Add support for extended hash + add support for output hash to custom buffer when supported

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 58 insertions, 3 deletions

diff --git a/libhashsum_init_keccak_256_hasher.3 b/libhashsum_init_keccak_256_hasher.3
index 6492401..f73ea91 100644
--- a/libhashsum_init_keccak_256_hasher.3
+++ b/libhashsum_init_keccak_256_hasher.3
@@ -16,6 +16,7 @@ libhashsum_init_keccak_256_hasher - initialise state for Keccak-256 hashing
 	size_t (*\fIprocess\fP)(struct libhashsum_hasher *\fPthis\fP, const void *\fPdata\fP, size_t \fPbytes\fP);
 	int (*\fIfinalise_const\fP)(struct libhashsum_hasher *\fPthis\fP, const void *\fPdata\fP, size_t \fPbytes\fP, unsigned \fPextra_bits\fP);
 	int (*\fIfinalise\fP)(struct libhashsum_hasher *\fPthis\fP, void *\fPdata\fP, size_t \fPbytes\fP, unsigned \fPextra_bits\fP, size_t \fPsize\fP);
+	void (*\fIstretch\fP)(struct libhashsum_hasher *\fPthis\fP, int \fPskip\fP, void *\fPbuffer\fP);
 	void (*\fIdestroy\fP)(struct libhashsum_hasher *\fPthis\fP);
 	union libhashsum_state { /* definition omitted */ } \fIstate\fP;
 };
@@ -91,7 +92,7 @@ no greater than
 .I hasher->finalise_const
 will be set to a pointer to the function to call
 once the entire text being hashed has been loaded,
-and to get the hash of the text. It's parameter
+and to get the hash of the text. Its parameter
 .I this
 shall be set to
 .IR hasher .
@@ -117,8 +118,16 @@ to a pointer to a buffer in
 containing the binary hash of the processed data.
 Otherwise, the function will return -1, and set
 .I errno
-to indicate the error. The function will failure
-if:
+to indicate the error. However, if the user has
+already set
+.I hasher->hash_output
+to a
+.RI non- NULL
+pointer, the function will output the binary hash
+to that pointer instead without redirecting
+.I hasher->hash_output
+(the application must make sure this buffer is
+sufficiently large). The function will failure if:
 .RS
 .TP
 .B EINVAL
@@ -150,6 +159,52 @@ shall be set to the size of the buffer
 is otherwise identical to
 .IR *hasher->finalise_const .
 .PP
+.I hasher->stretch
+will be set to
+.IR NULL ,
+however upon successful completion of
+.I *hasher->finalise
+or
+.IR *hasher->finalise_const ,
+.I hasher->stretch
+will be set to point to a function that can be
+used to extend the hash by
+.I hasher->hash_size
+bytes, and can be called repeated without limitation.
+The hash extent will be written to a buffer in
+.I hasher->state
+(which
+.I *hasher->finalize
+and
+.I *hasher->finalize_const
+also write the hash to), and
+.I hasher->hash_output
+will be set to point to this buffer.
+.IR *hasher->stretch 's
+parameter
+.I this
+shall be
+.IR hasher .
+Its parameter
+.I skip
+can be set to non-zero if the hash extent should
+be discarded
+.RI ( hasher->hash_output
+will not be set in this case).
+Its parameter
+.I buffer
+shall be
+.I NULL
+for the above described behaviour, or an sufficiently
+large buffer the function shall output the hash extent
+to. If
+.I buffer
+is
+.RI non- NULL ,
+.I hasher->hash_output
+will be set to
+.IR NULL ).
+.PP
 .I hasher->destroy
 will be set to a pointer to a function to to
 call, with