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authorH. Peter Anvin <hpa@zytor.com>2008-02-21 19:32:59 -0800
committerH. Peter Anvin <hpa@zytor.com>2008-02-21 19:32:59 -0800
commit7c028ed3b4fb62d42fad88c36ea86d904ceee86d (patch)
treea8a9cf7d0883c389b30f93b61a358146f623724e /doc
parentb73533206d9f5a4e718fdfaace6370ddd7f3628e (diff)
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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.
Diffstat (limited to 'doc')
-rw-r--r--doc/comboot.doc10
1 files changed, 9 insertions, 1 deletions
diff --git a/doc/comboot.doc b/doc/comboot.doc
index 46afc64c..c4e303af 100644
--- 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.