Update api

api.md

@@ -5,7 +5,7 @@ The following is a description of the public C/C++ functions exported by the exh
 
 
 ExhaleEncAPI* exhaleCreate()
------------------------------
+----------------------------
 
 **C declaration**
 
@@ -13,15 +13,19 @@ ExhaleEncAPI* `exhaleCreate`(int32_t* const inputPcmData, unsigned char* const o
 
 **C++ class declaration**
 
-*none*
+*none (class constructor)*
 
 **Purpose**
 
 create an *ExhaleEncAPI* object and return a pointer to it
 
+**Return value**
+
+the pointer to the newly created *ExhaleEncAPI* object
+
 
 unsigned exhaleInitEncoder()
------------------------------
+----------------------------
 
 **C declaration**
 
@@ -33,11 +37,15 @@ unsigned ExhaleEncAPI::`initEncoder`(unsigned char* const audioConfigBuffer, uin
 
 **Purpose**
 
-initialize an *ExhaleEncAPI* object for encoding
+initialize an *ExhaleEncAPI* object for encoding and allocate necessary object memory
+
+**Return value**
+
+zero (0) upon success, or nonzero (1-255 or 65535) in case of an error or if the *exhaleEnc* pointer is `NULL`
 
 
 unsigned exhaleEncodeLookahead()
----------------------------------
+--------------------------------
 
 **C declaration**
 
@@ -51,9 +59,13 @@ unsigned ExhaleEncAPI::`encodeLookahead`();
 
 encode the first (lookahead) frame with an *ExhaleEncAPI* object
 
+**Return value**
+
+the byte-size (2 < *b* < 65535) of the AU upon success, or nonzero (1, 2 or 65535) in case of an error or if the *exhaleEnc* pointer is `NULL`
+
 
 unsigned exhaleEncodeFrame()
------------------------------
+----------------------------
 
 **C declaration**
 
@@ -65,11 +77,15 @@ unsigned ExhaleEncAPI::`encodeFrame`();
 
 **Purpose**
 
-encode a regular frame with an *ExhaleEncAPI* object
+encode a regular PCM audio frame with an *ExhaleEncAPI* object
+
+**Return value**
+
+the byte-size (2 < *b* < 65535) of the AU upon success, or nonzero (1, 2 or 65535) in case of an error or if the *exhaleEnc* pointer is `NULL`
 
 
 unsigned exhaleDelete()
-------------------------
+-----------------------
 
 **C declaration**
 
@@ -81,4 +97,9 @@ ExhaleEncAPI::`~ExhaleEncAPI`(); *(class destructor)*
 
 **Purpose**
 
-free all dynamic memory allocated by an *ExhaleEncAPI* object
+free all dynamic memory allocated by an *ExhaleEncAPI* object. After calling this function, the *exhaleEnc* pointer can be set to `NULL`.
+
+
+**Return value**
+
+zero (0) upon success, or nonzero (65535) if the *exhaleEnc* pointer is `NULL`