/pb_decode.c
C | 552 lines | 410 code | 90 blank | 52 comment | 81 complexity | b4868d26849c009a86ff4374030cb196 MD5 | raw file
- /* pb_decode.c -- decode a protobuf using minimal resources
- *
- * 2011 Petteri Aimonen <jpa@kapsi.fi>
- */
- #ifdef __GNUC__
- /* Verify that we remember to check all return values for proper error propagation */
- #define checkreturn __attribute__((warn_unused_result))
- #else
- #define checkreturn
- #endif
- #include "pb.h"
- #include "pb_decode.h"
- #include <string.h>
- typedef bool (*pb_decoder_t)(pb_istream_t *stream, const pb_field_t *field, void *dest) checkreturn;
- /* --- Function pointers to field decoders ---
- * Order in the array must match pb_action_t LTYPE numbering.
- */
- static const pb_decoder_t PB_DECODERS[PB_LTYPES_COUNT] = {
- &pb_dec_varint,
- &pb_dec_svarint,
- &pb_dec_fixed32,
- &pb_dec_fixed64,
-
- &pb_dec_bytes,
- &pb_dec_string,
- &pb_dec_submessage
- };
- /**************
- * pb_istream *
- **************/
- bool checkreturn pb_read(pb_istream_t *stream, uint8_t *buf, size_t count)
- {
- if (stream->bytes_left < count)
- return false;
-
- if (!stream->callback(stream, buf, count))
- return false;
-
- stream->bytes_left -= count;
- return true;
- }
- static bool checkreturn buf_read(pb_istream_t *stream, uint8_t *buf, size_t count)
- {
- uint8_t *source = (uint8_t*)stream->state;
-
- if (buf != NULL)
- memcpy(buf, source, count);
-
- stream->state = source + count;
- return true;
- }
- pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize)
- {
- pb_istream_t stream;
- stream.callback = &buf_read;
- stream.state = buf;
- stream.bytes_left = bufsize;
- return stream;
- }
- /********************
- * Helper functions *
- ********************/
- static bool checkreturn pb_decode_varint32(pb_istream_t *stream, uint32_t *dest)
- {
- uint64_t temp;
- bool status = pb_decode_varint(stream, &temp);
- *dest = (uint32_t)temp;
- return status;
- }
- bool checkreturn pb_decode_varint(pb_istream_t *stream, uint64_t *dest)
- {
- uint8_t byte;
- uint8_t bitpos = 0;
- *dest = 0;
-
- while (bitpos < 64 && pb_read(stream, &byte, 1))
- {
- *dest |= (uint64_t)(byte & 0x7F) << bitpos;
- bitpos += 7;
-
- if (!(byte & 0x80))
- return true;
- }
-
- return false;
- }
- bool checkreturn pb_skip_varint(pb_istream_t *stream)
- {
- uint8_t byte;
- do
- {
- if (!pb_read(stream, &byte, 1))
- return false;
- } while (byte & 0x80);
- return true;
- }
- bool checkreturn pb_skip_string(pb_istream_t *stream)
- {
- uint32_t length;
- if (!pb_decode_varint32(stream, &length))
- return false;
-
- return pb_read(stream, NULL, length);
- }
- /* Currently the wire type related stuff is kept hidden from
- * callbacks. They shouldn't need it. It's better for performance
- * to just assume the correct type and fail safely on corrupt message.
- */
- static bool checkreturn skip(pb_istream_t *stream, pb_wire_type_t wire_type)
- {
- switch (wire_type)
- {
- case PB_WT_VARINT: return pb_skip_varint(stream);
- case PB_WT_64BIT: return pb_read(stream, NULL, 8);
- case PB_WT_STRING: return pb_skip_string(stream);
- case PB_WT_32BIT: return pb_read(stream, NULL, 4);
- default: return false;
- }
- }
- /* Read a raw value to buffer, for the purpose of passing it to callback as
- * a substream. Size is maximum size on call, and actual size on return.
- */
- static bool checkreturn read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size)
- {
- size_t max_size = *size;
- switch (wire_type)
- {
- case PB_WT_VARINT:
- *size = 0;
- do
- {
- (*size)++;
- if (*size > max_size) return false;
- if (!pb_read(stream, buf, 1)) return false;
- } while (*buf++ & 0x80);
- return true;
-
- case PB_WT_64BIT:
- *size = 8;
- return pb_read(stream, buf, 8);
-
- case PB_WT_32BIT:
- *size = 4;
- return pb_read(stream, buf, 4);
-
- default: return false;
- }
- }
- /* Decode string length from stream and return a substream with limited length.
- * Before disposing the substream, remember to copy the substream->state back
- * to stream->state.
