Merge pull request #511 from yvxiang/seek

Support seek write file

Author: lylei

src/sdk/bfs.h

@@ -54,6 +54,7 @@ class File {
     File() {}
     virtual ~File() {}
     virtual int32_t Pread(char* buf, int32_t read_size, int64_t offset, bool reada = false) = 0;
+    //for files opened with O_WRONLY, only support Seek(0, SEEK_CUR)
     virtual int64_t Seek(int64_t offset, int32_t whence) = 0;
     virtual int32_t Read(char* buf, int32_t read_size) = 0;
     virtual int32_t Write(const char* buf, int32_t write_size) = 0;

src/sdk/file_impl.cc

@@ -270,6 +270,9 @@ int32_t FileImpl::Pread(char* buf, int32_t read_len, int64_t offset, bool reada)
 int64_t FileImpl::Seek(int64_t offset, int32_t whence) {
     //printf("Seek[%s:%d:%ld]\n", _name.c_str(), whence, offset);
     if (open_flags_ != O_RDONLY) {
+        if (offset == 0 && whence == SEEK_CUR) {
+            return common::atomic_add64(&write_offset_, 0);
+        }
         return BAD_PARAMETER;
     }
     MutexLock lock(&read_offset_mu_);