From: Dr. Stephen Henson <steve@openssl.org>
Date: Tue, 16 Oct 2001 02:22:59 +0000 (+0000)
Subject: Update docs.
X-Git-Tag: OpenSSL_0_9_6c~26^2~121
X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff_plain;h=e72d734d5fef981371db695125cc1c3d236a8768

Update docs.
---

diff --git a/doc/crypto/EVP_DigestInit.pod b/doc/crypto/EVP_DigestInit.pod
index df17928b5d..b3a61f1c5d 100644
--- a/doc/crypto/EVP_DigestInit.pod
+++ b/doc/crypto/EVP_DigestInit.pod
@@ -2,9 +2,10 @@
 
 =head1 NAME
 
-EVP_DigestInit, EVP_DigestUpdate, EVP_DigestFinal, EVP_MAX_MD_SIZE,
-EVP_MD_CTX_copy, EVP_MD_type, EVP_MD_pkey_type, EVP_MD_size, EVP_MD_block_size,
-EVP_MD_CTX_md, EVP_MD_CTX_size, EVP_MD_CTX_block_size, EVP_MD_CTX_type,
+EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_DigestInit_ex, EVP_DigestUpdate,
+EVP_DigestFinal_ex, EVP_MD_CTX_cleanup, EVP_MD_CTX_destroy, EVP_MAX_MD_SIZE,
+EVP_MD_CTX_copy_ex EVP_MD_CTX_copy, EVP_MD_type, EVP_MD_pkey_type, EVP_MD_size,
+EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size, EVP_MD_CTX_block_size, EVP_MD_CTX_type,
 EVP_md_null, EVP_md2, EVP_md5, EVP_sha, EVP_sha1, EVP_dss, EVP_dss1, EVP_mdc2,
 EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj -
 EVP digest routines
@@ -13,14 +14,27 @@ EVP digest routines
 
  #include <openssl/evp.h>
 
- int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
+ void EVP_MD_CTX_init(EVP_MD_CTX *ctx);
+ EVP_MD_CTX *EVP_MD_CTX_create(void);
+
+ int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
  int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
+ int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md,
+        unsigned int *s);
+
+ int EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx);
+ void EVP_MD_CTX_destroy(EVP_MD_CTX *ctx);
+
+ int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out,const EVP_MD_CTX *in);  
+
+ int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
  int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md,
         unsigned int *s);
 
+ int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in);  
+
  #define EVP_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */
 
- int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in);  
 
  #define EVP_MD_type(e)			((e)->type)
  #define EVP_MD_pkey_type(e)		((e)->pkey_type)
@@ -50,25 +64,48 @@ EVP digest routines
 
 The EVP digest routines are a high level interface to message digests.
 
-EVP_DigestInit() initializes a digest context B<ctx> to use a digest
-B<type>: this will typically be supplied by a function such as
-EVP_sha1().
+EVP_MD_CTX_init() initializes digest contet B<ctx>.
+
+EVP_MD_CTX_create() allocates, initializes and returns a digest contet.
+
+EVP_DigestInit_ex() sets up digest context B<ctx> to use a digest
+B<type> from ENGINE B<impl>. B<ctx> must be initialized before calling this
+function. B<type> will typically be supplied by a functionsuch as EVP_sha1().
+If B<impl> is NULL then the default implementation of digest B<type> is used.
 
 EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the
 digest context B<ctx>. This function can be called several times on the
 same B<ctx> to hash additional data.
 
-EVP_DigestFinal() retrieves the digest value from B<ctx> and places
+EVP_DigestFinal_ex() retrieves the digest value from B<ctx> and places
 it in B<md>. If the B<s> parameter is not NULL then the number of
 bytes of data written (i.e. the length of the digest) will be written
 to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written.
-After calling EVP_DigestFinal() no additional calls to EVP_DigestUpdate()
-can be made, but EVP_DigestInit() can be called to initialize a new
+After calling EVP_DigestFinal_ex() no additional calls to EVP_DigestUpdate()
+can be made, but EVP_DigestInit_ex() can be called to initialize a new
 digest operation.
 
