Document and add extern "C" linkage declaration to the apr_random.h header.

git-svn-id: https://svn.apache.org/repos/asf/apr/apr/trunk@558224 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 98 insertions, 16 deletions

diff --git a/include/apr_random.h b/include/apr_random.h
index 9c0eac23a..29154358d 100644
--- a/include/apr_random.h
+++ b/include/apr_random.h
@@ -17,16 +17,33 @@
 #ifndef APR_RANDOM_H
 #define APR_RANDOM_H
 
-#include <apr_pools.h>
+/**
+ * @file apr_random.h
+ * @brief APR PRNG routines
+ */
+
+#include "apr_pools.h"
+#include "apr_thread_proc.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+/**
+ * @defgroup apr_random PRNG Routines
+ * @ingroup APR
+ * @{
+ */
 
 typedef struct apr_crypto_hash_t apr_crypto_hash_t;
 
 typedef void apr_crypto_hash_init_t(apr_crypto_hash_t *hash);
-typedef void apr_crypto_hash_add_t(apr_crypto_hash_t *hash,const void *data,
+typedef void apr_crypto_hash_add_t(apr_crypto_hash_t *hash, const void *data,
                                    apr_size_t bytes);
 typedef void apr_crypto_hash_finish_t(apr_crypto_hash_t *hash,
                                       unsigned char *result);
 
+
 /* FIXME: make this opaque */
 struct apr_crypto_hash_t {
     apr_crypto_hash_init_t *init;
@@ -36,39 +53,101 @@ struct apr_crypto_hash_t {
     void *data;
 };
 
+/**
+ * Allocate and initialize the SHA-256 context
+ * @param p The pool to allocate from
+ */
 APR_DECLARE(apr_crypto_hash_t *) apr_crypto_sha256_new(apr_pool_t *p);
 
+/** Opaque PRNG structure. */
 typedef struct apr_random_t apr_random_t;
 
-APR_DECLARE(void) apr_random_init(apr_random_t *g,apr_pool_t *p,
+/**
+ * Initialize a PRNG state
+ * @param g The PRNG state
+ * @param p The pool to allocate from
+ * @param pool_hash Pool hash functions
+ * @param key_hash Key hash functions
+ * @param prng_hash PRNG hash functions
+ */
+APR_DECLARE(void) apr_random_init(apr_random_t *g, apr_pool_t *p,
                                   apr_crypto_hash_t *pool_hash,
                                   apr_crypto_hash_t *key_hash,
                                   apr_crypto_hash_t *prng_hash);
+/**
+ * Allocate and initialize (apr_crypto_sha256_new) a new PRNG state.
+ * @param p The pool to allocate from
+ */
 APR_DECLARE(apr_random_t *) apr_random_standard_new(apr_pool_t *p);
+
+/**
+ * Mix the randomness pools.
+ * @param g The PRNG state
+ * @param entropy_ Entropy buffer
+ * @param bytes Length of entropy_ in bytes
+ */
 APR_DECLARE(void) apr_random_add_entropy(apr_random_t *g,
                                          const void *entropy_,
                                          apr_size_t bytes);
+/**
+ * Generate cryptographically insecure random bytes.
+ * @param g The RNG state
+ * @param random Buffer to fill with random bytes
+ * @param bytes Length of buffer in bytes
+ */
 APR_DECLARE(apr_status_t) apr_random_insecure_bytes(apr_random_t *g,
                                                     void *random,
                                                     apr_size_t bytes);
+
+/**
+ * Generate cryptographically secure random bytes.
+ * @param g The RNG state
+ * @param random Buffer to fill with random bytes
+ * @param bytes Length of buffer in bytes
+ */
 APR_DECLARE(apr_status_t) apr_random_secure_bytes(apr_random_t *g,
                                                   void *random,
                                                   apr_size_t bytes);
+/**
+ * Ensures that E bits of conditional entropy are mixed into the PRNG
+ * before any further randomness is extracted.
+ * @param g The RNG state
+ */
 APR_DECLARE(void) apr_random_barrier(apr_random_t *g);
+
+/**
+ * Return APR_SUCCESS if the cryptographic PRNG has been seeded with
+ * enough data, APR_ENOTENOUGHENTROPY otherwise.
+ * @param r The RNG state
+ */
 APR_DECLARE(apr_status_t) apr_random_secure_ready(apr_random_t *r);
+
+/**
+ * Return APR_SUCCESS if the PRNG has been seeded with enough data,
+ * APR_ENOTENOUGHENTROPY otherwise.
+ * @param r The PRNG state
+ */
 APR_DECLARE(apr_status_t) apr_random_insecure_ready(apr_random_t *r);
 
-/* Call this in the child after forking to mix the randomness
-   pools. Note that its generally a bad idea to fork a process with a
-   real PRNG in it - better to have the PRNG externally and get the
-   randomness from there. However, if you really must do it, then you
-   should supply all your entropy to all the PRNGs - don't worry, they
-   won't produce the same output.
+/**
+ * Mix the randomness pools after forking.
+ * @param proc The resulting process handle from apr_proc_fork()
+ * @remark Call this in the child after forking to mix the randomness
+ * pools. Note that its generally a bad idea to fork a process with a
+ * real PRNG in it - better to have the PRNG externally and get the
+ * randomness from there. However, if you really must do it, then you
+ * should supply all your entropy to all the PRNGs - don't worry, they
+ * won't produce the same output.
+ * @remark Note that apr_proc_fork() calls this for you, so only weird
+ * applications need ever call it themselves.
+ * @internal
+ */
+APR_DECLARE(void) apr_random_after_fork(apr_proc_t *proc);
+
+/** @} */
 
-   Note that apr_proc_fork() calls this for you, so only weird
-   applications need ever call it themselves.
-*/
-struct apr_proc_t;
-APR_DECLARE(void) apr_random_after_fork(struct apr_proc_t *proc);
+#ifdef __cplusplus
+}
+#endif
 
-#endif /* ndef APR_RANDOM_H */
+#endif /* !APR_RANDOM_H */
diff --git a/random/unix/apr_random.c b/random/unix/apr_random.c
index 41887d4b0..c6d671c6b 100644
--- a/random/unix/apr_random.c
+++ b/random/unix/apr_random.c
@@ -14,7 +14,10 @@
  * limitations under the License.
  */
 /*
- * See the paper "???" by Ben Laurie for an explanation of this PRNG.
+ * See the paper "On Randomness" by Ben Laurie for an explanation of this PRNG.
+ * http://www.apache-ssl.org/randomness.pdf
+ * XXX: Is there a formal proof of this PRNG? Couldn't we use the more popular
+ * Mersenne Twister PRNG (and BSD licensed)?
  */
 
 #include "apr.h"