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Diffstat (limited to 'src/upb_msg.h')
| -rw-r--r-- | src/upb_msg.h | 369 |
1 files changed, 369 insertions, 0 deletions
diff --git a/src/upb_msg.h b/src/upb_msg.h new file mode 100644 index 0000000..8910505 --- /dev/null +++ b/src/upb_msg.h @@ -0,0 +1,369 @@ +/* + * upb - a minimalist implementation of protocol buffers. + * + * Copyright (c) 2009 Joshua Haberman. See LICENSE for details. + * + * A upb_msg provides a full description of a message as defined in a .proto + * file. It supports many features and operations for dealing with proto + * messages: + * - reflection over .proto types at runtime (list fields, get names, etc). + * - an in-memory byte-level format for efficiently storing and accessing msgs. + * - serializing and deserializing from the in-memory format to a protobuf. + * - optional memory management for handling strings, arrays, and submessages. + * + * Throughout this file, the following convention is used: + * - "struct upb_msg *m" describes a message type (name, list of fields, etc). + * - "void *data" is an actual message stored using the in-memory format. + * + * The in-memory format is very much like a C struct that you can define at + * run-time, but also supports reflection. Like C structs it supports + * offset-based access, as opposed to the much slower name-based lookup. The + * format stores both the values themselves and bits describing whether each + * field is set or not. For example: + * + * parsed message Foo { + * optional bool a = 1; + * repeated uint32 b = 2; + * optional Bar c = 3; + * } + * + * The in-memory layout for this message on a 32-bit machine will be something + * like: + * + * Foo + * +------------------------+ + * | set_flags a:1, b:1, c:1| + * +------------------------+ + * | bool a (1 byte) | + * +------------------------+ + * | padding (3 bytes) | + * +------------------------+ upb_array + * | upb_array* b (4 bytes) | ----> +----------------------------+ + * +------------------------+ | uint32* elements (4 bytes) | ---+ + * | Bar* c (4 bytes) | +----------------------------+ | + * +------------------------+ | uint32 size (4 bytes) | | + * +----------------------------+ | + * | + * -----------------------------------------------------------------+ + * | + * V + * uint32 array + * +----+----+----+----+----+----+ + * | e1 | e2 | e3 | e4 | e5 | e6 | + * +----+----+----+----+----+----+ + * + * And the corresponding C structure (as emitted by the proto compiler) would be: + * + * struct Foo { + * union { + * uint8_t bytes[1]; + * struct { + * bool a:1; + * bool b:1; + * bool c:1; + * } has; + * } set_flags; + * bool a; + * upb_uint32_array *b; + * Bar *c; + * } + * + * Because the C struct emitted by the upb compiler uses exactly the same + * byte-level format as the reflection interface, you can access the same hunk + * of memory either way. The C struct provides maximum performance and static + * type safety; upb_msg provides flexibility. + * + * The in-memory format has no interoperability guarantees whatsoever, except + * that a single version of upb will interoperate with itself. Don't even + * think about persisting the in-memory format or sending it anywhere. That's + * what serialized protobufs are for! The in-memory format is just that -- an + * in-memory representation that allows for fast access. + * + * The in-memory format is carefully designed to *not* mandate any particular + * memory management scheme. This should make it easier to integrate with + * existing memory management schemes, or to perform advanced techniques like + * reference counting, garbage collection, and string references. Different + * clients can read each others messages regardless of what memory management + * scheme each is using. + * + * A memory management scheme is provided for convenience, and it is used by + * default by the stock message parser. Clients can substitute their own + * memory management scheme into this parser without any loss of generality + * or performance. + */ + +#ifndef UPB_MSG_H_ +#define UPB_MSG_H_ + +#include <stdbool.h> +#include <stdint.h> + +#include "upb.h" +#include "upb_table.h" +#include "upb_parse.h" + +#ifdef __cplusplus +extern "C" { +#endif + +/* Forward declarations from descriptor.h. */ +struct google_protobuf_DescriptorProto; +struct google_protobuf_FieldDescriptorProto; + +/* Message definition. ********************************************************/ + +/* Structure that describes a single field in a message. This structure is very + * consciously designed to fit into 12/16 bytes (32/64 bit, respectively), + * because copies of this struct are in the hash table that is read in the + * critical path of parsing. Minimizing the size of this struct increases + * cache-friendliness. */ +struct upb_msg_field { + union upb_symbol_ref ref; + uint32_t byte_offset; /* Where to find the data. */ + uint16_t field_index; /* Indexes upb_msg.fields. Also indicates set bit */ + upb_field_type_t type; /* Copied from descriptor for cache-friendliness. */ + upb_label_t label; +}; + +/* Structure that describes a single .proto message type. */ +struct upb_msg { + struct google_protobuf_DescriptorProto *descriptor; + size_t size; + uint32_t num_fields; + uint32_t set_flags_bytes; + uint32_t num_required_fields; /* Required fields have the lowest set bytemasks. */ + struct upb_inttable fields_by_num; + struct upb_strtable fields_by_name; + struct upb_msg_field *fields; + struct google_protobuf_FieldDescriptorProto **field_descriptors; +}; + +/* The num->field and name->field maps in upb_msg allow fast lookup of fields + * by number or name. These lookups are in the critical path of parsing and + * field lookup, so they must be as fast as possible. To make these more + * cache-friendly, we put the data in the table by value. */ + +struct upb_fieldsbynum_entry { + struct upb_inttable_entry e; + struct upb_msg_field f; +}; + +struct upb_fieldsbyname_entry { + struct upb_strtable_entry e; + struct upb_msg_field f; +}; + +/* Can be used to retrieve a field descriptor given the upb_msg_field ref. */ +INLINE struct google_protobuf_FieldDescriptorProto *upb_msg_field_descriptor( + struct upb_msg_field *f, struct upb_msg *m) { + return m->field_descriptors[f->field_index]; +} + +/* Initializes/frees a upb_msg. Caller retains ownership of d, but the msg + * will contain references to it, so it must outlive the msg. Note that init + * does not resolve upb_msg_field.ref -- the caller should do that + * post-initialization by calling upb_msg_ref() below. */ +bool upb_msg_init(struct upb_msg *m, struct google_protobuf_DescriptorProto *d); +void upb_msg_free(struct upb_msg *m); + +/* Clients use this function on a previously initialized upb_msg to resolve the + * "ref" field in the upb_msg_field. Since messages can refer to each other in + * mutually-recursive ways, this step must be separated from initialization. */ +void upb_msg_ref(struct upb_msg *m, struct upb_msg_field *f, union upb_symbol_ref ref); + +/* Looks up a field by name or number. While these are written to be as fast + * as possible, it will still be faster to cache the results of this lookup if + * possible. These return NULL if no such field is found. */ +INLINE struct upb_msg_field *upb_msg_fieldbynum(struct upb_msg *m, + uint32_t number) { + struct upb_fieldsbynum_entry *e = + (struct upb_fieldsbynum_entry*)upb_inttable_lookup( + &m->fields_by_num, number, sizeof(struct upb_fieldsbynum_entry)); + return e ? &e->f : NULL; +} +INLINE struct upb_msg_field *upb_msg_fieldbyname(struct upb_msg *m, + struct upb_string *name) { + struct upb_fieldsbyname_entry *e = + (struct upb_fieldsbyname_entry*)upb_strtable_lookup( + &m->fields_by_name, name); + return e ? &e->f : NULL; +} + +/* "Set" flag reading and writing. *******************************************/ + +INLINE size_t upb_isset_offset(uint32_t field_index) { + return field_index / 8; +} + +INLINE uint8_t upb_isset_mask(uint32_t field_index) { + return 1 << (field_index % 8); +} + +/* Functions for reading and writing the "set" flags in the msg. Note that + * these do not perform memory management associated with any dynamic memory + * these fields may be referencing. These *only* set and test the flags. */ +INLINE void upb_msg_set(void *s, struct upb_msg_field *f) +{ + ((char*)s)[upb_isset_offset(f->field_index)] |= upb_isset_mask(f->field_index); +} + +INLINE void upb_msg_unset(void *s, struct upb_msg_field *f) +{ + ((char*)s)[upb_isset_offset(f->field_index)] &= ~upb_isset_mask(f->field_index); +} + +INLINE bool upb_msg_is_set(void *s, struct upb_msg_field *f) +{ + return ((char*)s)[upb_isset_offset(f->field_index)] & upb_isset_mask(f->field_index); +} + +INLINE bool upb_msg_all_required_fields_set(void *s, struct upb_msg *m) +{ + int num_fields = m->num_required_fields; + int i = 0; + while(num_fields > 8) { + if(((uint8_t*)s)[i++] != 0xFF) return false; + num_fields -= 8; + } + if(((uint8_t*)s)[i] != (1 << num_fields) - 1) return false; + return true; +} + +INLINE void upb_msg_clear(void *s, struct upb_msg *m) +{ + memset(s, 0, m->set_flags_bytes); +} + +/* Scalar (non-array) data access. ********************************************/ + +/* Returns a pointer to a specific field in a message. */ +INLINE union upb_value_ptr upb_msg_getptr(void *data, struct upb_msg_field *f) { + union upb_value_ptr p; + p._void = ((char*)data + f->byte_offset); + return p; +} + +/* Arrays. ********************************************************************/ + +/* Represents an array (a repeated field) of any type. The interpretation of + * the data in the array depends