From 6c6abac272dcc0d5d966722812fd87ba4c3ff45b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
Date: Mon, 29 Aug 2011 15:38:31 +0200
Subject: [PATCH] (MD_UPDATE): New macro. (MD_PAD): New macro.
Rev: nettle/macros.h:1.4
---
macros.h | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 92 insertions(+)
diff --git a/macros.h b/macros.h
index 8a3e1688..1303ed91 100644
--- a/macros.h
+++ b/macros.h
@@ -131,4 +131,96 @@ do { \
} \
} while (0)
+
+/* Helper macro for Merkle-Damgård hash functions. Assumes the context
+ structs includes the following fields:
+
+ xxx state [...]; // State for the compression function
+ xxx count_low, count_high; // Two word block count
+ uint8_t block[...]; // Buffer holding one block
+ unsigned int index; // Index into block
+*/
+
+/* FIXME: Should probably switch to using uint64_t for the count, but
+ due to alignment and byte order that may be an ABI change. */
+
+#define MD_INCR(ctx) ((ctx)->count_high += !++(ctx)->count_low)
+
+/* Takes the compression function f as argument. NOTE: also clobbers
+ length and data. */
+#define MD_UPDATE(ctx, length, data, f) \
+ do { \
+ if ((ctx)->index) \
+ { \
+ /* Try to fill partial block */ \
+ unsigned __md_left = sizeof((ctx)->block) - (ctx)->index; \
+ if ((length) < __md_left) \
+ { \
+ memcpy((ctx)->block + (ctx)->index, (data), (length)); \
+ (ctx)->index += (length); \
+ goto __md_done; /* Finished */ \
+ } \
+ else \
+ { \
+ memcpy((ctx)->block + (ctx)->index, (data), __md_left); \
+ \
+ f((ctx)->state, (ctx)->block); \
+ MD_INCR(ctx); \
+ \
+ (data) += __md_left; \
+ (length) -= __md_left; \
+ } \
+ } \
+ while ((length) >= sizeof((ctx)->block)) \
+ { \
+ f((ctx)->state, (data)); \
+ MD_INCR(ctx); \
+ \
+ (data) += sizeof((ctx)->block); \
+ (length) -= sizeof((ctx)->block); \
+ } \
+ memcpy ((ctx)->block, (data), (length)); \
+ (ctx)->index = (length); \
+ __md_done: \
+ ; \
+ } while (0)
+
+#define MD_PAD(ctx, bits, shift, f, write) \
+ do { \
+ unsigned __md_i; \
+ uint##bits##_t __md_low, __md_high; \
+ __md_i = (ctx)->index; \
+ \
+ /* Set the first char of padding to 0x80. This is safe since there \
+ is always at least one byte free */ \
+ \
+ assert(__md_i < sizeof((ctx)->block)); \
+ (ctx)->block[__md_i++] = 0x80; \
+ \
+ if (__md_i > (sizeof((ctx)->block) - 2*sizeof((ctx)->count_low))) \
+ { /* No room for length in this block. Process it and \
+ pad with another one */ \
+ memset((ctx)->block + __md_i, 0, sizeof((ctx)->block) - __md_i); \
+ \
+ f((ctx)->state, (ctx)->block); \
+ __md_i = 0; \
+ } \
+ memset((ctx)->block + __md_i, 0, \
+ sizeof((ctx)->block) - 2*sizeof((ctx)->count_low) - __md_i); \
+ \
+ /* There are 2^shift bits in one block */ \
+ __md_high = ((ctx)->count_high << (shift)) \
+ | ((ctx)->count_low >> ((bits) - (shift))); \
+ __md_low = ((ctx)->count_low << (shift)) | ((ctx)->index << 3); \
+ \
+ write((ctx)->block \
+ + sizeof((ctx)->block) - 2*sizeof((ctx)->count_low), \
+ __md_high); \
+ write((ctx)->block \
+ + sizeof((ctx)->block) - sizeof((ctx)->count_low), \
+ __md_low); \
+ \
+ f((ctx)->state, (ctx)->block); \
+ } while (0)
+
#endif /* NETTLE_MACROS_H_INCLUDED */
--
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