Syslinux - Sep 2012 - [PATCH 1/1] lua: Enabling io.read() in Lua.c32 with some restrictions

From: Hung-chi Lihn <hlihn at google.com>

The current Lua.c32 does not enable io.read() due to some missing library
functions. However, this strongly limits the Lua script from getting user
inputs and reading files (even in pxelinux via TFTP).

This patch enables io.read() in Lua.c32 with some restrictions:
  1. the io.read("*line") is fully supported.
  2. the io.read("*number") is not supported due to the missing
buffering
in underlying file I/Os. However, the user can read a line using io.read()
and convert the string to numbers using the built in pattern matching and
number conversion features.
  3. io.read(bytes) is supported. However, io.read(0) will not be a valid
test for EOF due to the missing I/O buffering. io.read() will return nil if
EOF is encountered. This offers an alternative way to handle EOF.

Signed-off-by: Hung-chi Lihn <hlihn at google.com>
---
 com32/lua/src/liolib.c |   40 +++++++++++++++++++++++++++++-----------
 1 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/com32/lua/src/liolib.c b/com32/lua/src/liolib.c
index 3f27395..cf9dca2 100644
--- a/com32/lua/src/liolib.c
+++ b/com32/lua/src/liolib.c
@@ -18,12 +18,18 @@
 #include "lauxlib.h"
 #include "lualib.h"

-
+#ifdef SYSLINUX
+  #define NO_TMP_FILE    1
+  #define NO_READ_NUMBER 1
+  #define NO_TEST_EOF    1
+  #define NO_CLEAR_ERR   1
+  #define NO_F_SEEK      1
+  #define NO_F_SETVBUF   1
+#endif

 #define IO_INPUT       1
 #define IO_OUTPUT      2

-
 static const char *const fnames[] = {"input", "output"};


@@ -180,7 +186,7 @@ static int io_popen (lua_State *L) {
 }


-#ifndef SYSLINUX
+#ifndef NO_TMP_FILE
 static int io_tmpfile (lua_State *L) {
   FILE **pf = newfile(L);
   *pf = tmpfile();
@@ -271,7 +277,7 @@ static int io_lines (lua_State *L) {
 ** ====================================================== */

-#ifndef SYSLINUX
+#ifndef NO_READ_NUMBER /* No fscanf() and thus no read_number() */
 static int read_number (lua_State *L, FILE *f) {
   lua_Number d;
   if (fscanf(f, LUA_NUMBER_SCAN, &d) == 1) {
@@ -283,8 +289,9 @@ static int read_number (lua_State *L, FILE *f) {
     return 0;  /* read fails */
   }
 }
+#endif

-
+#ifndef NO_TEST_EOF  /* no buffering -> no ungetc() -> no EOF test */
 static int test_eof (lua_State *L, FILE *f) {
   int c = getc(f);
   ungetc(c, f);
@@ -315,7 +322,6 @@ static int read_line (lua_State *L, FILE *f) {
   }
 }

-#ifndef SYSLINUX                       /* Not used */
 static int read_chars (lua_State *L, FILE *f, size_t n) {
   size_t rlen;  /* how much to read */
   size_t nr;  /* number of chars actually read */
@@ -337,7 +343,9 @@ static int g_read (lua_State *L, FILE *f, int first) {
   int nargs = lua_gettop(L) - 1;
   int success;
   int n;
+#ifndef NO_CLEAR_ERR
   clearerr(f);
+#endif
   if (nargs == 0) {  /* no arguments? */
     success = read_line(L, f);
     n = first+1;  /* to return 1 result */
@@ -348,14 +356,22 @@ static int g_read (lua_State *L, FILE *f, int first) {
     for (n = first; nargs-- && success; n++) {
       if (lua_type(L, n) == LUA_TNUMBER) {
         size_t l = (size_t)lua_tointeger(L, n);
+#ifndef NO_TEST_EOF
         success = (l == 0) ? test_eof(L, f) : read_chars(L, f, l);
+#else  /* we don't have test_eof defined */
+        success = (l == 0) ? 1 : read_chars(L, f, l);
+#endif
       }
       else {
         const char *p = lua_tostring(L, n);
         luaL_argcheck(L, p && p[0] == '*', n, "invalid
option");
         switch (p[1]) {
           case 'n':  /* number */
+#ifndef NO_READ_NUMBER
             success = read_number(L, f);
+#else
+            return luaL_argerror(L, n, "\"*number\" not
supported");
+#endif
             break;
           case 'l':  /* line */
             success = read_line(L, f);
@@ -388,7 +404,6 @@ static int io_read (lua_State *L) {
 static int f_read (lua_State *L) {
   return g_read(L, tofile(L), 2);
 }
-#endif


