(ctr_crypt): Reorganized to call the encryption function with several

blocks at a time. Handle the case of a single block specially.

Rev: nettle/ctr.c:1.3

diff --git a/ctr.c b/ctr.c
index d94136c15c86ff79b70780f0b902716aa445e1b1..d217013cd36df25a5449f1dc0c58b210d14921ab 100644 (file)
--- a/ctr.c
+++ b/ctr.c
@@ -36,40 +36,93 @@
 #include "macros.h"
 #include "memxor.h"
 #include "nettle-internal.h"
-  
+
+#define NBLOCKS 4
+
 void
 ctr_crypt(void *ctx, nettle_crypt_func f,
          unsigned block_size, uint8_t *ctr,
          unsigned length, uint8_t *dst,
          const uint8_t *src)
 {
-  TMP_DECL(buffer, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE);
-  TMP_ALLOC(buffer, block_size);
-
   if (src != dst)
     {
-      for (; length >= block_size; length -= block_size, src += block_size, dst += block_size)
+      if (length == block_size)
        {
          f(ctx, block_size, dst, ctr);
-         memxor(dst, src, block_size);
          INCREMENT(block_size, ctr);
+         memxor(dst, src, block_size);
+       }
+      else
+       {
+         unsigned left;
+         uint8_t *p;     
+
+         for (p = dst, left = length;
+              left >= block_size;
+              left -= block_size, p += block_size)
+           {
+             memcpy (p, ctr, block_size);
+             INCREMENT(block_size, ctr);
+           }
+
+         f(ctx, length - left, dst, dst);
+         memxor(dst, src, length - left);
+
+         if (left)
+           {
+             TMP_DECL(buffer, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE);
+             TMP_ALLOC(buffer, block_size);
+
+             f(ctx, block_size, buffer, ctr);
+             INCREMENT(block_size, ctr);
+             memxor3(dst + length - left, src + length - left, buffer, left);
+           }
        }
     }
   else
     {
-      for (; length >= block_size; length -= block_size, src += block_size, dst += block_size)
+      if (length <= block_size)
        {
+         TMP_DECL(buffer, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE);
+         TMP_ALLOC(buffer, block_size);
+
          f(ctx, block_size, buffer, ctr);
-         memxor3(dst, src, buffer, block_size);
          INCREMENT(block_size, ctr);
-       }      
-    }
-  if (length > 0)
-    {
-      /* A final partial block */
+         memxor3(dst, src, buffer, length);
+       }
+      else
+       {
+         TMP_DECL(buffer, uint8_t, NBLOCKS * NETTLE_MAX_CIPHER_BLOCK_SIZE);
+         unsigned chunk = NBLOCKS * block_size;
+
+         TMP_ALLOC(buffer, chunk);
 
-      f(ctx, block_size, buffer, ctr);
-      memxor3(dst, src, buffer, length);
-      INCREMENT(block_size, ctr);
+         for (; length >= chunk;
+              length -= chunk, src += chunk, dst += chunk)
+           {
+             unsigned n;
+             uint8_t *p;         
+             for (n = 0, p = buffer; n < NBLOCKS; n++, p += block_size)
+               {
+                 memcpy (p, ctr, block_size);
+                 INCREMENT(block_size, ctr);
+               }
+             f(ctx, chunk, buffer, buffer);
+             memxor(dst, buffer, chunk);
+           }
+
+         if (length > 0)
+           {
+             /* Final, possibly partial, blocks */
+             for (chunk = 0; chunk < length; chunk += block_size)
+               {
+                 memcpy (buffer + chunk, ctr, block_size);
+                 INCREMENT(block_size, ctr);
+               }
+             f(ctx, chunk, buffer, buffer);
+             memxor3(dst, src, buffer, length);
+           }
+       }
     }
 }