# HG changeset patch
# User jbe
# Date 1428514629 -7200
# Node ID 11d03470ef199b6cfcdc963e93ac012a770a6bb8
# Parent  5e8eeb5b6c848f0cf3eb927db743bb620dd8048c
Refined buffer model for reading in I/O library

diff -r 5e8eeb5b6c84 -r 11d03470ef19 moonbridge_io.c
--- a/moonbridge_io.c	Wed Apr 08 18:38:14 2015 +0200
+++ b/moonbridge_io.c	Wed Apr 08 19:37:09 2015 +0200
@@ -35,7 +35,8 @@
   int nonblocking;
   int nopush;
   int readerr;
-  int readbufcnt;
+  int readbufin;
+  int readbufout;
   int writeerr;
   size_t writeleft;
 #if LUA_VERSION_NUM >= 503
@@ -123,7 +124,7 @@
   char terminator;
   luaL_Buffer luabuf;
   size_t luabufcnt = 0;
-  int endcnt;
+  int remaining;
   char *terminatorpos;
   ssize_t bytesread;
   handle = luaL_checkudata(L, 1, MOONBR_IO_HANDLE_MT_REGKEY);
@@ -140,66 +141,91 @@
     lua_pushliteral(L, "Previous read error");
     return 2;
   }
+  handle->readerr = 1;
   if (handle->fd < 0) goto moonbr_io_read_impl_eof;  /* fake EOF to simulate shutdown */
-  handle->readerr = 1;
   moonbr_io_handle_set_nonblocking(L, handle, nonblocking);
   if (!drain) luaL_buffinit(L, &luabuf);
   while (1) {
-    endcnt = -1;
-    if (maxread > 0 && handle->readbufcnt >= (size_t)maxread - luabufcnt) {
-      endcnt = maxread - luabufcnt;
+    remaining = -1;
+    if (
+      maxread > 0 &&
+      handle->readbufin - handle->readbufout >= (size_t)maxread - luabufcnt
+    ) {
+      remaining = maxread - luabufcnt;
     } else if (terminatorlen) {
-      terminatorpos = memchr(handle->readbuf, terminator, handle->readbufcnt);
-      if (terminatorpos) endcnt = 1 + (terminatorpos - handle->readbuf);
+      terminatorpos = memchr(
+        handle->readbuf + handle->readbufout,
+        terminator,
+        handle->readbufin - handle->readbufout
+      );
+      if (terminatorpos) remaining = 1 + (
+        terminatorpos - (handle->readbuf + handle->readbufout)
+      );
     }
-    if (endcnt >= 0) {
+    if (remaining >= 0) {
       if (!drain) {
-        luaL_addlstring(&luabuf, handle->readbuf, endcnt);
+        luaL_addlstring(
+          &luabuf,
+          handle->readbuf + handle->readbufout,
+          remaining
+        );
         luaL_pushresult(&luabuf);
       } else {
-        luabufcnt += handle->readbufcnt;
-        lua_pushinteger(L, luabufcnt);
+        luaL_pushresult(&luabuf);
+        lua_pop(L, 1);
+        lua_pushinteger(L, luabufcnt + remaining);
       }
-      handle->readbufcnt -= endcnt;
-      memmove(handle->readbuf, handle->readbuf + endcnt, handle->readbufcnt);
+      handle->readbufout += remaining;
+      if (handle->readbufout == handle->readbufin) {
+        handle->readbufin = 0;
+        handle->readbufout =0;
+      }
       handle->readerr = 0;
       return 1;
     }
-    if (!drain) luaL_addlstring(&luabuf, handle->readbuf, handle->readbufcnt);
-    luabufcnt += handle->readbufcnt;
-    handle->readbufcnt = 0;
+    if (!drain) luaL_addlstring(
+      &luabuf,
+      handle->readbuf + handle->readbufout,
+      handle->readbufin - handle->readbufout
+    );
+    luabufcnt += handle->readbufin - handle->readbufout;
     do {
       bytesread = read(handle->fd, handle->readbuf, MOONBR_IO_READBUFLEN);
     } while (bytesread < 0 && (errno == EINTR));
-    if (bytesread == 0 || (nonblocking && bytesread < 0 && (errno == EAGAIN || errno == EWOULDBLOCK))) break;
+    if (
+      bytesread == 0 || (
+        nonblocking &&
+        bytesread < 0 && (errno == EAGAIN || errno == EWOULDBLOCK)
+      )
+    ) {
+      handle->readbufin = 0;
+      handle->readbufout = 0;
+      if (!drain) {
+        luaL_pushresult(&luabuf);
+        if (!luabufcnt && bytesread == 0) {
+          lua_pop(L, 1);
+          moonbr_io_read_impl_eof:
+          lua_pushboolean(L, 0);
+          lua_pushliteral(L, "End of file");
+          handle->readerr = 0;
+          return 2;
+        }
+      } else {
+        if (!luabufcnt && bytesread == 0) lua_pushboolean(L, 1);
+        else lua_pushboolean(L, luabufcnt);
+      }
+      handle->readerr = 0;
+      return 1;
+    }
     if (bytesread < 0) {
       moonbr_io_errmsg();
       lua_pushnil(L);
       lua_pushstring(L, errmsg);
       return 2;
     }
-    handle->readbufcnt += bytesread;
-  }
-  if (!drain) {
-    luaL_addlstring(&luabuf, handle->readbuf, handle->readbufcnt);
-    luaL_pushresult(&luabuf);
+    handle->readbufin = bytesread;
+    handle->readbufout = 0;
   }
-  luabufcnt += handle->readbufcnt;
-  handle->readbufcnt = 0;
-  if (!drain) {
-    if (!luabufcnt && bytesread == 0) {
-      handle->readerr = 0;
-      moonbr_io_read_impl_eof:
-      lua_pushboolean(L, 0);
-      lua_pushliteral(L, "End of file");
-      return 2;
-    }
-  } else {
-    if (!luabufcnt && bytesread == 0) lua_pushboolean(L, 1);
-    else lua_pushboolean(L, luabufcnt);
-  }
-  handle->readerr = 0;
-  return 1;
 }
 
 static int moonbr_io_read(lua_State *L) {
@@ -454,7 +480,8 @@
   handle->nonblocking = -1;
   handle->nopush = -1;
   handle->readerr = 0;
-  handle->readbufcnt = 0;
+  handle->readbufin = 0;
+  handle->readbufout = 0;
   handle->writeerr = 0;
   handle->writeleft = 0;
   handle->writeqin = 0;