doc change for nerv_io

1 files changed, 93 insertions, 10 deletions

diff --git a/doc/nerv_io.md b/doc/nerv_io.md
index d452d5d..a417aa8 100644
--- a/doc/nerv_io.md
+++ b/doc/nerv_io.md
@@ -2,25 +2,108 @@
 Part of the [Nerv](../README.md) toolkit.
 
 ##Description##
-There are four classes in to deal with chunk data, which are __nerv.ChunkFile__, __nerv.ChunkFileHandle__, __nerv.ChunkInfo__, __nerv.ChunkData__. Below is the underlying C structs.
+The main class that the user uses to store and read parameter object to and from files is __nerv.ChunkFile__.  
+In the file, a parameter object will be saved using a standard format. First is the length(in byte) of this object, then a table which includes some meta information of the object, and a data area. Below is an example text file.  
+```
+[0000000000202]
+{type="nerv.ExampleP",info={message="just-a-try"},id="exampleP1"}
+3 3
+5.000000 5.000000 5.000000 
+5.000000 5.000000 5.000000 
+5.000000 5.000000 5.000000 
+1 3
+4.000000 4.000000 4.000000 
+[0000000000202]
+{type="nerv.ExampleP",info={message="just-a-try"},id="exampleP2"}
+3 3
+4.000000 4.000000 4.000000 
+4.000000 4.000000 4.000000 
+4.000000 4.000000 4.000000 
+1 3
+3.000000 3.000000 3.000000 
+```
+
+##Methods##
+* __ChunkFile ChunkFile(string fn, string mode)__  
+`mode` can be `r` or `w`, for reading or writing a file. The returned __ChunkFile__ will be ready to write or read objects which follows the __nerv.Param__ interface(using `write_chunk` and `read_chunk`). 
+* __void ChunkFile.write_chunk(ChunkFile self, Param p)__  
+Write `p` into the file. `p:write` will be called.
+* __Param ChunkFile.read_chunk(ChunkFile self, string id, table global_conf)__  
+Read the __Param__ object by id `id` from the file `self`. It will be constructed using `__init(id, global_conf)`. `p:read` will be called.
+
+##Examples##
+* An example showing how to use __ChunkFile__ to store and read parameter objects.
+```
+require 'io'
+do
+    local mt, mpt = nerv.class('nerv.ExampleP', 'nerv.Param')
+    function nerv.ExampleP:__init(id, global_conf)
+        self.id = id
+        self.global_conf = global_conf
+        self.matrix = nerv.MMatrixFloat(3, 3)
+        for i = 0, 2, 1 do
+            for j = 0, 2, 1 do
+                self.matrix[i][j] = 3
+            end
+        end
+        self.bias = nerv.MMatrixFloat(1, 3)
+        for i = 0, 2, 1 do
+            self.bias[i] = 2;
+        end
+        self:set_info({message = 'just-a-try'})
+    end
+    function nerv.ExampleP:addOne()
+        for i = 0, 2, 1 do
+            for j = 0, 2, 1 do
+                self.matrix[i][j] = self.matrix[i][j] + 1
+            end
+        end
+        for i = 0, 2, 1 do
+            self.bias[i] = self.bias[i] + 1
+        end
+    end
+    function nerv.ExampleP:read(pcdata)
+        self.matrix = nerv.MMatrixFloat.load(pcdata)
+        self.bias = nerv.MMatrixFloat.load(pcdata)
+    end
+    function nerv.ExampleP:write(pfhandle)
+        self.matrix:save(pfhandle) 
+        self.bias:save(pfhandle)
+    end
+end
+global_conf = {}
+do
+    local f = nerv.ChunkFile('../tmp', 'w')
+    local exampleP1 = nerv.ExampleP('exampleP1', global_conf)
+    local exampleP2 = nerv.ExampleP('exampleP2', global_conf)
+    exampleP1:addOne() 
+    exampleP1:addOne()
+    exampleP2:addOne()
+
+    f:write_chunk(exampleP1)
+    f:write_chunk(exampleP2)
+end
+do
+    local f = nerv.ChunkFile('../tmp', 'r')
+    local exampleP1 = f:read_chunk('exampleP1', global_conf)
+    local exampleP2 = f:read_chunk('exampleP2', global_conf)
+    print(exampleP1.matrix)
+    print(exampleP2.matrix)
+end
+```
+
+##Developer Notes##
+* There are four classes in to deal with chunk data, which are __nerv.ChunkFile__, __nerv.ChunkFileHandle__, __nerv.ChunkInfo__, __nerv.ChunkData__. Below is the underlying C structs.
 ```
 typedef struct ChunkFileHandle {
     FILE *fp;
 } ChunkFileHandle;
-
 typedef struct ChunkInfo {
     off_t offset, length;
 } ChunkInfo;
-
 typedef struct ChunkData {
     FILE *fp;
     char *data;
 } ChunkData;
 ```
-
-##Methods##
-* __ChunkFile ChunkFile.\_\_init(string mode, string fn)__  
-`mode` can be `r` or `w`, for reading or writing a file.
-
-##Developer Notes##
-In __Nerv.io__, a returned(by `ChunkFile.__init`) __nerv.ChunkFile__ will have a member `handle`, which is a __nerv.ChunkFileHandle__.  
\ No newline at end of file
+* In __Nerv.io__, a returned(by `ChunkFile.__init`) __nerv.ChunkFile__ will have a member `handle`, which is a __nerv.ChunkFileHandle__.  
\ No newline at end of file