-EVP_MD_CTX_copy() can be used to copy the message digest state from
+EVP_MD_CTX_cleanup() cleans up digest context B<ctx>, it should be called
+after a digest context is no longer needed.
+
+EVP_MD_CTX_destroy() cleans up digest context B<ctx> and frees up the
+space allocated to it, it should be called only on a context created
+using EVP_MD_CTX_create().
+
+EVP_MD_CTX_copy_ex() can be used to copy the message digest state from
 B<in> to B<out>. This is useful if large amounts of data are to be
-hashed which only differ in the last few bytes.
+hashed which only differ in the last few bytes. B<out> must be initialized
+before calling this function.
+
+EVP_DigestInit() behaves in the same way as EVP_DigestInit_ex() except
+the passed context B<ctx> does not have to be initialized, and it always
+uses the default digest implementation.
+
+EVP_DigestFinal() is similar to EVP_DigestFinal_ex() except the digest
+contet B<ctx> is automatically cleaned up.
+
+EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except the destination
+B<out> does not have to be initialized.
 
 EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest
 when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the
@@ -107,10 +144,10 @@ using, for example, OpenSSL_add_all_digests() for these functions to work.
 
 =head1 RETURN VALUES
 
-EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() return 1 for
+EVP_DigestInit_ex(), EVP_DigestUpdate() and EVP_DigestFinal_ex() return 1 for
 success and 0 for failure.
 
-EVP_MD_CTX_copy() returns 1 if successful or 0 for failure.
+EVP_MD_CTX_copy_ex() returns 1 if successful or 0 for failure.
 
 EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of the
 corresponding OBJECT IDENTIFIER or NID_undef if none exists.
@@ -135,9 +172,18 @@ transparent to the digest used and much more flexible.
 SHA1 is the digest of choice for new applications. The other digest algorithms
 are still in common use.
 
-The functions EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal(),
-did not return errors in OpenSSL versions before 0.9.7 or earlier. Software only
-versions of digest algorithms will never return error codes for these functions.
+For most applications the B<impl> parameter to EVP_DigestInit_ex() will be
+set to NULL to use the default digest implementation.
+
+The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are 
+obsolete but are retained to maintain compatibility with existing code. New
+applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and 
+EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context
+instead of initializing and cleaning it up on each call and allow non default
+implementations of digests to be specified.
+
+In OpenSSL 0.9.7 and later if digest contexts are not cleaned up after use
+memory leaks will occur. 
 
 =head1 EXAMPLE
 
@@ -170,10 +216,12 @@ digest name passed on the command line.
 	exit(1);
  }
 
- EVP_DigestInit(&mdctx, md);
+ EVP_MD_CTX_init(&mdctx);
+ EVP_DigestInit_ex(&mdctx, md, NULL);
  EVP_DigestUpdate(&mdctx, mess1, strlen(mess1));
  EVP_DigestUpdate(&mdctx, mess2, strlen(mess2));
- EVP_DigestFinal(&mdctx, md_value, &md_len);
+ EVP_DigestFinal_ex(&mdctx, md_value, &md_len);
+ EVP_MD_CTX_cleanup(&mdctx);
 
  printf("Digest is: ");
  for(i = 0; i < md_len; i++) printf("%02x", md_value[i]);
@@ -186,9 +234,6 @@ The link between digests and signing algorithms results in a situation where
 EVP_sha1() must be used with RSA and EVP_dss1() must be used with DSS
 even though they are identical digests.
 
-The size of an B<EVP_MD_CTX> structure is determined at compile time: this results
-in code that must be recompiled if the size of B<EVP_MD_CTX> increases.
-
 =head1 SEE ALSO
 
 L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>,
@@ -200,4 +245,7 @@ L<sha(3)|sha(3)>, L<digest(1)|digest(1)>
 EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are
 available in all versions of SSLeay and OpenSSL.
 
+EVP_DigestInit_ex(), EVP_DigestFinal_ex() and EVP_MD_CTX_copy_ex()
+were added in OpenSSL 0.9.7.
+
 =cut