Document intent at no longer providing file length a priori

We intend to no longer guarantee that we know the file size ahead of
time.

diff --git a/doc/comboot.doc b/doc/comboot.doc
index 46afc64..c4e303a 100644 (file)
--- a/doc/comboot.doc
+++ b/doc/comboot.doc
@@ -293,7 +293,7 @@ AX=0006h [2.08] Open file
        Input:  AX      0006h
                ES:SI   null-terminated filename
        Output: SI      file handle
-               EAX     length of file in bytes
+               EAX     length of file in bytes, or -1
                CX      file block size
 
        Open a file for reading.  The exact syntax of the filenames
@@ -304,6 +304,9 @@ AX=0006h [2.08] Open file
 
        Note: SYSLINUX considers a zero-length file to be nonexistent.
 
+       In 3.70 or later, EAX can contain -1 indicating that the file
+       length is unknown.
+
 
 AX=0007h [2.08] Read file
 
@@ -312,6 +315,7 @@ AX=0007h [2.08] Read file
                ES:BX   buffer
                CX      number of blocks to read
        Output: SI      file handle, or 0 if EOF was reached
+               EAX     number of bytes read [3.70]
 
        Read blocks from a file.  Note that the file handle that is
        returned in SI may not be the same value that was passed in.
@@ -319,6 +323,10 @@ AX=0007h [2.08] Read file
        If end of file was reached (SI=0), the file was automatically
        closed.
 
+       In 3.70 or later, EAX returns the number of bytes read.  This
+       will always be a multiple of the block size unless EOF is
+       reached.
+
        The address of the buffer (ES:BX) should be at least 512-byte
        aligned.  SYSLINUX guarantees at least this alignment for the
        COMBOOT load segment or the COM32 bounce buffer.