Merge pull request #5612 from ehmry/AsyncFile.setLen

asyncfile: setLen procedure for files

1 files changed, 21 insertions, 3 deletions

diff --git a/lib/pure/asyncfile.nim b/lib/pure/asyncfile.nim
index c58e6c11b..86cd8d1be 100644
--- a/lib/pure/asyncfile.nim
+++ b/lib/pure/asyncfile.nim
@@ -70,14 +70,16 @@ else:
       result = O_RDWR
     result = result or O_NONBLOCK
 
-proc getFileSize(f: AsyncFile): int64 =
+proc getFileSize*(f: AsyncFile): int64 =
   ## Retrieves the specified file's size.
   when defined(windows) or defined(nimdoc):
     var high: DWord
     let low = getFileSize(f.fd.Handle, addr high)
     if low == INVALID_FILE_SIZE:
       raiseOSError(osLastError())
-    return (high shl 32) or low
+    result = (high shl 32) or low
+  else:
+    result = lseek(f.fd.cint, 0, SEEK_END)
 
 proc openAsync*(filename: string, mode = fmRead): AsyncFile =
   ## Opens a file specified by the path in ``filename`` using
@@ -466,6 +468,22 @@ proc write*(f: AsyncFile, data: string): Future[void] =
       addWrite(f.fd, cb)
   return retFuture
 
+proc setFileSize*(f: AsyncFile, length: int64) =
+  ## Set a file length.
+  when defined(windows) or defined(nimdoc):
+    var
+      high = (length shr 32).Dword
+    let
+      low = (length and 0xffffffff).Dword
+      status = setFilePointer(f.fd.Handle, low, addr high, 0)
+      lastErr = osLastError()
+    if (status == INVALID_SET_FILE_POINTER and lastErr.int32 != NO_ERROR) or
+       (setEndOfFile(f.fd.Handle) == 0):
+      raiseOSError(osLastError())
+  else:
+    if ftruncate(f.fd.cint, length) == -1:
+      raiseOSError(osLastError())
+
 proc close*(f: AsyncFile) =
   ## Closes the file specified.
   unregister(f.fd)
@@ -498,4 +516,4 @@ proc readToStream*(f: AsyncFile, fs: FutureStream[string]) {.async.} =
       break
     await fs.write(data)
 
-  fs.complete()
\ No newline at end of file
+  fs.complete()