WSHUB-458: cborparser: Move ops outside of union

In its place, put an arbitrary `void *` pointer for reader context.  The
reader needs to store some context information which is specific to the
`CborParser` instance it is serving.  Right now, `CborValue::source::token`
serves this purpose, but the problem is that we also need a
per-`CborValue` context and have nowhere to put it.

Better to spend an extra pointer (4 bytes on 32-bit platforms) in the
`CborParser` (which there'll be just one of), then to do it in the
`CborValue` (which there may be several of) or to use a `CborReader`
object that itself carries two pointers (`ops` and the context, thus
we'd need an extra 3 pointers).

Author: sjlongland

src/cbor.h

@@ -390,8 +390,9 @@ struct CborParser
 {
     union {
         const uint8_t *end;
-        const struct CborParserOperations *ops;
-    } source;
+        void *ctx;
+    } data;
+    const struct CborParserOperations *ops;
     enum CborParserGlobalFlags flags;
 };
 typedef struct CborParser CborParser;

src/cborinternal_p.h

@@ -178,15 +178,15 @@ static inline bool can_read_bytes(const CborValue *it, size_t n)
 #ifdef CBOR_PARSER_CAN_READ_BYTES_FUNCTION
             return CBOR_PARSER_CAN_READ_BYTES_FUNCTION(it, n);
 #else
-            return it->parser->source.ops->can_read_bytes(it, n);
+            return it->parser->ops->can_read_bytes(it, n);
 #endif
         }
     }
 
     /* Convert the pointer subtraction to size_t since end >= ptr
      * (this prevents issues with (ptrdiff_t)n becoming negative).
      */
-    return (size_t)(it->parser->source.end - it->source.ptr) >= n;
+    return (size_t)(it->parser->data.end - it->source.ptr) >= n;
 }
 
 static inline void advance_bytes(CborValue *it, size_t n)
@@ -196,7 +196,7 @@ static inline void advance_bytes(CborValue *it, size_t n)
 #ifdef CBOR_PARSER_ADVANCE_BYTES_FUNCTION
             CBOR_PARSER_ADVANCE_BYTES_FUNCTION(it, n);
 #else
-            it->parser->source.ops->advance_bytes(it, n);
+            it->parser->ops->advance_bytes(it, n);
 #endif
             return;
         }
@@ -212,7 +212,7 @@ static inline CborError transfer_string(CborValue *it, const void **ptr, size_t
 #ifdef CBOR_PARSER_TRANSFER_STRING_FUNCTION
             return CBOR_PARSER_TRANSFER_STRING_FUNCTION(it, ptr, offset, len);
 #else
-            return it->parser->source.ops->transfer_string(it, ptr, offset, len);
+            return it->parser->ops->transfer_string(it, ptr, offset, len);
 #endif
         }
     }
@@ -233,7 +233,7 @@ static inline void *read_bytes_unchecked(const CborValue *it, void *dst, size_t
 #ifdef CBOR_PARSER_READ_BYTES_FUNCTION
             return CBOR_PARSER_READ_BYTES_FUNCTION(it, dst, offset, n);
 #else
-            return it->parser->source.ops->read_bytes(it, dst, offset, n);
+            return it->parser->ops->read_bytes(it, dst, offset, n);
 #endif
         }
     }

src/cborparser.c

@@ -354,7 +354,7 @@ static void cbor_parser_init_common(CborParser *parser, CborValue *it)
 CborError cbor_parser_init(const uint8_t *buffer, size_t size, uint32_t flags, CborParser *parser, CborValue *it)
 {
     cbor_parser_init_common(parser, it);
-    parser->source.end = buffer + size;
+    parser->data.end = buffer + size;
     parser->flags = (enum CborParserGlobalFlags)flags;
     it->source.ptr = buffer;
     return preparse_value(it);
@@ -380,7 +380,7 @@ CborError cbor_parser_init(const uint8_t *buffer, size_t size, uint32_t flags, C
 CborError cbor_parser_init_reader(const struct CborParserOperations *ops, CborParser *parser, CborValue *it, void *token)
 {
     cbor_parser_init_common(parser, it);
-    parser->source.ops = ops;
+    parser->ops = ops;
     parser->flags = CborParserFlag_ExternalSource;
     it->source.token = token;
     return preparse_value(it);