Add a new entrypoint to the hashes in libmd:

  char *
  FooFileChunk(const char *filename, char *buf, off_t offset, off_t length)
Which only hashes part of a file.
Implement FooFile() in terms of this function.

Submitted by:	roam

1 files changed, 20 insertions, 0 deletions

diff --git a/lib/libmd/mdX.3 b/lib/libmd/mdX.3
index cc44122..412aeba 100644
--- a/lib/libmd/mdX.3
+++ b/lib/libmd/mdX.3
@@ -18,6 +18,7 @@
 .Nm MDXFinal ,
 .Nm MDXEnd ,
 .Nm MDXFile ,
+.Nm MDXFileChunk ,
 .Nm MDXData
 .Nd calculate the RSA Data Security, Inc., ``MDX'' message digest
 .Sh LIBRARY
@@ -38,6 +39,8 @@
 .Ft "char *"
 .Fn MDXFile "const char *filename" "char *buf"
 .Ft "char *"
+.Fn MDXFileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"
+.Ft "char *"
 .Fn MDXData "const unsigned char *data" "unsigned int len" "char *buf"
 .Sh DESCRIPTION
 The MDX functions calculate a 128-bit cryptographic checksum (digest)
@@ -88,6 +91,23 @@ calculates the digest of a file, and uses
 .Fn MDXEnd
 to return the result.
 If the file cannot be opened, a null pointer is returned.
+.Fn MDXFileChunk
+is similar to
+.Fn MDXFile ,
+but it only calculates the digest over a byte-range of the file specified,
+starting at
+.Ar offset
+and spanning
+.Ar length
+bytes.
+If the
+.Ar length
+parameter is specified as 0, or more than the length of the remaining part
+of the file,
+.Fn MDXFileChunk
+calculates the digest from
+.Ar offset
+to the end of file.
 .Fn MDXData
 calculates the digest of a chunk of data in memory, and uses
 .Fn MDXEnd