &b); luaL_buffinit(L, &b);
rlen = LUAL_BUFFERSIZE; /* try to read that much each time */ rlen = LUAL_BUFFERSIZE / 2; /* to be doubled at 1st iteration */
do { do {
char *p = luaL_prepbuffer(&b); char *p;
if (rlen < (MAX_SIZE_T / 2))
rlen *= 2; /* double buffer size at each iteration */
if (rlen > tbr) rlen = tbr; /* cannot read more than asked */ if (rlen > tbr) rlen = tbr; /* cannot read more than asked */
p = luaL_prepbuffsize(&b, rlen);
nr = fread(p, sizeof(char), rlen, f); nr = fread(p, sizeof(char), rlen, f);
luaL_addsize(&b, nr); luaL_addsize(&b, nr);
tbr -= nr; /* still have to read 'tbr' chars */ tbr -= nr; /* still have to read 'tbr' chars */
@ -421,7 +427,7 @@ static int g_read (lua_State *L, FILE *f, int first) {
success = read_line(L, f, 0); success = read_line(L, f, 0);
break; break;
case 'a': /* file */ case 'a': /* file */
read_chars(L, f, ~((size_t)0)); /* read MAX_SIZE_T chars */ read_chars(L, f, MAX_SIZE_T); /* read MAX_SIZE_T chars */
success = 1; /* always success */ success = 1; /* always success */
break; break;
default: default: