perf(file): simplify the usage of flock

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>

examples/flock.lua

@@ -2,35 +2,26 @@
 
 local file = require 'eco.file'
 local time = require 'eco.time'
-local sys = require 'eco.sys'
 
 local fd, err = file.open('/tmp/lock-test', file.O_RDWR)
 if not fd then
     print('open fail:', err)
     return
 end
 
-while true do
-    local ok, errno, err = file.flock(fd, file. LOCK_EX)
-    if ok then
-        print('lock ok')
-        break
-    end
-
-    if errno ~= sys.EAGAIN then
-        print('lock fail:', err)
-        file.close(fd)
-        return
-    end
-    time.sleep(0.1)
+local ok, err = file.flock(fd, file.LOCK_EX)
+if not ok then
+    print('lock fail:', err)
+    file.close(fd)
+    return
 end
 
+print('locked')
+
 time.sleep(5)
 
-file.flock(fd, file. LOCK_UN)
+file.flock(fd, file.LOCK_UN)
 
 print('unlocked')
 
-time.sleep(5)
-
 file.close(fd)

file.c

@@ -443,8 +443,7 @@ static int eco_file_flock(lua_State *L)
     if (flock(fd, operation | LOCK_NB)) {
         lua_pushnil(L);
         lua_pushinteger(L, errno);
-        lua_pushstring(L, strerror(errno));
-        return 3;
+        return 2;
     }
 
     lua_pushboolean(L, true);

file.lua

@@ -2,6 +2,8 @@
 -- Author: Jianhui Zhao <zhaojh329@gmail.com>
 
 local file = require 'eco.core.file'
+local sys = require 'eco.core.sys'
+local time = require 'eco.time'
 
 local M = {}
 
@@ -78,4 +80,29 @@ function M.write(fd, data)
     return file.write(fd, data)
 end
 
+function M.flock(fd, operation, timeout)
+    local deadtime
+
+    if timeout then
+        deadtime = sys.uptime() + timeout
+    end
+
+    while true do
+        local ok, errno = file.flock(fd, operation)
+        if ok then
+            return true
+        end
+
+        if errno ~= sys.EAGAIN then
+            return false, sys.strerror(errno)
+        end
+
+        if deadtime and sys.uptime() > deadtime then
+            return false, 'timeout'
+        end
+
+        time.sleep(0.001)
+    end
+end
+
 return setmetatable(M, { __index = file })