Implement RESIZE-FILE

[pforth] / csrc / stdio / pf_fileio_stdio.c

diff --git a/csrc/stdio/pf_fileio_stdio.c b/csrc/stdio/pf_fileio_stdio.c
new file mode 100644 (file)
index 0000000..9a25092
--- /dev/null
+++ b/csrc/stdio/pf_fileio_stdio.c
@@ -0,0 +1,137 @@
+/***************************************************************
+** File access routines based on ANSI C (no Unix stuff).
+**
+** This file is part of pForth
+**
+** The pForth software code is dedicated to the public domain,
+** and any third party may reproduce, distribute and modify
+** the pForth software code or any derivative works thereof
+** without any compensation or license.  The pForth software
+** code is provided on an "as is" basis without any warranty
+** of any kind, including, without limitation, the implied
+** warranties of merchantability and fitness for a particular
+** purpose and their equivalents under the laws of any jurisdiction.
+**
+****************************************************************/
+
+#include "../pf_all.h"
+
+#ifndef PF_NO_FILEIO
+
+#include <limits.h>            /* For LONG_MAX */
+
+typedef int bool_t;
+
+/* Copy SIZE bytes from File FROM to File TO.  Return non-FALSE on error. */
+static bool_t CopyFile( FileStream *From, FileStream *To, long Size)
+{
+    bool_t Error = TRUE;
+    size_t Diff = Size;
+    size_t BufSize = 512;
+    char *Buffer = pfAllocMem( BufSize );
+    if( Buffer != 0 )
+    {
+       while( Diff > 0 )
+       {
+           size_t N = MIN( Diff, BufSize );
+           if( fread( Buffer, 1, N, From ) < N ) goto cleanup;
+           if( fwrite( Buffer, 1, N, To ) < N ) goto cleanup;
+           Diff -= N;
+       }
+       Error = FALSE;
+
+      cleanup:
+       pfFreeMem( Buffer );
+    }
+    return Error;
+}
+
+/* Shrink the file FILE to NEWSIZE.  Return non-FALSE on error.
+ *
+ * There's no direct way to do this in ANSI C.  The closest thing we
+ * have is freopen(3), which truncates a file to zero length if we use
+ * "w+b" as mode argument.  So we do this:
+ *
+ *   1. copy original content to temporary file
+ *   2. re-open and truncate FILE
+ *   3. copy the temporary file to FILE
+ *
+ * Unfortunately, "w+b" may not be the same mode as the original mode
+ * of FILE.  I don't see a away to avoid this, though.
+ *
+ * We call freopen with NULL as path argument, because we don't know
+ * the actual file-name.  It seems that the trick with path=NULL is
+ * not part of C89 but it's in C99.
+ */
+static bool_t TruncateFile( FileStream *File, long Newsize )
+{
+    bool_t Error = TRUE;
+    if( fseek( File, 0, SEEK_SET ) == 0)
+    {
+       FileStream *TmpFile = tmpfile();
+       if( TmpFile != NULL )
+       {
+           if( CopyFile( File, TmpFile, Newsize )) goto cleanup;
+           if( fseek( TmpFile, 0, SEEK_SET ) != 0 ) goto cleanup;
+           if( freopen( NULL, "w+b", File ) == NULL ) goto cleanup;
+           if( CopyFile( TmpFile, File, Newsize )) goto cleanup;
+           Error = FALSE;
+
+         cleanup:
+           fclose( TmpFile );
+       }
+    }
+    return Error;
+}
+
+/* Write DIFF 0 bytes to FILE. Return non-FALSE on error. */
+static bool_t ExtendFile( FileStream *File, size_t Diff )
+{
+    bool_t Error = TRUE;
+    size_t BufSize = 512;
+    char * Buffer = pfAllocMem( BufSize );
+    if( Buffer != 0 )
+    {
+       pfSetMemory( Buffer, 0, BufSize );
+       while( Diff > 0 )
+       {
+           size_t N = MIN( Diff, BufSize );
+           if( fwrite( Buffer, 1, N, File ) < N ) goto cleanup;
+           Diff -= N;
+       }
+       Error = FALSE;
+      cleanup:
+       pfFreeMem( Buffer );
+    }
+    return Error;
+}
+
+/* Return non-FALSE if the double-cell unsigned number LO/HI
+ * is greater then LONG_MAX.
+ */
+static bool_t IsGreaterThanLongMax( ucell_t Lo, ucell_t Hi )
+{
+    return (Hi != 0) || (Lo > LONG_MAX);
+}
+
+ThrowCode sdResizeFile( FileStream *File, ucell_t SizeLo, ucell_t SizeHi )
+{
+    bool_t Error = TRUE;
+    if( !IsGreaterThanLongMax( SizeLo, SizeHi ) )
+    {
+       long Newsize = (long) SizeLo;
+       if( fseek( File, 0, SEEK_END ) == 0 )
+       {
+           long Oldsize = ftell( File );
+           if( Oldsize != -1L )
+           {
+               Error = ( Oldsize <= Newsize
+                         ? ExtendFile( File, Newsize - Oldsize )
+                         : TruncateFile( File, Newsize ));
+           }
+       }
+    }
+    return Error ? THROW_RESIZE_FILE : 0;
+}
+
+#endif /* !PF_NO_FILEIO */