 static int io_readline (lua_State *L) {
@@ -441,7 +456,7 @@ static int f_write (lua_State *L) {
   return g_write(L, tofile(L), 2);
 }

-#ifndef SYSLINUX
+#ifndef NO_F_SEEK
 static int f_seek (lua_State *L) {
   static const int mode[] = {SEEK_SET, SEEK_CUR, SEEK_END};
   static const char *const modenames[] = {"set", "cur",
"end", NULL};
@@ -456,8 +471,9 @@ static int f_seek (lua_State *L) {
     return 1;
   }
 }
+#endif

-
+#ifndef NO_F_SETVBUF
 static int f_setvbuf (lua_State *L) {
   static const int mode[] = {_IONBF, _IOFBF, _IOLBF};
   static const char *const modenames[] = {"no", "full",
"line", NULL};
@@ -488,8 +504,8 @@ static const luaL_Reg iolib[] = {
   {"open", io_open},
   {"output", io_output},
   {"popen", io_popen},
-#ifndef SYSLINUX
   {"read", io_read},
+#ifndef NO_TMP_FILE
   {"tmpfile", io_tmpfile},
 #endif
   {"type", io_type},
@@ -502,9 +518,11 @@ static const luaL_Reg flib[] = {
   {"close", io_close},
   {"flush", f_flush},
   {"lines", f_lines},
-#ifndef SYSLINUX
   {"read", f_read},
+#ifndef NO_F_SEEK
   {"seek", f_seek},
+#endif
+#ifndef NO_F_SETVBUF
   {"setvbuf", f_setvbuf},
 #endif
   {"write", f_write},

From: Hung-chi Lihn <hlihn at google.com>

The current Lua.c32 does not enable io.read() due to some missing library
functions. However, this strongly limits the Lua script from getting user inputs
and reading files (even in pxelinux via TFTP).
 
This patch enables io.read() in Lua.c32 with some restrictions:
  1. the io.read("*line") is fully supported.
  2. the io.read("*number") is not supported due to the missing
buffering in underlying file I/Os. However, the user can read a line using
io.read() and convert the string to numbers using the built in pattern matching
and number conversion features.
  3. io.read(bytes) is supported. However, io.read(0) will not be a valid test
for EOF due to the missing I/O buffering. io.read() will return nil if EOF is
encountered. This offers an alternative way to handle EOF.

Signed-off-by: Hung-chi Lihn <hlihn at google.com>
---
Resubmit to fix the broken submission due to automatic word-wrap.

 com32/lua/src/liolib.c |   40 +++++++++++++++++++++++++++++-----------
 1 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/com32/lua/src/liolib.c b/com32/lua/src/liolib.c
index 3f27395..cf9dca2 100644
--- a/com32/lua/src/liolib.c
+++ b/com32/lua/src/liolib.c
@@ -18,12 +18,18 @@
 #include "lauxlib.h"
 #include "lualib.h"
 
-
+#ifdef SYSLINUX
+  #define NO_TMP_FILE    1
+  #define NO_READ_NUMBER 1
+  #define NO_TEST_EOF    1
+  #define NO_CLEAR_ERR   1
+  #define NO_F_SEEK      1
+  #define NO_F_SETVBUF   1
+#endif
 
 #define IO_INPUT	1
 #define IO_OUTPUT	2
 
-
 static const char *const fnames[] = {"input", "output"};
 
 
@@ -180,7 +186,7 @@ static int io_popen (lua_State *L) {
 }
 
 
-#ifndef SYSLINUX
+#ifndef NO_TMP_FILE
 static int io_tmpfile (lua_State *L) {
   FILE **pf = newfile(L);
   *pf = tmpfile();
@@ -271,7 +277,7 @@ static int io_lines (lua_State *L) {
 ** ====================================================== */
 