on the type. */ +struct upb_array { + union upb_value_ptr elements; + uint32_t len; /* Measured in elements. */ +}; + +/* Returns a pointer to an array element. */ +INLINE union upb_value_ptr upb_array_getelementptr( + struct upb_array *arr, uint32_t n, upb_field_type_t type) +{ + union upb_value_ptr ptr; + ptr._void = (void*)((char*)arr->elements._void + n*upb_type_info[type].size); + return ptr; +} + +/* These are all overlays on upb_array, pointers between them can be cast. */ +#define UPB_DEFINE_ARRAY_TYPE(name, type) \ + struct name ## _array { \ + type *elements; \ + uint32_t len; \ + }; + +UPB_DEFINE_ARRAY_TYPE(upb_double, double) +UPB_DEFINE_ARRAY_TYPE(upb_float, float) +UPB_DEFINE_ARRAY_TYPE(upb_int32, int32_t) +UPB_DEFINE_ARRAY_TYPE(upb_int64, int64_t) +UPB_DEFINE_ARRAY_TYPE(upb_uint32, uint32_t) +UPB_DEFINE_ARRAY_TYPE(upb_uint64, uint64_t) +UPB_DEFINE_ARRAY_TYPE(upb_bool, bool) +UPB_DEFINE_ARRAY_TYPE(upb_string, struct upb_string*) + +/* Defines an array of a specific message type. */ +#define UPB_MSG_ARRAY(msg_type) struct msg_type ## _array +#define UPB_DEFINE_MSG_ARRAY(msg_type) \ + UPB_MSG_ARRAY(msg_type) { \ + msg_type **elements; \ + uint32_t len; \ + }; + +/* Memory management *********************************************************/ + +/* One important note about these memory management routines: they must be used + * completely or not at all (for each message). In other words, you can't + * allocate your own message and then free it with upb_msgdata_free. As + * another example, you can't point a field to your own string and then call + * upb_msg_reuse_str. */ + +/* Allocates and frees message data, respectively. Newly allocated data is + * initialized to empty. Freeing a message always frees string data, but + * the client can decide whether or not submessages should be deleted. */ +void *upb_msgdata_new(struct upb_msg *m); +void upb_msgdata_free(void *data, struct upb_msg *m, bool free_submsgs); + +/* Given a pointer to the appropriate field of the message or array, these + * functions will lazily allocate memory for a string, array, or submessage. + * If the previously allocated memory is big enough, it will reuse it without + * re-allocating. See upb_msg.c for example usage. */ + +/* Reuse a string of at least the given size. */ +void upb_msg_reuse_str(struct upb_string **str, uint32_t size); +/* Like the previous, but assumes that the string will be by reference, so + * doesn't allocate memory for the string itself. */ +void upb_msg_reuse_strref(struct upb_string **str); + +/* Reuse an array of at least the given size, with the given type. */ +void upb_msg_reuse_array(struct upb_array **arr, uint32_t size, + upb_field_type_t t); + +/* Reuse a submessage of the given type. */ +void upb_msg_reuse_submsg(void **msg, struct upb_msg *m); + +/* Serialization/Deserialization. ********************************************/ + +/* This is all just a layer on top of the stream-oriented facility in + * upb_parse.h. */ + +struct upb_msg_parse_state { + struct upb_parse_state s; + bool merge; + bool byref; + struct upb_msg *m; +}; + +/* Initializes/frees a message parser. The parser will write the data to the + * message data "data", which the caller must have previously allocated (the + * parser will allocate submsgs, strings, and arrays as needed, however). + * + * "Merge" controls whether the parser will append to data instead of + * overwriting. Merging concatenates arrays and merges submessages instead + * of clearing both. + * + * "Byref" controls whether the new message data copies or references strings + * it encounters. If byref == true, then all strings supplied to upb_msg_parse + * must remain unchanged and must outlive data. */ +void upb_msg_parse_init(struct upb_msg_parse_state *s, void *data, + struct upb_msg *m, bool merge, bool byref); +void upb_msg_parse_reset(struct upb_msg_parse_state *s, void *data, + struct upb_msg *m, bool merge, bool byref); +void upb_msg_parse_free(struct upb_msg_parse_state *s); + +/* Parses a protobuf fragment, writing the data to the message that was passed + * to upb_msg_parse_init. This function can be called multiple times as more + * data becomes available. */ +upb_status_t upb_msg_parse(struct upb_msg_parse_state *s, + void *data, size_t len, size_t *read); + +/* Parses the protobuf in s (which is expected to be complete) and allocates + * new message data to hold it. This is an alternative to the streaming API + * above. "byref" works as in upb_msg_parse_init(). */ +void *upb_alloc_and_parse(struct upb_msg *m, struct upb_string *s, bool byref); + + +/* Text dump *****************************************************************/ + +void upb_msg_print(void *data, struct upb_msg *m, FILE *stream); + +#ifdef __cplusplus +} /* extern "C" */ +#endif + +#endif /* UPB_MSG_H_ */ |