[PATCH] Remove alignment constraint from the sha*_read_ctx functions.

[Jim Meyering]

FYI, I've just pushed this:

        Remove alignment constraint from the sha*_read_ctx functions.
        * lib/sha256.c (set_uint32): New function.
        (sha256_read_ctx, sha224_read_ctx): Use it.
        * lib/sha512.c (set_uint64): New function.
        (sha512_read_ctx, sha384_read_ctx): Use it.
        * lib/sha256.h: Remove warning about alignment constraint.
        * lib/sha512.h: Likewise.
        Prompted by similar changes in gnulib's sha1 and md[45] modules.

---
 ChangeLog    |    9 +++++++++
 lib/sha256.c |   27 ++++++++++++++++-----------
 lib/sha256.h |   12 +++---------
 lib/sha512.c |   27 ++++++++++++++++-----------
 lib/sha512.h |    7 ++-----
 5 files changed, 46 insertions(+), 36 deletions(-)

diff --git a/lib/sha256.c b/lib/sha256.c
index 8f4bb95..4a632c9 100644
--- a/lib/sha256.c
+++ b/lib/sha256.c
@@ -1,7 +1,7 @@
 /* sha256.c - Functions to compute SHA256 and SHA224 message digest of files or
    memory blocks according to the NIST specification FIPS-180-2.

-   Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2005, 2006, 2008 Free Software Foundation, Inc.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -85,18 +85,25 @@ sha224_init_ctx (struct sha256_ctx *ctx)
   ctx->buflen = 0;
 }

-/* Put result from CTX in first 32 bytes following RESBUF.  The result
-   must be in little endian byte order.
+/* Copy the value from v into the memory location pointed to by *cp,
+   If your architecture allows unaligned access this is equivalent to
+   * (uint32_t *) cp = v  */
+static inline void
+set_uint32 (char *cp, uint32_t v)
+{
+  memcpy (cp, &v, sizeof v);
+}

-   IMPORTANT: On some systems it is required that RESBUF is correctly
-   aligned for a 32-bit value.  */
+/* Put result from CTX in first 32 bytes following RESBUF.  The result
+   must be in little endian byte order.  */
 void *
 sha256_read_ctx (const struct sha256_ctx *ctx, void *resbuf)
 {
   int i;
+  char *r = resbuf;

   for (i = 0; i < 8; i++)
-    ((uint32_t *) resbuf)[i] = SWAP (ctx->state[i]);
+    set_uint32 (r + i * sizeof ctx->state[0], SWAP (ctx->state[i]));

   return resbuf;
 }
@@ -105,18 +112,16 @@ void *
 sha224_read_ctx (const struct sha256_ctx *ctx, void *resbuf)
 {
   int i;
+  char *r = resbuf;

   for (i = 0; i < 7; i++)
-    ((uint32_t *) resbuf)[i] = SWAP (ctx->state[i]);
+    set_uint32 (r + i * sizeof ctx->state[0], SWAP (ctx->state[i]));

   return resbuf;
 }

 /* Process the remaining bytes in the internal buffer and the usual
-   prolog according to the standard and write the result to RESBUF.
-
-   IMPORTANT: On some systems it is required that RESBUF is correctly
-   aligned for a 32-bit value.  */
+   prolog according to the standard and write the result to RESBUF.  */
 static void
 sha256_conclude_ctx (struct sha256_ctx *ctx)
 {
diff --git a/lib/sha256.h b/lib/sha256.h
index 32f26ba..9fd83c9 100644
--- a/lib/sha256.h
+++ b/lib/sha256.h
@@ -1,6 +1,6 @@
 /* Declarations of functions and data types used for SHA256 and SHA224 sum
    library functions.
-   Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2005, 2006, 2008 Free Software Foundation, Inc.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -53,20 +53,14 @@ extern void sha256_process_bytes (const void *buffer, 
size_t len,
 /* Process the remaining bytes in the buffer and put result from CTX
    in first 32 (28) bytes following RESBUF.  The result is always in little
    endian byte order, so that a byte-wise output yields to the wanted
-   ASCII representation of the message digest.
-
-   IMPORTANT: On some systems it is required that RESBUF be correctly
-   aligned for a 32 bits value.  */
+   ASCII representation of the message digest.  */
 extern void *sha256_finish_ctx (struct sha256_ctx *ctx, void *resbuf);
 extern void *sha224_finish_ctx (struct sha256_ctx *ctx, void *resbuf);


