Parser: modify the zero-copy string API

Instead of just one function (_cbor_value_get_string_chunk), we now have
_cbor_value_begin_string_iteration, _cbor_value_finish_string_iteration,
_cbor_value_get_string_chunk_size, and _cbor_value_get_string_chunk.

The "begin" function positions the pointer at the first chunk. That's
what makes "get_size" possible, since it doesn't need to check for any
state. The "finish" funcntion allows the caller to distinguish an error
parsing the string from an error parsing the next value.

Signed-off-by: Thiago Macieira <[email protected]>

Author: thiagomacieira

src/cborparser.c

@@ -1147,7 +1147,7 @@ static CborError get_string_chunk(CborValue *it, const void **bufferptr, size_t
  */
 
 CborError _cbor_value_get_string_chunk(const CborValue *value, const void **bufferptr,
-                                                        size_t *len, CborValue *next)
+                                       size_t *len, CborValue *next)
 {
     CborValue tmp;
     if (!next)