-#ifndef SYSLINUX
+#ifndef NO_READ_NUMBER /* No fscanf() and thus no read_number() */
 static int read_number (lua_State *L, FILE *f) {
   lua_Number d;
   if (fscanf(f, LUA_NUMBER_SCAN, &d) == 1) {
@@ -283,8 +289,9 @@ static int read_number (lua_State *L, FILE *f) {
     return 0;  /* read fails */
   }
 }
+#endif
 
-
+#ifndef NO_TEST_EOF  /* no buffering -> no ungetc() -> no EOF test */
 static int test_eof (lua_State *L, FILE *f) {
   int c = getc(f);
   ungetc(c, f);
@@ -315,7 +322,6 @@ static int read_line (lua_State *L, FILE *f) {
   }
 }
 
-#ifndef SYSLINUX			/* Not used */
 static int read_chars (lua_State *L, FILE *f, size_t n) {
   size_t rlen;  /* how much to read */
   size_t nr;  /* number of chars actually read */
@@ -337,7 +343,9 @@ static int g_read (lua_State *L, FILE *f, int first) {
   int nargs = lua_gettop(L) - 1;
   int success;
   int n;
+#ifndef NO_CLEAR_ERR
   clearerr(f);
+#endif
   if (nargs == 0) {  /* no arguments? */
     success = read_line(L, f);
     n = first+1;  /* to return 1 result */
@@ -348,14 +356,22 @@ static int g_read (lua_State *L, FILE *f, int first) {
     for (n = first; nargs-- && success; n++) {
       if (lua_type(L, n) == LUA_TNUMBER) {
         size_t l = (size_t)lua_tointeger(L, n);
+#ifndef NO_TEST_EOF
         success = (l == 0) ? test_eof(L, f) : read_chars(L, f, l);
+#else  /* we don't have test_eof defined */
+        success = (l == 0) ? 1 : read_chars(L, f, l);
+#endif
       }
       else {
         const char *p = lua_tostring(L, n);
         luaL_argcheck(L, p && p[0] == '*', n, "invalid
option");
         switch (p[1]) {
           case 'n':  /* number */
+#ifndef NO_READ_NUMBER
             success = read_number(L, f);
+#else
+            return luaL_argerror(L, n, "\"*number\" not
supported");
+#endif
             break;
           case 'l':  /* line */
             success = read_line(L, f);
@@ -388,7 +404,6 @@ static int io_read (lua_State *L) {
 static int f_read (lua_State *L) {
   return g_read(L, tofile(L), 2);
 }
-#endif
 
 
 static int io_readline (lua_State *L) {
@@ -441,7 +456,7 @@ static int f_write (lua_State *L) {
   return g_write(L, tofile(L), 2);
 }
 
-#ifndef SYSLINUX
+#ifndef NO_F_SEEK
 static int f_seek (lua_State *L) {
   static const int mode[] = {SEEK_SET, SEEK_CUR, SEEK_END};
   static const char *const modenames[] = {"set", "cur",
"end", NULL};
@@ -456,8 +471,9 @@ static int f_seek (lua_State *L) {
     return 1;
   }
 }
+#endif
 
-
+#ifndef NO_F_SETVBUF
 static int f_setvbuf (lua_State *L) {
   static const int mode[] = {_IONBF, _IOFBF, _IOLBF};
   static const char *const modenames[] = {"no", "full",
"line", NULL};
@@ -488,8 +504,8 @@ static const luaL_Reg iolib[] = {
   {"open", io_open},
   {"output", io_output},
   {"popen", io_popen},
-#ifndef SYSLINUX
   {"read", io_read},
+#ifndef NO_TMP_FILE
   {"tmpfile", io_tmpfile},
 #endif
   {"type", io_type},
@@ -502,9 +518,11 @@ static const luaL_Reg flib[] = {
   {"close", io_close},
   {"flush", f_flush},
   {"lines", f_lines},
-#ifndef SYSLINUX
   {"read", f_read},
+#ifndef NO_F_SEEK
   {"seek", f_seek},
+#endif
+#ifndef NO_F_SETVBUF
   {"setvbuf", f_setvbuf},
 #endif
   {"write", f_write},