 /* Put result from CTX in first 32 (28) bytes following RESBUF.  The result is
    always in little endian byte order, so that a byte-wise output yields
-   to the wanted ASCII representation of the message digest.
-
-   IMPORTANT: On some systems it is required that RESBUF is correctly
-   aligned for a 32 bits value.  */
+   to the wanted ASCII representation of the message digest.  */
 extern void *sha256_read_ctx (const struct sha256_ctx *ctx, void *resbuf);
 extern void *sha224_read_ctx (const struct sha256_ctx *ctx, void *resbuf);

diff --git a/lib/sha512.c b/lib/sha512.c
index 230296e..e0109f8 100644
--- a/lib/sha512.c
+++ b/lib/sha512.c
@@ -1,7 +1,7 @@
 /* sha512.c - Functions to compute SHA512 and SHA384 message digest of files or
    memory blocks according to the NIST specification FIPS-180-2.

-   Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2005, 2006, 2008 Free Software Foundation, Inc.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -92,18 +92,25 @@ sha384_init_ctx (struct sha512_ctx *ctx)
   ctx->buflen = 0;
 }

-/* Put result from CTX in first 64 bytes following RESBUF.  The result
-   must be in little endian byte order.
+/* Copy the value from V into the memory location pointed to by *CP,
+   If your architecture allows unaligned access, this is equivalent to
+   * (__typeof__ (v) *) cp = v  */
+static inline void
+set_uint64 (char *cp, u64 v)
+{
+  memcpy (cp, &v, sizeof v);
+}

-   IMPORTANT: On some systems it is required that RESBUF is correctly
-   aligned for a 64-bit value.  */
+/* Put result from CTX in first 64 bytes following RESBUF.
+   The result must be in little endian byte order.  */
 void *
 sha512_read_ctx (const struct sha512_ctx *ctx, void *resbuf)
 {
   int i;
+  char *r = resbuf;

   for (i = 0; i < 8; i++)
-    ((u64 *) resbuf)[i] = SWAP (ctx->state[i]);
+    set_uint64 (r + i * sizeof ctx->state[0], SWAP (ctx->state[i]));

   return resbuf;
 }
@@ -112,18 +119,16 @@ void *
 sha384_read_ctx (const struct sha512_ctx *ctx, void *resbuf)
 {
   int i;
+  char *r = resbuf;

   for (i = 0; i < 6; i++)
-    ((u64 *) resbuf)[i] = SWAP (ctx->state[i]);
+    set_uint64 (r + i * sizeof ctx->state[0], SWAP (ctx->state[i]));

   return resbuf;
 }

 /* Process the remaining bytes in the internal buffer and the usual
-   prolog according to the standard and write the result to RESBUF.
-
-   IMPORTANT: On some systems it is required that RESBUF is correctly
-   aligned for a 64-bit value.  */
+   prolog according to the standard and write the result to RESBUF.  */
 static void
 sha512_conclude_ctx (struct sha512_ctx *ctx)
 {
diff --git a/lib/sha512.h b/lib/sha512.h
index cc32165..7ee3ac4 100644
--- a/lib/sha512.h
+++ b/lib/sha512.h
@@ -1,6 +1,6 @@
 /* Declarations of functions and data types used for SHA512 and SHA384 sum
    library functions.
-   Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2005, 2006, 2008 Free Software Foundation, Inc.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -54,10 +54,7 @@ extern void sha512_process_bytes (const void *buffer, size_t 
len,
 /* Process the remaining bytes in the buffer and put result from CTX
    in first 64 (48) bytes following RESBUF.  The result is always in little
    endian byte order, so that a byte-wise output yields to the wanted
-   ASCII representation of the message digest.
-
-   IMPORTANT: On some systems it is required that RESBUF be correctly
-   aligned for a 64 bits value.  */
+   ASCII representation of the message digest.  */
 extern void *sha512_finish_ctx (struct sha512_ctx *ctx, void *resbuf);
 extern void *sha384_finish_ctx (struct sha512_ctx *ctx, void *resbuf);

--
1.5.4.rc5.1.ge6bfe