- */
- static bool checkreturn make_string_substream(pb_istream_t *stream, pb_istream_t *substream)
- {
- uint32_t size;
- if (!pb_decode_varint32(stream, &size))
- return false;
-
- *substream = *stream;
- if (substream->bytes_left < size)
- return false;
-
- substream->bytes_left = size;
- stream->bytes_left -= size;
- return true;
- }
- /* Iterator for pb_field_t list */
- typedef struct {
- const pb_field_t *start;
- const pb_field_t *current;
- int field_index;
- void *dest_struct;
- void *pData;
- void *pSize;
- } pb_field_iterator_t;
- static void pb_field_init(pb_field_iterator_t *iter, const pb_field_t *fields, void *dest_struct)
- {
- iter->start = iter->current = fields;
- iter->field_index = 0;
- iter->pData = (char*)dest_struct + iter->current->data_offset;
- iter->pSize = (char*)iter->pData + iter->current->size_offset;
- iter->dest_struct = dest_struct;
- }
- static bool pb_field_next(pb_field_iterator_t *iter)
- {
- bool notwrapped = true;
- size_t prev_size = iter->current->data_size;
-
- if (PB_HTYPE(iter->current->type) == PB_HTYPE_ARRAY)
- prev_size *= iter->current->array_size;
-
- iter->current++;
- iter->field_index++;
- if (iter->current->tag == 0)
- {
- iter->current = iter->start;
- iter->field_index = 0;
- iter->pData = iter->dest_struct;
- prev_size = 0;
- notwrapped = false;
- }
-
- iter->pData = (char*)iter->pData + prev_size + iter->current->data_offset;
- iter->pSize = (char*)iter->pData + iter->current->size_offset;
- return notwrapped;
- }
- static bool checkreturn pb_field_find(pb_field_iterator_t *iter, int tag)
- {
- int start = iter->field_index;
-
- do {
- if (iter->current->tag == tag)
- return true;
- pb_field_next(iter);
- } while (iter->field_index != start);
-
- return false;
- }
- /*************************
- * Decode a single field *
- *************************/
- static bool checkreturn decode_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iterator_t *iter)
- {
- pb_decoder_t func = PB_DECODERS[PB_LTYPE(iter->current->type)];
-
- switch (PB_HTYPE(iter->current->type))
- {
- case PB_HTYPE_REQUIRED:
- return func(stream, iter->current, iter->pData);
-
- case PB_HTYPE_OPTIONAL:
- *(bool*)iter->pSize = true;
- return func(stream, iter->current, iter->pData);
-
- case PB_HTYPE_ARRAY:
- if (wire_type == PB_WT_STRING
- && PB_LTYPE(iter->current->type) <= PB_LTYPE_LAST_PACKABLE)
- {
- /* Packed array */
- size_t *size = (size_t*)iter->pSize;
- pb_istream_t substream;
- if (!make_string_substream(stream, &substream))
- return false;
-
- while (substream.bytes_left && *size < iter->current->array_size)
- {
- void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
- if (!func(&substream, iter->current, pItem))
- return false;
- (*size)++;
- }
- return (substream.bytes_left == 0);
- }
- else
- {
- /* Repeated field */
- size_t *size = (size_t*)iter->pSize;
- void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
- if (*size >= iter->current->array_size)
- return false;
-
- (*size)++;
- return func(stream, iter->current, pItem);
- }
-
- case PB_HTYPE_CALLBACK:
- {
- pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
-
- if (pCallback->funcs.decode == NULL)
- return skip(stream, wire_type);
-
- if (wire_type == PB_WT_STRING)
- {
- pb_istream_t substream;
-
- if (!make_string_substream(stream, &substream))
- return false;
-
- while (substream.bytes_left)
- {
- if (!pCallback->funcs.decode(&substream, iter->current, pCallback->arg))
- return false;
- }
-
- stream->state = substream.state;
- return true;
- }
- else
- {
- /* Copy the single scalar value to stack.
- * This is required so that we can limit the stream length,
- * which in turn allows to use same callback for packed and
- * not-packed fields. */
- pb_istream_t substream;
- uint8_t buffer[10];
- size_t size = sizeof(buffer);
-
- if (!read_raw_value(stream, wire_type, buffer, &size))
- return false;
- substream = pb_istream_from_buffer(buffer, size);
-
- return pCallback->funcs.decode(&substream, iter->current, pCallback->arg);
- }
- }
-
- default:
- return false;
- }
- }
- /* Initialize message fields to default values, recursively */
- static void pb_message_set_to_defaults(const pb_field_t fields[], void *dest_struct)
- {
- pb_field_iterator_t iter;
- pb_field_init(&iter, fields, dest_struct);
-
- /* Initialize size/has fields and apply default values */
- do
- {
- if (iter.current->tag == 0)
- continue;
-
- /* Initialize the size field for optional/repeated fields to 0. */
- if (PB_HTYPE(iter.current->type) == PB_HTYPE_OPTIONAL)
- {
- *(bool*)iter.pSize = false;
- }
- else if (PB_HTYPE(iter.current->type) == PB_HTYPE_ARRAY)
- {
- *(size_t*)iter.pSize = 0;
- continue; /* Array is empty, no need to initialize contents */
- }
-
- /* Initialize field contents to default value */
- if (PB_HTYPE(iter.current->type) == PB_HTYPE_CALLBACK)
- {
- continue; /* Don't overwrite callback */
- }
- else if (PB_LTYPE(iter.current->type) == PB_LTYPE_SUBMESSAGE)
- {
- pb_message_set_to_defaults(iter.current->ptr, iter.pData);
- }
- else if (iter.current->ptr != NULL)
- {
- memcpy(iter.pData, iter.current->ptr, iter.current->data_size);
- }
- else
- {
- memset(iter.pData, 0, iter.current->data_size);
- }
- } while (pb_field_next(&iter));
- }
- /*********************
- * Decode all fields *
- *********************/
- bool checkreturn pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
- {
- uint32_t fields_seen = 0; /* Used to check for required fields */
- pb_field_iterator_t iter;
- int i;
-
- pb_message_set_to_defaults(fields, dest_struct);
-
- pb_field_init(&iter, fields, dest_struct);
-
- while (stream->bytes_left)
- {
- uint32_t temp;
- int tag;
- pb_wire_type_t wire_type;
- if (!pb_decode_varint32(stream, &temp))
- {
- if (stream->bytes_left == 0)
- break; /* It was EOF */
- else
- return false; /* It was error */
- }
-
- if (temp == 0)
- break; /* Special feature: allow 0-terminated messages. */
-
- tag = temp >> 3;
- wire_type = (pb_wire_type_t)(temp & 7);
-
- if (!pb_field_find(&iter, tag))
- {
- /* No match found, skip data */
- if (!skip(stream, wire_type))
- return false;
- continue;
- }
-
- fields_seen |= 1 << (iter.field_index & 31);
-
- if (!decode_field(stream, wire_type, &iter))
- return false;
- }
-
- /* Check that all required fields (mod 31) were present. */
- for (i = 0; fields[i].tag != 0; i++)
- {
- if (PB_HTYPE(fields[i].type) == PB_HTYPE_REQUIRED &&
- !(fields_seen & (1 << (i & 31))))
- {
- return false;
- }
- }
-
- return true;
- }
- /* Field decoders */
- /* Copy destsize bytes from src so that values are casted properly.
- * On little endian machine, copy first n bytes of src
- * On big endian machine, copy last n bytes of src
- * srcsize must always be larger than destsize
- */
- static void endian_copy(void *dest, void *src, size_t destsize, size_t srcsize)
- {
- #ifdef __BIG_ENDIAN__
- memcpy(dest, (char*)src + (srcsize - destsize), destsize);
- #else
- UNUSED(srcsize);
- memcpy(dest, src, destsize);
- #endif
- }
- bool checkreturn pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest)
- {
- uint64_t temp;
- bool status = pb_decode_varint(stream, &temp);
- endian_copy(dest, &temp, field->data_size, sizeof(temp));
- return status;
- }
- bool checkreturn pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
- {
- uint64_t temp;
- bool status = pb_decode_varint(stream, &temp);
- temp = (temp >> 1) ^ -(int64_t)(temp & 1);
- endian_copy(dest, &temp, field->data_size, sizeof(temp));
- return status;
- }
- bool checkreturn pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest)
- {
- #ifdef __BIG_ENDIAN__
- uint8_t bytes[4] = {0};
- bool status = pb_read(stream, bytes, 4);
- if (status) {
- uint8_t bebytes[4] = {bytes[3], bytes[2], bytes[1], bytes[0]};
- memcpy(dest, bebytes, 4);
- }
- return status;
- #else
- UNUSED(field);
- return pb_read(stream, (uint8_t*)dest, 4);
- #endif
- }
- bool checkreturn pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest)
- {
- #ifdef __BIG_ENDIAN__
- uint8_t bytes[8] = {0};
- bool status = pb_read(stream, bytes, 8);
- if (status) {
- uint8_t bebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4],
- bytes[3], bytes[2], bytes[1], bytes[0]};
- memcpy(dest, bebytes, 8);
- }
- return status;
- #else
- UNUSED(field);
- return pb_read(stream, (uint8_t*)dest, 8);
- #endif
- }
- bool checkreturn pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest)
- {
- pb_bytes_array_t *x = (pb_bytes_array_t*)dest;
-
- uint32_t temp;
- if (!pb_decode_varint32(stream, &temp))
- return false;
- x->size = temp;
-
- /* Check length, noting the space taken by the size_t header. */
- if (x->size > field->data_size - offsetof(pb_bytes_array_t, bytes))
- return false;
-
- return pb_read(stream, x->bytes, x->size);
- }
- bool checkreturn pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest)
- {
- uint32_t size;
- bool status;
- if (!pb_decode_varint32(stream, &size))
- return false;
-
- /* Check length, noting the null terminator */
- if (size + 1 > field->data_size)
- return false;
-
- status = pb_read(stream, (uint8_t*)dest, size);
- *((uint8_t*)dest + size) = 0;
- return status;
- }
- bool checkreturn pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest)
- {
- bool status;
- pb_istream_t substream;
-
- if (!make_string_substream(stream, &substream))
- return false;
-
- if (field->ptr == NULL)
- return false;
-
- status = pb_decode(&substream, (pb_field_t*)field->ptr, dest);
- stream->state = substream.state;
- return status;
- }